Unit 3

Question 1

What are the direct products of B-oxidation?

Answer 1

NADH and FADH2 & Acetyl-CoA

Question 2

An 11-year-old girl is brought to the emergency department by her father. He reports she has recently been very thirsty and needing to make frequent trips to the bathroom. At her soccer game today, she complained of lightheadedness and that the symptoms did not resolve even after drinking a power beverage. A rapid dipstick test revealed glucose in her urine and further diagnostics are consistent with a diagnosis of type 1 diabetes. Evaluation of this girl’s liver would reveal an increased rate of which of the following processes?

Answer 2

Ketogenesis

Question 3

What is the role of adipose in metabolism?

Answer 3

Storage of triacylglycerols

Question 4

ATP can be generated by many metabolic pathways in the body. Which of the following processes generates the most ATP?

Answer 4

Fatty acid β-oxidation

Question 5

An individual is on a hunger strike and has not eaten in 13 days. Which of the following best describes their metabolic state?

Answer 5

The brain will be preferentially oxidizing ketones.

Question 6

An individual goes to bed around 8 pm and doesn’t wake up until 9 am the next morning. During this time, which of the following is the primary oxidizable substrate in the skeletal muscle?

Answer 6

Free fatty acids

Question 7

A 10-year-old boy is brought to the emergency department by his father. He reports his son has recently been very thirsty and needing to make frequent trips to the bathroom. Physical examination revealed a thin boy, in the 30th percentile for height and weight. A rapid dipstick test revealed glucose in his urine. Evaluation of this boy’s blood would reveal decreased levels of which of the following compounds or hormones?

Answer 7

Insulin

Question 8

The process of ketogenesis refers to the conversion of acetyl-CoA to which of the following compounds?

Answer 8

D-3-hydroxybutyrate or β-hydroxybutyrate

Question 9

A 22-year-old woman engaging in a political protest goes on a hunger strike on a prominent corner in a city park. She refuses all offers of food except for water through the first 2 weeks. Under these conditions there is a decreased reliance on which of the following pathways for fuel?

Answer 9

Gluconeogenesis

Question 10

Under fasting conditions (ratio of insulin to glucagon <1), elevated glucagon will activate which of the following enzymes?

Answer 10

Hormone sensitive lipase

Question 11

In the fasted state, fatty acyl-CoAs are transported across the mitochondrial membrane. The transport of fatty acids via carnitine palmitoyl transferase I (CPTI) can be directly inhibited by which of the following compounds?

Answer 11

Malonyl-CoA

Question 12

How essential is FAS?

Answer 12

Essential in embryonic development; without FA synthase, heterozygotes die in utero

Question 13

An increase in the ratio of insulin to glucagon will increase the activity of which of the following enzymes?

Answer 13

4 (acetyl-coa carboxylase, PFK2, and glycogen synthase)

Question 14

Which of the following enzymes is correctly paired with its allosteric inhibitor?

Answer 14

Acetyl-CoA carboxylase: palmitoyl-CoA

Question 15

In the case of a deficiency of biotin, which of the following enzymes required for fatty acid metabolism will be impaired?

Answer 15

Acetyl-CoA carboxylase

Question 16

A defect in the thioesterase subunit of fatty acid synthase would impair which of the following activities of the enzyme complex?

Answer 16

Liberation of newly assembled palmitate from the enzyme

Question 17

Malate can be converted to pyruvate in the cytosol. Which of the following compounds is directly generated in this conversion and is essential for fatty acid synthesis?

Answer 17

NADPH

Question 18

Under fasting conditions, acetyl-CoA carboxylase will be inhibited by an increase in which of the following compounds?

Answer 18

fatty acyl-CoA

Question 19

Under conditions when glucose oxidation is elevated, the acetyl-CoA produced will allosterically activate which of the following enzymes leading to an increase in the production of oxaloacetate?

