Biochemistry

Question 1

Regulation of Citrate Syntase

Answer 1

Positive Regulation By Citrate

Question 2

Regulation of Isocitrate Dehydrogenase

Answer 2

Positive by ADP and Ca2+

Negative by NADH

Question 3

Regulation of a-ketoglutarate Dehydrogenase

Answer 3

Positive by Ca2+

Negative by NADH

Question 4

Regulation of Malate Dehydrogenase

Answer 4

Negative by NADH

Question 5

What are precursors of Acetyl-CoA

Answer 5

Glucose (via pyruvate)
Alanine (via Pyruvate)
Ethanol
Ketone body (Acetate)
Fatty Acid (Palmitate)

Question 6

Why isn’t oxaloacetate a regulator?

Answer 6

The equilibrium between oxaloacetate and malate favors malate so at any time there is only a small amount of oxaloacetate available

Question 7

How is PDH inhibited?

Answer 7

PDC Kinase phosphorylates a serine residue on E1 in response to Acetyl Coa, and NADH
PDC Phosphotase hydrolyses this phosphate to activate it in response to ADP and pyruvate and Calcium

Question 8

What TCA cycle intermediates are used in biosynthesis

Answer 8

Citrate - Fatty Acid Synthesis
a-Ketoglutarate - AA synthesis, GABA
Succinyl CoA - Heme
Malate - Gluconeogenesis
Oxaloacetate - AA synthesis

Question 9

What does pyruvate carboxylase do?

Answer 9

Catalyzes addition of CO2 to Pyruvate to make oxaloacetate in anapleurotic reaction

Requires biotin, activated by acetyl-coa

Question 10

What is E1

Answer 10

Pyruvate Carboxylase
Requires TPP
Carboxylates Pyruvate to form covalent intermediate

Question 11

What is E2

Answer 11

Transacylase
Requires Lipoic Acid (SS bond)
Grabs acyl group and transfers it onto CoASH, Subsequently reduces FAD on E3

Question 12

What is E3

Answer 12

Dihydrolipoyl Dehydrogenase
Requires FAD and NAD
FAD is reduced to FADH2 and subsequently reduces NAD to NADH

Question 13

What is riboflavin a precursor to?

Answer 13

Vitamin B3

Precursor to FAD and FMN

Question 14

What is Niacin?

Answer 14

Precursor to NAD

Question 15

What is Thiamine?

Answer 15

Vitamin B1
Necessary for TPP
Can easily become deficient in alcoholics and the malnourished

Question 16

What is pantothenic acid?

Answer 16

Precursor to CoA

Widely distributed in foods

Question 17

What regulates Hexokinase?

Answer 17

Glucose 6 P

Question 18

What regulates PFK-1

Answer 18

F26BP, AMP are positive

H+, Citrate, and ATP are negative

Question 19

What conditions cause lactic acidosis

Answer 19

Circulatory insufficiency
Anemia
Mitochondrial enzyme defects
Poisons
Cancer
Ethanol Intoxication
Hepatic Failure

Question 20

What transporters don’t exist

Answer 20

oxaloacetate
NAD/NADH
AcCoA

Question 21

What carriers do exist?

Answer 21

Malate
Aspartate
Glutamate
Pyruvate
A-Ketoglutarate

Question 22

Where is the glycerol phosphate shuttle?

Answer 22

Most tissues

Question 23

Where is the malate aspartate shuttle?

Answer 23

Mainly liver, kidney, and heart

Question 24

What is the malate aspartate shuttle?

Answer 24

Requires transaminase reaction of aspartate to aketoglutarate and oxaloacetate to malate
Oxaloacetate reduced to malate in cytosol which is transported and reduces NAD in the IMM to NADH for the ETC
Oxaloacetate inside is transaminated to aspartate which is shuttled out and transaminated back to oxaloacetate
Transamination also converts glutamate ot akg on inside and back outside

Question 25

What cells produced lactate?

Answer 25

RBC

Working Muscle

Question 26

What cells use lactate?

Answer 26

Liver
Resting muscle
Heart

Question 27

What tissues are dependent on anaerobic glycolysis?

Answer 27

Red cells
White cells
Lens of eye
Kidney medulla
Exercising muscle

Question 28

Describe the cori cycle

Answer 28

Liver uses 2lactate and 6 ATP to create glucose which goes to the RBC and undergoes glycolysis to create 2lactate and 2 ATP which cycle back to the liver