Biology Cells: Parts & Characteristics

Hi, welcome back to www.educator.com, this is the lesson on cells, parts and characteristics.0000

When we talk about cells as being the basic unit for life,0008

you have to consider that microscope is the key to really finding that out.0011

Prior to the 1600s, cells were not highly known, cells were not known to people as being the building block of life.0016

They would look at something and it was moving, and behaving like something if that is moving and that is alive.0026

Prior to 1600s, looking at something like coral in an intertidal committee or a sponge,0032

they might think that is not alive, and it is not moving.0038

But when you look closely, they got cells in it and those cells are definitely alive.0043

This was the key to advancement in cellular study.0048

If we trace the major events in terms of microscope development and used in science,0050

in the 1600’s Anton van Leeuwenhoek, he was very instrumental in terms of the first guy to actually use a simple compound microscope,0057

having some lenses together and zooming in on something and saying like,0070

I can see that little body, that little cell, he did not called it that, but I can see that little unit.0075

Now that I am looking up close, it makes more sense how the whole exists.0083

This guy was very instrumental in terms of coming up with a cool way to zoom in and see the details.0088

Also in that same century Robert Hooke, an English scientist, he is the one who coined the term cell.0096

Now, it is just it is a common term, you know cells.0106

But when you think about the reason why he came up with that, he was looking at cork,0110

he is looking at basically the bark of this cork trees that you would find in parts of Portugal, for instance.0115

If you slice cork very thin, you see that it looks like almost like little cells.0122

I am saying cells with you knowing what that means.0135

When Robert Hooke was looking at these basically dead plant cells,0139

and just kind of looking at the shell of the cell wall of these plants,0146

he thought like they look like little cells where a monk in a monastery would live,0149

like a little tiny dormitory or room, and that is why he called them cells.0156

It just happen to be because he was looking at cork and looking at these dead,0162

desiccated plant cells that we have that very common important term now.0166

You know the next couple hundred years, there were more and more advances,0172

in terms of getting better and better microscopes.0176

More lenses compounding the magnification greater and greater.0178

And then, you get to the 1800s where these two scientists had big contributions on their own fields.0182

Matthias Schleiden, a botanist, he is the one who really specialized in looking at plants cells and realizing what is through plant cells.0189

Theodore Schwann, he is the animal cell guy.0199

Schwann cells, actually his name inspired the name for a kind of insulatory cell0202

that is wrapped around the axons of neurons in animals.0209

This is the plant guy and this is the animal guy.0213

Flash forward, decades and decades later to the next century.0217

To the 1930s, you do not just have light microscopes anymore.0222

All of these scientists up here relied on light and lenses,0226

magnifying an image and bouncing light off that so you can see what is reflected back at you.0233

But if you want to get smaller and smaller, you have to get to the point0238

where light is not as effective beyond 1500 or 2000 times magnification.0242

When you get to 5000 times, 10,000 times, 50,000 times magnified, you need to rely on electron microscopes.0250

In the 1930’s/1940’s, you start to have these which are really good at figuring out the shape of that molecule.0258

What does the inside of a mitochondrion look like, a very important cell organelle?0269

These have to do with bouncing electrons off a particular molecule, a particular item.0275

The way that they bounce off and they make an image, a very grainy image0283

but something that informs us about the shape of really, really tiny things.0288

Today, there are two main kinds, there is scanning electron microscopes and transmission electron microscopes.0294

In general, scanning electron microscopes give you a very good image,0300

in terms of like what a cell looks like as a whole, its shape and its structure.0304

Transmission electron microscopes give you a really good idea of the way that parts are, inside of cells,0310

in terms of their precise structure.0317

The cell theory, this is made of three tenets, three important points that all have to be true0322

for the cell theory to make sense as a whole.0330

The three tenets, these are agreed upon by all life scientists.0333

In the future, it is possible might be modified but as it is now this is the cell theory.0340

The first tenet, all organisms are composed of one or more cells.0345

If you have something that is not made of cells, it is not alive.0349

It has to be made of at least 1 cell, 2 cells, 16 cells, a hundred trillion cells,0353

and then we call it an organism that is alive.0359

The cell is the basic unit of structure and function for organisms, meaning every structure in a body, in a living being,0361

and every function, in terms of every activity that organism is doing, it has to do with the cells inside of it.0369

The reason why you have brain looks the way it does,0376

the structure of your brain comes down to the individual cells inside of it, notice mostly neurons.0379

The function of your brain, every single activity, every single action your brain does has to do with the cells inside of it.0385

All cells come from free existing cells, that is self-explanatory.0394

You cannot get a cell unless it is from another cell and this is called biogenesis, life creating life.0399

The only example of abiogenesis meaning life coming from no life would be the very first cells on earth.0415

It might seem contradictory to say that at one point at time, this was not true but there are reasons for that.0423

The lessons on evolution and the history of life, I will bring that up in more detail.0433

The reason why you have your cells is they came from your parents’ cells.0437

They have their cells because they came from their parents’ cells, and so on and so forth.0442

All the way back to the first humans and we can keep tracing back our ancestry0447

to the very first life forms for about 3 ½ billion years ago.0451

This picture down here, this is a zoomed in, it is a little bit grainy0457

but this is a zoomed in of blue green algae also known as the cyano bacteria.0461

You could see the little chains of these individual cells, these are alive.0466

When you are not zooming into it, it just makes seem a water look kind of greenish, a little bit murky.0472

But, there are billions and billions of these, when you are looking at a slightly greenish body of water in nature.0479

The characteristics of life, what is true of every living being and these are generalization but these are true.0490

Display organization, there is a certain kind of building in terms of how an organism is put together.0498

Even something that looks a morphs at first glance like this, this looks like just a blob,0506

but this is a perimysium, this is a living single celled organism.0513

Unicellular, if you want to call it that.0518

This does display organization, it has a rim around the whole circumference, that is called a plasma membrane.0520

If you look really carefully, there are tiny little hair like structures jutting out of it, they are called cilia.0529

Inside, there is a nucleus, there are lysosomes, there are ribosomes, there all these structures that looked organize,0537

in terms of kind of where they are at and how they behave with respect to one another.0547

Grow and develop, every organism has the ability to grow, to take on more matter and organize it as itself.0552

In terms of development, a lot of organisms start out as one cell.0561

As they grow, they develop tissues, they develop cells that have very particular functions.0565

