Cells Notes

Summary

This video introduces the cell as the smallest unit of life, exploring cell theory and its importance in biology. It explains the differences between prokaryotic and eukaryotic cells, focusing on their structures and functions. The lecture covers topics such as the surface area-to-volume ratio, organelles like mitochondria, chloroplasts, and ribosomes, and the roles of the nucleus and plasma membrane. Additionally, it touches on cell walls, the differences between plant, animal, and bacterial cells, and concludes with a brief discussion of fungi, specifically yeast cells.

Takeaways

• 🔬 Cell theory states that all living things are made up of cells, and new cells come from pre-existing cells.
• 🌱 Cells vary in shape and function; examples include amoebas, plant cells, red blood cells, nerve cells, and bacterial cells.
• 🧫 Cells exchange nutrients and waste through their membrane, and their size is limited by the surface area to volume ratio.
• 🧬 Prokaryotic cells (bacteria and archaea) do not have membrane-bound organelles or a true nucleus, while eukaryotic cells (plants and animals) do.
• 🦠 Prokaryotes are always unicellular, while eukaryotes can be unicellular or multicellular.
• 🌿 Plant cells have structures like cell walls and chloroplasts that animal cells do not.
• 🧪 The plasma membrane controls what enters and leaves the cell, and is composed of hydrophilic heads and hydrophobic tails.
• ⚡ Mitochondria are the powerhouse of the cell, involved in cellular respiration and energy production (ATP).
• 🧱 Ribosomes translate mRNA into proteins, and are found in both prokaryotic and eukaryotic cells.
• 🍞 Yeast is a eukaryotic fungus, not a bacterium or animal, and plays a role in fermentation (like bread rising).

Q & A

What is the cell theory and why is it important?

Cell theory is a fundamental tenet of biology, stating that all living things are made up of cells, cells are the smallest unit of life, and new cells arise from pre-existing cells. It is important because it describes the basic principles of how life functions at the cellular level.

Why are cells considered the smallest units of life?

Cells are considered the smallest units of life because they can perform all the functions necessary for life, including energy conversion, growth, and reproduction. Anything smaller, like parts of a cell, cannot independently sustain life.

How do amoeba move, and what is cytoplasmic streaming?

Amoeba move by extending their plasma membrane to create projections called pseudopodia, into which their cytoplasm flows. This movement process is called cytoplasmic streaming, allowing the amoeba to move and capture food.

What is the significance of surface area to volume ratio in cells?

The surface area to volume ratio limits the size of cells because as a cell grows, its volume increases faster than its surface area, reducing its ability to efficiently exchange nutrients, gases, and waste. Cells need to maintain a high surface area relative to their volume for efficient transport across their membranes.

What are the differences between prokaryotic and eukaryotic cells?

Prokaryotic cells, like bacteria, lack a membrane-bound nucleus and organelles. They are usually unicellular and simpler in structure. Eukaryotic cells, found in plants, animals, and fungi, have a membrane-bound nucleus and organelles, and can be either unicellular or multicellular.

Why do bacteria have no membrane-bound organelles?

Bacteria are prokaryotic, meaning they do not have membrane-bound organelles. Instead, their cellular components, like DNA and ribosomes, float freely in the cytoplasm, with only the plasma membrane enclosing the cell.

What is the function of the plasma membrane in cells?

The plasma membrane controls what enters and exits the cell, maintaining an internal environment that supports cellular processes. It is composed of a phospholipid bilayer with embedded proteins that allow selective transport of substances.

What organelles are involved in protein synthesis and transport?

Protein synthesis begins with ribosomes, either free in the cytoplasm or attached to the rough endoplasmic reticulum (ER). Proteins synthesized on the ER are then transported to the Golgi apparatus, where they are modified, sorted, and sent to their destination.

What is apoptosis and how do lysosomes play a role in it?

Apoptosis is programmed cell death, a process important for development and maintaining cellular health. Lysosomes, which contain digestive enzymes, help break down the cell's components during apoptosis, ensuring the controlled destruction of damaged or unnecessary cells.

How are plant cells different from animal cells?

