carbohydrate metabolism 3 WF

Question 1

glycolytic pathway?

Answer 1

glucose-6-P -> fructose-6-P -> fructose-1,6-bisP -> (dihydroxy-acetone-P) -> glyceraldehyde-3-P -> oxidised to produce 2ATP and reduces NAD+ to NADH. produces pyruvate.

Question 2

glycogen -> pyruvate ATP consumption/production?

Answer 2

consumes 1ATP
produces 4ATP
net balance is 3ATP per glucose

Question 3

glucose -> pyruvate ATP consumption/production?

Answer 3

consumes 2ATP
produces 4ATP
net balance is 2ATP per glucose

Question 4

how is pyruvate reduced to lactate

Answer 4

with reoxidation of reduced NADH to NAD+

Question 5

only source of ATP in red blood cells?

Answer 5

anaerobic respiration

Question 6

name for reverse of glycolytic pathway?

Answer 6

gluconeogenesis

Question 7

where does gluconeogenesis occur

Answer 7

liver and kidney

Question 8

precursors of glucose

Answer 8

lactate (from anaerobic metabolism)
glycerol
glucogenic amino acids (protein degradation)

Question 9

can Acetyl-CoA be converted to glucose?

Answer 9

NO!

Question 10

pentose phosphate pathway occurs in which tissues?

Answer 10

liver, adipose tissue, mamillary gland

Question 11

pentose-phosphate pathway oxidation reactions - products and stuff

Answer 11

G-6-P -> ribulose-5-phosphate
with product of CO2 and 2 molecules of NADPH

Question 12

products of ribulose-5-phosphate and their functions?

Answer 12

ribose 5-P used for DNA/RNA synthesis

xylulose 5-P

Question 13

anti-oxidant function of glutathione?

Answer 13

oxygen can react with peptides (especially in RBCs) to produce peroxides (bad)

glutathione reduces peroxides and the glutathione is oxidised to a disulphide which is reduced back to glutathione by reduced NADP

Question 14

most common genetic disorder in humans? features?

Answer 14

G6PDH deficiency
low activity, red blood cells undergo haemolysis. can be exacerbated by drugs.

Question 15

metabolism of fructose?

Answer 15

fructose comes from metabolism of sucrose.
phosphorylated by fructokinase

Question 16

deficiency of F-1-P aldolase features? (enzyme in fructose metabolism)

Answer 16

build-up of fructose-1-P
results in fructose intolerance
consequences are inhibition of glycogen breakdown, gluconeogenesis, oxidative phosphorylation.
-> hypoglycaemia, lactic acidaemia

Question 17

metabolism of galactose?

Answer 17

metabolised in liver by galactokinase.
converted to glucose-1-P

Question 18

deficiency of galactose metabolism enzymes causes what?

Answer 18

Galactosaemia
galactose-1-P accumulates in liver causing hepatomegaly, jaundice, swelling of eyes, cataracts etc

Question 19

alcohol metabolism features?

Answer 19

absorbed in stomach
most important oxidation is alcohol dehydrogenase pathway

Question 20

alcohol dehydrogenase pathway summarised?

Answer 20

ethanol oxidised to acetyl-CoA

Question 21

mutation in alcohol oxidation pathway?

Answer 21

isoform of aldehyde dehydrogenase in mitochondria with low Km value.

build-up of ethanal, side effects of nausea etc - alcohol intolerance

Question 22

drugs for alcohol addiction? mechanism?

Answer 22

disulfiram/Antabuse
inhibits aldehyde dehydrogenase leading to unpleasant symptoms

Question 23

metabolism of toxic alcohols?

Answer 23

alcohol dehydrogenase metabolises methanol or ethylene glycol (anti-freeze) to toxic substances

Question 24

inhibition of alcohol dehydrogenase for toxic alcohol ingestion?

Answer 24

ethanol (competitive substrate) or fomepizole (inhibitor)