Glucose Oxidation & Shuttles

Question 1

Mention the three principal phases of cellular respiration

Answer 1

1. Oxidation of fuels
2. Conversion of energy from fuel oxidation into high energy phosphate bond
3. Utilization of high phosphate bond energy

Question 2

The convergent product of oxidation of most fuels

Answer 2

Acetyl CoA

Question 3

Complete oxidation of acetyl CoA occurs in …… and produces ….&….

Answer 3

Tricarboxylic acid cycle

NADH & FADH2

Question 4

Define the electron transport chain

Answer 4

A process in which electrons are transferred from NADH and FADH2 to O2.

Question 5

Enumerate processes requiring ATP

Answer 5

Muscle contraction, maintaing intracellular Na concentration, anabolic pathways & detoxification.

Question 6

The ETC occurs in ….., while …..&….. occur in mitochondrial matrix.

Answer 6

Inner mitochondrial membrane

TCA & oxidation of fatty acids

Question 7

Compare aerobic & anaerobic glycolysis fate of NADH & pyruvate

Answer 7

A: NADH reoxidized in ETC, pyruvate completely oxidized in TCA cycle.
An: NADH reoxidised by conversion of pyruvate to lactate.

Question 8

Examples of anaerobic glycolysis

Answer 8

In RBCs , kidney medulla & exercising muscle

Question 9

NADH is indirectly transferred to inside the mitochondria by …..

Answer 9

Shuttle mechanism (malatae aspartate shuttle & glycerophosphate shuttle)

Question 10

Describe the steps of malate shuttle

Answer 10

Electrons from NADH convert oxaloacetate to malate by cytosolic malate dehydrogenase.
Malate crosses the inner mitochondrial membrane by special translocase.
Electrons of malate reform NADH, and oxaloacetate is reformed (by mitochondrial malate dehydrogenase) which is converted by AST to aspartate which is transported out by aspartate/glutamate exchange translocase.

Question 11

The major shuttle is

Answer 11

Glycerol phosphate shuttle

Question 12

Describe the mechanism of glycerol phosphate shuttle

Answer 12

Cytoplasmic Glycerol 3-phosphate dehydrogenase uses electrons from NADH to convert DHAP to GAP which diffuses to mitochondria then its electrons are donated to give FADH2 (gives 2 ATP in ETC)

Question 13

PDC reaction is one of

Answer 13

Oxidative decarboxylation

Question 14

Mention the 3 enzymes of PDC

Answer 14

Pyruvate dehydrogenase, dihydrolipoyl transacetylase & dihdrolipoyl dehydrogenase

Question 15

Mention the coenzymes of PDC

Answer 15

Thiamin pyrophosphate, lipoic acid, CoASH, FAD and NAD+.

Question 16

…….. inhibits pyruvate dehydrogenase while ….. activates it. (Covalent modification)

Answer 16

Phosphorylation

Dephosphorylation

Question 17

PDC kinase is inhibited by ….&…., while it is activated by ….&…… .

Answer 17

ADP & pyruvate

Acetyl CoA & NADH

Question 18

Mention the regulation of PDC phosphatase in the heart

Answer 18

Calcium is required for its activity
Increased mitochondrial Ca++ during rapid contraction activates the phosphatase, thereby increasing the amount of active PDC.

Question 19

Describe the hormonal regulation of PDC

Answer 19

Insulin favor the active, dephosphorylated form, while glucagon favors the phosphorylated, inactive form.

Question 20

Mention the fates of pyruvate

Answer 20

Converted to: alanine, lactate, acetyl CoA, oxaloacetate.

Question 21

…..&…. Are irreversible enzyme acting on pyruvate, while ….&…. Are reversible

Answer 21

Pyruvate carboxylase, PDC

LDH, transamination

Question 22

Dietary deficiency of thiamin pyrophosphate results in the following diseases:

Answer 22

Beriberi

Wernicke-Korsakoff syndrome

Question 23

Alcohol addiction result in deficiency of ….

Answer 23

Thiamin pyrophosphate

Question 24

…. Inhibits lipoic acid containing enzymes such as …..&….. .

Answer 24

Arsenite

PDC & alpha-ketoglutarate dehydrogenase complex

Question 25

Abnormalities in the PDC lead to accumulation of ….

Answer 25

Lactate