Biochemistry- Metabolism: Glycolysis, Krebs and ETC

Question 1

glycolysis starting and ending materials, products and reactants

Answer 1

Reactants: glucose, 2 ADP + 2 NAD+ + 2Pi-> 2 Pyruvate + 2 ATP + 2NADH + 2H+

Question 2

which step of glycolysis is rate limiting ? what enzyme is used?

Answer 2

step that produces fructose-1,6 bisphosphate , uses PFK enzyme

Question 3

How is PFK controlled by ATP/ADP levels?

Answer 3

activated by ADP, inhibited by ATP

Question 4

Steps of glycolysis ( main products only)

Answer 4

glucose -> G-6P -> F-6P -> F-1,6BP -> 2-triose phosphate (3GP) -> 1,3-BPG -> 3-PG - > 2 PG -> PEP - Pyruvate

Question 5

In which steps of glycolysis are byproducts formed

Answer 5

ATP-> ADP:
glucose-> G-6P :ATP->ADP
F-6P -> F-1,6BP: ATP->ADP

ADP-> ATP
1,3-BPG-> 3PG: ADP-> ATP
PEP-> Pyruvate: ADP->ATP

H2O
2-PG-> PEP : H2O out

NAD+ + Pi-> NADH + H-
2 triose phosphate (3GP)-> 1,3-BPG

Question 6

what happens to pyruvate formed from glycolysis in aerobic conditions?

Answer 6

2 pyruvate ( per 1 glucose) -> acetyl coA + 2 CO2- > Krebs cycle

Question 7

what happens to pyruvate in anaerobic conditions?

Answer 7

fermentation:
2 pyruvate + NADH -> 2lactic acid + NAD + via lactate dehydrogenase
forms 2 ATP and regenerates NAD+

Question 8

where does glycolysis occur?

Answer 8

in the cytosol

Question 9

Krebs cycle - where it occurs and how many turns of the cycle come from 1 molecule of glucose

Answer 9

occurs in the mitochondria, 2 turns of the cycle/ glucose

Question 10

overall reaction of krebs - reactants and products

Answer 10

acetyl coA + 3 NAD+ + 1 FAD + ADP + Pi-> 2 CO2 + 1 coA + 3 NADH + 3 H+ + 1 FADH2 + 1 GTP ( turns to ATP via substrate level phosphorylation)
cycle = 2 turns , numbers above = per 1 turn

Question 11

krebs cycle steps ( main products )

Answer 11

acetyl coA -> citrate -> isocitrate -> alpha-ketoglutarae -> succinyl coA-> succinate -> fumarate -> malate -> oxaloacetate , back to start of cycle

Question 12

other products formed from krebs- where they occurred

Answer 12

CO2 produced from isocitrate -> a-keotglutarate and a-ketoglutarate-> succinyl coA

NADH + H+ produced in same steps as CO2 , with an added one produced when malate-> oxaloacetate

GTP produced when succinyl coA-> succinate

FADH2 produced when succinate-> fumarate

Question 13

ETC 4 main complex names

Answer 13

iron-sulfur, cytochromes c, b , a and coenzyme Q

Question 14

where does NADH enter the ETC

Answer 14

through NAD specific dehydrogenase flavoproteins

Question 15

where do e- from FADH2 enter the ETC

Answer 15

directly at coenzyme Q

Question 16

how many molecules of ATP do FADH2 vs NADH produce?

Answer 16

NADH= 3 molecules of ATP
FADH2= 1 ATP

Question 17

what kind of gradient exists in the IMM for the ETC?

Answer 17

electrochemical

Question 18

what is the final e- acceptor at the end of the ETC?

Answer 18

oxygen , accepts e- from cytochrome A to produce H2O

Question 19

what is the realistic net yield of ATP aerobic respiration ?

Answer 19

30-32 ATP per molecule of glucose

Question 20

where does substrate level phosphorylation occur in krebs cycle?

Answer 20

in the krebs cycle, when GTP is made from GDP and Pi

Question 21

when does oxidative phosphorylation occur?

Answer 21

at the end of the ETC , when ATP is produced by coupling the flow of e- from NADH and FADH2 to O2

Question 22

what type of force drives the movement of H ions against their concentration gradients to create energy?

Answer 22

proton motive force

Question 23

where are the H+ ions in the ETC pumped to drive the proton electrochemical gradient?

Answer 23

from mitochondrial membrane into the intermembrane space

Question 24

which enzyme uses the electrochemical gradient to produce ATP?

Answer 24

ATP synthase

Question 25

when does substrate level phosphorylation occur in glycolysis?

Answer 25

in the production of pyruvate

Question 26

which coenzyme is the oxidizing agent in glycolysis?

Answer 26

NAD+