Metabolism I. How foods store energy (most of this section was i.docx

Metabolism
I. How foods store energy (most of this section was introduced
in chapter 1):
a. Background: what IS energy? I hate defining energy; it’s an
intangible concept. It is the ability to do work, or, to make
something change (ex, move). Anyway, energy comes in two
basic forms: potential (stored) energy, and kinetic (the energy
of movement.)
i. Kinetic energy: the energy of movement. Includes a ball
flying through the air, or a molecule bouncing around in space.
Heat is a form of kinetic energy: the random movement of
molecules/atoms (the faster they go, the hotter it gets). Kinetic
energy also includes a rubber band flying through the air toward
the back of your little sister's head.
ii. Potential energy: stored energy. When you stretch the rubber
band back and aim it at your sister, you know that there is
stored energy in that rubber band, because when you let go it
will move, and will do work (startle your sister). Energy is
stored in chemical bonds, so when chemical bonds are broken,
energy is released. Cells take advantage of the fact that
chemical bonds store energy. They purposefully break bonds to
use the released energy.
iii. Energy conversions: energy is converted between forms.
When you pull the rubber band back, you are converting kinetic
energy (moving your hand & the rubber band) to stored energy.
Whenever energy is converted between forms, some of the
energy is converted to heat, whether you mean to do that or not.
So, when cells break chemical bonds to release energy to do
work, some heat is always produced.
Homeotherms (warm-blooded animals) take advantage of that

fact to maintain stable temperatures. We "waste" tons of energy,
just contracting & releasing muscles constantly to break bonds
& release heat. Your pet boa constrictor (“cold-blooded”) can
go without food for much longer than your pet guinea pig
because the boa wastes much less energy on heat production.
iv. Ways that cells store energy: for our purposes, what you
need to know is that cells can store energy in chemical bonds
(see below) and by maintaining concentration gradients of
certain chemicals (we’ll get to that way later)
b. We know our bodies can extract energy from carbohydrates,
protein and fats. Therefore, we know that energy is STORED in
food, in the nutrients I just mentioned. So, how is energy
stored in these nutrients? Well, as you know nutrients are
simply chemicals. Carbs, proteins, and fats are each specific
types of MOLECULES: substances that are made of many
elements bound together. Carbs are made of Carbon (C),
Oxygen (O) and Hydrogen (H); fats are made of C, H and a
little bit of O; and proteins are made of C, H, O, and Nitrogen
(N)
c. Anyway, the elements that make up these nutrients are bound
together in specific ways. We’ll get to that in later chapters.
Well, it turns out that energy is stored in chemical bonds. For
example, in a molecule of the sugar “glucose,” there are 6 C, 12
H and 6 O. These atoms are bound together, but there is
tension, or energy, in the bonds between the atoms. It’s THIS
energy, the energy in chemical bonds, that our bodies access
when we eat food. Each individual cell in our bodies gets some
of the nutrients from food, and breaks the bonds of those
nutrients to release the energy stored there.
Cells don’t actually use the energy stored in food to do work
directly. Instead, they extract energy stored in foods to
recharge their batteries. Cells use a specific kind of battery to

do virtually all of their work. This battery is a chemical called
ATP (Adenosine TriPhosphate). ATP is like a rechargeable
double-A battery to the cell: one ATP can be used to do one job.
When it is used, it is split into a Phosphate (Pi) and Adenosine
DiPhosphate (ADP). When I say “split,” I literally mean that
ATP was one molecule, and then it gets ripped in two: a Pi and
an ADP. Energy from food, then, is used to recharge the battery
by allowing the cell to re-attach the ADP to the Pi… making
ATP again!
What’s an example of a job a cell might do?
Here’s one example: recall that absorption of water-soluble
nutrients requires channels that allow each nutrient to move into
a cell from the lumen of the small intestine. Sometimes, this
movement through the channel requires energy. Calcium is an
example: when a calcium atom is absorbed, energy is required…
specifically, the absorption of one calcium atom requires one
ATP to be split. The energy from ATP splitting allows the cell
to “pull” the calcium inside.
Here’s another example: when a muscle contracts, that means
hundreds of muscle CELLS all get shorter together. Within
each muscle cell, there is protein apparatus working to pull the
ends of the cell closer… making it shorter. In order to run this
apparatus, each cell must split millions of ATP molecules (there
are millions of parts to the apparatus, each one requires energy).
For the muscle cells to keep working, they must continue to use
food energy to recharge the ATPs they’ve used. So, the cells
will take in glucose and fatty acids from the blood; then they
can recharge their ATP batteries and keep working.
d. Vitamins are made of molecules of C, H, O (and some other
elements) too! Why can’t we get any energy from them?
Because cells don’t have the machinery to break their bonds and
get their energy! Our cells only have the machinery to break
the bonds of carbs, proteins and fats to get energy. By the way,
vitamins do HELP to get energy from carbs, proteins and fats.

