Unit 2 - Pyruvate Oxidation & Krebs Cycle

Question 1

2 options to happen after Glycolysis

Answer 1

1) oxygen pressent
2) insufficent oxygen

Question 2

Oxygen Present after Glycolysis

Answer 2

pyruvate and hydrogen acceptors (NADH and FADH) enter the mitochondria for the Krebs Cycle ( aerobic respiration)

Question 3

Insufficient Oxygen after Glycolysis

Answer 3

the pyruvate stays in the cytoplasm where it is converted to lactic acid or ethanol in anaerobic respiration

Question 4

Pyruvate Oxidation

Answer 4

second step in cellular respiration
- intermediate step between glycolysis and Krebs
- 2 pyruvate mols transported from cytoplasm and matrix
- aerobic = occurs in presence of O

Question 5

3 Steps of pyruvate oxidation

Answer 5

1) carboxyl group removed
2) NAD+ is reduced to NADH
3) acetyl CoA is made

Question 6

1) Carboxyl group is removed

Answer 6

a carboxyl group is snipped off the pyruvate (decarboxylation) and releases as a molecule of CO2, leabing behind a 2c mol

Question 7

2) NAD+ is reduced to NADH

Answer 7

2c mol from step 1 is oxidized forming an acetyl group. the e- lost in the oxidation r picked up by NAD+ along w a proton to form NADH and a H+

Question 8

3) Acetyl CoA is made

Answer 8

the acetyl group is transferred to coenzyme A = an acetyl coa

Question 9

Overall rxn

Answer 9

2pyruvate + 2NAD + 2CoA = 2 acetyl-CoA + 2NADH + 2H + 2CO2

Question 10

CoA contains?

Answer 10

sulphur and hydrogen functional groups (-SH)

Question 10

Coenzyme-A (CoA)
what is it?

Answer 10

a carrier that helps enzymes hold and modify mols (its a derivative of Vitamin B)

Question 10

CoA

Answer 10

also known as a carrier mol and will carry the acetyl group to the kreb’s cycle

Question 11

codes we use of CoA

Answer 11

• CoASH (unbonded coenzyme-A)
• CoA (attached to another mol)

Question 12

Pyruvate Oxidation

Answer 12

pyruvate oxidation happens twice for every glucose mol
so for every glucose mol used in glycolysis, two pyruvate and 2 CoA mols r made

Question 13

Krebs Cycle

Answer 13

or Citric Acid Cycle
- two mols of acetly CoA go into krebs cycle
- two CO2 mols r releases as watste product

Question 14

Oxidative Phosphorylation

Answer 14

2 mols r reduced NAD r formed and go into the ETC

Question 15

Breathing supplies what?

Answer 15

oxygen to our cells and removes CO2
- breathing provides for the exchange of O2 and CO2 between an organism and its environment

Question 16

Krebs Cycle discovered by who

Answer 16

Sir hans krebs discovered a series of metabolic reactions in 1937 later winning a nobel prize

Question 17

Krebs cycle

Answer 17

• each step is catalyzed by a specific enzyme (8)
• occurs in mitochondrial matrix
• Net 2 ATP made
• cycle begins and ends w oxaloacetate
• cycle turns twice for every glucose mol oxidized

Question 18

-beginning of cycle

Answer 18

acetyl-CoA enters the cycle and combines w ox-a-lo-acetate to make the 6c compound citrate

Question 19

During 8 steps of krebs cycle

Answer 19

citrate undergoes a number of reactions releasing CO2 and ATP in a number of steps

• citrate ie eventually converted into oxaloacetate so it can be used again

Question 20

step 1 of krebs

Answer 20

Acetyl-CoA reacts w a mol of Oxaloacetate to from citrate. CoA is released

Question 21

step 2 of krebs

Answer 21

citrate is rearranged to isocitrate

Question 22

step 3 of krebs

Answer 22

isocitrate is converted to a-ketoglutarate by losing carbon dioxide and H atoms that reduce NAD+ to NADH

Question 23

steps 4 of krebs

Answer 23

a-ketoglutarate is converted to Succinyl-CoA where a CO2 is removed coenzyme A is aded and 2 H atoms r reduce NAD+ to NADH

Question 24

step 5 of krebs

Answer 24

the release of CoA from succinyl CoA produces succinate: the energy rleased converts GDP to GTP which in turn converts ADP to ATP by subsrate-level phosphorylation. ONLY ATP MADE directly in Krebs

Question 25

step 6 of krebs

Answer 25

succinate is converted to fumarate. FAD is reduced to FADH

Question 26

step 7 of krebs

Answer 26

fumarate is converted to malate via the addition of water

Question 27

step 8 of krebs

Answer 27

malate is oxidized to oxaloacetate, reducing NAD+ to NADH + H+. Oxaloacetate with acetyl-CoA to re-enter the cycle

Question 28

Overall rxn for 2 cycles

Answer 28

2acetly-CoA + 6NAD + 2FAD +2ADP +2Pi = 4CO2 + 6NADH + 6H + 2FADH2 + 2ATP + 2CoA

Question 29

Krebs Cycle summary

Answer 29

• 4 co2
• 2 ATP
• 6 NADH
• 2 FADH2

Question 30

Fate of glucoses carbon atoms

Answer 30

glucose = 2 pyruvate = 2 acetyl-Coa + 2CO2 = 4CO2

Question 31

How many oxidation rxn occurs in krebs where

Answer 31

4 times

Question 32

where does the condensation rxn occur

Answer 32

combining the two-carbon acetyl group with a four-carbon oxaloacetate molecule to form a six-carbon molecule of citrate.

Question 33

where does the isomerization rxn occur

Answer 33

step 2

Question 34

where does substrate level phosphorylation occur

Answer 34

mitochondria matrix