Plant cells have a rigid cell wall and chloroplasts for photosynthesis, which animal cells lack. They also typically have a large central vacuole for storage, whereas animal cells may have smaller, less prominent vacuoles.

Outlines

00:00

🔬 Introduction to Cell Theory and Its Significance

The video introduces the concept of cell theory, emphasizing that cells are the smallest units of life. It explains that all living organisms are made of cells, and new cells arise only from existing cells through division. The video showcases various examples of cells, such as amoebas, plant stem cells, red blood cells, nerve cells, and bacterial cells. The discussion also touches upon the importance of surface area to volume ratio in cells and how it limits their size.

05:01

🦠 Prokaryotic Cells and Their Simple Structure

This section delves into the characteristics of prokaryotic cells, specifically bacteria and archaea. It describes the absence of membrane-bound organelles in prokaryotes and highlights the differences between prokaryotic and eukaryotic cells. The discussion also covers the different shapes of bacteria (coccus, bacillus, and spirillum) and the roles of structures like flagella, cilia, and pili in these cells.

10:03

🧫 Eukaryotic Cells: Complexity and Organelles

The focus shifts to eukaryotic cells, which are more complex than prokaryotic cells. It explains the presence of membrane-bound organelles such as the nucleus, endoplasmic reticulum, and Golgi apparatus. The cytoskeleton's role in maintaining cell structure and enabling movement is discussed, along with the nucleus's function in housing DNA and directing cellular activities. The section also introduces mitochondria as the powerhouse of the cell, responsible for energy production through cellular respiration.

15:04

🌱 Cell Walls, Chloroplasts, and Unique Plant Cell Structures

This final section covers structures unique to plant cells, such as cell walls and chloroplasts, which are involved in photosynthesis. It explains the role of chloroplasts in capturing light energy and converting it into chemical energy. The section also touches on vacuoles, lysosomes, and the process of programmed cell death (apoptosis). The video concludes with a brief discussion on fungi, highlighting yeast as a eukaryotic fungus used in bread-making, and contrasting fungal cells with other cell types.

Keywords

💡Cell

A cell is the smallest unit of life, fundamental to all living organisms. In the video, cells are described as the basic building blocks of life, with each cell being capable of performing life functions such as exchanging nutrients and waste. Examples include red blood cells, nerve cells, and bacterial cells.

💡Cell Theory

Cell theory is a fundamental concept in biology that states all living organisms are made up of cells, and that new cells come only from pre-existing cells. The video explains that anything smaller than a cell, such as cell parts, is not considered alive. The theory is central to understanding life at the cellular level.

💡Eukaryote

Eukaryotes are organisms with complex cells that contain a nucleus and membrane-bound organelles. In the video, examples of eukaryotic cells include plant, animal, and fungi cells. Eukaryotes can be unicellular (like protists) or multicellular (like humans and plants).

💡Prokaryote

Prokaryotes are simple, unicellular organisms that lack a nucleus and membrane-bound organelles. The video identifies bacteria and archaea as prokaryotes, highlighting their simple structure, which includes ribosomes and DNA located in a nucleoid region.

💡Cell Membrane

The cell membrane, or plasma membrane, is a protective barrier that controls what enters and exits a cell. It consists of a lipid bilayer with embedded proteins, allowing for selective permeability. In the video, it’s described as the structure that maintains the cell's internal environment.

💡Surface Area to Volume Ratio

This ratio describes how a cell's surface area compares to its volume, which affects its ability to efficiently exchange materials with its environment. The video explains that as cells grow larger, this ratio decreases, limiting the cell's efficiency and constraining its size.

💡Organelle

Organelles are specialized structures within a cell that perform specific functions. The video mentions various organelles, such as mitochondria (energy production), the nucleus (genetic control), and chloroplasts (photosynthesis in plant cells). Each organelle contributes to the overall functioning of the cell.

💡Ribosome

Ribosomes are cellular structures that synthesize proteins by translating mRNA. In the video, ribosomes are present in both eukaryotic and prokaryotic cells, and can be either free-floating in the cytoplasm or attached to the endoplasmic reticulum.

