Fermentation
Summary
TLDRThis educational video explores cellular respiration and fermentation, focusing on how cells generate ATP in the absence of oxygen. It explains glycolysis, the first stage of fermentation, and contrasts it with two types of fermentation: lactic acid and alcoholic. The video highlights the role of yeast in alcoholic fermentation and the conversion of glucose to ethanol and carbon dioxide, yielding two ATP per glucose molecule. It also discusses lactic acid fermentation, used by muscle cells during oxygen debt, which also produces two ATP per glucose but is less efficient than cellular respiration. The video concludes by questioning the necessity of the slower, oxygen-dependent cellular respiration, which extracts more energy from glucose, leaving behind only water and carbon dioxide.
Takeaways
- 🔬 Fermentation is an alternative process to cellular respiration, allowing glucose breakdown without oxygen or mitochondria.
- ⚡ Fermentation is a catabolic pathway that generates ATP anaerobically in the cytoplasm, requiring no special organelles.
- 🍞 Yeast undergoes alcoholic fermentation, producing carbon dioxide (which makes bread rise) and ethanol (which is used in alcoholic beverages).
- 💨 Alcoholic fermentation involves two steps: glycolysis and alcohol formation, where glucose is broken down into ethanol and carbon dioxide.
- 🔥 The main purpose of the second stage of fermentation is to regenerate NAD+ for glycolysis, ensuring the process can continue.
- 🚗 Ethanol, the waste product of alcoholic fermentation, still contains a lot of energy, as seen by its use as fuel in race cars.
- 💪 Muscle cells can perform lactic acid fermentation when oxygen is low, producing 2 ATP per glucose molecule, compared to 36 ATP in aerobic respiration.
- 🧪 In lactic acid fermentation, glucose is converted to lactic acid, and like alcoholic fermentation, it regenerates NAD+ for glycolysis.
- ⏱️ Although fermentation is fast and simple, cellular respiration yields far more energy, making it preferable when oxygen is available.
- ❓ The purpose of fermentation is to ensure ATP production when oxygen is unavailable, although it is less efficient compared to aerobic respiration.
Q & A
What is cellular respiration and how does it differ from fermentation?
-Cellular respiration is a process where cells use oxygen to convert glucose into ATP. It's a more efficient process that occurs in the presence of oxygen and primarily in mitochondria. Fermentation, on the other hand, is an anaerobic process that occurs without oxygen and in the cytoplasm, producing less ATP but can happen when oxygen is scarce or mitochondria are absent.
What are the two stages of fermentation?
-The two stages of fermentation are glycolysis and waste product formation. Glycolysis is the breakdown of glucose into two pyruvate molecules, producing two ATP and two NADH. Waste product formation involves converting pyruvate into either ethanol and carbon dioxide (alcoholic fermentation) or lactate (lactic acid fermentation), and it's crucial for regenerating NAD+ for continued glycolysis.
How many ATP molecules are produced from glycolysis in fermentation?
-From glycolysis, two ATP molecules are produced for every glucose molecule that is broken down into two pyruvate molecules.
What is the net profit of ATP in alcoholic fermentation?
-The net profit of ATP in alcoholic fermentation is two ATP molecules per glucose molecule, considering the two ATP invested at the beginning of glycolysis are not recovered in the fermentation process.
What is the role of NADH and NAD+ in fermentation?
-NADH and NAD+ play a critical role in fermentation as they are part of the redox reactions that allow the process to continue. NAD+ is required for glycolysis, and NADH is produced. The second stage of fermentation regenerates NAD+ from NADH, which is essential for glycolysis to continue.
Why is the second stage of fermentation necessary?
-The second stage of fermentation is necessary to regenerate NAD+ from NADH, which is required for the glycolysis process to continue. Without this regeneration, glycolysis would not be sustainable as it relies on NAD+ to convert glucose into pyruvate.
What are the waste products of alcoholic fermentation?