It is definitely true on us, we produce.0571

Yes, it is true that some organisms humans for instance can be sterile, they are not able to have children.0574

But in terms of what our DNA is telling our species, in general, we are meant to reproduce.0581

We are meant to make more individuals and life makes more life.0587

Reproduction goes hand in hand with life.0591

Response to stimuli, it might not always be obvious like you know someone turning their head in response to light or sound,0594

but even this perimysium cell responds to stimuli, to activities or signals in the environment.0601

There will be a chemical signal that tells us like, there is food over there,0611

or there is something coming next to me that could eat me, so it moves in the opposite direction.0615

It is responding to chemical stimuli.0619

Maintain homeostasis, homeostasis means literally same state and maintaining homeostasis is really the key to staying alive.0622

We do this whether we are sweating or shivering.0633

Sweating would be your body's response to increased body temperature.0636

Sweating out some water can actually cool down your body, that is homeostasis,0640

so your body does not overheat to the point where cells are getting damaged, that is permanent damage.0645

Opposite with shivering, your body temperature is a little too cold,0651

your brain makes your muscles contract and relax really quickly to generate heat energy.0655

Those were both simple examples of how your body maintains a balance internally,0660

with respect to what is happening outside of it, and can evolve.0666

This will make more sense with the evolution lesson but an individual organism cannot evolve.0670

I was born homosapiens sapiens that is the species, I will perish as that particular species.0676

Populations over time can evolve, a population is a group of organisms of the same species in an area.0688

The ability to evolve goes hand in hand with life.0695

Any cell has DNA in it, if it is alive and functioning.0700

DNA overtime can be changed gradually to give you some very different characteristics and that is the key to evolution.0704

Prokaryote versus eukaryote, if you look at all the cells that had ever been discovered or studied on earth,0715

they fit into one of these two categories.0722

I mean it, all cells can be included in one of these two categories.0724

First one, prokaryote, the other term in terms of an adjective would be prokaryotic.0729

I can call a cell prokaryotic or say that is a prokaryotic cell.0740

It means before the kernel which sounds silly but pro means before,0744

and karyote comes from karyos, a Greek word that means kernel or nut.0750

I had a student several years ago who was fluent in Greek and she said that karyos can also mean walnut.0757

When she said that, something down in me that help you remember what this actually means,0768

and I will it draw it for you in a second.0772

But what does before the kernel has to do with, is it means that these cells,0775

they do not have a nucleus or other membrane bound organelles.0781

The kernel is referring to the nucleus, this round body inside the cell.0784

If you look at every single bacterial cell in nature and all prokaryotes or bacteria, all bacteria are prokaryotes,0790

none of them have a nucleus.0799

Here is a bacterial cell, you will have DNA in the center and you will have this things called ribosomes,0803

these are not membrane bound organelles.0810

You will have a cell wall from the outside but there will not be a round nucleus.0813

There will not be things called Golgi apparatus or lysosomes,0819

these are some of the things I will teach you about, later on this lesson.0824

Prokaryotes, no membrane bound organelles especially nucleus.0827

The have evolved before the nucleus came into being and they did just fine without a nucleus.0832

On the other hand, eukaryote is every other cell this means true kernel or true walnut.0840

It has a nucleus and other membrane bound organelles.0847

The examples really every other cell on earth, animal cells, plant cells, cells of different fungi.0850

And then, the one in the previous slide that perimysium, that is a single cell protist, it is also eukaryotic.0857

This whole walnut thing, the reason it has meaning to me is because if you crack open a walnut just the right way,0865

there is the shell rim you kind of see this shape.0875

I mean, more or less that is kind of the shape you see,0887

when you look at kind of the half of the nuts that is in the walnut shell.0889

When that student, the one who spoke Greek told me that it makes sense now.0893

Because when you look at the nucleus of a eukaryote or eukaryotic cell, you will see this.0897

This is a duplicated chromosome which you are going to see a lot more later on in these lessons,0907

when we talked about DNA and cell division.0913

If you use your imagination, you can see how this looks like that, somewhat.0916

These are inside of a nucleus so you know this is kind of a basic prokaryotic cell.0923

Here, we sliced it in half an animal cell, here is a nucleus.0933

Inside, you would see from far away but you would see these guys inside of there.0944

This is very typical of a eukaryotic cell and actually, there should be an even number0955

if it is sexually reproducing but they will make more sense when we talk about meiosis.0960

But you do see these chromosomes in certain periods of time within these eukaryotic cells,0965

whether it is an animal cell, a plant cell, or fungi.0972

You also would see all kinds of other stuff, ER, we are doing a very quick drawing.0974

You would see Golgi apparatus which looks like stacks of membranes.0981

You would see things called lysosomes, and of course you would see ribosomes as well.0985

Without ribosomes and these are not membrane bound because they were found in here.0992

Without ribosomes, a cell could not exist because ribosomes allow you to make proteins.0997

There is your basic designation between prokaryotic cells and eukaryotic cells.1006

Here is a computer generated image of the cell parts within a plant cell.1015

Like I mentioned earlier with the cork cells that Robert Hooke looked at,1019

you can see that boxy look here with this green border, that is the cell wall.1023

The yellow inside, if you look carefully that is actually the plasma membrane also called the cell membrane.1030

Here is that nucleus, and certain times when the cells actually dividing,1036

within here, the nucleus would actually break apart and those little X shapes looking chromosomes.1041

Some people call them like butterflies.1053

You would see them, and this of course is a eukaryotic cell.1055

Here is your nucleus, here is all your other membrane bound organelles.1059

Anything that is a sack like structure is membrane bound.1064

Here is your nucleus, we will talk about the 6 in next few slides, ER, Golgi apparatus,1068

vesicles coming from the Golgi, mitochondria, the key to getting a useful energy source inside of the cell.1075

Chloroplasts how a plants actually make sugars than can be broken down on the mitochondria.1083

This huge thing here looks like a reservoir of water, that is what it is.1089

Let us say water vacuole, it is like a kind of large central vacuole inside the cell.1095

And then, the cytoskeleton, there is other parts I will tell you about in the next few slides.1102

First one, let us start in the outside, the plasma membrane also called the cell membrane.1108

It is the rim of every cell, the exception being if the cell has a cell wall that would be on the outside.1113