💡Mitochondria

Mitochondria are known as the powerhouses of the cell, responsible for producing ATP through cellular respiration. The video highlights that mitochondria have their own DNA and replicate independently, which supports the theory of endosymbiosis.

💡Chloroplast

Chloroplasts are organelles found in plant cells that carry out photosynthesis, converting sunlight into chemical energy. The video explains that chloroplasts contain their own DNA and are essential for the plant’s ability to create its own food.

Highlights

Introduction to cell theory: all living things are made up of cells, and cells are the smallest units of life.

Cells come from pre-existing cells, and new cells are formed through division.

Example of amoeba: Amoebas move by cytoplasmic streaming, extending their plasma membrane and flowing into projections.

Different cell shapes and functions: plant cells, red blood cells, nerve cells, and bacterial cells have diverse forms based on their roles.

Surface area to volume ratio limits cell size: smaller cells exchange nutrients and waste more efficiently.

Strategies for increasing surface area: cells can be long, narrow, or have frills like microvilli to maximize surface area.

Eukaryotic vs. Prokaryotic cells: Eukaryotes have membrane-bound organelles and nucleus, while prokaryotes (like bacteria) do not.

Bacteria are unicellular organisms with ribosomes, DNA, plasma membranes, and sometimes cilia or flagella for movement.

Cell walls and membrane-bound organelles are unique to plant cells, which distinguish them from bacterial and animal cells.

All cells have common components: plasma membrane, cytoplasm, ribosomes, and a region containing DNA (nucleus or nucleoid).

Plasma membrane structure: made of lipids with hydrophilic heads and hydrophobic tails, regulating what enters and exits the cell.

Mitochondria, the 'powerhouse of the cell,' are responsible for cellular respiration and contain their own DNA.

Ribosomes are found in all cells and are responsible for translating mRNA into proteins, either free in cytoplasm or on the ER.

Endoplasmic Reticulum and Golgi apparatus: proteins are synthesized in the ER and further modified and sorted by the Golgi apparatus.

Lysosomes break down waste, foreign invaders, and even the cell itself during programmed cell death (apoptosis).

