Topic 5: Respiration

Question 1

What are autotrophic organisms?

Answer 1

Organisms that make their own food

Question 2

What are heterotrophic organisms?

Answer 2

Organisms which eat and digest other organisms to get food and energy from cellular respiration

Question 3

What is cellular respiration?

Answer 3

The process by which energy is transferred from the chemical bonds in respiratory substrates to form ATP

Question 4

What is aerobic respiration?

Answer 4

Respiration in the presence of oxygen

Question 5

What is ATP?

Answer 5

Adenosine triphosphate

Question 6

Give some characteristics of ATP

Answer 6

Energy currency

Universal

Question 7

Name and give the reaction which forms ATP

Answer 7

Phosphorylation

ADP + Pi —-> ATP + H2O

Question 8

Describe the structure of ATP

Answer 8

A DNA molecule with two extra phosphate groups

Question 9

What enzyme breaks down ATP?

Answer 9

ATPase

Question 10

Is the formation of ATP exothermic or endothermic?

Answer 10

Exothermic

Question 11

Name all the stages of aerobic respiration

Answer 11

Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation

Question 12

Where does glycolysis take place?

Answer 12

Cytoplasm

Question 13

Where does the glucose for glycolysis come from?

Answer 13

From the blood

Form the breakdown of glucagon in the muscles and liver

Question 14

Summarise the stages of glycolysis

Answer 14

Glucose is phosphorylated
Phosphorylated carbon is broken down into two molecules of G3P
G3P oxidised to pyruvate

Question 15

How is glucose phosphorylated in glycolysis?

Answer 15

Two phosphate groups are added to the glucose using two ATP molecules

Question 16

Why do you need to phosphorylate glucose in glycolysis?

Answer 16

It raises its energy level so its more reactive

Makes it unable to pass through the cell membrane

Question 17

How is G3P converted into pyruvate?

Answer 17

Loses a hydrogen atom which is picked up by a molecule of NAD which is reduced to NADH.

Question 18

How many ATP molecules are made for every molecule of G3P that’s oxidised?

Answer 18

2

Question 19

What is the net number of ATP molecules produced in glycolysis

Answer 19

2

Question 20

What determines what happens to pyruvate once it’s been formed?

Answer 20

Whether there is enough oxygen or not

Question 21

If there is not enough oxygen present in an animal, what happens to pyruvate?

Answer 21

Pyruvate is reduced to lactate (lactic acid)

NADH —> NAD

Question 22

Why is the regeneration of NAD important?

Answer 22

To carry on glycolysis in aerobic respiration

Question 23

If there isn’t enough oxygen present in plants, what happens to pyruvate?

Answer 23

Pyruvate is decarboxylated to ethanal and then reduced to ethanol

Question 24

What does the breakdown of pyruvate anaerobically in plants produce?

Answer 24

Ethanol and carbon dioxide

Question 25

Why is the fermentation of glucose irreversible in plants?

Answer 25

Because the carbon dioxide dissipates/diffuses

Question 26

What is the link reaction?

Answer 26

The reaction which links glycolysis to the Krebs cycle

Question 27

Summarise the link reaction

Answer 27

Pyruvate is decarboxylated to acetate which joins to coenzyme A to form acetyl coenzyme A

Question 28

What does NAD do in the link reaction?

Answer 28

It becomes NADH because the pyruvate is dehydrogenated

Question 29

In the presence of oxygen, where does pyruvate go?

Answer 29

It's transported across the inner and outer mitochondrial membrane into the matrix by active transport

Question 30

Where does the link reaction take place?

Answer 30

Matrix of the mitochondria

Question 31

Where does the Krebs cycle take place?

Answer 31

In the mitochondrial matrix?

Question 32

What is the purpose of the Krebs cycle?

Answer 32

To make the NADH and FADH needed in the electron transport chain

Question 33

Summarise the Krebs cycle

Answer 33

Acetate + oxaloacetate --> 6C 6C decarboxylated to 5C: CO2 and NADH formed 5C decarboxylated to 4C: CO2 and NADH formed 4C to another 4C: ATP 4C to another 4C: FADH 4C to oxaloacetate: NADH

Question 34

For every glucose molecule, how many times does the Krebs cycle go around?

Answer 34

Twice

Question 35

Summarise the products of the Krebs cycle

Answer 35

3 NADH 1 FADH 2 CO2 1 ATP

Question 36

Where does oxidative phosphorylation take place?

Answer 36

Inner mitochondrial matrix

Question 37

Summarise the events of oxidative phosphorylation

Answer 37

NADH and FADH are oxidised so they lose a H H ---> H+ + e- Electrons passed down chain and release energy H+ is pumped through proteins into inter-membrane space with energy H+ ions flood into the matrix through ATP synthase, forming ATP Electrons passed onto oxygen to combine with 2 H+ molecules to form water

Question 38

What does oxidative phosphorylation mean?

Answer 38

The formation of ATP using energy from oxidation in the electron transport chain

Question 39

Give another term for water in the ETC

Answer 39

The terminal electron acceptor