Kaiser

Question 0

What are the different ways, in general, that someone can develop steatorrhea?

Answer 0

• Gallbladder deficient in bile production
• Pancreas deficient in enzyme production (lipases)
• Intestinal mucosa cells deficient in absorption of lipid micelles

Question 1

Which carbon on a fatty acid is the target of B-oxidation?

Answer 1

The third carbon from the carboxyl end. COOH is #1, then alpha, then beta.

Question 2

What is the effect of abetalipoproteinemia on the body?

Answer 2

No chylomicrons, LDL, or VLDL, which means no long chain FA absorption, GI problems, cognitive problems, vitamin deficiency

Question 3

What breaks down chylomicrons, and what is it activated by?

Answer 3

Lipoprotein lipase (LPL) is activated by Apo C-II, which is on the surface of VLDL and chylomicrons. Deficiencies in either one result in high plasma chylomicron/VLDL levels and poor absorption of their contents. Need to restrict fat in diet.

Question 4

Long chain FAs are transported from the cytosol to the mitochondrial matrix via _______.

Answer 4

the carnitine palmitoyl shuttle

Question 5

After FAs are transferred to the mitochondrial matrix as fatty acyl-CoA, what are the steps of B-oxidation?

Answer 5

1. Oxidation, using FAD
2. Hydrolysis, with water
3. Oxidation, with NAD+
4. Thiolysis, with CoA

Question 6

Odd chain FA degradation uses _____, ATP, and CO2 to convert propionyl CoA (3-carbon) to a 4-carbon acyl-CoA, and then uses ______ to produce succinyl CoA.

Answer 6

Biotin, coenzyme form of vitamin B12

Question 7

How many NADH and FADH2 are produced in each round of B-oxidation? What are their ATP equivalents? How many ATP can be produced from each Acetyl CoA? What is the energy investment of B-oxidation?

Answer 7

1 each. NADH = 3 ATP. FADH2 = 2 ATP.
Acetyl CoA = 12 ATP
2 ATP are invested in formation of the acyl-CoA.

Question 8

What is Zellweger syndrome?

Answer 8

No functional peroxisomes, where alpha-oxidation usually occurs. Cannot break down FAs longer than 25 carbons. Fatal within 1 year.

Question 9

What is Refsum syndrome?

Answer 9

Cannot do alpha-oxidation, therefore cannot degrade phytanic acid (a branched chain FA) and it accumulates.

Question 10

What is the primary source of energy for the brain during starvation conditions?

Answer 10

3-hydroxybutyrate (a ketone body). The brain cannot utilize fatty acids because it does not do B-oxidation.

Question 11

Ketone bodies are produced from ____ in the _____.

Answer 11

Acetyl CoA, liver

Question 12

What are the four reactions (general terms) that occur in FA synthesis?

Answer 12

Condensation (malonyl-ACP and acetyl-ACP), reduction (NADPH), dehydration, reduction (NADPH)

Question 13

Malonyl CoA (FA synthesis) is derived from acetyl CoA. What cofactor does this reaction use?

Answer 13

Biotin-E (and ATP). Adds a COO- to acetyl CoA.

Question 14

Which enzyme catalyzes the degradation of citrate into OAA and Acetyl CoA? (opposite rxn of first step of TCA cycle)

Answer 14

Citrate lyase

Question 15

What are the 5 lipogenic enzymes?

Answer 15

Acetyl CoA carboxylase, FA synthase, citrate lyase, malic enzyme, dehydrogenase from PPP

Question 32

Where are gangliosides degraded?

Answer 32

Lysosomes

Question 33

Gangliosides are derived from _____, which are derived from _____, which is derived from ____.

Answer 33

glycosphingolipids, ceramide, sphingosine

Question 34

Sphingomyelin is a type of phospholipid made from ____ and ___, which is a type of phospholipid on its own.

Answer 34

ceramide, phosphatidylcholine (PC)

Question 35

What do statins do and what is their mechanism of action?

Answer 35

Lower plasma cholesterol levels by inhibiting HMG-CoA reductase, the rate-controlling enzyme of cholesterol synthesis, thereby reducing the rate of cholesterol synthesis. Low cholesterol levels are recognized by the liver, which then increases LDL uptake to compensate, further lowering plasma cholesterol.

(Endogenous synthesis of cholesterol is responsible for about half of the cholesterol in the blood. Dietary cholesterol is the other half).

Question 36

Intracellular _______ inhibits cholesterol synthesis by inhibiting the release of a DNA-binding protein that increases expression of the ______ gene.

Answer 36

cholesterol, HMG-CoA reductase.

SREBP-2 is the binding protein

Question 37

Explain why familial hypercholesterolemia results in such high plasma cholesterol/LDL levels.

Answer 37

Defective LDL receptors prevent intake of LDL/cholesterol from blood (all tissues). Hepatocytes with low intracellular cholesterol won’t inhibit HMG-CoA reductase gene expression appropriately, leading to excessive cholesterol production (and release to blood). Cholesterol also inhibits LDL receptor gene expression, so low cholesterol will result in too many LDL receptors.