Vitamins are part of the machinery!
II. Some Reminders of Energy Basics:
a. Energy in carbs, proteins and fats are stored in chemical
bonds. We’ll see more specifically how later on! Anyway, the
actual chemicals that cells split to release energy are glucose,
fatty acids, glycerol (remember, from triglycerides), and amino
acids.
Now, recall that when amino acids are used for energy, they
must first be deaminated. The remaining carbon chain ends up
as glucose OR a derivative of glucose or fatty acids. Glycerol
is actually a glucose derivative. So, when it comes to using
chemicals for energy, cells really use glucose, fatty acids, or
some derivative of them!
b. Recall also that the energy stored in glucose and fatty acids
is NOT used by cells directly to do work; instead, cells use the
energy from food to make ATP.
Again, ATP is like a AA battery. When a cell needs to do a job,
it will split ATP and use the energy released to do the job.
When ATP is split, the remnants of the split are ADP and Pi
(inorganic phosphate). See the picture provided in your book to
help clarify this split.
Energy from glucose and fatty acids are simply used to re-attach
ADP and Pi and make more ATP. It’s like ATP is a
rechargeable battery: the cell depletes the battery doing a job.
To recharge the battery, it needs a larger energy source (like the
electric socket you would use). That larger energy source is
food.
Glucose has enough energy to “recharge” about 36-38 ATP
batteries. Fatty acids, since there are so many of different
lengths, vary. The longer the fatty acid, the more energy it

stores!
III. An introduction/overview of the processes used to extract
energy from nutrients to “recharge” ATP- Gycolysis and
Aerobic Respiration. Both processes include many steps.
Virtually every step is driven by a specific enzyme.
a. Glycolysis- ONLY glucose undergoes this process. The term
literally means “splitting glucose.” And that’s exactly what
happens, glucose gets split in two.
This is a 10-step process that occurs in the CYTOSOL- general
fluid of the cell. So, that means that the enzymes that drive this
process are floating around in the general fluid of the cell.
During glycolysis, glucose is split into two pieces. Those
pieces are called pyruvate. This initial split releases enough
energy to allow the cell to recharge 2 ATP; that is, the cell
gains 2 ATP batteries.
Glycolysis does NOT require O2; it is anaerobic. And it’s a
way for a cell to get ATP fast!
b. Aerobic Respiration-
The remnants of glycolysis (pyruvates) and all other energy-
providing nutrients such as fatty acids, go through this process.
This is a very complex series of reactions that occurs within
MITOCHONDRIA. Mitochondria are isolated “rooms” in the
cell where the enzymes that drive the reactions of aerobic
respiration are kept.
This is where the remainder of the energy from glucose will be
extracted (remember, after glycolysis the 2 pyruvates are still
storing about 34 ATPs worth of energy!). This is an extremely
efficient process. However, it takes a little longer to kick in to
full steam than does glycolysis, if a cell’s energy needs increase
suddenly. However, once it gets going, it can pump out serious

amounts of ATP!
This process is THE reason… not one of the reasons, THE
reason… that you need to breath in O2 approximately every 3-5
seconds every minute of your life. This process NEEDS O2.
Cells of your body do it constantly, and they therefore require a
constant source of O2. Since it requires O2, it is called an
aerobic process.
c. What happens to glucose after it’s been split up and depleted
of its energy?
Well, remember that glucose is C6H12O6. When it is split up,
its Cs and Os stick together to form CO2 (carbon dioxide). It’s
Hs join up with the O2 provided by your breathing to form
H2O.
You then breathe out the CO2 as waste, and the H2O becomes
part of the water used by your body. This is why food can
provide more water than is revealed by it’s absolute water
content; this is metabolic water!
IV. More detail about Aerobic Respiration, using glucose as the
example- You have learned a little bit about glycolysis, in
which a molecule of glucose was split into 2 pyruvates. Now,
you will see what happens to those 2 pyruvates.
a. An overview before we get to the details:
i. The pyruvates are taken into a mitochondrion, where each
will be converted to a compound called acetyl
ii. The rest of aerobic respiration involves 2 complicated
processes; each requires many steps and many enzymes. Lucky
for you, you won’t be required to know all of the steps and
enzymes; just the overall events and outcomes. The two
processes are called:

1. The TCA, or Krebs, or Citric Acid cycle- in this process, H
atoms are carefully removed from each acetyl. The H atoms
carry energy-rich electrons. They will then be transported to:
2. The Electron Transport Chain (ETC)- in this process, the H
atoms will give up their energy-rich electrons. Energy will be
sapped from the electrons and used to make ATP. The ETC
occurs along the inner membrane of mitochondria.
b. Some reminders before the details:
i. Keep in mind that cells always keep a stockpile of ADP
(adenosine DIphosphate) and Pi (inorganic phosphate) around.
That is, there are always ADP and Pi floating around in a cell
and in mitochondria. To “make” ATP, the cell uses energy to
attach the Pi to the ADP. Remember, this is like “recharging” a
battery.
ii. Remember that food molecules are made of atoms: carbon,
oxygen, hydrogen, etc. Atoms are composed of subatomic
particles such as protons, neutrons and electrons. The energy in
food, at least the portion that cells are able to extract, is
actually in the electrons. Electrons have a lot of energy, they
zip around constantly!
iii. The electrons that cells are able to get to in food molecules
are electrons associated with hydrogen (H) atoms. An H atom
consists simply of one proton and one electron, and the proton
(H+) is perfectly stable in water. So, an H atom can easily give
up its high-energy electron for the cell to use.
iv. The electrons in food are HIGH energy: think about it this
way: a plant makes glucose using energy from the sun. Energy
from the sun causes the electrons in glucose to speed up. So the
electrons in food molecules are zipping around extra fast. Now,
when you ingest food, your cells are able to extract some of that
energy, we’ll say by causing the electrons to slow down. When
electrons (or anything) lose energy, that energy has to go
somewhere. The Electron Transport Chain is a mechanism that

is able to capture the energy given off by electrons as they slow
down. The captured energy is used to recharge ATP.
c. More details:
i. The intermediate step after glycolysis: Pyruvates are
converted to acetyl.
1. First, pyruvates will be transported into a mitochondrion.
2. Next, they will each have a C, 2 Os, and a H atom chopped
off. The C and 2 Os will join up to form CO2. The CO2 will
diffuse out of the cell and into the blood. When the CO2 gets to
the lungs, you will breathe it out.
3. After the C, 2Os, and H are chopped off, what’s left is an
unstable compound called acetyl. Acetyl has 2 C and 3 H and
some Os. It will be stabilized when a substance called
coenzyme A (coA) attaches to it. You can think of coA as a
shuttle for acetyl, bringing acetyl safely to the enzymes of the
next process, the TCA cycle.
4. The H atom that was given off will be taken to the ETC by a
different shuttle.
ii. The Citric Acid cycle: in this process, the H atoms that still
remain on each acetyl will be carefully removed. This is a
multiple step process. The cell can’t just rip off the H’s
because if it did, what would be left would be highly unstable
and would run rampant in the cell, causing all sorts of harmful
reactions. So, this must be done very carefully.
What happens is that coA takes acetyl to the first enzyme of the
TCA cycle in the mitochondrion. The coA lets go of acetyl,
which then immediately attaches to a molecule called
oxaloacetate. Again, this is a stabilizing mechanism.
Oxaloacetate is simply a carrier to keep acetyl stable. When
acetyl attaches to oxaloacetate, a new compound is formed:

citrate.
Anyway, then a series of enzymes carefully rearranges the
chemical bonds of citrate in a step-by-step manner. The point is
to release H atoms in a safe way. In fact, that pretty much sums
up the point of the Citric Acid cycle: to release H atoms from
molecules in a safe way.
Each time a H atom is released, it will be immediately picked
up by a “molecular shuttle van,” a molecule that will shuttle the
H to the ETC. The shuttle vans will drop off H at the ETC, and
return to the TCA to pick up more Hs. The molecular shuttle
vans used to transport H from the TCA to the ETC are
Nicotanamide Adenine Dinucleotide (NAD+) and Flavin
Adenine Dinucleotide (FAD).
Remember that acetyl also had some Cs and Os. They are
useless to the cell; and, in a couple of steps, the Cs and Os that
acetyl contributed to citrate are chopped off and released as
waste: CO2.
iii. The ETC: in this process, the energy of the electrons from H
atoms is collected and used to make ATPs.
How is this done? I know you’re just dying to find out. We
will only consider the bare basics of the process:
Mitochondria have machinery for extracting energy from the
electrons in those hydrogen atoms. Remember they are high
energy electrons, because plants put energy from the sun into
them. Again, to help envision that, think of the electrons as
being hot potatoes straight out of the oven.
To get the energy out of those electrons, the mitchondria does
something interesting: it removes the electrons from the protons
(now we have H+, a proton, rather than H, an atom). The
electrons are passed along a series of proteins in the
mitochondria. Literally: each electron is taken from the H by a

protein. That protein then hands off the electron to another
protein, then to another protein, etc.
With each pass, the electron loses energy. If you think about
the hot potato, you can imagine that it is getting cooler every
time it gets tossed. It is losing some heat to the air. Well, in
mitochondria, that lost “heat,” or energy, can actually be
collected by the cell.
When the cell collects enough energy from the electrons, it will
use THAT energy to recharge the ATP! The cell has gotten
energy from food, and made more ATP! It can keep doing
work! By the way, the enzyme used for this in mitochondria is
called “ATP synthase.” It’s the only enzyme name in the whole
process I’ll ask you to know.
Back to our electrons. By the time the electron gets to the final
protein in the “chain,” it has lost a lot of energy. You can think
of it as being cool, or moving slowly. The cell has gotten all
the energy it can out of the electron. But, electrons are not safe
to have roaming around. They cause free radical/oxidative
damage… and they are the reason we need to ingest
antioxidants!
To manage those low-energy but dangerous electrons, the cell
makes sure there is plenty of oxygen around. Oxygen LOVES
electrons. An oxygen will grab a couple of spent electrons, and
then form a bond with a couple of the H+ that are still hanging
around, and make water! Now we have a safe, stable and
necessary compound keeping us safe from the electrons. And
this is THE reason we must breathe constantly, by the way, to
make sure there is enough oxygen to grab the electrons. That
should help you understand that cells are constantly using and
recharging ATP.
If you don’t have enough oxygen to pick up spent electrons, the

entire process of aerobic respiration shuts down!
d. Misc:
i. Many B-vitamins are integral parts of glycolysis and/or
Aerobic Respiration. For example,
1. B1 (riboflavin) is part of FAD;
2. B3 (niacin) is part of NAD;
3. B5 (pantothenic acid) is part of coA
4. Review the vitamins chapters for more.
ii. Oxaloacetate is made from carbohydrates; it’s actually part
of the reason we need to ingest some carbs.
iii. Remember, the overall process of aerobic respiration yields
about 34-36 ATP PER glucose (that’s for every two pyruvates).
Add that to the 2 from glycolysis, and the cell gets a total of
about 36-38 ATP for each glucose.
iv. All of the processes within the mitochondria are dependent
on the presence of adequate O2. If there is a lack of O2, the
electron-tossing enzymes cannot give up their electrons, and the
WHOLE system gets backed up, all the way back to pyruvate.
In fact, if there’s not enough O2, pyruvates will not be coverted
to acetyl. Will consider what happens then later.
V. To summarize:
a. Glycolysis- only glucose goes through this process, not fatty
acids. Occurs in the cytosol; glucose is split into two
pyruvates; the cell gains 2 ATP; no oxygen is required; this is a
relatively fast way to get ATP
b. Aerobic respiration- pyruvates and fatty acids go through this
process. Occurs in mitochondria; includes the Citric Acid
Cycle (H atoms are safely removed from molecules and taken to
the ETC) and the ETC (energy is removed from the electrons of