Transcripts

hello and welcome back the day we want

to talk about the cell and it is the

smallest unit of life so first we want

to talk about cell theory and this is

the theory that describes everything we

know about cells

it is a fundamental tenet of biology and

it goes a little bit like this all

living things are made up of cells and

cells are the smallest bits of life that

you can get a cell is the smallest

living thing anything smaller than a

cell is not alive you just have parts of

a cell or something completely different

and cells don't just come out of nowhere

you have to have a cell that divides and

that is how you get new cells from

pre-existing cells

so there's cell theory and here are some

examples of some cells right you have an

amoeba here and these are really cool if

you're my main class I'll show you a

video of something called cytoplasmic

streaming these guys move around by

extending out there remembering their

plasma membrane here and then they flow

into the projection it's very cool so if

you remind me I will show your video

neat stuff okay this is a cell inside of

a plant stem and you can see that these

two things are different right cells are

the shape of cell it's going to follow

its function okay here's a little red

blood cell right and I think they're

really cute because they look like

little baskets and in fact they carry

oxygen and then you have a nerve cell if

this is going to conduct signals to and

from the brain and then here you have a

bacterial cell right you have a nice

little bacillus that's the shape it's a

rod shape here and of course some of

these you are familiar with because they

make you super sick right and in some

cases you're not familiar with them but

you probably have bacterial cells on you

then you actually have people cells so

in that fun ok so the first question

that I want to ask you though is by your

cells so small thing you have to look at

surface area in this case right cells

exchange nutrients they exchange waste

products they exchange gases across

their membrane and they need to be able

to have enough surface area to move

those Prada

or you know whatever efficiently okay

nutrients and waste out is essentially

what we're looking at if they if they

get too big right remember as they get

big they're going to need more nutrients

and make more less okay so as they get

bigger though their surface area to

volume ratio decreases and so you have a

need for more stuff but you actually

have less space relatively to get it

across and so cells are limited by this

surface area to volume ratio okay so

strategies for increasing surface area

so cells can be larger include their

shape they can be long and narrow right

they can have frills like if you think

about the microview i in in your

intestines that that extends the surface

area cells can have those too but if you

have just a regular ol round cell it

will always be the smallest okay okay

so here's your first question you're

told that's the cells on a microscope

slide our plant animal or bacteria okay

you look at them through the microscope

and see cell walls and membrane-bound

organelles you're going to conclude that

the cells are or could be okay so could

they be plant animal or bacterial maybe

either plant or bacterial they're only

animal cells they're only bacteria or

they're only plant cells well this is

where we need to start asking ourselves

what is unique or what are the hallmarks

of different kinds of cells it turns out

that if you have cell walls and membrane

bound organelles the only thing that you

could be is a plant cell okay the

question becomes why all right well you

have two basic types of cells eukaryotes

and prokaryotes your prokaryotes are

going to be your bacteria and then

animal and plant cells are going to be

the eukaryotes so why is a bacterial

prokaryote and everything else is

eukaryote

okay it has no DNA has no membrane-bound

nucleus it has cilia earth a single cell

well we know that bacteria are single

cells right they're unicellular okay it

does not have member I ain't sorry

membrane-bound nucleus it does not have

any membrane bound organelles it's just

got stuff inside of it the only membrane

it's got is gonna be the plasma marine

so the answer is actually the no

membrane-bound nucleus cilia are just a

little protection they look like little

hairs they hope of travel but the one I

want to talk about most though too is

the answer but it has no DNA that's

crazy talk if you have no DNA you're not

alive you're not a cell okay all living

things have DNA

it is the genetic material is the

instructions for what they are and we

will talk about DNA more but I just

wanted to touch on that really quick all

right so prokaryotes they're unicellular

all of them all of them are unicellular

they don't have structures surrounded by

membranes so it means they have no

organelles they have very few internal

structures at all actually they've got

ribosomes and that's pretty exciting and

the two groups right the two domains

that are prokaryotic are bacteria and

archaea and we will talk about the

differences between those more when we

start talking about funny alright so

prokaryotic cells super simple

they've got some ribosomes they have

some DNA in them that's great yeah and

then they are surrounded by a plasma

membrane they may they have us typically

have a syllable okay

and the cell walls going to differ

depending on what kind of bacteria you

have you might have heard something like

gram-positive and gram-negative the

differences between those have a lot to

do with the cell membrane is already so

long not meal memory cell wall and then

some of them actually have capsule and

then you have these little guys out here

this the cilia and then you oftentimes

have a flagella every projection out

here has to one of two functions

flagella and cilia are for movement and

the P lie are for sexual

production okay and then over here you