It will be superficial to this plasma membrane.1121

But every single cell on earth has a plasma membrane.1125

It is made up of the same basic components.1129

It is protective and regulatory, of course it is kind of like a fence.1132

It is kind of like that outer border unless there is a cell wall.1137

It is going to be regulatory, only certain things is going to be let in, only certain things are going to be let out.1142

If you let everything in and everything out then the cells are going to be vulnerable to1147

whatever might be in the outer environment, and would lose things that are important to it.1153

For that reason, cells are known as semi permeable.1157

What semi permeable means is simply, if it was just permeable in general,1163

just completely permeable, anything will go back and forth.1173

But semi permeable tells us that like, only certain things are let through, based on what is needed or what is not needed.1177

That is the characteristic of every single functional cell, it is not going to let everything through, it is semi permeable.1185

It is membrane is semi permeable.1192

It is composed of a bilayer of phospholipids also called a phospholipid bilayer.1194

Here it is, if you would take a cross section like sliced through the cell and look at it,1200

see what is inside of that little line that we see inside of like a microscope view, if you zoom in close, you can see the two layers.1207

Here is the one layer and here is the second layer.1216

The lumen of the cell means like, this is the space within a cell, a lot of times they are called the intracellular space.1221

Here is the extra cellular space outside of the cell.1228

In here, you would see the rest the organelles and here is an aqueous layer, you still would probably see fluid there as well.1232

Notice that, facing the fluid on both sides, you have these heads.1239

When they zoom in, they show you, here it is, these are known as polar or hydrophilic heads.1248

Remember earlier, when we are talking about water, water is a polar molecule.1254

This is a polar molecule, it gets along with water, chemically or electrically.1258

Polar is okay with water, that is why both of these sets of hydrophilic heads are facing the water,1265

outside the cell and inside the cell.1275

Hydrophilic literally meaning loving water.1277

Philia is a Greek form of love, hydro, water, hydrophilic love of water.1280

With nonpolar which gets along with lipids, lipids are non polar, they do not like mixing with water.1286

It also known as hydrophobic, afraid of water, that is the tails.1294

These tails, let me use purple for them, there are two.1298

These phospholipids actually look very similar to triglycerides which we covered a little bit earlier in this course.1307

The difference is that, instead of it being a typical triglyceride like,1313

here is a glycerol and 3 fatty acid chains, there is just two.1317

These are hydrocarbon or fatty acid tails.1322

And taking the place of where that third one would be is actually a phosphate unit,1326

which helps make up this hydrophilic head on this part and this part here.1333

You could see how they are oriented, there is this buffer region, a lipidy buffer on the inside made of these tails, like this.1338

But the heads are facing the inner aqueous region and the outer aqueous region.1345

This is a nice kind of like double border.1350

It is a fence that is kind of like doubly effective, in terms of it having this buffer and keeping the outside separate from the inside.1357

Inside, there are proteins imbedded.1365

What is not represented here is if, let me show you here with this.1368

There is a protein, they would call this an integral protein.1377

It is actually spinning the length of this phospholipid bilayer and this protein could serve several functions.1380

It could be for transport, meaning it might have a little like hallway inside of it where stuff can go in and stuff can go out.1388

It might be a gated protein, it only opens and closes when needed.1397

It could be for identification, your cells have very particular proteins in their plasma membranes1404

that are slightly different from mine.1409

We are the same species but if I were to donate an organ to you, your body would be like, this does not belong here.1411

The reason why your body knows that is the proteins are slightly different, they would see in form.1419

Sometimes, proteins are just for identification purposes, sometimes for attachment.1423

Proteins allow cells to be bonded with other cells attached other cells.1428

The reason why my skin does not tear part here is, I have proteins that are holding together my skin cells.1433

If those get damaged then the tissues are going to fall apart.1443

A lot of times they are for attachments to neighboring cells or to neighboring layers.1447

Sometimes, there are enzymes imbedded in the plasma membrane,1452

for the sake of changing a molecule, breaking it apart, building something, initiating a reaction.1457

In general, this plasma membrane can be called the fluid mosaic model, that is the term for the fluidity of this.1465

There had been study suggesting that these little phospholipids, they do not just stay put.1472

They are constantly moving around with respect to each other.1478

If you would be looking down on the cell, it would look like a sea of moving parts.1481

Those phosphate heads would be moving, it would look like an ocean.1488

They can move out a million times a second, which I cannot even imagine, but there have been studies confirming that.1491

The reason why it is called a fluid mosaic model is,1503

a mosaic means it has a lot of different pieces altogether like a tile mosaic.1506

Because it is not just the phosphate heads,1512

you would see all kinds of different proteins scattered throughout this phospholipid bilayer.1514

You would see what are called glycoproteins, little bits of cholesterol imbedded in here1519

to help with the buffer, in terms of temperature and fluidity.1526

The fluid mosaic model is a term for how we understand the plasma membrane.1531

For the rest of this lesson, I am going to compare the parts of the cell to a city, like an analogy.1536

Like I mentioned before, this is like the fence on the outside of the city.1542

This will help keep it straight, in terms of all the different part of the cell and how they influence one another.1547

Next is the nucleus, if we are going to maintain this city analogy, the nucleus would be very much like City Hall.1555

That is what running the city, making the rules, making sure people understand how that works.1569

The nucleus very much is like the brain of the cell.1574

The nucleus, this spherical structure, it is got a double membrane made of the phospholipid bilayer, like I mention before.1579

It is also in here, it is not just in the plasma membrane.1589

Inside of it, it got the DNA, deoxyribonucleic acid in a nuclear envelope.1592

Notice this term here, nuclear envelope and they say outer membrane and inner membrane,1597

because I said it is a double layer of those phospholipid bilayers.1602

The nuclear envelope, there it is.1607

Inside, you got something called chromatin.1611

They are labeling it here, chromatin, you got the heterochromatin, do not worry about the difference.1613

Basically, chromatin is all of the genetic information, the DNA and associated proteins that are helping organize it.1619

Those proteins are typically called histones.1627

When we talk about how DNA is arranged inside of a chromosome in future lessons,1631

you will see histones specifically and how DNA is kind of wrapped around those histones.1636

Chromatin is all that stuff on the inside.1643

Nuclear pores permit the passage of molecules in and out.1647

If you look carefully, they are labeling the nuclear pores right there, right there, stuff goes in, stuff goes out.1650

