Quiz 15 Lipids

β oxidation of myristyl-CoA (14:0) yields:

7 acetyl CoA + 6 FADH2 + 6 NADH + 6 H+.

Phosphorylation of perilipin:

triggers the release of a coactivator for adipose triglyceride lipase.

During triacylglycerol hydrolysis, hormone-sensitive lipase catalyzes the release of:

monoacylglycerol and a single free fatty acid.

Select all that apply. Epidemiological evidence suggests that consumption of a large amount of saturated fatty acids and trans fat promotes:

thrombosis, obesity, atherosclerosis, type 2 diabetes

Identify the compound shown.

an intermediate in fatty acid activation

How many rounds of β oxidation would be required for a 16-carbon fatty acyl chain to be degraded to acetyl CoA?

7

Which compound is an intermediate in ketogenesis?

3-hydroxy-3-methyl-glutaryl CoA

Where is adipose tissue located in a human body?

under the skin (subcutaneous fat) and around the inner organs (visceral fat)

Which organs or tissues prefer to use ketone bodies such as acetoacetate as a fuel energy source instead of glucose?

heart muscle and renal cortex

The activation of fatty acids for degradation takes place in two steps. What is the intermediate formed and why is activation necessary for β oxidation to occur?

Acyl adenylate; only the activated form of the fatty acid can react with coenzyme A.

Which statement about ketone bodies is TRUE?

Acetone and D-3-hydroxybutyrate can be obtained from acetoacetate.

The main priority of metabolism during starvation is:

preserving muscle proteins.

How does activated fatty acid move to the mitochondrial matrix?

The activated fatty acid moves across the outer mitochondrial membrane through a porin channel. Acetyl carnitine shuttles across the inner mitochondrial membrane by a translocase.

Which enzyme–substrate pair is CORRECT?

thiolase – 3-ketoacyl CoA

The hormone induces lipolysis, whereas inhibits the process.

glucagon; insulin

Which compound does β oxidation begin from?

acyl CoA

The increase in acetyl CoA during starvation inhibits the enzyme:

pyruvate dehydrogenase.

What stereoisomer is a regular substrate in the β oxidation pathway?

trans-Δ2-enoyl CoA

Coenzyme(s) involved in the degradation of saturated fatty acyl CoA include(s):

FAD and NAD+.

In the absence of insulin, most acetyl CoA:

enters ketogenesis.

Acetoacetate is formed from acetyl CoA and can spontaneously turn to:

acetone.

Which process makes the following reaction irreversible?

hydrolysis of inorganic pyrophosphate

The products of lipolysis are glycerol and free fatty acids. What is the role of these compounds?

Glycerol can be phosphorylated to D-glyceraldehyde 3-phosphate, which can enter both glycolytic and gluconeogenic pathways. Free fatty acids can be oxidized to succinyl CoA, which enters the citric acid cycle.

The first step of β oxidation is:

oxidation by FAD.

Hormone-sensitive lipase acts in:

mobilization of triacylglycerols

D-glyceraldehyde 3-phosphate can be converted:

into pyruvate or glucose in the liver.

Every biochemistry student knows that most naturally occurring unsaturated fatty acids are cis fatty acids. Why, then, do so many fat-containing foods come with the notation “Contains no trans fats”?

Vegetable oils are often hydrogenated to form trans unsaturated fatty acids to preserve shelf life.

How does formation of acetyl CoA by β oxidation not only provide energy for cellular respiration but also spare glucose?

Acetyl CoA derived from fatty acids inhibits pyruvate dehydrogenase, the enzyme that converts pyruvate into acetyl CoA.

Which compound is able to move across the inner mitochondrial membrane?

acyl carnitine

What protein triggers mobilization of triacylglycerols?

perilipin

What can promote ketone body formation?

accumulation of acetyl CoA

Untreated, chronic ketone body production will:

decrease blood pH levels.

Which enzyme catalyzes the conversion of acetoacetate into D-3-hydroxybutyrate?

D-3-hydroxybutyrate dehydrogenase

Which statement about starvation is TRUE?

Carbohydrate reserves are exhausted in a single day.

The ketogenic diet:

requires high-fat, adequate-protein, and low-carbohydrate consumption.

The availability of ____ determines whether acetyl CoA, made from fatty acids, can enter the citric acid cycle.

oxaloacetate

How many molecules of acetyl CoA are involved in a single round of ketogenesis?

3

During starvation, the brain begins to consume an appreciable amount of ketone bodies ____ days after the beginning of the starvation state.

3

The compound ____ is considered one of the ketone bodies.

β hydroxybutyrate

The main site of ketogenesis is:

the liver cells.

Which enzyme is bound to the outer mitochondrial membrane? Select all that apply.

acyl CoA synthetase, carnitine acyltransferase I