-The waste products of alcoholic fermentation are ethanol and carbon dioxide. These are the end products of the conversion of pyruvate into aldehydes and then into ethanol.
How does lactic acid fermentation differ from alcoholic fermentation?
-In lactic acid fermentation, pyruvate is converted into lactate (lactic acid) instead of ethanol and carbon dioxide. This type of fermentation does not produce gas, and the net ATP yield is also two ATP per glucose molecule.
Why do muscle cells use lactic acid fermentation during intense exercise?
-Muscle cells use lactic acid fermentation during intense exercise when oxygen supply is insufficient to meet the energy demands. This allows them to continue producing ATP, albeit at a lower yield (2 ATP per glucose) compared to aerobic respiration (36 ATP per glucose).
What is the relationship between fermentation and the rise of bread?
-The carbon dioxide produced as a waste product during alcoholic fermentation by yeast is what causes bread to rise. The yeast ferments the sugars in the dough, creating carbon dioxide gas which gets trapped, leading to the expansion of the dough.
Why is cellular respiration more efficient than fermentation?
-Cellular respiration is more efficient than fermentation because it completely oxidizes glucose in the presence of oxygen, yielding approximately 36 ATP per glucose molecule, compared to the 2 ATP produced by fermentation. Additionally, the byproducts of cellular respiration (water and carbon dioxide) do not contain any leftover energy, unlike ethanol produced in fermentation.
Outlines
🔬 Cellular Respiration and Fermentation
This paragraph introduces the topic of cellular respiration and fermentation. It explains that cellular respiration involves using glucose and oxygen to produce ATP, but in the absence of oxygen or mitochondria, cells resort to fermentation. Fermentation is a quicker, simpler process that doesn't require oxygen or complex organelles. It breaks down glucose into ATP through glycolysis and waste product formation. The paragraph details the process of glycolysis, which splits glucose into two phosphoglyceraldehyde molecules, converting them to phosphoglycerate, and finally into pyruvate, yielding a net gain of two ATP. It also introduces two types of fermentation: lactic acid fermentation, which produces lactate and two ATP, and alcoholic fermentation, which produces ethanol and carbon dioxide, also yielding two ATP.
🍺 Alcoholic Fermentation and Lactic Acid Fermentation
This paragraph delves into the specifics of alcoholic fermentation using yeast as an example. It explains how glycolysis is the first step, leading to the production of two pyruvate molecules and two NADH, along with a net gain of two ATP. The second stage involves converting pyruvate into aldehyde, releasing carbon dioxide, and then into ethanol by oxidizing NADH back to NAD+. This stage is crucial for regenerating NAD+, which is necessary for the continuation of glycolysis. The paragraph contrasts fermentation with cellular respiration, highlighting that respiration is more efficient, yielding 18 times more energy. It also discusses lactic acid fermentation, which regenerates NAD+ by converting pyruvate into lactate, again for the purpose of sustaining glycolysis. The paragraph concludes by emphasizing the role of lactic acid fermentation in muscle cells during periods of oxygen debt, allowing them to continue producing ATP when oxygen is scarce.
Mindmap
Keywords
💡Cellular Respiration
💡Anaerobic Environment
💡Fermentation
💡Glycolysis
💡Mitochondria
💡ATP
💡Lactic Acid Fermentation
💡Alcoholic Fermentation
💡NAD+ and NADH
💡Pyruvate
💡Ethanol
Highlights
Cellular respiration generates ATP by burning glucose in the presence of oxygen.
Fermentation is an anaerobic process that occurs without oxygen and without mitochondria.
Fermentation allows cells to burn glucose for ATP in the absence of oxygen.
Fermentation consists of glycolysis and waste product formation.
Glycolysis splits glucose into two molecules of phosphoglyceraldehyde (2pg).
Glycolysis produces two ATP through substrate level phosphorylation.
At the end of glycolysis, two pyruvate molecules are produced, yielding a net profit of two ATP.