can see that there are three basic types

of bacteria in terms of their shape

bacteria oftentimes are classified by

their shape here you have caucus as in

like streptococcus or Staphylococcus and

then here you have the cilium right

that's the shape here bacillus is the

rod shape and then here you have spur

ileum and these are these cool spiral

shapes okay eukaryotes and that's what

we're going to be dealing with because

we're made up of eukaryotic cells these

are organisms that have a nucleus they

actually also have membrane bound

organelles and stuff like that but being

key there is the the actual form nucleus

they can either be unicellular as in the

case of the protists or they can be

multicellular plants and animals good

example of that and then fungi can

either be unicellular or multicellular

all right so eukaryotic cells you're

actually looking at an animal so here

you've seen this picture a million times

before I'm sure we're going to talk

about each of these things and then

here's just an example of a plant cell

versus an animal cell because they are

different in some respects in some

respects they're the same we'll discuss

that too so structures present in plant

cells but not in animal cells include

mitochondrion vacuoles ribosomes in the

ER chloroplasts in the cell wall

lysosomes or the and the Golgi apparatus

okay well plant cells have chloroplasts

in a cell wall if you think back to the

microscope question we saw the cell wall

situation there but they also have

chloroplasts and we'll talk about those

at the end

okay so basic cell structure each cell

has four common components no matter

what it is whether it's per carry on or

you carry it it has plasma membrane it

has cytoplasm that's not jelly stuff and

their ribosomes in it ribosomes are

really important we'll talk about them

later in the course it has a region

containing DNA whether it's just a

nucleoid region as an appropiate or an

actual nucleus as an eukaryote and then

there are biochemical molecules and

biochemical pathways that are the

processes of life and a lot of those are

actually very similar

similar right you have to transport

across the plasma membrane you have to

make sure that you can get wastes in an

outer braid which is part of the

transport but also to where it needs to

go in the cell it's making all sorts of

products that help it be alive or do

whatever it needs to do so let's start

with the plasma membrane this is going

to control what enters and leaves the

cell and it's very complex it's very

cool actually it's made of lipids right

and you have those are hydrophobic and

it's cool because you have this

hydrophilic head and you have these

hydrophobic tails and they're attracted

to each other and this is what allows

for you to have a water-based fluid on

the outside and a water-based fluid on

the inside and then you'll have proteins

and carbohydrates combinations of those

the proteins will actually span through

the plasma membrane which allows things

to come in and out they can be gates or

channels that allow for particles and to

move in and out right and then you have

some proteins that have attachments on

them here's a carbohydrate this forms a

glycoprotein these can be identifiers

they can be used to tether to other

cells whatever so the plasma membrane is

very interesting and it's very active

now in a eukaryotic cell right we've got

the plasma membrane they can have micro

villi or not they talked about the

cytoplasm now we want to talk about the

cytoplasmic organelles right the

cytoskeleton and unfortunately we're not

going to talk a whole lot about the

cytoskeleton but the cytoskeleton is

really cool it's made of actin and

microtubules and we will talk a little

bit about the cytoskeleton when we start

talking about mitosis but this is what

allows the cell to habit structure it's

what allows things like amoeba to move

and also transport of materials

throughout the cell the cell is really

like a city or a factory and there's all

kinds of things going on and so the

cytoskeleton can be thought of in some

ways one of the functions of

cytoskeleton is a highway system okay

and then all of these we're about to

talk about your nuclear envelope really

important

it's got pores

which are made of proteins their nuclear

pores there are a lot like the pores or

channels on the plasma membrane because

you have to get things in and out of the

nucleus and we'll talk about that later

on nuclear plasma nuclei and then of

course nucleoli and then of course DNA

right and we'll talk a lot about

chromosomes and DNA later

so cytoplasmic cytoplasm it's the

jelly-like stuff primary component water

we talked about that organelles let's

start with the nucleus because it's the

most important right it directs the cell

activities it's got the DNA right the

genetic material it's the site of all of

your DNA synthesis and your RNA

transcription and processing we'll talk

about that later on and then it is

separate right it is its own little

unique area and you can see that whose

nucleus yeah anyways by the way I love

this picture because you can see the

cytoskeleton that Corrine is all the

cytoskeleton very cool stuff and I just

said that this was most important that's

not actually true there everything is

equally important so now the nucleus is

not the only organelle that has DNA so

who else has DNA well it turns out that

ribosomes do not have DNA but they are

made of RNA and we'll talk that later in

the course as well but both mitochondria

and chloroplasts have DNA and we will

talk about why in a later class in this

unit nucleolus this is actually inside

the nucleus itself it's just a region

where you have some condensed DNA and

it's where all of the ribosomal RNA is

transcribed the ribosomal RNA like the

messenger RNA is going to leave the

nucleus through the nuclear force the

nuclear membrane that's the nuclear

envelope it surrounds the nucleus we've

talked about that a little bit already

