G6PDH deficiency

Question 1

the pentose phosphate pathway starts from

Answer 1

Glucose- 6 Phosphate

Question 2

the PPP is an important source of NADPH required for

Answer 2

• reducing power for biosynthesis
• maintenance of GSH levels
• detoxification reactions

Question 3

PPP produceds

Answer 3

C5- sugar ribose

Question 4

ribose is required for

Answer 4

nucleotides

DNA & RNA

Question 5

rate limiting enzyme of PPP

Answer 5

glucose- 6- phosphate dehydrogenase (G6PDH)

Question 6

Why does depletion of NADPH lead to compromised defences against oxidative damage?

Answer 6

Key cellular defence mechanisms against oxidative damage require NADPH for function:

• glutathione (GSH) reductase
• catalase
• thioltransferase system

Question 7

glutathione reductase

Answer 7

glutathione reductase uses NADPH as electron donor

Question 8

catalase

Answer 8

NADPH is a structural component of catalase

Question 9

glutathione is a

Answer 9

tripeptide synthesised by body to protect agaisnt oxidative damage

Question 10

how does GSH need NADPH

Answer 10

1) Thiol group of Cys (on GSH) donates e- to ROS
2) GSH then reacts with another GSH to form disulphide (GSSG)
3) GSSG reduced back to GSH by glutathione reductese which catalyses the transfer of electrons from NADPH to disulphide bone

Question 11

PPP therefore essential

Answer 11

in protecting against free radocal damage

Question 12

outline how G6PDH deficiency makes an individual vulnerable to oxidative damage

Answer 12

1) decreased G6PDH activity limits the amount of NADPH
2) NADPH required for reduction of oxidised glutathione (GSSG) back to reduced glutathione (GSH)
3) lower GSH means less protection against damage from oxidative stress

Question 13

what can cause oxidative stress

Answer 13

infection
drugs (anti-malarials)
broad beans

Question 14

symptoms and signs of G6PDH deficiency

Answer 14

• anaemia
• jaundice
• dark urine
• heinz bodies

Question 15

G6PDH deficiency and anaemia

Answer 15

decreased Hb conc due to increase protein damage and lipid peroxidation causing haemolysis

• increase in bilirubin cause jaundice
• increase reticulocyte count due to increased RBC production to keep Hb up

Question 16

G6PDH deficiency and jaundice

Answer 16

bilirubin is the yellow by-product of RBC breakdown produced from metabolism of the haem group of haemoglobin

• normally excreted in bile and urine

Question 17

jaundice is caused by

Answer 17

high bilirubin levels

Question 18

heinz bodies

Answer 18

• dark staining within RBC resulting from precipitated haemoglobin
• bind to cell membrane altering rigidity
• increased mechanical stress when cells squeeze through small capillaries
• spleen removes bound Heinz bodies resulting in blister cells