Exam about Nutrition, only chat me if you're Nutrition major or related to NUTR

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?