HMP pathway

Question 1

HMP pathway occur in ……..

Answer 1

cytoplasm

Question 2

(in HMP pathway) ……. ATP is directly consumed or produced.

Answer 2

no ATP

Question 3

(in HMP pathway) oxidation of glucose is direct at …………& produce ……..

Answer 3

carbon 1,3 without cleavage
NADH+H

Question 4

(in HMP pathway )
glucose6-p is decarboxylated at ……..to produce ……

Answer 4

C1
P-pentose

Question 5

(in HMP pathway )
oxidative phase is ………but non oxidative phase is ………..

Answer 5

irreversible
reversible

Question 6

( in HMP pathway )
to enter non-oxidative phase we start with ……………..

Answer 6

3 molecule of ribulose-5P

Question 7

list fate of products of non-oxidative phase (in HMP pathway)

Answer 7

1. if energy is needed :
   the glycolytic intermediates “ fructose6-p & glyceraldhyde3-p “continue glycolysis to produce energy.
2. if there is enough energy :
   the glycolytic intermediates regenerate glucose by gluconeogenesis

Question 8

NADPH-dependent FA synthesis in ………

Answer 8

liver, lactating mammary glands & adipose tissue

Question 9

NADPH- dependent steroids synthesis in ……

Answer 9

testes , ovaries , placenta & adrenal cortex

Question 10

NADPH-dependent glutathione reductase in ……………….

Answer 10

erythrocytes

Question 11

in HMP pathway , the rate limiting enzyme is ………..

Answer 11

G6PD

Question 12

illustrate the regulation of HMP pathway

Answer 12

1. availability of NAD :
   accumulation of NADPH allosterically inhibits G6PD.
2. insulin:
   induce G6PD in well fed state
   * at level of non-oxidative :
   - cell need both NADPH+H & P-pentose = perform oxidative phase only
   - cell need NADH+H > P-pentose as in RBCs & fatty acids synthesis in adipose tissue = perform both oxidative & non-oxidative phase to give glycolytic intermediates
   - cell need P-pentose > NADPH+H = perform the reverse of non-oxidative phase as in muscle which lack G6PD enzyme

Question 13

list the importance of HMP pathway

Answer 13

1. synthesis of P-pentose
2. synthesis of reduced coenzyme NADH+H

Question 14

list chc of P-pentose synthesis

Answer 14

1. no pentokinase in our cells
2. P-pentose enter in synthesis of nucleotides
3. important in rapidly dividing tissues as BM
4. DNA, RNA , ATP , NAD , NADP &cAMP

Question 15

what’s the importance of NADH+H ?

Answer 15

1. used in synthetic reductive pathway as :
   FA synthesis , cholesterol , vit D3 & sex H
2. essential for integrity of RBCs membrane:
   - detoxicate H2O2 in RBCs = dec hemolysis
   - NADPH+H is important to keep ferrous iron of Hb in its reduced form to prevent accumulation of met Hb
3. eye lens : maximum con. in lens preserves its transparency
4. bactericidal effect :
   MQ produce superoxide radical during killing the bacteria , “ respiratory burst “
5. synthesis of NO
   - endothelium derived relaxing factor (VD)
   - prevent platelet aggregation & neurotransmitter
6. essential for hydroxylation reaction in liver by enzyme cytochrome P450 heme-monooxygenase for detoxification of toxins

Question 16

list cause of defective transketolase

Answer 16

• deficiency of thiamine pyrophosphate
• defective binding between transketolase & Tpp ( thiamine pyrophosphate)

Question 17

what’s the clinical picture of defective transketolase?

Answer 17

• neuropsychiatric disorder “ Wernicke Korsakoff syndrome”:
  paralysis of eye movement
  ataxia “abnormal gait “
  defective mental ability

Question 18

list cause of G6PD deficiency (favism)

Answer 18

1. X-linked , affect mainly males
2. deficiency of G6PD = dec NADH+H :
   - inability to detoxicate H2O2 in RBCs lead to oxidation of membrane proteins , hemolysis
   - maintain the reduced state of Hb-SH group

Question 19

list clinical picture of favism.

Answer 19

1. Heinz body :
   oxidation of Hb-HS group form denaturated insoluble mass attach to cell membrane
2. oxidation of membrane proteins make RBCs to be rigid (less deformable) & removed by spleen, liver
3. dec Hb level , hemolytic anemia, jaundice and black urine

Question 20

what’s the precipitating factor ofG6PD deficiency symptoms ?

Answer 20

1. fava beans
2. antipyretic, antibiotic as sulfa & anti malarial drugs.
3. infection “ free radical formed in WBCs can diffuse to RBCs “

Question 21

list ttt of favism

Answer 21

1. avoid this food & drug
2. transfusion of packed RBCs
3. intake of antioxidant as vit C , E , A