module 5 - 18.3 the krebs cycle

Question 1

what happens during the krebs cycle? (stage 1-5)

Answer 1

1. link reaction delivers acetyl groups into Krebs Cycle, they are attached to coenzyme A
2. the acetyl group combines with the oxaloacetate to form the 6-carbon citrate
3. coenzyme A is returned to link reaction
4. citrate molecule is decarboxylated and dehydrogenated to produce 5-carbon intermediate, co2 and reduced NAD
5. the 5C intermediate is decarboxylated and dehydrogenated to produce 4-carbon intermediate, co2 and reduced NAD

Question 2

what happens during the Krebs cycle? (stage 6-9)

Answer 2

6. the 4 carbon intermediate undergoes substrate level phosphorylation to make ATP from ADP+Pi
7. the 4-carbon intermediate is dehydrogenated to produce reduced FAD
8. the 4-carbon intermediate is dehydrogenated to produce reduced NAD
9. last 3 reactions convert the 4-carbon intermediate into oxaloacetate, allows Krebs cyle to turn once more

Question 3

what is a cofactor?

Answer 3

inorganic ions such as:
- chloride ion and amylase
- magnesium ion and DNA polymerase

Question 4

what is a coenzyme?

Answer 4

organic molecules like vitamins, loosely bound to the enzymes

Question 5

what are prosthetic groups?

Answer 5

inorganic ions/organic molecules that are tightly bound to enzymes

Question 6

what are the products of ONE TURN of the Krebs cycle?

Answer 6

• 3 reduced NADs
• 1 reduced FAD
• 1 ATP
• 2 CO2 molecules

Question 7

what are the coenzymes in respiration?

Answer 7

• NAD
• FAD
• CoA (coenzyme A)

Question 8

what are NAD, FAD ABD CoA made from?

Answer 8

NAD - vitamin B3
FAD - vitamin B2
CoA - B5

Question 9

what are the coenzymes used for in respiration?

Answer 9

used to move protons, electrons and functional groups between enzymes

Question 10

what happens to NAD during respiration?

Answer 10

• NAD accepts 1 hydrogen atom and an electron OR 1 proton and 2 electrons
• NAD reduced to reduced NAD
• NAD and NAD+ are the oxidised forms
• reduced NAD and NADH are the reduced forms

Question 11

what is the reaction for NAD during respiration?

Answer 11

NAD+ + H+ + 2e- ⇌ NADH

Question 12

what happens to FAD during respiration?

Answer 12

• FAD accepts 2 hydrogen atoms or 2 protons and 2 electrons
• FAD is reduced to reduced FAD
• FAD is the oxidised form
• FADH2 is the reduced form

Question 13

how can reduced NAD/FAD be written?

Answer 13

reduced NAD: NADH
reduced FAD: FADH2

Question 14

what is the reaction for FAD during respiration?

Answer 14

FAD + 2e- + 2H+ → FADH2

Question 15

what is reduced NAD/NADH used for?

Answer 15

• used in last stage of aerobic respiration to produce ATP from ADP + Pi
• done by oxidative phosphorylation
• 1 reduced NAD can be used to produce 3 ATP molecules

Question 16

what is reduced FAD/FADH2 used for?

Answer 16

• used in last stage of aerobic respiration to produce ATP from ADP +Pi
• done by oxidative phosphorylation
• 1 reduced FAD can be used to produce 2 ATP molecules

Question 17

what is oxidation?

Answer 17

adding oxygen/removing hydrogen

Question 18

what is reduction?

Answer 18

adding hydrogen/removing oxygen

Question 19

what is a redox reaction?

Answer 19

one molecule oxidised, one molecule reduced - happens at the same time

Question 20

where does glycolysis happen?

Answer 20

cytoplasm

Question 21

where does the link reaction happen?

Answer 21

mitochondrial matrix

Question 22

where does the Krebs cycle happen?

Answer 22

mitochondrial matrix