miok Andreea ina Kandra or the

powerhouse of the cell this is the site

of cellular respiration which is the

energy process that's what's going to

generate ATP they do contain DNA and

they can replicate them

cells they are in endosymbionts and we

will talk about this in a later lecture

I've just kind of introduced it here but

we'll talk about that later on

here are some mitochondria a pretty

exciting now the interesting thing about

mitochondria is like chloroplasts they

have a double membrane all of the other

organelles in the cell have single

membranes but they actually have an

outer and inner membrane and that's

going to be important when we start

talking about this endo symbiote thing

frybo zomes ribosomes are found in all

cells remember not just two carriers but

all cells they are the things that

translate mRNA into proteins and

proteins do all kinds of exciting things

that we will talk about later on okay

now they can either be free in the

cytoplasm or they can be attached to the

endoplasmic reticulum because what we're

going to talk about now the endoplasmic

reticulum is a layered membrane that is

actually attached to the nuclear

membrane and you can see that it's right

here okay and then it continues on and

then over here is going to be the Golgi

apparatus you can see that a little bit

right here and though there's a there's

a progression from the nucleus to the

endoplasmic reticulum to the Golgi body

right Golgi apparatus

so this is where proteins a lot of

protein most proteins are actually going

to be synthesized they are synthesized

on the membrane of the endoplasmic

reticulum they are put into the inner

space right the lumen interspaces women

of the the ER right in a pleasant

reticulum and that is where they are

going to be folded and modified in any

way that's necessary then they'll be

sent to the Golgi apparatus which is

here and the golgi is actually going to

sort them package them into vesicles and

it will send them where they need to go

sometimes there'll be some more

modifications that need to be made and

they're made in the Golgi bodies they

also make lysosomes which we're going to

talk about later on - okay lysis or now

actually lysosomes these are the

digestive bodies right they can digest

nutrients right and so they can

store enzymes that break down food they

can transport materials to the cell

membrane for removal right and here's

the other thing that's really important

they will destroy cell organelles and

the cell itself as well as foreign

invaders

so the lysosomes are a defense mechanism

but they also when it's time cells

undergo something called apoptosis which

is a program cell death the lysosomes

will be activated and they will break

down the cell as its as its dying and

also when you have necrosis of the cells

and that's an injury driven cell death

they'll take care of that as well

vacuoles these are just sacks they just

hold stuff until it's sent off to do

whatever it's supposed to do so they're

just bags so which of the following is

not involved in the synthesis or

modification of new molecules well if

you're paying attention at all and what

I just said it would be vacuoles they

only store stuff ribosomes the

endoplasmic reticulum and the Golgi

apparatus are either involved in

synthesis that would be the right zones

and ER and Golgi or modification all

right now cell wall talked about the

cell wall animal cells don't have these

plants algae and bacteria do they have

this tough outer structure it provides

additional support it protects the cell

from pressures especially if it's a cell

that will move plants it's what gives it

that rigid structure you know so very

important and when I'm going to talk

about a whole lot because we're not

talking about plants but they're

actually really really cool and plants

cells have plant cells have a little bit

different process of mitosis cellular

reproduction because of the cell wall

and we've all talked about that a little

teeny bit all right and then plants

right also have algae and some bacteria

to plants also have chloroplasts and

chloroplasts contain their own DNA they

also contain chlorophyll which is what

is responsible for

synthesis or at least driving

photosynthesis we are not going to talk

about photosynthesis in this class

although it is super interesting these

are also endosymbionts cyanobacteria as

opposed to purple bacteria and again

we'll talk about that in the later

lecture and they have that same double

membrane which is so important to this

indocin the other thing and then of

course here is just a plant cell which

you've already seen now there are some

other things right like I don't know

about you but I love some delicious

bread and the driving force of bread is

yeast it's alive it's why you put it in

warm water it's why it makes all the

delicious gas bubbles that makes your

bread awesome right and so what is it

though is it a prokaryote is a bacteria

is it a eukaryote right

is it a eukaryotic fungus is it an

animal or a plant well we can start off

by saying there are no eukaryotic

bacteria no no no no no so B is just

wrong okay it's not a bacteria it's not

a plant so is it an animal or fungus

some people call yeast an animal but

that's actually not correct yeast is a

fungus and here is just a picture a

fungus cells are different they are

eukaryotic they do have a cell wall but

it's made of chitin as opposed to

peptidoglycan or cellulose or whatever

depending on whether it's a bacteria or

plant and so there's different structure

but it's got the same basic organelles

in it and it does all the same stuff and

so you don't really need to know about

the fungus cells but I just thought it

would be interesting because we all love

mushrooms okay maybe not all of us but

some of us love mushrooms and well yeast

products yeah okay and that is it for

this one you will of course will have

mini quiz and thanks for listening to

see you next time