Biochemistry Pathways

Question 1

RLE of glycolysis

Answer 1

step 3) phosphofructokinase-1

Question 2

enzymes of irreversible steps of glycolysis ‘thermodynamic barriers’

Answer 2

step 1) glucokinase / hexokinase
step 3) phosphofructokinase-1
step 9) pyruvate kinase

Question 3

irreversible steps of glycolysis

Answer 3

step 1) glucose –> glucose-6-phosphate
step 3) fructose-6-phosphate –> fructose-1-6-bisphosphate
step 9) Phosphoenolpyruvate –> pyruvate

Question 4

what step does fluride inhibit in glycolysis

Answer 4

step 8) 2-PG –> PEP
removes Mg2+ & causes irreversible inhibition of enzyme enolase

Question 5

what does Arsenate inhibit in glycolysis

Answer 5

stage 6) glyceraldehyde-3-P –> 1-3-bisphosphoglycerate
competes with PO4 for binding site on 1-3-BPG, no ATP produced

Question 6

what step of glycolysis uses NADH

Answer 6

step 5) glyceraldehyde-3-phosphate –> 1-3-bisphosphoglycerate
uses: 2 NAD+ –> 2 NADH

Question 7

what steps of glycolysis use (cost) ATP?

Answer 7

ATP –> ADP
step 1
step 3

Question 8

whats steps of glycolysis produce ATP?

Answer 8

ADP –> ATP
step 6) 1-3-bisphosphoglycerate –> 3-phosphoglycerate
step 9) PEP –> pyruvate

Question 9

what upregulates glycolysis?

Answer 9

insulin
ADP
AMP
Fructose-2-6-BP
Fructose-1-6-BP (at step 9)

Question 10

what downregulates glycolysis

Answer 10

ATP
citrate
glucagon
alanine (at step 9)
acetyl-COA (at atep 9)

Question 11

what gluconeogenesis enzymes differ from glycolysis?

Answer 11

(from top of glycolysis flowchart)
step 1) Glucose-6-phosphate
step 3) fructose-1-6-bisphosphate 1

Question 12

how much energy produced from glycolysis

Answer 12

2 ATP
2 NADH

Question 13

how much energy is produced from gluconeogenesis

Answer 13

4 ATP
2 GTP
2 NADH

Question 14

gluconeogenesis can also occur from oxaloacetate in the TCA cycle via what enzyme?

Answer 14

oxaloacetate (TCA) –> PEP (Gluconeogenesis)
enzyme: PEP carboxykinase

Question 15

in gluconeogenesis what co-factor does the enzyme require to convert pyruvate –> oxaloacetate

Answer 15

B7 (Biotin)
with pyruvate carboxylase
(occurs in mitochondria)

Question 16

what stages of TCA cycle require co-factors

Answer 16

B1, B2, 3B, B5, lipoic acid

step 1) pyruvate –> acetyl-CoA
enzyme: pyruvate dehydrogenase

step 6) a-ketoglutarate –> succinyl-CoA
enzyme: a-ketoglutarate dehydrogenase

Question 17

what step of gluconeogenesis uses GDP as phosphate donor

Answer 17

oxaloacetate –> PEP
(step 2)

Question 18

Pyruvate can be converted to ( ) or ( ) during intense exercise or starvation states & using which enzymes

Answer 18

cori cycle: lactate
lactate dehydrogense (LDH)
cahill cycle: alanine:
alanine transaminase (ALT)

Question 19

how much energey is produced by TCA cycle

Answer 19

2 cycles:
3 NADH (= 2.5 ATP)
1 FADH2 (= 1.5 ATP)
1 GTP per acetyl-CoA (= 1ATP)
2 Co2
….. 20 ATP

Question 20

what is the RLE of TCA cycle

Answer 20

isocitrate dehydrogenase
isocitrate –> a-ketoglutarate
step 4: (from pyruvate)

Question 21

what enzymes of TCA cycle use NADH

Answer 21

step 4) isocitrate dehydrogenase
isocitrate –> a-ketoglutarate
step 5) a-ketoglutarate dehydrogenase
a-ketoglutarate –>succinyl-CoA
step 9) malate dehydrogenase
malate –> oxaloacetate

Question 22

what step uses FADH2 in TCA cycle

Answer 22

step 7) succinate dehydrogenase
succinate –> fumerate

Question 23

what enzyme of TC cycle odes arsenite inhibit

Answer 23

step 1) pyruvate dehydrogenase
pyruvate –> acetyl-CoA

Question 24

what step of TCA uses GTP

Answer 24

step 6) succinate thiokinase
succinyl-CoA –> succinate

Question 25

what are the regulatory enzymes in TCA cycle

Answer 25

step 2) citrate synthase
step 4) isocitrate dehydrogenase (RLE)
step 5) a-ketoglutarate dehydrogenase