You sometimes will have hormones that would signal a cell like, we need a certain protein and we need it right now.1660

That hormone will go all the way inside the nucleus in affect the reading of the DNA and making of a signal to go out of the nucleus.1666

Constantly, the nuclei which is plural for nucleus, let me write it down, the nuclei of your cells,1675

if the cells are metabolic reactive, they are constantly making RNA.1682

It is kind of like a photocopy of DNA that tells a cell how to make protein.1686

Yes, it is pretty much like the brain of the cell.1692

Like City Hall is in charge of the city, it contains the codes for how to make every single protein in a cell.1695

How to make every cell part, how to maintain it, and how to keep the cell alive.1701

It also has something called a nucleolus.1706

Here is the nucleolus which is like a mini nucleus, in a sense.1709

It makes ribosomes, that is the purpose of it.1714

Ribosomes which we willactually label in this drawing, this little pink dots, up close they look a little different.1718

But in cell diagrams, they look just like dots from far away.1725

These are little protein factories.1729

Without the nucleus or the nucleolus specifically making these, a cell would not be able to stay alive.1732

That is the summary on the nucleus, next up ribosome.1739

Ribosomes are found in every single cell on earth.1745

Nucleus would not be, if you remember a prokaryote does not have a nucleus.1747

It still has DNA but it is not in a spherical structure inside of the cell.1751

Every single cell on earth, prokaryote and eukaryote has ribosomes, these are not membrane bound.1757

They do make proteins, that is what they do.1765

Here you got two sub units, they actually have this unit of measure of 200 angstroms1768

for the actual length of this which is very tiny.1774

This right here is a large sub unit, this is a small sub unit.1777

A lot of times it is depicted like this, more simply.1783

If you use your imagination and tilt it on this side, you could see how they have this.1788

This is looking from that angle like at the bottom, but you got the large sub unit and a small sub unit.1792

It got inside of it, RNA and protein roving in a very particular way to give you this sort of form, this globular kind form.1799

Inside of here, you have another kind of RNA that will move through, it is called messenger RNA.1810

These things called tRNA has come down in here and assemble an amino acid chain.1815

That is how we actually physically make proteins, more about that in future lesson.1820

They are found throughout the cytoplasm, this is a term for all that fluid area inside of a cell that is bound by the plasma membrane.1824

They can be free or bound, what that means is a free ribosomes, it can be the floating around anywhere.1832

It can be next to the plasma membrane, it can be very close to nucleus, just kind of floating reading the RNA.1838

Also, they can be bound, they physically will dock on what is called the ER,1847

the endoplasmic reticulum which you are going to hear about next.1852

They use various kinds of RNA to some of proteins, I mention those a moment ago mRNA, tRNA,1856

inside of it there is ribosomal RNA, also known as rRNA.1862

Amazingly, there can be a million of them in one cell which is really hard to picture but1866

these are little factories that are making a very important product for the cell.1872

To maintain that little city analogy, these are factories, little shops.1878

You can think of it as a shop that produces a certain product and that product is protein.1889

The protein is like the major exports, the thing that the city relies on to stay functioning and to stay alive.1899

Next up, the endoplasm reticulum which in Latin literally means little net inside the cell.1911

It kind of does look like a net, if you use your imagination.1918

It is also known as the ER for short, not an emergency room, endoplasmic reticulum.1922

It is typically adjacent to the nucleus, like right outside of the nucleus.1927

If you look very carefully at this animal cell here, there is the nucleus and there is the ER which we are zooming into here.1929

If this was the ER, the nucleus will be right there.1939

It does look like membranous hallway, like you can imagine different molecules weaving through here,1946

as it goes through the different membranes.1952

It is a site of numerous chemical reactions, depending on where you are in this ER,1956

you got different stuff going on.1960

Sometimes it is proteins being made, lipid parts being made.1962

Ribosomes are doing a lot of work in this area, you can see all those yellow dots, those are ribosomes.1968

ER can be rough or smooth, the rough part looks like if you were to touch,1973

it almost looks like and feel like sand paper, it will be rough because there are ribosomes.1979

This looks kind of smooth, here there are no ribosomes, that is why it is a smooth ER.1984

Like I said, rough has ribosomes mainly for protein synthesis.1989

If you remember from the previous slide, ribosomes there are those little protein making factories or shops.1994

If you got a bunch of these protein makers on here, you would expect that there will be a lot of protein making.2002

The reason why it is important on this membrane is, once the protein is made,2009

it can be wrapped up in a little membrane phospholipid bilayer unit.2012

It is the same membranous structure you see in the plasma membrane.2017

That little membrane sac can take the protein to the next organelle, which you are going to hear about in a second.2020

The smooth ER right here, depending on the cell you would have more smooth ER than rough ER.2028

There is not always majority rough, something like a liver cell, we have a lot of smooth ER2035

because of the making of lipid products in that particular organ.2041

And also the breakdown of certain chemicals, certain toxins, you would need more extensive smooth ER.2046

There are no ribosomes here, it is mainly for lipid synthesis and storage,2053

the making of fats and the secreting of fats for the health of the cell.2058

That is ER, to maintain that city analogy, this would be,2063

I’m going to call it a special cart or you could think of it as a pathway.2068

But imagine that, when these products are made at the factory,2078

there is a special cart that ships them to where they need to go within the city.2081

This special cart allows those products, those proteins to go out to where they need to go to.2088

Next up, the Golgi apparatus also known as the Golgi complex, the Golgi body, depending on what source you look it up in.2095

But Golgi apparatus is a very common term for it, named after an Italian scientist Golgi discovered it.2102

It looks like flattened membranous sacs.2110

Often times, you will see it like this.2113

A cross section I have seen before kind of looks more like this, looks very similar to this image.2115

You will see little, they call them secretory vesicles, little sacks with kind of pinch off of them.2125

Similar to what I was talking about with the ER, how a protein can be trapped or contained within the membrane.2132

You will have secretory vesicles going to the Golgi and leaving the Golgi, and here is why.2140

The Golgi packages, finalizes, and transports proteins that have come from that ER.2145

Typically, you will see the Golgi neighboring the ER in a cell.2151

Imagine, this is like a postal office or Post office.2156

That special cart takes that protein product to a post office, where it is packaged, tagged with a certain zip code,2165

a chemical zip code attached on that particular protein so that it goes to the final destination where it needs to be.2175