Fermentation comes in different variations, including lactic acid fermentation and alcoholic fermentation.
In alcoholic fermentation, glucose is broken down into ethanol and carbon dioxide, producing two ATP.
Yeast is an organism that performs alcoholic fermentation, which is used in bread rising and alcohol production.
The second stage of fermentation regenerates NAD+ for glycolysis by oxidizing NADH to NAD+.
Cellular respiration is more efficient than fermentation, yielding 18 times more energy from glucose.
Ethanol is a high-energy molecule, but fermentation leaves energy behind due to the lack of complex organelles.
Lactic acid fermentation breaks down glucose into lactic acid, also yielding two ATP.
Muscle cells can perform lactic acid fermentation during oxygen debt to produce ATP.
Muscle cells are facultative anaerobes, preferring cellular respiration when oxygen is available.
The purpose of fermentation is to provide a fast, easy way to get ATP without oxygen and complex organelles.
Aerobic respiration is a slower, more complex process that extracts more energy from molecules.
Transcripts
welcome back to our fourth video in our
three-part series yeah I know doesn't
make much sense to me either
but we've been talking about cellular
respiration where we've been using our
cellular fuel glucose and burning it in
the presence of oxygen to generate ATP
approximately 36 but what happens in an
anaerobic environment when we don't have
oxygen and what would a cell do if it
lacked mitochondria where most of
respiration occurs well the answer is
fermentation fermentation is a simpler
and faster alternative to cellular
respiration it allows us to burn glucose
without oxygen and without complex
organelles like mitochondria
fermentation is a catabolic pathway that
breaks down glucose for ATP it's
anaerobic like we said it occurs in the
cytoplasm requires no special organelles
to set of reactions that occurs in two
stages glycolysis and what we're going
to call for now waste product formation
now we've already spent a lot of time on
God calluses in fact we already looked
at a video and if you want to see that
video the more detailed look at
glycolysis click right over here but for
now I'm just going to run through a
quick version of glycolysis just running
through the steps so in the first step
we split glucose into two pgl
phosphoglyceraldehyde and that costs us
two ATP
in our energy investment step the 2pg al
are converted to be pgl when we reduce
nad plus into NADH the B pgl are then
converted to pga phosphoglycerate and we
produce out the first two of our ATP by
substrate level phosphorylation and in
the final step the pga are converted
into two pyruvate and we make two more
ATP for net profit of two ATP like I
said if you want a more detailed
description of how this occurs go back
to our video that we dental glycolysis
the links over here
now at the end of glycolysis we have two
pyruvate and then those two pyruvate can
enter in what we call fermentation and
fermentation comes a lot of different
variations we can see all these
different end products of the different
types of fermentation but for our
purposes we're going to focus in on two
lactic acid fermentation and alcoholic
fermentation let's compare the two just
by looking at their formulas an
alcoholic form fermentation we break
down glucose into alcohol ethanol we get
to carbon dioxide as a product and we
make a profit of two ATP for every one
glucose and lactic acid fermentation we
take that same glucose and we break it
down to lactate or lactic acid and
produce again two ATP so let's take a
closer look at the details and we'll do
alcoholic fermentation first so we need
an organism that does alcoholic
fermentation how about yeast yeast does
alcohol fermentation in fact it's
because G's produces carbon dioxide that
it makes bread to rise and it's the
ethanol or alcohol that yeast produce as
a waste product that makes alcoholic
beverages alcoholic so let's look at the
metabolic pathway we start with
glycolysis this is step one of all
fermentation reactions and I've
condensed glycolysis here in this
diagram from glucose and I skipped all
the way to the end of pyruvate we see
our two nadh being produced and a net
profit of two ATP I've just skip the
intermediate details in the second stage
of fermentation if it's alcoholic
fermentation the two pyruvates are
converted into two molecules of aldehyde
and in doing so we release to carbon
dioxide then the two aldehydes are
converted into ethanol
by the oxidation of NADH to NAD+ so we
