Citric acid cycle + terminal respiration

Question 1

What is the citric acid cycle?

Answer 1

Series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins

Produces NADH, FADH2 and CO2

(NADH + FADH2 then used to make ATP)

Question 2

Where does the citric acid cycle take place?

Answer 2

Mitochondrial matrix

Question 3

Where is acetyl CoA made?

Answer 3

Mitochondrial matrix

Question 4

Which multi sub-unit enzyme is used to convert pyruvate into Acetyl CoA?

Answer 4

Pyruvate dehydrogenase

Question 5

What mechanism stops the citric acid cycle from producing excess AT by controlling entry into the cycle?

Answer 5

Pyruvate dehydrogenase is regulated by it’s immediate products and ATP

If there is enough ATP, then the conversion of pyruvate to Acetyl CoA is slowed/stopped, so entry into cycle stopped

If the cell needs energy, higher concentrations of pyruvate and ADP cause the reaction to proceed

Question 6

True or false

There are 3 points of enzyme control within the citric acid cycle?

Answer 6

False

2 points within CAC
1 point before (Pyruvate => A.CoA)

Question 7

Why is the Citric acid cycle described as being amphibolic?

Answer 7

Serves both catabolic + anabolic processes

Question 8

Which produces more ATP, substrate-level phosphorylation or oxidative phosphorylation?

Answer 8

Oxidative

Question 9

Where does oxidative phosphorylation take place?

Answer 9

Mitochondria

Question 10

Most NADH and FADH2 is produced from the CAC in the mitochondria, but substrate level phosphorylation occurs in the cytoplasm, producing some NADH, which can’t cross the membrane.

What system is used to overcome this problem?
Outline it’s mechanism

Answer 10

Glycerol phosphate shuttle

1. NADH passes electrons onto FAD (via G-3-P)
2. FADH2 passes electrons onto electron transport chain

Question 11

How many enzymes make up the electron transport chain?

Answer 11

4

Question 12

Which enzyme in the electron transport chain does not shoot H+ ions into the inter membrane space of the mitochondria?

Answer 12

2nd

Question 13

Describe what happens in the 1st and 2nd enzymes, in the electron transport chain.

Answer 13

NADH/FADH2 oxidised at complex 1/2 respectively, and their electrons are channeled up the Fe-S centre

2 electrons added to Q (ubiquinone) to form QH2 (ubiquinol)

Complex 1 pumps H+ out the top, into the inter membrane space

Question 14

What is the purpose of the heme groups within complex 1,2 and 3?

Answer 14

Acts as a trap door for electrons

Ensures electrons go into ubiquinone

Question 15

What happens in complex 3 in the electron transport chain?

Answer 15

Takes electrons from QH2 and passes them to cytochrome c

Also pumps protons into inter membrane space

Question 16

True or false?

Each QH2 molecule yields 2 reduced cytochrome c molecules

Answer 16

Yeah boi

Question 17

Describe what happens at complex 4 in the electron transport chain?

Answer 17

Takes electrons from cytochrome C

Channeled through Fe-S centre

Passes them to O2

Also pumps protons into inter membrane space

Question 18

Summarise what processes produce NADH and FADH2.

Answer 18

NADH - Glycolysis, Beta oxidation, Citric acid cycle

FADH2 - Beta oxidation, Citric acid cycle, NADH via glycerol phosphate shuttle

Question 19

How does the electron transport chain lead to ATP production?

Answer 19

H+ pumping creates concentration gradient

Move down concentration gradient via ATP synthase

Proton motive force - energy release stored by converting ADP + Pi into ATP

ATP released into mitochondrial matrix and is taken away to do stuff in the body

Question 20

ATPase (synthase) is made of two main parts, F0 and F1. What does each part do?

Answer 20

F0

• membrane bound
• 10 subunits
• proton conducting unit

F1

• protrudes into mitochondrial matrix
• catalyses ATP synthesis
• uses the proton motive force energy collected in F0

Question 21

How many protons are used to produce one molecule of ATP?

Answer 21

3

3 protons = 1 ATP

Question 22

Which is a more efficient out of NADH and FADH2 in terms of ATP generation?

Answer 22

NADH

2.5 : 1 for NADH and 1.5 : 1 for FADH2

Question 23

If the inner mitochondrial membrane becomes permeable to H+, this can lead to extreme body temperature rises (malignant hyperthermia).

Describe how the temperature increase is caused?

Answer 23

Proton gradient is not maintained

Electrons pass through ETC and combine with O2 to form H2O

But no ATP is made

Energy from electron travelling along the terminal respiration system is released instead as heat

Question 24

What is the name for the mechanism that ATPase utilises to generate ATP?

Answer 24

Binding-change mechanism