Metabolism XII

Question 1

What results from a carnitine deficiency?

Answer 1

Inability to transport long chain fatty acids into the mitochondria resulting in a toxic accumulation (p.113)

Question 2

What are the symptoms of a carnitine deficiency?

Answer 2

Weakness, hypotonia, hypoketotic hypoglycemia (p.113)

Question 3

Where is the citrate shuttle located?

Answer 3

Inner mitochondrial membrane (p.113)

Question 4

What does the citrate shuttle transport?

Answer 4

Citrate from the mitochondiral matrix into the cell cytoplasm to be converted into acetyl CoA and to undergo fatty acid synthesis (p.113)

Question 5

Where is the carnitine shuttle located?

Answer 5

Inner mitochondrial membrane (p.113)

Question 6

What does the carnitine shuttle transport?

Answer 6

Acetyl CoA from the cell cytoplasm into the mitochondrial matrix for transformation into Acyl-CoA for subsequent Degradation. Acyl-CoA is broken down by beta oxidation into ketone bodies and substrates for the TCA cycle (p.113)

Question 7

What enzyme inhibits the transport of Acyl-CoA through the carnitine shuttle into the mitochondrion for fatty acid degredation?

Answer 7

Malonyl-CoA (p.113)

Question 8

What are fatty acids and amino acids metabolized to in the liver?

Answer 8

Ketone bodies –> Acetoacetate and b-hydroxybutryate to be used in muscle and in the brain (p.113)

Question 9

What substrate becomes depleted in prolonged starvation and in diabetic ketoacidosis?

Answer 9

Oxaloacetate is depleted for gluconeogenesis. This stalls the TCA cycle (p.113)

Question 10

How does alcoholism stall the TCA cycle?

Answer 10

Excess NADH shunts oxaloacetate to malate (p.113)

Question 11

What are ketone bodies synthesized from?

Answer 11

From HMG-CoA (p.113)

Question 12

What are ketone bodies metabolized to in the brain?

Answer 12

Into 2 molecules of acetyl-CoA (p.113)

Question 13

How are ketone bodies excreted?

Answer 13

In the urine (p.113)

Question 14

What does the urine test for ketones fail to detect?

Answer 14

B-hydroxybutyrate (p.113)

Question 15

When is stored ATP used as a metabolic fuel in exercise?

Answer 15

Within seconds (p.114)

Question 16

When is creatine phosphate used as a metabolic fuel in exercise?

Answer 16

Within seconds (p.114)

Question 17

What are the primary sources of metabolic fuel in exercise over minutes and hours?

Answer 17

Aerobic metabolism, Fatty acid oxidation, anaerobic glycolysis (p.114)

Question 18

In which two locations is glucose prioritized during fasting and starvation?

Answer 18

In the brain and in RBCs (p.114)

Question 19

Describe the metabolic processes associated with a fed state (right after a meal).

Answer 19

Glycolysis and aerobic respiration occur. Insulin stimulates lipid, protein, and glycogen storage (p.114)

Question 20

Describe the metabolic processes associated with a fasting state (between meals).

Answer 20

Hepatic glycogenolysis (major metabolic process) and hepatic gluconeogenesis occur. Minor adipose release of FFAs. Glucagon and adrenaline stumulate the use of fuel reseves (p.114)

Question 21

How are glucose levels preserved in starvation of 1-3 days?

Answer 21

Hepatic glycogenolysis, adipose release of FFAs, muscle and liver shift fuel use from glucose to FFAs, hepatic gluconeogenesis from peripheral tissue lactate and alanine and from adipose tissue glycerol and propionyl-CoA (from odd chain fatty acids). Glycogen reserve are depleted after day 1. RBCs lack mitochondria so can’t use ketones (p.114)

Question 22

How are energy levels preserved in starvation after 3 days?

Answer 22

Main source energy is adipose stores (ketone bodies become the main source of energy from the brain and heart). After these are depleted, vital proteins are degradated causing organ failure and death (p.114)

Question 23

What determines survival time in prolonged starvation?

Answer 23

Amount of adipose stores (p.114)

Question 24

What is the rate limiting step in cholesterol synthesis?

Answer 24

Conversion of HMG-CoA to mevalonate by enzyme HMG-CoA Reductase (p.114)

Question 25

How is the majority of plasma cholesterol esterified?

Answer 25

2/3 of plasma cholesterol is esterified by lecithin-cholesterol acyltransferase (LCAT) (p.114)

Question 26

What is the mechanism of action of statins?

Answer 26

Inhibition of HMG-CoA reductase (p.114)