the H atoms and used to make ATP); the cell gains about 34-36
more ATP; oxygen is required; this takes longer than glycolysis
to start providing ATP but provides much more ATP than
glycolysis
VI. Some Other Aspects of Cellular Respiration:
a. How fatty acids are used for ATP-
Remind yourself of the structure of fatty acids. They are long
chains of C, H, and one O. With the help of water, fatty acids
are chopped up at every 2nd C. The pieces left over are acetyl.
coA stabilizes these acetyls, and they go right into the Citric
Acid cycle.
*So, can fatty acids be used to make ATP in the absence of O2?
Why or why not?
When LOTS of fatty acids are being used for energy, like if you
are diabetic, on a low-carb diet, or exercising for extended
periods, sometimes excess acetyls get made. There will be a
backup, basically not enough Citric Acid enzymes and
oxaloacetates are available to accept the acetyls. So, cells have
a way of sharing their excess energy with other cells: the
acetyls are converted to other 2-C substances called ketone
bodies.
Ketone bodies can leave the cell and enter the blood (acetyls
cannot). Other cells of the body can take in the ketone bodies,
convert them to acetyls, and use them for energy. In fact, even
neurons can use ketone bodies for energy.
If you are using all your ketone bodies, or excreting them
through breath or urine, you may be in a state of ketosis, but not
dangerous ketoacidosis. On the other hand, if enough ketone
bodies build up in your blood, they can change the pH
dangerously; this ketoacidosis can be life threatening. This is
primarily a concern for Type I diabetics.

b. How amino acids are used for ATP
When amino acids are used to make ATP, they must first be
deaminated. The C-chain that is left over is something related
to either glucose (for example, it could be pyruvate) or to fatty
acids (for example, it could be acetyl).
Each amino acid has a different fate, based on its structure.
The amino group becomes ammonia; liver cells will
immediately convert ammonia to the less toxic urea, which will
be excreted.
The vitamin B6 is required for deamination (and
transamination) of amino acids; therefore, it is required for
efficient metabolic processes.
c. What happens if there isn’t enough O2 to support ATP needs
Let’s say you’ve decided to lift a couch over your head. Here
you’ve got muscle cells in your arms, legs and back that were
resting, using very little ATP, and all of a sudden you’re going
to ask them to do this work that requires massive amounts of
ATP.
Well, these cells are having a normal blood supply to them (so-
adequate, but not lots of O2 are getting to them), and their
mitochondrial enzymes are not really warmed up at this point.
Remember that glycolysis yields ATP much faster than aerobic
respiration.
When you lift the couch, there’s no way that aerobic respiration
will be able to supply that much ATP that quickly. It will take
a while for blood flow to increase enough to provide enough O2
and for the enzymes to get warmed up.
So, TONS of glucose gets split as glycolysis powers your

lifting. That means, TONS of pyruvate gets produced. That
means, there’s not enough oxygen yet to allow all those
pyruvates to enter mitochondria and be converted to acetyl!
So, the excess pyruvates will be converted to another 3-C
compound, lactic acid (lactate). Lactic acid, unlike pyruvate,
can leave the cell.
In this way, cells can share all that excess energy with other
cells. It’s really the liver that uses lactic acid. Its cells can use
lactic acid to make and use pyruvate for energy, or it can attach
2 lactic acids together and make glucose, which can then enter
the blood for other cells to use.
d. Making and storing fuels (a lot of this will be review but this
is a good place to “bring it all together”)
i. Making and storing glucose
1. Making glucose: gluconeogenesis. Why do we need glucose
to be available in the blood? Would you expect
gluconeogenesis to occur right after you’ve eaten or several
hours later?
Anyway, gluconeogenesis occurs in the liver. Liver cells can
make glucose out of the structures we’ve considered that have 3
or more carbons: pyruvate, lactate, glycerol, even oxaloacetate.
What about –acetyl? Nope, it only has 2 carbons and can’t be
used to make glucose.
Also, since fatty acids are always broken down into –acetyls,
fatty acids cannot be used to make glucose.
2. Storing glucose

a. Glucose is stored as glycogen… glycogen is just a chain of
glucose linked together.
b. The amount of glycogen you can store is limited because it is
heavy… too heavy to be dragging around with you all the time.
c. Glycogen is stored primarily in the liver (shares glucose with
the blood when needed) and in muscle (keeps glucose for itself
to ensure fast access to ATP). Other tissues store it but these
are the only 2 we will consider.
ii. Making and storing fats (lipogenesis)
1. Making glycerol- glycerol can be made from the other 3-
carbon structures (pyruvate, lactate), glucose, and amino acids.
2. Making fatty acids- fatty acids are made by attaching –
acetyls together. Anything that can be broken down to –acetyls
can be used to make fatty acids… that means glucose, amino
acids, pyruvate.
So, glucose can be converted to fat but fat cannot be converted
to glucose.
3. Storing fatty acids: triglycerides
a. Triglycerides are stored primarily in adipose
b. When body cells need fuel (ex, fasting, long term exercise
etc), the fatty acids are released to the blood
c. Good to know: RESTING muscle cells use fatty acids as their
preferred fuel source… so the more muscle you have, the more
fat you burn just sitting there!
iii. Making and storing amino acids