Membranous vesicles which is just a term for like container membrane.2182

These vesicles will fuse with it that had come from the ER, containing an amino acid chain2188

or polypeptide also known as a protein product.2194

They go through the layers that protein gets modified, put together with other proteins.2197

Like I said, little chemical sugar molecules can be attached to it, to give off like a zip code2203

where it needs to be and then it pinches off, and it ends up going to the destination.2209

And that is a summary of how it happens.2215

They go in one end, they come out on another end, and that is the Golgi apparatus also known as the cell’s post office.2219

Okay, we are going to review what we learned over so far.2228

We have a plenty of others to talk about but I just want to show you especially how these things are related.2231

We started with the plasma membrane, all of this yellow wrapped around, made of that phospholipid bilayer.2236

Well guess what, the nucleus also has phospholipid in its envelope.2243

The ER, phospholipids, the Golgi made of phospholipid membranes, coincidence that they all have the same.2248

Actually no, it is not a coincidence, it is meant to be that way.2258

This is known as the endomembrane system.2262

I have not covered all of the parts of the endomembrane system.2265

Another one is the lysosome which is around here somewhere, where the lysosomes.2271

A peroxisome is similar to a lysosome, that could be a lysosome right here in blue.2278

Any of these little sac or membranous parts tend to be part of the endomembrane system, there are some exceptions.2283

What that means is, there are little phospholipid bilayers can fuse and interchangeable to another, and that is for convenience.2290

Imagine that, you have instructions coming out of the nucleus going to the ER, you wrap it up in little sac.2300

If that sac is not compatible, that vesicle is not compatible with Golgi, it will be more arduous for it to work out.2306

That sac can easily fuse with the Golgi, those parts just can go together quite simply.2314

And then, when that product leaves these little Golgi vesicles, if they needed to go out of the cell,2321

maybe they have little sac of hormones that need to be sent out into the bloodstream,2326

that sac can easily fuse and dump out the parts it was containing and that is called exocytosis.2331

It can actually dump those things out.2341

Thanks to the endomembrane system, those are compatible.2343

Parts that are not compatible, the chloroplast and the mitochondria, they are stand alone.2346

You will see in the future slides in this lesson, they do not easily fuse with those thing.2354

A vacuole is another example that can fuse.2361

A vacuole, its border has that same kind of membrane and things can fuse with the vacuole or lysosome, or even a peroxisome.2364

Ribosomes definitely are not part of it because remember, ribosome are not membrane bound.2376

They are like two little chunks that fit together like this.2381

Moving on, mitochondrion, plural mitochondria.2386

Do not say mitochondrions, that is not a word.2391

Mitochondria plural, the majority of your cells that have mitochondria would have many of them.2393

These are membrane bound organelles, not part of the inner membrane system now.2401

They have their own DNA and ribosomes, that is the amazing thing.2406

That inside of here, there actually is mitochondrial DNA and ribosomes that are unique to this mitochondrion.2410

With both of this and chloroplast, coming up next,2420

there is a lot of evidence suggesting that this is the descendant of a previously independent cell.2423

That a long time ago, billions of years ago ended up inside of a larger cell, and it work out, it persisted.2430

When that cell divided, the mitochondria divided and stayed with it.2437

We have mitochondria, plenty of plants have mitochondria, fungi do.2444

Mitochondria very important, in terms of producing energy for the cell.2450

It has an outer double membrane, it also has phospholipids.2457

But the structure of it and the proteins in there are not compatible with the endomembrane system that I mentioned before.2463

Inside, there is a highly folded inner membrane called that cristae.2471

All of these yellow, you can see it is kind of weaving, that is highly folded and compacted in there.2475

The reason why it is highly folded is important.2482

You have a lot more membrane in here, when it is folded up.2485

Just like how the outside of your brain is fold.2488

Those convolutions of brain can jam packed a lot more matter into that area when it is folded.2491

It is the same idea here, you have a lot more chemical reactions happening inside the mitochondria,2496

Thanks to the cristae and it is folded up.2502

What does it do, it is responsible for producing energy storing molecules known as ATP, adenosine triphosphate.2506

This will come up a lot more in the unit on cellular respiration and in photosynthesis.2513

This is kind of like energy currency for the cell.2518

You take in food, you and I, we have two, we are known as heterotrophs.2523

We have to take food in as energy source from outside ourselves, we cannot make our own food.2528

Whether what you do with those sugars, those lipids, those proteins to give your cells energy?2534

You cannot just take a sugar and attach it to a part of a cell and be like move.2538

No, that sugar is to be broken down and kind of transferred into this form known as ATP which can easily be spent.2543

Like I said, it is like energy cash for the cell.2551

You can spend it on doing anything in the cell that requires energy.2554

That is with this wonderful structure does, it helps break down sugars, organic compounds, to give you this energy currency.2558

This structure is very much kind of like, I would call it a hydraulic dam.2566

This is what energizes the city, hydraulic dam has lot to do with water movement that ends up fueling the electricity source.2577

But in here, the dam is not that far off because you will see,2589

when you look at the lessons on cellular respiration, there are these enzymes imbedded in the cristae called ATP synthase.2593

It is actually an enzyme that makes this.2602

As charged particles, specifically protons, move through that ATP synthase, it spins and it is kind of like water moving through a water wheel,2603

except it is charged particles spinning an enzyme that helps make this.2614

The mitochondria very much the power source for the cell city.2619

Chloroplast found in plants cells, you would not find these in animal cells.2626

I have heard of one animal that is ever been discovered,2632

it is a kind of sea slug that does have chlorophyll inside of its cells which is a pivot molecule that allows it to absorb sunlight.2635

Its body is shaped like a leaf but it still has to eat and it does not have a chloroplast.2643

It does make chlorophyll in little bits but I stand by my point that these are only found in plant cells not in animal cells.2651

They are membrane bound organelles with their own DNA and ribosomes,2660

that should sound familiar because we just said that with mitochondrion on the previous slide.2662

Inside of here, there is DNA and the ability to make ribosomes.2668

And that is important because like in the mitochondria, there is a lot metabolically going on in this structure.2672

It kind of regulates itself.2679

Just like in mitochondria, there is an outer double membrane and there are folded membranes on the inside, but for a different purpose.2682

