14. Energetic efficiency of metabolic conversions

Question 1

Energy (ME) -> ATP
efficiency = variable/constant

ATP -> work
Efficiency = variable/constant

Answer 1

Energy (ME) -> ATP
Efficiency = variable
ATP -> work
Efficiency ~25% (constant)

Question 2

ATP production: general formula?

Answer 2

S + O2 -> ATP + CO2 + H20 + B + heat

Different factors can be, or become, limiting

Question 3

ATP production: formula with glucose? How much ATP yield?

Answer 3

C6H12O6 + 6H2O -> 6CO2 + 6H2O + 2816 kj/mol

30 mol ATP yield

Question 4

ATP production glucose: aerobic vs anaerobic?
Which is more efficient?

Answer 4

Anaerobic: glu-> 2 pyruvate-> 2 lactate + 2 ATP
Aerobic: glu -> 2 pyruvate -> 2 acCoA -> TCA cycle = 30 ATP

Anaerobic is more efficient (75% vs 35%)

Question 5

glucose -> 2 lactate
muscle glycogen -> 2 lactate

Which is more efficient? Why?

Answer 5

muscle glycogen -> 2 lactate + 88 kj/mol (3 ATP)
Because with glycogen -> glucose-6-p, no energy is needed. However, glucose -> gl-6-ph = 1 ATP cost.

Question 6

So there is ‘aerobic’ and ‘anaerobic’ oxidation: oxidative phosphorylation and glycolysis + TCA cycle
There is also ‘aerobic’ and ‘anaerobic’ ATP: mitochondria (TCA) and cytoplasm (glycolysis). This is because

Answer 6

glycolysis can happen in absence of oxygen until pyruvate, in TCA cycle this cannot happen (even though it does not USE oxygen).

Question 7

Ratio ATP cyto:mito = 1:14. Cyt ATP ~7% of total ATP
Because more glycolysis will occur than oxidative phosphor, cyto ATP contribution will go up. Anaerobic will be faster.

Answer 7

ok

Question 8

What does the performance-enhancing microbe Veillonella atypica do in athletes?

Answer 8

Functions via lactate -> propionate -> improved performance

Question 9

Hypoxia conditions: ATP-production will happen via anaerobic glycolysis (lactate). This needs support of ….

Answer 9

gluconeogenesis from lactate: cori cycle!

Question 10

Product inhibition: if lactate increases very much, it will block the enzyme converting …. > ….

Answer 10

pyruvate > lactate

Question 11

Hypoxia: lot of lactate, which has to be cleared immediately when produced. Cori cycle + lactate shuttle come in, but why does our body not want to use anaerobic metaobolism for a long time?

Answer 11

Cori cycle = net -6 ATP, this is why your body does not want to use anaerobic metabolism for a long time. It will take a lot of energy to reconvert (and thus get rid of) lactate.

Question 12

Why could lactate be used as biomarker of energy status?

Answer 12

Lactate is known as by-product of glycolysis, during heavy exercise
▪ An-aerobic ATP production with lactate as by-product:
* requires a shift from fat to glucose as energy substrate
* increases energy expenditure when lactate has to be cleared via gluconeogenesis

Question 13

Thermogenic effects of a meal: depends on ingested nutrients and metabolic settings. Place nutrietns in descending order of thermogenic effects :
Fats, Ch, protein

Answer 13

(proteins > carbohydrates > fat)

Question 14

Ingested ME is/is not corrected for energetic costs of PPM (post prandial metabolism)

Answer 14

is not

Question 15

Kidney breaking down … to make …. results in …. under extreme fasting conditions.

Answer 15

Amino acids
Glucose
Ketone bodies

Question 16

What is it and how is the BMR measured?

Answer 16

➢ energy expenditure in the post-absorptive state
➢ measured under conditions of thermal neutrality
➢ awake but completely at rest (e.g. viewing Netflix series

Question 17

What is often measured instead of BMR and why?

Answer 17

RMR: resting metabolic rate. Often measured as it is easier to measure without taking the thermal neutrality into account.
➢ energy expenditure at rest
➢ not measured under strictly controlled conditions