1. Can we make all 20 amino acids?
2. Making amino acids:
-Cell builds the carbon backbone (R-group + -COOH)
-Then swipes an amino group (-NH2) from another amino acid:
“transamination”
3. Storing amino acids: where are amino acids stored?
a. Amino acid pool: cells’ interior & blood
b. Proteins
VII. Regulation of Metabolism: How the body decides what to
buildup/breakdown and when. Don’t spend too much time on
this; I just want to give you a general overview so that you can
think about when/why you will be storing nutrients, breaking
them down, making glucose, etc.
a. Hormones- tell cells which fuel sources to use and when;
make sure the right fuel sources are available. Remember,
blood glucose must always be maintained to feed the brain, and
that’s the point of what all these hormones do! When you are
fasting, most cells use fatty acids because they can, but also to
save available glucose for the brain. This should be review,
but:
i. Insulin- released after a meal
1. Take in and use glucose for energy (most cells)
2. Take in and store glucose as glycogen (liver & muscle cells)
3. Take in and store triglycerides (adipose cells)

4. Take in amino acids to make proteins (many cells)
ii. Glucagon- increases hours after last meal
1. Breakdown glycogen and release glucose to blood (liver
cells)
2. Release fatty acids (adipose cells)
3. Use fatty acids for energy (many body cells)
iii. Epinephrine & Cortisol- work with glucagon, esp. fasting &
starvation
1. Gluconeogenesis (liver cells)
2. Breakdown proteins for amino acids so that amino acids may
be used for gluconeogenesis (starts with muscle cells)
3. Release fatty acids (adipose cells)
4. Epinephrine & cortisol have many other functions!
b. Fasting/starvation- events that occur in terms of fuel
availability and use follow a predictable pattern, guided by the
above hormones.
Time after last meal
Hormone/s
Events
0-4 hours
Insulin
Cells use glucose; blood glucose declines
Hours
Glucagon
Glucose replenished with liver glycogen;
liver cells switch to f.a.
Many hours/ days
Glucagon/ Epi&Cortisol

Gluconeogenesis; amino acid pool tapped into
More body cells switch to f.a.
Metabolism begins to slow
Weeks
G, E & C
Excess use of f.a. has created many ketone bodies; they become
an important energy source for brain & RBC.
Metabolism drops dramatically (body temp drops, heart rate
drops, etc.)
Many weeks
G, E & C
Nutrient deficiencies apparent
Immune system function impaired
Muscle tissue broken down for amino acids
Proteins not “wasted” on growth, hair, etc.
Organs digested for proteins/amino acids
VIII. Alcohol-
Alcohol is processed primarily in the liver. It’s processing
slows entry of acetyl into the Citric Acid Cycle. This causes
acetyls to be made into fatty acids for storage… leading to fat
accumulation in the liver. Chronically, this can lead to severe
liver damage and liver disease.
Please read sections in the text addressing adverse effects of
[excess] alchol consumption, and benefits of [moderate] alcohol
consumption and safe drinking
IX. Some questions to help you think about this material (these

are NOT due, they are just to help you study/think):
a. Which 3 nutrient classes include nutrients that cells can use
for energy?
b. Describe the general structure of a mitochondrion.
c. Compare and contrast glycolysis and aerobic respiration.
d. Can fatty acids be used in glycolysis?
e. Does glucose enter aerobic respiration directly, as glucose?
f. Why do cells produce more CO2 when they are very active vs.
when they are less active?
g. What chemical is split by cells to do WORK directly?
h. Describe generally what a coenzyme is. How are the B-
vitamins related?
i. List several functions of liver cells (this goes back to earlier
readings).
j. How many carbons does glucose have? Pyruvate? Acetyl?
Lactic acid?
k. How many hydrogen atoms does glucose have?
l. What is the point of the Citric Acid cycle?
m. Where is the usable energy actually located in a hydrogen
atom?
n. How many pyruvates is glucose split into during glycolysis?
o. Where are the pyruvates taken after glycolysis?

