Open Answers (Final)

Question 1

What is the Km difference between Glucokinase and Hexokinase?

Answer 1

Glucokinase: High Km, around 10 mM (low affinity)

Hexokinase: Low Km, less than 1 mM (high affinity)

Question 2

3 ways to decrease blood cholesterol levels:

Answer 2

1. Inhibit cholesterol synthesis via Statins
2. Activate LCAT
3. Low cholesterol diet
4. Increase LDL receptor numbers

Question 3

Metabolic effects of LXR (its function)

Answer 3

1. Bile acid synthesis increased
2. Cholesterol Efflux increased
3. LDL receptor density decreased (ubiquination of LDLR’s)

Question 4

What are the enzymes in carbohydrate metabolism that are responsible for insulin secretion from pancreatic beta cells?

Answer 4

Glucokinase and PFK-1

weird question. basically, glycolysis regulating enzymes

Question 5

What happens to the rate of glycolysis during hypoxia?

What enzyme determines the rate of this state?

What regulates this? What hormones regulate it?

Answer 5

Increases

PFK-1 determines

PFK-2 upregulates PFK-1, and PFK-2 is regulated by insulin (stimulated) and glucagon (inhibited)

Question 6

Allosteric Activators and Inhibitors of PFK1:

Answer 6

Activators: AMP + Fructose 2,6 Bisphosphate (the most potent activator)

Inhibitors: ATP + Citrate

Question 7

What enzyme produces GTP in the TCA cycle?

Answer 7

Succinyl-CoA synthetase

(that name describes the reverse reaction to the normal order of the TCA cycle. the enzyme is also known as Succinate Thiokinase)

Question 8

Substrates, products, and coenzymes of Methylmalonyl CoA Racemase

Answer 8

Substrate: D-methylmalonyl-CoA

Product: L-methylmalonyl-CoA

don’t know about coenzymes

(racemases are also called epimerases bc they just convert between epimers)

Question 9

Substrate, product, coenzymes of Methylmalonyl CoA Mutase

Answer 9

Substrate: L-methylmalonyl-CoA

Product: Succinyl CoA (which can enter TCA cycle)

Coenzyme: Enzyme form of Vitamin B12 (deoxyadenosyl cobalamin)

Question 10

Substrates and Products of Pyruvate Dehydrogenase

Answer 10

Substrate: Pyruvate, S-CoA, NAD+

Product: Acetyl-CoA, CO2, NADH + H

Question 11

Which organs and tissues primarily use glucose from glycolysis for energy?
(I hope this is just worded badly and means which organs depend mostly on glucose for energy and not other substrates)

Answer 11

Red blood cells, testis, brain, adrenal medulla, cornea

Question 12

What organs will be affected by glycogen storage disease?

Answer 12

Liver, skeletal muscle

Question 13

Name an inhibitor of mitochondrial ATP synthase

Answer 13

Oligomycin

Question 14

Substrates, products, cofactors of IMP dehydrogenase

Answer 14

Substrate: IMP, H2O, NAD+

Product: Xanthosine Monophosphate, NADH + H

Don’t know cofactors

Question 15

What is the major protein for LDL?

Answer 15

B100

Question 16

Explain the monosaccharide bond between units of glycogen

Answer 16

Elongation: alpha 1-4 bonds
Branching: alpha 1-6 bonds

Question 17

Explain the monosaccharide unit and bond between them in sucrose:

Answer 17

Glucose: alpha 1 carbon

to Fructose: 2 beta carbon

Question 18

Explain the monosaccharide unit and bond between them in Lactose

Answer 18

Galactose: beta 1 carbon
Glucose: beta 4 carbon

Question 19

Position and configuration of the OH group in primary bile acids:

Answer 19

3 alpha, 7 alpha, 12 alpha

all are in alpha configuration

Question 20

Substrate, Product, and Coenzyme of Threonine Dehydratase:

Answer 20

Substrate: Threonine

Product: alpha ketobutyrate + ammonia

Cofactor: PLP

Question 21

Substrate, Product, Coenzyme of Glycogen phosphorylase:

Answer 21

Substrate: Glycogen, Pi

Product: Glucose 1-P

Coenzyme: not sure, but debranching enzyme and alpha 1,6 glucosidase are necessary to continue going

Question 22

Precursors of LDL? Via what enzyme?

Answer 22

LDL comes from IDL (and VLDL before that) via Hepatic Lipase

Question 23

How many ATP are produced in the TCA cycle?

Answer 23

3 NADH -> 9 ATP
1 FADH2 -> 2 ATP
1 GTP -> 1 ATP

So 12 per acetyl-CoA, 24 per glucose molecule

Question 24

What is the intermediate in FA synthesis? Prosthetic group?

Answer 24

Intermediate: Malonyl-ACP

Prosthetic Group: ACP (acyl carrier protein)

Question 25

What enzymes in FA synthesis reduce NADPH?

Answer 25

3 ketoacyl-ACP reductase

Enoyl Reductase

Question 26

Enzymes responsible for covalent modification of PDH:

Answer 26

Pyruvate Dehydrogenase Kinase: inhibits PDH

Pyruvate Dehydrogenase Phosphatase: activates/removes the inhibiting phosphates of PDH

Question 27

What is the cofactor of Complex I in oxidative phosphorylation?

Answer 27

NADH

Question 28

What does PP1 (protein phosphatase 1) do?

Answer 28

1. Removes phosphate from glycogen phosphorylase kinase (inhibition)
2. Removes phosphate from glycogen phosphorylase (inhibition)
3. Removes phosphate from glycogen synthase (activation)

Question 29

What does phosphoglucomutase do?

Answer 29

Converts 3-phosphoglycerate to 2-phosphoglycerate (reversible)

Question 30

What enzyme in glucose metabolism is located in the ER membrane?

Answer 30

Glucose 6 Phosphatase