Question

1. Myristoyl-CoA is a saturated fatty acid with 14 carbons attached to coenzyme A. How many molecules of ATP would be generated from the complete oxidation of a single molecule of myristoyl-CoA? Important notes: Recall that the investment of 2 ATP is required to generate Myristoyl-CoA from myristate. Do not include these 2 ATP in your calculations of ATP yield. Assume that each molecule of NADH corresponds to 2.5 ATP synthesized, and each molecule of FADH₂ leads to 1.5 ATP synthesized.

2. What are TWO major differences between glucokinase (expressed in the liver) and hexokinase (expressed in most other tissues)?

a. Glucokinase has a lower affinity for glucose than hexokinase.

b. Glucokinase has a higher affinity for glucose than hexokinase.

c. Glucokinase is allosterically activated by glucose, hexokinase is not.

d. Glucokinase is allosterically inhibited by glucose, hexokinase is not.

e. Hexokinase is allosterically inhibited by glucose 6-phosphate, glucokinase is not.

3. To which anabolic pathway in the liver do fatty acids NOT contribute?

a. They are incorporated into liver fat droplets and could cause fatty liver disease.

b. They are exported into the bloodstream as fatty acids bound to serum albumin.

c. They are incorporated into lipoproteins and exported into the bloodstream.

d. They contribute to synthesizing new glucose via gluconeogenesis.

4. What is an important piece of evidence suggesting that fermentation is an important source of energy during high-intensity exercise?

a. Gluconeogenesis is activated in the liver

b. Phosphocreatine levels drop in the muscle

c. ATP levels drop in the muscle

d. pH levels drop in the blood

5. Which of the pathways below is NOT a major source of energy for a 1,000m foot race?

a. ATP from oxidative phosphorylation of fatty acids

b. ATP from oxidative phosphorylation of glycogen

c. ATP from lactate fermentation in the muscle

d. ATP regenerated from phosphocreatine

Answer 1

Question 1

Answer: Myristoyl-CoA is a 14 carbon containing saturated fatty acid that is metabolized by beta-oxidation. Each round of beta-oxidation results in the removal of two carbon units called as acetyl-CoA from Myristoyl-CoA and formation of 1 NADH and 1 FADH2. For complete oxidation of Myristoyl-CoA (14 carbons), six rounds of beta-oxidation is required. This results in formation of 7 acetyl-CoA, 6 NADH and 6 FADH2 molecules. Each acetyl CoA enters citric acid cycle and produces 1 ATP, 3 NADH and 1 FADH2. So, 7 molecules of Acetyl CoA produces 7 ATP, 21 NADH and 7 FADH2 molecules. Each molecule of NADH and FADH2 produces 2.5 ATP and 1.5 ATP, respectively via electron transport chain.

Total number of NADH molecules produced from beta-oxidation and citric acid cycle are 6 + 21 = 27 NADH

Each molecule of NADH produces 2.5 ATP. So, 27 molecules of NADH produces 27 X 2.5 = 67.5 ATP

Total number of FADH2 molecules produced from beta-oxidation and citric acid cycle are 6 +7 =13

Each molecule of FADH2 produces 1.5 ATP. So, 13 molecules of FADH2 produces 13 X 1.5 = 19.5 ATP

Total number of ATP produced = ATP produced from NADH + ATP produced from FADH2 + ATP produced in citric acid cycle.

= 67.5 + 19.5 + 7 = 94 ATP molecules.

As two ATP are used to convert Myristic acid to Myristoyl-CoA,

NET ATP yield = Total ATP produced - ATP used to generate Myristoyl-CoA.

NET ATP yield = 94 -2 = 92 ATP

Number of ATP generated from the complete oxidation of a single molecule of Myristoyl-CoA = 92 ATP.