Glycolysis #2

Question 1

What are the different fates of pyruvate?

Answer 1

1. complete oxidation of pyruvate to CO2 in the Krebs cycle

2. conversion to lactate (anaerobic conditions)

Question 2

Triglycerides + glycolysis

Answer 2

~ triglycerides can be hydrolysed to form glycerol
~ glycerol can be converted into DHAP
~ DHAP is added to the glycolysis pathway in step 5

Question 3

Glycolysis is… (energetics)

Answer 3

overall exergonic = favoured
~ glucose –> pyruvate = exergonic
~ ADP + Pi –> ATP +H2O = endergonic

Question 4

Which are the regulated/irreversible steps in glycolysis?

Answer 4

step 1: glucose –> glucose-6-phosphate
- hexokinase
step 3: fructose-6-phosphate –> fructose -1,6-bisphosphate
- phosphofructokinase
step 10: phospho,enol,pyruvate (PEP) –> pyruvate
- pyruvate kinase

Question 5

Regulation of phosphofructokinase (PFK) - activity (glycolysis)

Answer 5

~ step 3
increases activity = AMP + fructose-2,6-bisphosphate
decreases activity = ATP, NADH, H+, citrate or long chain fatty acids
~ first committed step

Question 6

PFK + ATP

Answer 6

PFK = phosphofructokinase
~ ATP lowers affinity of PFK for F-6-P
~ binds to regulatory site

Question 7

PFK + fructose -2,6-bisphosphate

Answer 7

PFK = phosphofructokinase
~ increases affinity for F-6-P
~ decreases effect of ATP
~ increased F-6-P lvls = increase in F-2,6-BP lvls

Question 8

PFK regulation in muscles

Answer 8

~ primary control = AMP:ATP ratio
~ AMP reverse effects of ATP
~ pH falls during exercise = lactic acid = increased H+ = PFK inhibition = prevents acid damage

Question 9

PFK regulation in the liver

Answer 9

~ inhibition by citrate and ATP

~ activation by F-2,6-BP - lvls rise with blood glucose

Question 10

Regulation of hexokinase

Answer 10

~ step 1
~ inhibited by G6P = product inhibition
Function:
~ allows cell to maintain sufficient lvls of G6P
~ allows glucose in blood to be available for glucokinase (lower affinity + not G6P inhibited)

Question 11

Regulation of pyruvate kinase (glycolysis)

Answer 11

~ step 10
increased activity: PEP and F-1,6-BP
decreased activity: ATP, citrate, long-chain fatty acids + alanine

Question 12

Types of pyruvate kinase + regulation

Answer 12

M (muscle) form = allosteric regulation by ATP, PEP and F-1,6-BP
L (liver) form = allosteric regulation by ATP, PEP and F-1,6-BP AND controlled by phosphhorylation