Answer 19

Pyruvate carboxylase

Question 20

NADPH is essential for fatty acid synthesis and can be generated by which two enzymes? (+ indicates NADPH can be produced by the enzyme; - indicates the enzyme does not produce NAPDH)

Answer 20

1 (G-6-P dehydrogenase and malic enzyme)

Question 21

If you go to the Dr.’s office and have blood drawn for a lipid panel. Prior to the test you are asked to fast for 24 hours. In reviewing the results, which lipoprotein is most reflected by your blood levels of triacylglycerol?

Answer 21

VLDL

Question 22

In abetalipoproteinemia, lipoproteins containing apoB are not formed and lipid droplets accumulate in the intestine and liver. So in these individuals what is the level of plasma triacylglycerides and cholesterol?

Answer 22

Plasma TAGs- 24 mg/dL
total cholesterol- 5 mg/dL

LOW for both

Question 23

Which of the following is not required for the transport of newly synthesized fatty acid tissue to the adipose?

Answer 23

Carnitine to shuttle the fatty acids out of the mitochondria

Question 24

Nascent chylomicrons interact with HDL particles within circulation. Which of the following Apo proteins are obtained from HDL during this interaction?

Answer 24

ApoCII and ApoE

Question 25

A 16-year-old woman presents to her primary care physician for a follow up visit. At her initial visit, 3 months ago, her serum cholesterol was 255 mg/dL (above normal). Today her serum triglycerides are reported to be 260 mg/dL (above normal) . She finds this very disappointing as she started a strict dietary regime reducing all fats and cholesterol, replacing them with a high carbohydrate diet. You tell her that high carbohydrate diets can increase serum triglyceride levels in some individuals. This can be attributed to an increase in the synthesis of which of the following lipoproteins?

Answer 25

VLDL

Question 26

The interaction of chylomicrons with lipoprotein lipase is stimulated by which of the following Apo proteins?

Answer 26

ApoC II

Question 27

Which of the following best describes the role of HDL particles?

Answer 27

HDL particles are required for the transport of cholesterol from peripheral tissues to the liver

Question 28

Which of the following is the major source of extracellular cholesterol for human tissues?

Answer 28

LDLs

Question 29

Lecithin:cholesterol acyl tranferase (LCAT) is a plasma enzyme associated with HDL particles. Which of the following best describes its role in cholesterol transport?

Answer 29

Esterifies cholesterol to trap it in HDL particles

Question 30

In reverse cholesterol transport, HDL interacts with the ABC transporters to move cholesterol from the cell to the HDL. This also requires the activity of which of the following enzymes?

Answer 30

Lecithin cholesterol acyltranferase (LCAT)

Question 31

Under fasted conditions, glucagon is elevated, which of the following enzymes will be phosphorylated and inactive?

Answer 31

HMG-CoA reductase

Question 32

A 45-year-old man is found to have elevated serum cholesterol of 300mg/dL after a 12 hr fast. Which of the following lipoproteins would be the largest contributor to a measurement of plasma cholesterol in a normal person following a 12-hr fst?

Answer 32

HDLs and LDLs

Question 33

Under cellular conditions when cholesterol is low, which of the following is a true statement regarding the sterol response element binding protein?

Answer 33

It will be associated with the sterol response element (SRE) in the DNA

Question 34

What is the purpose of cholesterol esterification within the cell? (The conversion of cholesterol to cholesteryl ester)

Answer 34

Esterification traps cholesterol in the cell

Question 35

A 45-year-old man has a mild heart attack and a history of vascular disease. He is placed on a Mediterranean diet and statin drug therapy. Which of the following will be the most likely result of this drug therapy?

Answer 35

Low blood LDLs

Question 36

Bile salts are synthesized from cholesterol and are used for the emulsification of dietary lipids. What is the primary fate of bile salts during digestion?

Answer 36

They are reabsorbed in the ileum

Question 37

A 10-year-old female presents with chest pain and xanthomas over her elbows and knees. Her father died of a heart attack at age 35. Her mother has high cholesterol. Her physician suspects heterozygous familial hypercholesterolemia in the parents with homozygous disease in the daughter. This disease results from mutations in the receptor for low-density lipoprotein (LDL) or the ligand portion of its apoprotein coat. Which of the following apoproteins might be mutated?