These are not called cristae, these little bit of a grain pancakes are called thylakoids.2689

Let me highlight that in green, thylakoids.2696

One stack of them, you can see it a little here is a granum, there is a granum, plural would be grana.2700

You can see if you look at this stacks, we have plenty of grana inside of the chloroplast.2713

The area outside of the grana labeled here is called the stroma.2721

Right now, I am tracing over where the stroma is, the fluid outside of the fluid filled thylokoids.2726

The parts of the chloroplast do correspond to the different phases of photosynthesis.2734

There is a whole lesson on that, if you look in the future lessons in this class.2740

The purpose of the chloroplast is responsible for producing sugars through photosynthesis, like I said.2746

Plants autotrophic meaning they make their own food, they provide their own food energy.2753

A plant make sugars, thanks to this.2763

And then, it would send out the glucose as the sugars to be broken down in a mitochondrion to give the cell ATP.2765

Plant cells typically have mitochondria, as well.2772

This is very much like the cellular plant for the city.2776

In cell city analogy, like we had seen before, they leave out the chloroplast because they are taking it from the point of an animal cell.2785

An animal cell does not have of a chloroplast.2793

If you want to have some image of what this does inside of a cell or what it can do for a city, that is very much like the cellular plant.2795

Vacuole/vesicles, I have included these in the same slide because they structurally look very similar.2805

A vacuole is a temporary storage container and a vesicle has something contained in it,2811

and it is typically going somewhere.2818

It is going from the ER to the Golgi or from the Golgi to the plasma membrane.2821

The difference in these two is really what they contain.2824

They are both membranous sac for storage and transport.2828

Vacuoles can contain food or water.2832

Typically in a plant cell, you would see water vacuoles.2835

We saw that in the image earlier in this lesson, it look like a big lake.2840

These food vacuoles, you can also see in plant cells.2846

Once they have made a bunch of sugars through photosynthesis in that chloroplast, they will store them away.2851

One place is called an amyloplasts, and that would be a place for them to store starch.2857

The storage of food whether it is in animal cell or plant cell, they would call it a food vacuole.2865

Like I have said earlier, in plants, they tend to be large central water vacuoles, looking like a big lake as you see down here.2871

The vesicles structurally the same border, in terms of that little phospholipid sac.2879

It is for transfer from cellular products or wastes.2886

A vesicle can go from the ER to the Golgi.2889

Bringing it, approaching the Golgi to get modified package transported from the Golgi to the plasma membrane.2892

It could contain hormones then to be dumped out then that vesicle will fuse with a plasma membrane.2898

It might have wastes, maybe invading viruses were eaten up by part of the cell which you will hear about in a second.2906

And then, a vesicle fuses with it and takes those broken up pieces of the virus,2915

which is now waste, and dump it outside the cell, that can also happen.2922

This is a connection of the water filled vacuole that you will see in a plant cell.2927

These terms having to do with osmosis and the concentration of ions or salts in and out of the cell.2933

This is basically explaining how you would get a plant cell getting really puffy,2942

getting filled with water in that vacuole, or losing some water and getting kind of shriveled up.2947

These terms will come up a lot more when we talk about osmosis with transporting another cell.2954

You can see that, this is known as turgid meaning it is quite puffy.2960

Water ended up pouring inside of this because it was more highly concentrated with salt and other ions.2965

And that drew in the water to fill in this big vacuole, now you have what is called turgor pressure, coming from this word.2972

Turgor pressure that is pushing on the plasma membrane which is then pushing on the cell wall.2981

The opposite is happening here, there was so much water that left,2985

that you can see that the cell just kind of desiccated and shriveled, so much water left out of that large central vacuole.2989

In terms of the cell city analogy, I mean, these are just like storage containers or transporting containers for the products,3000

and the different items that are associated with those factories or shops.3015

Lysosome comes from the words of lyse and some, which means a body that breaks down stuff.3022

The word lyse means to break down, to split apart.3034

That these do, these are little membranous sacs that has enzymes inside of them that are meant for breaking things down.3042

It could be the breakdown of macromolecules, maybe the plant cell and animal cell has stored a polysaccharide3048

that is being broken apart to little bits of sugars to be made in ATP, that energy molecule.3055

The breakdown of those macromolecules can happen a lot quicker, if you have lysosomes that are doing that.3063

The breakdown of damage cellular parts, maybe the Golgi apparatus is really beat up and damaged,3068

and a lysosome will go over and eat up its little parts and help break it down.3074

And then, those parts could be recycled to rebuild the Golgi apparatus.3079

Break down of foreign bodies and invaders, whether it is a virus, bacteria or fungal body.3085

If it enters the cell and has been identified as foreign, and does not belong there,3091

the lysosomes can be stimulated to fuse or be kind of like eat it up.3095

The little enzymes inside of it will help break down those molecules.3099

You will notice that some of these little enzymes are represented with happy faces.3105

Very happy for the cell but not happy for the virus or bacteria that it is eating up.3109

They contain digestive enzymes typically.3115

They are meant to break stuff down, they are not meant to just end up all over the place in the cell.3119

And I say that because, it is very important to say it contained in the membranes.3126

I have heard this, that if every lysosome inside of the cell were to burst simultaneously, it would cause autolysis.3131

Autolysis meaning self-breakdown, it would literally destroy the cell.3141

Another term is apoptosis, if that was stimulated to happen,3148

like it is supposed to happen inside of a cell that is programmed to cell death, apoptosis as a result of autolysis.3153

If all of these simultaneously were to leak, it will break up all the parts of the cell.3162

How does it relate to the city? A lysosome would be waste disposal area, garbage dump,3169

whatever you want to call it, recycling plant.3187

There are a lot of terms you could give to this, related to how a city works.3189

Centrioles found in pairs not typically in plants.3194

It is made of a cylindrical brain of microtubules and if you look very carefully here you can see that.3202

They are both cylindrical, you can see how they are kind of perpendicular to one another.3207

Very carefully, if you look here, you have got these little yellow rods.3212

Each of these is a microtubules which is a protein rod, basically.3218

You could see there are 9 groups of them kind of lined up in a cylindrical form.3223

They are contained within centrosome, these two would be in a region that is known as the centrosome.3229

Two centrioles and a centrosome, they have an important function in cell division.3241

