Krebs Cycle

Question 1

GR: the naming of TCA cycle.

Answer 1

Due to involvement of tricarboxylates (citrate & isocitrate)

Question 2

The percentage of energy of TCA cycle

Answer 2

Two thirds

Question 3

The final products of TCA cycle

Answer 3

3 NADH, 1 FADH2 , 1 GTP

Question 4

Mention the reactants & products of citrate synthase reaction

Answer 4

R: acetyl CoA, oxaloacetate
P: citrate

Question 5

Mention the type of reaction of isocitrate dehydragenase & its products

Answer 5

Oxudation & decarboxylation

Alpha-ketoglutarate, CO2, NADH

Question 6

The action of aconitase

Answer 6

Citrate to isocitrate

Question 7

Mention the components of alpha-ketoglutarate dehydrogenase complex

Answer 7

3 enzymes: ketoglutarate dehydrogenase, dihydrolipoyl transacetylase, dihydrolipoyl dehydrogenase.
3 coenzymes: TPP, CoASH, NAD, FAD, lipoic acid.

Question 8

Mention the products of alpha-ketoglutarate enzyme complex

Answer 8

CO2, NADH, succinyl CoA

Question 9

Alpha-ketoglutarate is inhibited by

Answer 9

Arsenite

Question 10

The only enzyme in TCA which uses substrate level phosphorylation

Answer 10

Succinate thiokinase

Question 11

Mention the products of succinate dehydrogenase reaction

Answer 11

Fumarate & FADH2

Question 12

Succinate dehydrogeanse is inhibited by

Answer 12

Maolnate

Question 13

Mention the R & P of fumarase

Answer 13

Fumarate, malate

Question 14

Mention the products of malate dehydrogenase reaction

Answer 14

Oxaloacetate & NADH

Question 15

Describe the energy yield of complete oxidation of glucose

Answer 15

1. 6-8 from aerobic glycolysis
2. 6 ATP from oxidative decarboxykation of 2 pyruvates
3. 24 from Krebs cycle

Question 16

Mention vitamins required for TCA cycle

Answer 16

Niacin, riboflavin, thiamin, pantothenic acid

Question 17

Mention factors of coarse control of TCA cycle

Answer 17

Oxygen

Concentration of ADP

Question 18

Mention enzymes activated by Ca++

Answer 18

Citrate synthase, isocitrate dehydrogenase, alpha-ketoglutarate dehydroagenase

Question 19

The dehydrogenases of TCA cycle are activated by

Answer 19

High ADP/ATP, Hight NAD/NADH

Question 20

Citrate synthase is allosterically inhibted by

Answer 20

ATP, long chain fatty acyl CoA & citrate

Question 21

Mention anabolic reaction involving TCA

Answer 21

Heme synthesis, fatty acid synthesis, gluconeogenesis, transamination.

Question 22

Mention role of TCA in lipogenesis

Answer 22

High carbohydrate meal leads to citrate efflux and cleavage into acetyl units for cytosolic fatty acid synthesis

Question 23

Role of TCA in fasting

Answer 23

Gluconeogenic precursors are converted to malate which leaves the mitochondria for cytosolic part of gluconeogenesis.

Question 24

Mention role of TCA in AA syntehsis

Answer 24

Alpha-ketoglutarate is converted to glutamate

Oxaliacetate is converted to aspartate

Question 25

Tye only enzyme of TCA found in inner mitochondrial membrane

Answer 25

Succinate dehydrogenase

Question 26

Define anapkerotic reactions

Answer 26

Pathways or reactions that replenish intermediates of the TCA cycle.

Question 27

Mention an example of anaplerotic enzyne & its action

Answer 27

Pyruvate carboxylase | Adds CO2 to pyruvate forming oxaloacetate

Question 28

Coenzymes/factors of pyruvate carboxylase are ……., it is activated by …… .

Answer 28

Biotin & ATP | Acetyl CoA

Question 29

Mention the molecular bases of cystic fibrosis

Answer 29

Deletion of codon of phenylalanine in the gene of CFTR protein

Question 30

The action of CFTR & result of its loss

Answer 30

Chloride channel | Production of thick, sticky secretions in the lung & pancreas

Question 31

C/P of cystic fibrosis

Answer 31

It affects the lungs where thick mucus builds up causing repeated chest infections and breathing difficulties and the pancreas where blockages cause digestive problems

Question 32

Alpha1-antitrypsin is synthesized by

Answer 32

Liver, alveolar monocytes & macrophages

Question 33

Describe the pathogenesis & C/P of alpha1-antitrypsin deficiency

Answer 33

Its configuration is altered leading to prevention of its release from hepatocytes so serum levels are decreased leading to loss of protection against proteases such as neutrophils elastase. This leads to destruction of alveolar walls & causes emphysema.

Question 34

Mention the effects of smoking on alpha1-antitrypsin

Answer 34

Causes oxidation & subsequent inactivation of methionine in alpha1-antitrypsin (Methionine 358 in alpha1-antitrypsin is required for binding of alpha1-antitrypsin to its target elastase).