call the second stage alcohol formation
so glycolysis followed by alcohol
formation so let's summarize here we
have the overall formula its anaerobic
we need no oxygen it's in the cytoplasm
we need to know organelles it comes in
two stages glycolysis where we break
down glucose into two pyruvate molecules
producing two NADH and yielding to ATP
and then alcohol formation the two
pyruvate are converted into two
aldehydes while two carbon dioxides are
released then the two aldehydes are
converted into two ethanol by oxidizing
two NADH into two nad plus the two waste
products of this reaction are carbon
dioxide and alcohol which both diffuse
from the cells well this raises an
interesting question why why do stage
two let's look back at the flowchart
here everything that we're going to get
kind of on the positive side from
fermentation we get from glycolysis the
whole point of fermentation was to get
energy out of glucose and we only are
going to earn two ATP and we have those
two ATP by the end of glycolysis and so
we might as well just stop here pyruvate
what's the point of method making two
molecules carbon dioxide and ethanol
which are waste products and not use by
the cell well I'm going to give you a
hint
you see the alcohol formation stage -
this allows us to regenerate NAD+ for
glycolysis
we've been reducing NAD+ during
glycolysis to make nadh after a while we
have a limited supply of NAD+ and so if
we don't oxidize NADH to return the NAD+
back to glycolysis we can't do this part
at the top over and over again let's do
one more interesting thing
let's compare fermentation to cellular
respiration we see that instead of
respiration we use oxygen and our energy
yield is 18 times greater so the
question is where is the rest of the
energy up here how do we get so much
more energy out of glucose here and the
answer is the energy is left behind an
ethanol ethanol is a high-energy
molecule how high energy well you can
run racecars on it
that's pretty high energy without the
complex machinery of an organelle like
mitochondria we're not able to tap into
all the energy that's available in this
glucose and we just leave it behind
ethanol now let's look at lactic acid
fermentation here's the formula glucose
breaks down into lactic acid and we get
a profit of 2 ATP so here we have
glycolysis again in a shortened version
glucose to pyruvate making 2 NADH in a
profit of 2 ATP in lactate formation the
two pyruvate are converted into two
molecules of lactate or lactic acid and
again we should see that the only reason
to have this second reaction is to
regenerate NAD+ for glycolysis the type
of fermentation that a cell employs you
know whether it be alcoholic or lactate
form fermentation lactic acid
fermentation it depends on the type of
cell and the enzymes that has available
but one interesting thing is that muscle
cells have the ability to do lactic acid
fermentation now ideally muscle cells
would do cellular respiration where for
every one glucose molecule you'd get 36
ATP because in lactic acid fermentation
for every one glucose
you only make two ATP so our yield is
much much lower and so when you're
running your cells on lattic acid
fermentation you're going to run out of
energy pretty quick I snapped this whole
photo of myself working out the other
day I don't believe that but muscle
cells are facultative anaerobes that
means when oxygen is available they'll
use it so as much as you can deliver
oxygen to your muscles the more
efficiently you can burn glucose 36 ATP
for every one glucose but in times of
oxygen debt instead of muscle cells
being having no ATP production they can
switch over to lactic acid fermentation
and at least get 2 ATP for every one
glucose rather than zero so to wrap up I
have a couple questions what's the
purpose of fermentation if fermentation
is a fast easy way to get ATP without
oxygen and without requiring complex
organelles then why is there a slower
more complex process involving oxygen I
think we kind of just hinted at that in
aerobic respiration the alternative to
fermentation we break down molecules to
get much more to get more energy out of
them and the leftover products have no
useful energy left in them remember our
byproducts of cellular respiration were
just water and carbon dioxide comparing
that to the fact that racecars can use
alcohols fuel I think we can see a
difference so that does it on our series
on respiration and fermentation review
the videos and send questions if you
have them
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