p. What happens to pyruvates if there is not enough O2 to
support aerobic respiration? How is this helpful to other cells
of the body?
q. When pyruvates will continue on in aerobic respiration, what
substance are they converted to within the mitochondria?
r. What coenzyme will stabilize this substance? From what
vitamin is this coenzyme derived?
s. Acetyl will then enter which process of aerobic respiration?
t. When acetyl enters the first process of aerobic respiration,
coA will release it. When acetyl is released from coA, what
other substance will it join up with?
u. During the Citric Acid cycle, the remaining H atoms on each
acetyl are carefully removed. Why must these atoms be so
painstakingly removed; why can’t the cell just pluck them all
off at once?
v. Where (to what process, and where in the mitochondrion does
it occur) will the H atoms go, once they are removed?
w. Name the substances that will pick up the H atoms and carry
them to the next process. From what vitamins are each of these
“shuttle vans” derived?
x. Once the H atoms get to the ETC, what will happen to them,
right away?
y. What happens to their electrons?
z. Name the enzyme that makes ATP in the electron transport
chain.

aa. What is the role of O2 in aerobic respiration?
ab. Why is water a bi-product of aerobic respiration?
ac. Why are ALL of the processes of aerobic respiration
aerobic, even though O2 is only actually used during the ETC?
ad. Whenever C and O are lost from molecules during cellular
respiration, what happens to them?
ae. Provide an example of a real-life cell and situation in which
lots of ATP would be needed quickly, but not enough O2 would
be available for cellular respiration to make enough ATP. What
process would have to provide the bulk of the ATP in this
situation? Why would lactic acid be produced in this situation?
af. When fatty acids are used for energy by a cell, how are they
processed?
ag. Can fatty acids be used to provide energy anaerobically?
Why or why not? Explain this on the level of where they enter
the energy pathways.
ah. What substances will be produced when lots of fatty acids
are being used for energy?
ai. Why are these substances valuable sources of energy; that is,
what is different about them compared with fatty acids?
aj. Can you have too many of these substances in your blood?
What is this condition called?
ak. What needs to happen to amino acids before they can be
used for energy? What happens to the amino groups?
al. Explain generally, and provide some examples, of which

types of substances can be used to make glucose and which
types of substances can be used to make fatty acids.
am. Why would liver cells want to make glucose?
an. When would acetyl be used to make fatty acids rather than
be used to produce ATP?
ao. Can excess dietary fatty acids be stored as glycogen?
ap. What B-vitamin is required for deamination and
transamination reactions?
aq. Which can provide more ATP: one glucose, or one oleic acid
molecule (review fats to remind yourself how many carbons
oleic acid has)
ar. Why is ketosis an important adaptation for starvation (I’m
thinking of two reasons)?
as. Why does gluconeogenesis increase during
fasting/starvation?
at. Explain the physiological processes that occur during
feasting, fasting for several hours, and fasting/starvation
beyond several hours. Be sure to mention: i)storage of carbs,
proteins and fats as fat, ii) storage of glycogen, iii)
gluconeogenesis, iv) deamination and use of
proteins/breakdown of body proteins to use for energy, vi) what
nutrient/s brain cells are using for energy when, vii)what
nutrient/s other body cells are using for energy when.
au. What is the chemical name of the alcohol that we drink?
av. Define “moderate” alcohol intake.

aw. Name the enzyme in liver cells and the stomach that
processes alcohol.
ax. Explain some negative effects on the liver, the brain, and
vitamin adequacies that can occur as a result of excess alcohol
intake.
ay. Are there any positive effects of moderate alcohol intake?
PAGE
1
Created by Terri Stilson for NUTR&101

Metabolism I. How foods store energy (most of this section was i.docx

Recommended

Recommended

More Related Content

Similar to Metabolism I. How foods store energy (most of this section was i.docx

Similar to Metabolism I. How foods store energy (most of this section was i.docx (20)

More from ARIV4

More from ARIV4 (20)

Recently uploaded

Recently uploaded (20)

Metabolism I. How foods store energy (most of this section was i.docx