Lecture 9 - Energetics

Question 1

What is energetics?

Answer 1

• How animals convert glucose, lipids and proteins to energy
• Measuring what’s being utilized as an energy source in the body

Question 2

Glycolysis

Answer 2

first step in breaking down glucose

Question 3

Products of glycolysis

Answer 3

2 pyruvate, 2 ATP, and 2 NADH

Question 4

Where does glycolysis occur?

Answer 4

cytosol

Question 5

Do we put ATP into glycolysis?

Answer 5

Yes

Question 6

Products of Kreb’s/TCA/CAC

Answer 6

• 1 ATP for each pyruvate
• 4 NADH
• 1 FADH2

Question 7

Where does the Kreb cycle take place?

Answer 7

• mitochondria

Question 8

Products of ETC

Answer 8

• each NADH provides 3 ATP
• each FADH2 provides 2 ATP
• glycolysis and TCA produce 10 NADH and 2 FADH2 per glucose molecule = 34 ATP total

Question 9

Where does ETC take place?

Answer 9

In the membrane of mitochondria

Question 10

How is acetate activated?

Answer 10

acetate + coenzyme A = acetyl coenzyme A

Question 11

What does acetyl coenzyme A do?

Answer 11

• enters the Kreb’s cycle to yield 12 ATP/mole
• BUT 2 moles ATP required for activation of Acetate = net 10 ATP/acetate

Question 12

How is propionate oxidized? Why?

Answer 12

• it is another SCFA that we can use to generate energy
• propionate to succinyl-CoA to malate to phosphoenolpyruvate to acetyl CoA
• acetyl CoA goes into the Kreb’s cycle

Question 13

How many ATP do we get per propionate?

Answer 13

22 ATP - 4 ATP = 18 ATP/propionate
- about half the amount that we get from glucose

Question 14

How are fatty acids metabolized?

Answer 14

Beta-oxidation
- FAs are just long chains of carbon and we now need to break them down into 2 carbon units

Question 15

What happens at each step of beta-oxidation?

Answer 15

• we break off 2 carbon units and get 5 ATP and 1 Acetyl CoA

Question 16

When palmitate undergoes beta-oxidation, how much ATP is generated?

Answer 16

131 ATP - 2 ATP = net 129 ATP/palmitate

Question 17

How are non-esterified fatty acids aka FFA mobilized from adipose tissues?

Answer 17

• Hormone-sensitive lipase (HSL) simulates the release of NEFA
• NEFA bound to albumin circulates in the blood
• some are directly used by peripheral tissues and oxidized
• majority are taken up by the liver

Question 18

Fat metabolism in the liver aka what does the liver do with FAs?

Answer 18

• re-esterified and stored as TG
• TG is incorporated into VLDL
• Beta-oxidation to make acetyl CoA
  = complete oxidation (used as an energy course) or synthesize ketone bodies (pre-digestion of fatty acids)

Question 19

Characteristics of ketone bodies

Answer 19

• water soluble (can go around the body similar to glucose and unlike FAs which are bound to albumen)
• decrease lipolysis rate
• normal fuel in muscles

Question 20

How are ketone bodies utilized?

Answer 20

• incomplete beta-oxidation = end up with acetoacetate
• cannot be broken down in the liver so it’s sent out to other tissues in the form of ketone bodies where it can be broken down into Acetoacetyl CoA then 2 Acetyl CoA which enter the Kreb’s cycle

Question 21

Ketosis

Answer 21

• generated in post absorptive state, particularly starvation from mobilized fatty acids
• results from liver’s limited capacity to oxidize fatty acids

Question 22

What happens when ketone bodies decarboxylate?

Answer 22

They decarboxylate to acetone (volatile) and is detected in breath and urine

Question 23

Where do glucogenic amino acids enter the Kreb’s cycle?

Answer 23

at many different points depending on their structure

Question 24

Where do ketogenic amino acids enter the Kreb’s cycle?

Answer 24

• become acetoacetyl CoA or Acetyl CoA to enter the Kreb’s cycle

Question 25

What do we use to determine how much energy we are getting out of a diet?

Answer 25

• bomb calorimetry

Question 26

Why are we most interested in metabolizable energy?

Answer 26

• this is what the animal is actually getting out of the gross energy
• collect GE and DE to get ME

Question 27

Direct calorimetry

Answer 27

• direct measurement of heat:
  feed energy - fecal energy - urinary energy

Question 28

Indirect calorimetry

Answer 28

• based on biochemical principles and known combustion values
• Glucose + O2 and Fat + O2; both yield CO2 and H2O but in different amounts

Question 29

In regards to indirect calorimetry, by measuring CO2 vs O2 what do we get?

Answer 29

Respiratory Quotient

Question 30

What happens if only Glucose is oxidized in the body?

Answer 30

• for every L of O2 we get 5 Kcal of energy
• RQ = 1

Question 31

What happens if only Fat is oxidized in the body?

Answer 31

• for every L of O2 we get 4.71 Kcal of energy
• RQ = 0.70

Question 32

What are the extremes of RQ?

Answer 32

0.7 to 1.0

Question 33

How do we measure protein?

Answer 33

• by measuring how much nitrogen we have in the urine
• N in urine = utilization of aa as an energy source

Question 34

How do we correct for protein oxidation

Answer 34

• end up with non-protein RQ which falls btw 0.7 and 1.0
• Co2 produced minus protein CO2 produced
• O2 consumed minus protein O2 consumed

Question 35

What does total heat produced indicate?

Answer 35

Energy gained from metabolizing protein, CHO, and fat

Question 36

What 3 data points do we need to begin total heat produced calculations?

Answer 36

1. O2 consumed, L
2. CO2 produced, L
3. Urine N excreted, g