Cells Notes
Summary
TLDRThis 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
🔬 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.
🦠 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.
🧫 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.
🌱 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.
Mindmap
Keywords
💡Cell
💡Cell Theory
💡Eukaryote
💡Prokaryote
💡Cell Membrane
💡Surface Area to Volume Ratio
💡Organelle
💡Ribosome
💡Mitochondria
💡Chloroplast
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
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