L10-11 biochem

Question 1

________ is the precursor for the synthesis of:

• fatty acids
• cholesterol
• ketone bodies
• steroids
• acetyl choline

Answer 1

Acetyl coA

Question 2

three processes play a central role in aerobic metabolism:
1- _________
2-_________
3-_________

Answer 2

1- Citric acid cycle
2-electron transport
3-oxidative carboxylation

Question 3

the _______ is amphibolic; that is, it plays a role in both catabolism and anabolism

Answer 3

Citric acid cycle

Question 4

• final common pathway for the oxidation of carbohydrates, amino acids, FA to CO2 and H2O (or Acetyl CoA)
• this oxidation provides energy for the production of the majority of ATP
• occurs in mitochondria (near ETC)
• aerobic pathway

Answer 4

TCA cycle/ Krebs cycle/ citric acid cycle

Question 5

• bi functional enzyme (oxidation, decarboxylation)
• allosteric enzyme, inhibited by ATP and NADH, activated by ADP and NAD+ (a low energy signal) and Ca+2

Answer 5

Isocitrate dehydrogenase

Question 6

the ONLY TCA enzyme that is located in the inner mitochondrial membrane and linked directly to ETC

Answer 6

Succinate dehydrogenase (complex2)

Question 7

TCA cycle results in \_\_ NADH, \_\_ FADH, \_\_ GTP
NADH is gained in those reactions:
1- isocitrate dehydrogenase
2-α-ketoglutarate dehydrogenase
3-malate dehydrogenase

Answer 7

3 NADH, 1 FADH, 1 GTP

Question 8

in citric acid cycle, the substrate-level phosphorylation reaction is catalyzed by ______ releasing GTP

Answer 8

Succinyl-CoA synthase

Question 9

Inhibition of TCA
1-Aconitase inhibited by ______
2-α-ketoglutarate inhibited by ______
3- succinate dehydrogenase inhibited by ______

Answer 9

1- Fluoroacetate (non-competitive)
2- Arsenite (non-competitive)
3- Malonate (competitive)

Question 10

how many ATP molecules is generated from one turn of citric acid cycle?

Answer 10

12 ATP

Question 11

how many ATP molecules are generated by one glucose molecule under aerobic conditions?

Answer 11

38 ATP

Question 12

TCA cycle regulation:

A. by activation/inhibition of enzymes
a1) most important regulated enzymes are _______, _______, and _______

B.by availability of ADP
b1)effects of _____ ADP will lead to acceleration in Krebs cycle.

Answer 12

a1) Citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase complex.
- -
b1) elevated

Question 13

A key anaplerotic reaction is catalyzed by pyruvate carboxylase which carboxylates pyruvate forming _______

Answer 13

OAA (oxaloacetate)

Question 14

roles of Vitamins in TCA cycle:
1- ____: a cofactor for succinate dehydrogenase in the form of FAD
2-____: electron acceptor, in the form of NAD
3-____: as thiamine pyrophosphate, coenzyme in α-ketoglutarate dehydrogenase reaction
4-____: as part of coenzyme A such as acetyl-CoA and succinyl-CoA
5-____: in CO2 fixation reaction to compensate oxaloacetate concentration

Answer 14

1- riboflavin
2- niacin
3- thiamine (vitamin B12)
4- pantothenic acid
5- Biotin

Question 15

• fumarase catalyzes the reversible hydration/dehydration of fumarate to malate
• Fumarase deficiency is an _____ _____ metabolic disorder, that will lead to mental retardation and autism.

Answer 15

Autosomal recessive

Question 16

congenital deficiency of pyruvate complex leads to _______

Answer 16

lactic acidosis