Welcome back to BOGObiology! tThis
screencast is going to talk about
cellular respiration. We're going to
discuss what it is, how it works, and why
it's important. Before we can get started
we need to review two important types of
energy in biology.
The first is glucose and the second is
ATP. Glucose, the type of energy that is
found in food. ATP or adenosine
triphosphate is a type of energy that is
found in cells. I showed it here as a
battery because it is a rechargeable and
reusable form of energy.
Unfortunately for our cells, you can't
simply feed them glucose directly. What
we can do instead, however, is harness the
power of the glucose and use it to
recharge low energy molecules of ADP
inside the cell. When the energy in the
ATP molecule is depleted, it converts
back into ADP. Provided that a plentiful
supply of glucose is available, we can
harness its energy to continuously
recharge molecules of ADP into ATP. This
is why it's often helpful to have a small
snack if you're feeling a little bit
tired.
It's also important to appreciate how
photosynthesis relates to respiration.
Notice is the products of photosynthesis
are the same as the reagents of
respiration.
This means that we can use the products
of photosynthesis to run the process of
restoration, and the product of
respiration in order to run
photosynthesis. There are two major
categories of cellular respiration;
aerobic and anaerobic. Aerobic respiration
occurs when oxygen is present. We
consider this type of respiration to be
more efficient because it makes more ATP
and it's more sustainable. Anaerobic
respiration occurs when there is not
enough oxygen present. We consider it to
be less efficient because it makes less
ATP and it can only be used in the short
term. Now let's look at the process of
respiration a little bit more closely.
Respiration is going to occur in
both the cytoplasm and inside of
organelles called the mitochondria. Notice
again that we're taking the reagents of
glucose, oxygen, and an uncharged molecule
of ADP and using it to create carbon
dioxide, a little bit of heat, some water
and the recharged molecule of ATP. If you
look at the respiration in the context
of the hierarchy of life, respiration is
happening down here at the organelle
level inside the mitochondria and in the
cell's cytoplasm.
However, in order for respiration to
occur effectively at this level, the levels
above it also need to be functioning
perfectly. In order for this process to
work, the organism itself needs to be
breathing. Following that, the air has to
enter the lungs pass through simple
squamous tissue, into the circulatory
system, out through more simple squamous
tissue, into the cell in question, and
then enter the cytoplasm and mitochondria.
If any one of these steps goes wrong or
if the organism fails to gather enough
food from their environment, they won't
be able to continue cellular respiration.
As with many things in biology,
the more you learn about respiration the
less you are amazed that it ever goes
wrong, and the more you are amazed that
it ever succeeds!
Now let's begin to examine the process of
cellular respiration a little bit more
closely because, let's face it, that's
probably exactly why you're watching
this video. Remember that there are two
basic types of respiration; aerobic and
anaerobic. Using aerobic respiration, we
can recharge about 38 molecules of ATP.
Using anaerobic respiration, we can only
recharge two molecules. Both types
of cellular respiration begin with a
process called glycolysis, where we put
in a molecule of glucose and generate a
net product of two ATP. Beyond that
however, we're going to follow one of two
distinct pathways, depending on whether
or not there is oxygen present. If there
isn't any oxygen present, we enter what's
called anaerobic respiration, and then
generate lactic acid or alcohol. When
humans do anaerobic respiration, we
generate lactic acid which is probably a
good thing because otherwise working out
would make us drunk!
This is also the reaction that causes
yogurt to have its "tangy" flavor.
Some organisms produce alcohol instead
of lactic acid when they undergo
anaerobic respiration. Yeast is a really
good example of this. When you put yeast
into a sealed container with no
additional oxygen, it generates alcohol
and it also generates carbon dioxide.
This is why, if you make wine and you
leave it in a sealed container, it
becomes bubbly. Notice however that both
kinds of anaerobic respiration don't
generate any more ATP; all of the ATP
that is made during anaerobic
respiration has already been made
during glycolysis. We make a total of two
ATP molecules during the course of the
whole anaerobic respiration process. If
your goal is to generate as much
recharged ATP as possible,
aerobic respiration is definitely your
best bet. If there is enough oxygen
present, the organism will undergo what's
called the prep steps to begin the
process of aerobic respiration. This first
set of chemical reactions generates some
carbon dioxide as a by-product. This
first bit takes place in the cytoplasm
just like glycolysis did. The next
set of chemical reactions are called the
Kreb's Cycle and they take place not in
the cytoplasm but in the mitochondria.
This set of chemical reactions generates
some carbon dioxide as well as two
molecules of ATP. So far aerobic
respiration isn't doing a whole lot
better than anaerobic respiration in
terms of recharging a lot of ATP
molecules. The last step in aerobic
respiration is our real money-maker;
it's called the electron transport chain.
In this particular part of cellular
respiration, we add in oxygen, undergo a
series of complex chemical reactions and
generate a bunch of water molecules plus
a whopping 34 ATP. Oxygen is very important for
running the electron transport chain. If
there isn't enough oxygen available to
keep up with the demand, the organism is
forced to undergo anaerobic respiration
which only generates a small amount of
recharged ATP molecules and thus makes a
lot less energy available. Again,
think back to this diagram. Now that
you've learned a little more about how
cellular respiration works, see if you can
figure out why you can sustain
aerobic respiration for much longer than
you can anaerobic respiration. If you
think you can answer this key question,
definitely leave a comment in the field
below. As always, please remember to be
honest and cite your sources.
I've listed the resources that I used to
make this video below, and if you like to
cite my work, there's a ready-made APA
citation in the video description. As
always, thanks for watching and don't
forget to subscribe!