When you see a cell dividing, I will give you a very brief image of what is known as metaphase.3248

Here is the centriole pairs, the centriole pairs they get duplicated before a cell is going to divide and they end up with the poles.3254

Here is the plasma membrane, centrioles, centrioles.3265

Lined up down the center, this is after the nucleus would break down, these are 4 duplicated chromosomes.3269

What I am drawing here is microtubules, beside is the microtubules and the centrioles.3281

These are kind of little protein ropes that are anchored by the centrioles here and the centrioles here.3289

You can see how they hold them down, these threads.3296

What is going to happen next is these microtubules will get shortened.3299

As they get shortened, they pull on these little X and split them in half.3305

So that you can get the duplicated chromosomes or pieces of DNA moving to where it going to become two different cells, eventually.3309

That is a very rough drawing but showing you how these participate in cell division and their anchors for the spindle apparatus.3320

This term is describing what I drew here, this is the spindle, a spindle apparatus that allows those chromosomes to be pulled apart.3328

In terms of the cell city analogy, I do not have a representation here for centrioles.3338

Just know that, they really serve an important function when it comes to splitting apart chromosomes, particularly in animal cells.3345

The cytoskeleton, I just mentioned a part of the cytoskeleton in the previous slide, when I said microtubules.3356

The cytoskeleton forms a framework or scaffolding for the cell.3364

It kind of holds it together and prevents the cell from collapsing in this fluidly blob.3368

The cytoskeleton is very much like the skeleton of the cell.3375

Those parts are pushing on the inside of the plasma membrane.3380

It provides a network of protein fibers for travel, as well.3384

There are really cool videos out there on the internet that show a motor protein walking along a microtubule,3389

a transport vesicle to the surface of the plasma membrane.3398

That motor protein, it looks like it is alive but it is not.3404

It is much smaller than a cell and the motor protein is walking3408

because ATP molecules are being attached and broken apart to shift it.3418

And it does not walk along the microtubule, because these protein fibers can service like little pathways or roads3423

throughout the cell to get from one organelle to another.3432

The cytoskelton is made of major roads, some smaller roads, and then the little tiny roads that connect houses in a neighborhood.3435

The major highways are the thickest units or microtubules.3446

These are the thickest of these protein rods by far.3451

This is how a microtubule is built, it is a helical arrangement of tightly round tubulin protein units.3456

These are all little amino acids strung together to make up tubulin.3466

If you cut a microtubule and look at, this is what you would see.3475

You would see there is α tubulin and β tubulin, there are two slightly different forms.3477

Intermediate filaments, these are more thin compared to the microtubules.3481

The way I remember is, intermediate like in the middle is literally in the middle of this one and that one.3492

Microfilaments not made of tubular, they are actually made of actin, typically, just a different protein.3498

These are the thinnest, by far.3504

These little microfilaments, do not think they are useless.3513

They are actually very important, when a cell like an amoeba, they tend to be like a morphs,3516

and you would see ribosomes and all kinds of vesicles throughout.3524

But the way that amoebas form their pseudopodia,3528

looks almost like these kind of fake feet like they are crawling through the water.3532

The way that they make these little angulations of their plasma membrane is,3536

they change the way that microfilaments are pulling or letting go on the inside of the plasma membrane.3542

That all comes down to using ATP, that energy molecule, to manipulate the shape of the cytoskeleton.3549

But, that is how they literally kind of crawl through water is their cytoskeleton.3555

Cilia, cilia are like little cell hairs.3563

The singular word would be cilium, so this is plural.3566

I wrote the plural word for this slide because generally on cells, when you see them, you are going to see a lot of them.3570

They are short, numerous projections, that look like cellular hairs.3577

This is a micrograph image, it is a zoomed in thousands of times, you are looking at the surface of human cells.3581

Chances are, this is in the bronchial lining, you have a lot of cilia in your respiratory tree that helps sweep up mucus.3589

Like the centriole units, it is made up of a ring of microtubules.3600

A little bit different structurally but each one of these little hair like structures that is projecting out of the plasma membrane,3605

if you look carefully, you can see little dots here.3612

All those little dots in this drawing, those are phospholipid heads.3618

Those phosphate heads, part of that phospholipid unit.3623

They are sticking out through the plasma membrane.3629

If you do cut them in half, there is a ring of microtubules.3631

They move back and forth to make the entire cell move.3635

It is almost like ores on a robot.3638

They move a lot like ores back and forth, back and forth as if you are rowing with a robot.3641

I say that because the next slide has a different structure that does not move in that way, these move back and forth.3651

Sometimes, if we are talking about a perimysium and I am not going to draw all of them,3657

a perimysium is a single celled organism that would have tons of cilia all on the outside of it.3665

The cilia move back and forth in a timely fashion to make this cell move wherever it wants to go,3671

inside of a lake, or a pond, or wherever it might be.3680

They move very fast, it is impressive when we look at them alive under microscope,3684

how quickly they can move, thanks to the cilia.3689

Also in our body, it is not moving the cell as a unit or as a whole.3693

Really, our cilia inside of our bronchial tree, specially is to move substances outside of the cell.3701

Imagine that this is not a perimysium but this is just a cell imbedded in your bronchial tree lining.3707

Imagine that this is a section of the bronchial tree and here is where air moves in and out.3719

You got all these little cilia that are projecting into what is called the lumen or the passageway of your bronchial tree.3730

As mucus is generated, you do not want the mucus to just end up pulling in your lungs and you suffocating on your own fluids.3741

You would not to be able to sweep that up and out.3749

Without these cilia, you will be more likely to drown in your own fluid, get something like pneumonia.3751

These help keep us alive, the cilia inside of our bodies.3757

Flagellum, this is another structure for movement, very different from cilia, there are some commonalities.3764

But plural for this, you would not say flagellums, you would say flagella.3771

If a cell had three tails, look at those three flagella.3775

It is long compared to the cilia, much longer.3779

It is like a tail like projection coming out of plasma membrane.3782

Made of a ring of microtubules, just like cilia.3786

If you are to take this experiment and cut through the flagellum and looked down on it,3791

you would actually see the same basic components looking down.3797

It is just that the length of it and the movement of it is very different.3801

Instead of moving back and forth like an ore, these move in a whip like motion to propel a cell through fluid.3805

