Krebs cycle

Question 1

where does the Krebs cycle occur?

Answer 1

in the mitochondrial matrix

Question 2

is the Krebs cycle aerobic or anaerobic?

Answer 2

aerobic, NAD+ is reduced into NADH USING oxygen

Question 3

what do we have left after glycolysis

Answer 3

• 4 atp
• 2 nadh
• 2 pyruvate (3c)

(small yield of glucose)

Question 4

what happens in Krebs cycle

Answer 4

• the final breakdown of glucose
• produces co2

Question 5

transition reaction

Answer 5

• pyruvate is oxidized (3C to 2C)
• NAD is converted to NADH
• CO2 is removed and Co-A is added

Question 6

1)

Answer 6

acetyl CoA adds its 2C to oxyloacetate (4C) to produce citrate (6C)

Question 7

2)

Answer 7

• Citrate converted to IsoCitrate catalyzed by enzyme aconite
• removal & addition of H2O from citrate molecule

Question 8

3)

Answer 8

• isocitrate is converted into a-ketoglutarate in a reaction catalyzed by isocitrate dehydrogenase

Question 9

4)

Answer 9

• isocitrate is oxidized: NAD+ is reduced to NADH
• carboxyl group (COO-) is removed and exits as CO2
• 6C to 5C alpha-ketoglutarate

Question 10

5)

Answer 10

• a-ketogulutrate is oxidized and NAD+ is reduced to NADH
• again COO- is removed as cO2
• CoA is re-attached
• 5C to 4C succinyl CoA

Question 11

6)

Answer 11

• CoA is replaced by a PO4 group
• Succinyl-CoA (4C) — succinate (4C)
• PO4 group passed to GDP -> GTP
• GTP is then transformed into ATP
• for prokaryotes & plants, ATP is made directly

Question 12

7)

Answer 12

*Succinate is oxidized & electrons are transferred to FAD+ to form FADH2
*FADH2 is similar to NADH and goes to the ETC
FAD+ = flavin adenine dinucleotide comes from riboflavin (B-Vitamin)
*Succinate (4C) –> Fumarate (4C)

Question 13

8)

Answer 13

*Addition of H2O to form 4C Malate

Question 14

9)

Answer 14

*Malate is oxidized to form Oxaloacetate which can regenerate the Krebs Cycle
*NAD+ is reduced to NADH

Question 15

gain per pyruvate

Answer 15

For each pyruvate:
* 4 NADH formed, 1 FADH2
* 1 ATP (as GTP)
* Double this to get the total for 1 glucose molecule

Carbons
– It takes 3 turns of the Krebs cycle for the 1st set of C’s from acetyl-CoA to be removed

Question 16

what determines if a pyruvate enters Krebs?

Answer 16

if its in the presence of o2 where it will then enter the transition stage