Respiration

Question 1

Where does aerobic respiration occur?

Answer 1

In the cytoplasm & mitochondria

Question 2

Where does anaerobic respiration occur?

Answer 2

Only in the cytoplasm

Question 3

What are the 4 steps of aerobic respiration?

Answer 3

Glycolysis
Link reaction
Kreb’s cycle
Oxidative phosphorylation

Question 4

What is glycolysis?

Answer 4

Process by which a glucose molecule is converted to 2 molecules of pyruvate
Occurs in both aerobic and anaerobic respiration

Question 5

What is the first step of glycolysis?

Answer 5

• 2 phosphate molecules are added to produce hexose bisphosphate
• glucose phosphorylation makes glucose more reactive so it can be split more easily
• phosphate molecules are taken from 2 hydrolysed ATP molecules

Question 6

What is the second step of glycolysis?

Answer 6

Hexose bisphosphate is split to produce 2 triose phosphate molecules

Question 7

What is the third step of glycolysis?

Answer 7

• dehydrogenase removes a hydrogen atom from each of the triose phosphate molecules
• oxidation + each H atom is accepted by an NAD+ molecule to produce NADH
• phosphates from each triose phosphate molecule are used to produce 2 ATP molecules each

Question 8

What is the final result of glycolysis?

Answer 8

2 pyruvate molecules
2 NADH+ molecules
Net of 2 ATP

Question 9

How does pyruvate get into the mitochondrial matrix?

Answer 9

It’s actively transported across by pyruvate H+ symport

Question 10

What is the link reaction?

Answer 10

The conversion of 2 pyruvates to two 2-carbon acetyl groups through decarboxylation and dehydrogenation

Question 11

What is the link reaction catalysed by?

Answer 11

Pyruvate dehydrogenase

Question 12

What is the process of the link reaction?

Answer 12

• a carboxyl group is removed producing CO2
• Hydrogen atoms are removed from pyruvate and are accepted by NAD+ to form NADH
• acetyl group combines with coenzyme A to produce acetylCoA

Question 13

What is the Krebs cycle?

Answer 13

A series of enzyme catalysed reactions that occur to oxidise the acetylCoA produced in the links reaction
For every glucose molecule there are 2 turns of the Krebs cycle

Question 14

What is the first step of the Krebs cycle?

Answer 14

Acetyl group is release from acetylCoA

Question 15

What is the second step of the Krebs cycle?

Answer 15

2C acetyl group combines with 4C oxaloacetate to form the 6C compound citrate

Question 16

What is the third step of the Krebs cycle?

Answer 16

Citrate is decarboxylated + dehydrogenated to produce a CO2 molecule, an NADH+ molecule and a 5C compound

Question 17

What is the fourth step of the Krebs cycle?

Answer 17

5C compound is decarboxylated + dehydrogenated to produce a CO2 molecule, an NADH+ molecule and a 4C compound

Question 18

What is the fifth step of the Krebs cycle?

Answer 18

4C compound temporarily combines with CoA + ATP is produced

Question 19

What is the name of the process by which ATP is produced from ADP + Pi?

Answer 19

Substrate level phosphorylation

Question 20

What is the sixth step of the Krebs cycle?

Answer 20

4C compound is dehydrogenated to form a different 4C compound and FADH

Question 21

What is the seventh step of the Krebs cycle?

Answer 21

New 4C compound is dehydrogenated to produce oxaloacetate + NADH
Catalysed by isomerase

Question 22

What is the final product of the Krebs cycle?

Answer 22

3 NADH
2 CO2
1 ATP
1 FADH

Question 23

What does oxidative phosphorylation involve?

Answer 23

Electron transport chain

Chemiosmosis

Question 24

Where does oxidative phosphorylation occur?

Answer 24

In the inner membrane of the mitochondria

Question 25

What is the first step of oxidative phosphorylation?

Answer 25

- NADH gives up electrons to NADH dehydrogenase - FADH gives up electrons to electron carrier - forms NAD + FAD

Question 26

What is the second step of oxidative phosphorylation?

Answer 26

As electrons move down to the next carrier they lose some energy which is used to pump H ions across to the intermembrane space This continues as electrons move further down the chain

Question 27

What is the final step of oxidative phosphorylation?

Answer 27

Electrons combine with oxygen to form water which frees the chain so the process can repeat This process creates an electrochemical gradient

Question 28

What happens in chemiosmosis?

Answer 28

- H ions move down an electrochemical gradient through ATP synthase - provides energy for ATP synthesis from ADP + Pi - produces a lot of ATP (26-32 molecules)

Question 29

What happens during anaerobic respiration in animals?

Answer 29

Only glycolysis continues + pyruvate acts as a hydrogen acceptor to form lactated and oxidised NAD

Question 30

What happens to the lactate produced in anaerobic respiration?

Answer 30

Transported to liver via bloodstream where it is oxidised to pyruvate Can enter link reaction in liver cells or be converted to glycogen

Question 31

What happens during anaerobic respiration in some microorganisms?

Answer 31

Only glycolysis continues Pyruvate is decarboxylated to form ethanal Ethanal is reduced to ethanol using NADH to produce oxidised NAD for further glycolysis