glycolysis

Question 1

what is the overall equation for glycolysis?

Answer 1

glucose + 2Pi (fr ATP) + 2ADP + 2NAD+ → 2pyruvate + 2ATP + 2NADH+ H2O + 2H+

Question 2

what are the functions of glycolysis? (3)

Answer 2

1. generate ATP without the need for oxygen
2. provide substrates for further oxidation & ATP generation
3. provide intermediates for biosynthesis & regulation

Question 3

where does glycolysis take place? (cell + organelle)

Answer 3

cytoplasm, all cells!!

Question 4

explain which enzymes are upregulated in the presence of insulin (2)

Answer 4

high glucose/fed→ insulin release→

• upregulate PFK2→ increased fructose 2,6 biphosphate→ upregulate PFK1
• upregulate PK

→upregulate glycolysis

Question 5

explain which enzymes are inhibited by glucagon (2)

Answer 5

low glucose/fasting→ increased glucagon→

• inhibit PFK2→ PFK1
• inhibit PK

→ downregulate glycolysis (so glucose can be used for more impt function)

Question 6

explain which enzymes are inhibited by ATP or citrate

Answer 6

high energy state→ ATP/citrate→ don’t need so much ATP

• inhibit PFK1
• inhibit PK

→ downregulate glycolysis

Question 7

explain which enzymes are upregulated by AMP

Answer 7

low energy state→ ATP converted to ADP→ AMP (ADP + ADP)

• upregulate PFK1
• upregulate PK

→ upregulate glycolysis→ generate more ATP

Question 8

explain the pathophysiology of pyruvate kinase deficiency + compensatory mechanisms (2)

Answer 8

fall in ATP→ affects cell integrity→ hemolysis→ decreased O2 delivery

compensation:
1. increased PK synthesis in liver
2. increase 2,3-BPG in RBCs to increase O2 delivery to tissues (no DNA to make more PK or mitochondria to make more ATP)

Question 9

what sugars can enter glycolysis? (2)

Answer 9

1. fructose
2. galactose

Question 10

explain how fructose enters glycolysis

Answer 10

fructose→(fructokinase)→ fructose-1-phosphate →(aldolase B)→→ G3P

Question 11

explain how galactose enters glycolysis

Answer 11

galactose→ [galactokinase]→ galactose-1-P (+UDP glucose)→ [G1P uridyltransferase]→ glucose-1-p (+UDP-galactose)→→ glucose-6-p

UDP glucose & UDP-galactose are isomers
UDP-galactose→ UDP glucose→ glycogen synthesis!

Question 12

what is fructosuria?

Answer 12

fructokinase deficiency→ fructose doesn’t break down→ accumulates and gets cleared fr urine

Question 13

what is the pathophysiology of fructose intolerance?

Answer 13

aldolase B deficiency→ accumulation of F1P→ depletes phosphate required for glycolysis (F1P metabolism uses P) + decreases fructose entering glycolysis→ ATP depletion

Question 14

what is galactosemia?

Answer 14

G1P uridyltransferase deficiency→ accumulation of G1P→ TOXIC!!→ cataract

Question 15

explain how NAD+ can be regenerated under anaerobic conditions

Answer 15

pyruvate→ [lactate dehydrogenase]→ lactate

lactate dehydrogenase converts NADH→ NAD+

Question 16

explain how NAD+ can be regenerated under aerobic conditions

Answer 16

oxphos in mitchondria

Question 17

what are the possible pathways of pyruvate? (5)

Answer 17

1. pyruvate ↔ glucose (glycolysis/gluconeogenesis)
2. pyruvate ↔ [LDH] ↔ lactic acid
3. pyruvate → [PDH] → aceytl CoA (→TCA cycle)
4. pyruvate → [PC] → oxaloacetate (→ TCA cycle or gluconeogenesis)
5. pyruvate ↔ [ALT] ↔ alanine (cahill cycle)