1. Glycolysis

Question 1

what is glycolysis

Answer 1

oxidation of 1 glucose to 2 pyruvate - catabolic/exergonic

Question 2

what 4 components does glycolysis require

Answer 2

1) 1 glucose
2) 2 ATP
3) 2 NAD+
4) 4 ADP

Question 3

what are the main products of glycolysis

Answer 3

1) 2 pyruvate
2) 4 ATP - net gain = 2 ATP
3) 2 NADH

Question 4

what are the 3 main regulatory steps in glycolysis

Answer 4

1 - glucose to glucose-6-P by HEXOKINASE (or glucokinase)

2 - fructose-6-P to fructose-1,6-bisP by PHOSPHOFRUCTOKINASE (main regulatory step)

3 - phosphoenolpyruvate to pyruvate by PYRUVATE KINASE

Question 5

what is the difference between hexokinase and glucokinase

Answer 5

hexokinase

• all tissues
• higher affinity to glucose: lower Km, always active
• regulated by product: inhibited by high [glucose-6-P]

glucokinase

• liver
• lower affinity to glucose: higher Km, only active after meal
• regulated by substrate availability: stimulated by high [glucose]

Question 6

how is phosphofructokinase regulated

Answer 6

allosterically in muscle:

• inhibited by high ATP
• stimulated by high AMP

hormonal regulation in liver:

• inhibited by glucagon
• stimulated by insulin

Question 7

how is pyruvate kinase regulated

Answer 7

• inhibited by glucagon

- stimulated by insulin

Question 8

name 2 important intermediates of glycolysis

Answer 8

1. DHAP

2. 2,3-BPG

Question 9

in which cells is DHAP produced and why

Answer 9

• adipose and liver
• DHAP is converted to glycerol phosphate via GLYCEROL 3-PHOSPHATE DEHYDROGENASE, which is used for:
  • phospholipid synthesis (polar head)
  • triacylglycerol synthesis (= glycerol phosphate + fatty acids)

Question 10

in which cells is 2,3-BPG produced and why

Answer 10

• RBCs

- regulation of haemoglobin O2 affinity (decreases affinity)

Question 11

how is NAD+ required for glycolysis regenerated in different tissues

Answer 11

• most tissues with O2 supply: via oxidative phosphorylation (NADH to NAD+ at ETC)
• but in RBCs (lack MT) and in reduced O2 conditions (eg muscle and gut): via lactate dehydrogenase

Question 12

which reaction does lactate dehydrogenase catalyse

Answer 12

pyruvate + NADH + H+ to lactate + NAD+

Question 13

what are the 2 fates of lactate

Answer 13

travels via blood to:

1- heart… converted back to pyruvate via lactate dehydrogenase… oxidised for energy production

2- liver/kidney… converted back to pyruvate via lactate dehydrogenase… converted to glucose via gluconeogenesis… returns to tissues