Imagine that my arm is a flagellum, it is anchored in a plasma membrane,3811

like my chest and back area is the surface of the plasma membrane.3818

This does not move back and forth like that, that would be cilia.3822

This moves kind of like you are turning a wheel back and forth.3826

As I turn the wheel back and forth, look what happens.3831

That is how a flagella moves, that is what would propel a sperm trying to find the egg in a female.3834

The only human cell that you would have flagella is sperm.3841

Sorry ladies, you do not make cells with flagella.3846

But you actually not only see these on animals,3849

there some plants that actually do have a flagella on their gametes, plants sperm, I know it sounds weird.3851

They are structurally different from animal sperm but two examples are ferns and moss, they are known to make sperm.3858

Those little cells need a fluid medium to move through and reach the egg.3867

Cells typically have only one or two.3874

A male human sperm is supposed to have just one tail but they can come out with two.3877

They could come out with more, more have been discovered in some cells.3883

I have heard of up to 8, at a certain point, it gets pretty crowded.3887

I mean, how much better is 8, compared to 6, compared to 4?3892

Sometimes, there are too many of these flagella because of a mistake, like I said, human sperm must have 1.3897

There are other cells in nature dinoflagaments, a single celled protist in the ocean have many flagella.3905

It helps them kind of spin in different ways and orient themselves in different ways, inside of the ocean.3914

Cell wall is on the outside of the plasma membrane, not in animal cells.3922

You would never see a cell wall in animal cells.3927

They tend to be more kind of a rounded in shape.3930

It really does depend on which cells, like in neuron it would be very long.3933

But plant cells like this image here, this computer generated image, is very boxy, thanks to the cell wall.3938

Fungal cells have their own cell walls, bacterial cells have cell walls, made of different material.3945

It is extra protection and rigidity for the cell, it helps them keep a certain shape.3951

Think about this, plants do not have a skeleton, we have a skeleton as a vertebrate,3958

as an animal that walks around on land.3964

We have our posture and ability to move around.3968

A plant helping to keep its kind of rigidity to rise up, reach the sun,3971

be competitive with other plant species is what I meant.3978

You wanted to have some kind of rigidity with the cells being stacked upon each other.3982

The plants cell wall is not just for protection but also rigidity.3987

Then you get a bunch of water pressure, especially inside of that vacuole, that large central vacuole,3991

and that help push on the inside of the plant cell wall and provide that turgor pressure.3997

There is actually a two layer wall and there these little pores called plasmo dasmata.4004

It happen to be connecting them, I think that is what they meant to draw here.4011

Plasmo dasma is one and plural would be plasma dasmata.4019

Those are the pores inside of the cell wall connecting plant cells to each other.4029

In plants, all this green stuff is made of cellulose.4034

It is a polysaccharide made of glucoses linked together, helps give it a good structure.4039

In bacteria, usually but not all species you tend to see peptidoglycan making up a bacterial cell wall.4045

Part protein based, part sugar based, that is how you get the peptidoglycan.4055

And then in fungi, a different polysaccharide they are made of chitin.4061

This is that same polysaccharide that is an insect exoskeleton, or exoskeletons of crustaceans,4066

one of the many pieces of it is connecting animals and fungi in the revolutionary tree.4073

But in fungi, different polysaccharide than cellulose, chitin cell walls for mushrooms and the like.4079

Then, cytoplasm, I’m just going to draw a brief picture here.4088

There is a cell, nucleus, this is eukaryotic, it looks three dimensional enough.4092

The cytoplasm is the fluid filled region of a cell between the nucleus and the inside of the plasma membrane.4103

Imagine that this is our phospholipid bilayer, here is our nuclear envelope, from here to here,4108

all of that is called the cytoplasm, all of this.4117

The majority of the organelles are in the cytoplasm.4124

It is a site for the majority of the cellular reactions, not a surprise.4127

The inside of the nucleus is not called the cytoplasm.4131

I have seen the word nucleoplasm or nuclear fluid but the cytoplasm is all of this.4134

It is also referred to as the cytosol, when we are talking about the fluid itself that is in the cytoplasm, cytosol.4142

Finally, just to review some similarities, differences between animal cells and plant cells.4152

Here is an image of an animal cell and a plant cell.4157

You have seen this several times in this lesson, this is the first time we are seeing this.4161

Let us start in order we went, these are the organelles you would see in both.4165

You would see the nucleolus, the nucleus, you would see the ER, both rough and smooth.4172

Four, that would be a little vesicle that is pinched off of the ER going to the Golgi.4183

You would definitely see that in plants as well.4190

Number 6, there is the Golgi, you need to have the Golgi to finalize package and transfer of those proteins.4194

Ribosomes, you certainly would see ribosomes in plant cells, all those black dots.4201

Mitochondria, number 9, you definitely see them.4207

Right here, they are in a different color in this image, here is mitochondria, mitochondria.4212

There is no centrioles in this picture, if you look carefully, there are not any.4219

Here are the centrioles, this is one example of something you would see in an animal cell that tends not be in a plant cell.4223

Lysosomes, number 12, you sometimes do see lysosomes in plant cells.4231

I am just going to assume that blue dot, that little sac is a lysosome.4238

In some plants cells, lysosomes have been discovered but not in all plant cells.4245

Number 10, could this be food vacuoles.4251

You definitely would see a water vacuole here, vacuoles can be found in both.4254

Plasma membranes, we do not leave that out.4260

Fourteen, that is the yellow right here, that is the plasma membrane.4263

Number 7 is showing you a very small part of the cytoskeleton.4269

It looks like a little thread, remember that is microtubules, intermediate filaments,4273

microfilaments, making up a scaffolding inside the cell, you would definitely see that here too.4277

You can see little bits of the cytoskeleton in the plant cell.4282

I’m going to circle some things in the plant cell that are not over here.4286

Of course chloroplasts, you would not see chloroplast.4290

Here is another chloroplast but this one, we are looking inside of it.4295

You are not going to see chloroplast inside of animal cells.4299

Animal cells require the intake of food, they are not making their own food like a plant cell.4303

And of course the plant cell wall, you do not see that boxy outer cellulose wall here.4309

You see a very kind of rounded out, typical looking animal cell structure.4317

That is a reminder of a lot of these parts inside of the cells and general differences between animal cells vs. plant cells.4322

Thank you for watching www.educator.com.4331