Answer 37

B100

Question 38

Which of the following best describes the mechanism of action of statins and describes why this drug is an effective therapy for iindividuals with hypercholesterolemia?

Answer 38

Inhibit 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, a key regulator of cholesterol synthesis.

Question 39

The cellular uptake of LDL increases intracellular cholesterol levels. This has which of the following impacts on de novo cholesterol synthesis?

Answer 39

Increases degradation of HMG-CoA reductase

Question 40

The LDL receptor is also highly regulated in the cell. Which of the following proteins targets the LDL receptor for degradation?

Answer 40

Proprotein convertase subtilisin/kexin type 9 (PSK9)

Question 41

VLDL particles have which of the following combinations of apoproteins in their mature form?

Answer 41

ApoB100, ApoCII, ApoE

Question 42

A 45-year-old man is found to have an elevated serum triglycerides of > 730mg/dL. He tells you he forgot to fast before his visit and he ate a full breakfast of bacon and eggs before the labs were drawn. Which of the following lipoproteins would be the largest contributors to a measurement of plasma triglycerides in this situation?

Answer 42

Chylomicrons and VLDLs

Question 43

Shortly after meal high in fat, you would expect an elevation of which of the follow lipoproteins in circulation?

Answer 43

Chylomicrons

Question 44

A 5-year old presents to her primary care physician. Her mother is concerned due to persistent diarrhea which is worse when eating fatty foods. The child also has some clinical signs of a deficiency in vitamins A, D, E and K (fat soluble vitamins). Based on this information the child likely has a deficiency in the ability to synthesize which of the following lipoproteins?

Answer 44

Chylomicrons

Question 45

What is the primary lipid component of a VLDL particle?

Answer 45

Triacylglycerols

Question 46

In liver, which of the following key inhibitory events ensures that newly synthesized palmitoyl-CoA is not immediately oxidized?

Answer 46

Inhibition of carnitine–palmitoyl transferase-I (CPT-I) by malonyl-CoA.

Question 47

During the fasted state, lipolysis is facilitated by the action of hormone sensitive lipase. This enzyme requires which of the following modifications for activation?

Answer 47

Phosphorylation

Question 48

A 47-year-old male is prescribed a statin (HMG-CoA reductase inhibitor) to manage his elevated LDL cholesterol. What is the initial mechanism of action for obtaining the desired effect in this man?

Answer 48

Decreasing hepatic cholesterol biosynthesis

Question 49

Secondary bile salts are generated by bacterial modification of primary bile salts in the intestinal lumen. These modifications have which of the following impacts on bile salt solubility?

Answer 49

Decrease solubility The decrease in solubility of secondary bile salts allows for them to be excreted in the feces rather than reabsorbed.

Question 50

A 10-year-old female presents with chest pain and xanthomas over her elbows and knees. Her father died of a heart attack at age 35. Her mother has high cholesterol. Her physician suspects heterozygous familial hypercholesterolemia in the parents with homozygous disease in the daughter. This disease results from mutations in the receptor for low-density lipoprotein (LDL) or the ligand portion of its apoprotein coat. Which of the following apoproteins might be mutated?

Answer 50

B100

Question 51

Insulin stimulates lipogenesis through several mechanisms. Which of the following is not an insulin stimulated process that enhances lipogenesis?

Answer 51

Decreased activity of the pyruvate dehydrogenase complex

Question 52

Fatty acid synthase is a multimeric enzyme complex. Which of the following subunits contains pantothenic acid as a cofactor?

Answer 52

Acyl carrier protein (ACP)

Question 53

An increase in the ratio of insulin to glucagon leads to which of the following metabolic shifts?

Answer 53

Acetyl-CoA carboxylase will become dephosphorylated and active

Question 54

During fatty acid synthesis, after the initial step involving acetyl-CoA, the fatty acid chain is elongated by the addition of which of the following compounds?

Answer 54

Malonyl-CoA