Key Area 2 - Cellular Respiration

Question 1

What is respiration?

Answer 1

Respiration is a series of metabolic pathways which results in the release of energy from foodstuff and the regeneration of ATP (adenosine triphosphate). All three domains of life (archaea, bacteria and eukaryotes) carryout respiration pathways within their cells.

Question 2

Which domains of life carry out respiration pathways in their cells?

Answer 2

All 3 domains of life - archaea, bacteria, eukaryotes.

Question 3

What is ATP?

Answer 3

ATP is the energy-carrying compound used in cells. It can release energy quickly.

Question 4

How is ATP synthesised?

Answer 4

ATP is synthesised (made) when ADP joins with an inorganic phosphate to form ATP. This requires energy which is then stored in the bond joining the third phosphate to the second.

Question 5

Write the equation for the synthesis of ATP.

Answer 5

.

Question 6

What name is given to the addition of a phosphate to a molecule?

Answer 6

Phosphorylation.

Question 7

How is energy released from ATP?

Answer 7

To release energy the bond between the second and third phosphate is broken.

Question 8

Write the equation for the breakdown of ATP.

Answer 8

.

Question 9

Name the 3 stages of respiration.

Answer 9

Glycolysis

Citric Acid Cycle

Electron Transport Chain

Question 10

Where does glycolysis take place?

Answer 10

Glycolysis occurs in the cytoplasm.

Question 11

What molecule is broken down during glycolysis?

Answer 11

Glucose (6C)

Question 12

What does glucose get broken down into?

Answer 12

2 molecules of pyruvate (3C)

Question 13

What happens during the “energy investment phase” in glycolysis?

Answer 13

2 molecules of ATP are required to phosphorylate glucose and the intermediates in glycolysis.

Question 14

What is NAD?

Answer 14

NAD is a coenzyme that acts as a hydrogen carrier.

Question 15

What happens to the coenzyme NAD during glycolysis?

Answer 15

Hydrogen ions and electrons from intermediates during glycolysis reduce NAD to form NADH.

Question 16

What enzyme is responsible for the synthesis of NADH from NAD, electrons and H+?

Answer 16

Dehydrogenase

Question 17

What happens during the “energy pay-off stage” in glycolysis?

Answer 17

More ATP is generated than is required. For every glucose molecule 4 molecules of ATP are generated.

Question 18

What is the net gain of ATP from glycolysis?

Answer 18

2 ATP

Question 19

Draw a diagram to represent the process of glycolysis.

Answer 19

.

Question 20

Does glycolysis require oxygen?

Answer 20

Oxygen is not required for glycolysis to take place.

Question 21

If oxygen is available ( in aerobic conditions) what happens to the pyruvate molecules?

Answer 21

If oxygen is available the pyruvate diffuses into the central matrix of the mitochondria.

Question 22

Draw and label a mitochondrion.

Answer 22

.

Question 23

What happens to pyruvate in the central matrix of the mitochondria?

Answer 23

Pyruvate molecules get broken down into an acetyl group that combines with Coenzyme A to form acetyl Coenzyme A. Carbon dioxide is released and one molecule of NADH is produced.

Question 24

Where does the Citric Acid cycle take place?

Answer 24

The Citric Acid cycle takes place in the central matrix of the mitochondria.

Question 25

What does the acetyl group from the Acetyl CoA join with in the Citric Acid cycle?

Answer 25

The acetyl group from the acetyl CoA joins with oxaloacetate to form citrate.

Question 26

What controls the reactions of the Citric Acid cycle?

Answer 26

Enzymes

Question 27

What does citrate get converted into?

Answer 27

Citrate gets converted into oxaloacetate in the Citric Acid cycle.

Question 28

What 3 reactions take place as citrate gets converted into oxaloacetate?

Answer 28

ATP is synthesised from ADP and Pi. Carbon dioxide is released from intermediates. Hydrogen ions and electrons are removed from citrate and intermediates by dehydrogenase enzymes and pass them to NAD to form NADH.

Question 29

What happens to the carbon dioxide produced during respiration?

Answer 29

Carbon dioxide diffuses out to the mitochondria and out of the cell.

Question 30

What happens to the NADH produced during glycolysis and the citric acid cycle?

Answer 30

NADH is passed on to the electron transport chain on the inner membrane of the mitochondrion.

Question 31

Draw a diagram to represent glycolysis and the Citric Acid cycle.

Answer 31

.

Question 32

What is the electron transport chain?

Answer 32

The electron transport chain is a series of carrier proteins attached to the inner mitochondrial membrane. ATP synthesis takes place here.

Question 33

Where do the electrons in the electron transport chain come from?

Answer 33

The electrons come from the NADH which was made during glycolysis and the citric acid cycle.

Question 34

What happens to the electrons in the electron transport chain?

Answer 34

Electrons are passed along a series of proteins in the electron transport chain. Energy from these electrons is used to pump hydrogen ions (H+) across the inner mitochondrial membrane.

Question 35

What is ATP Synthase?

Answer 35

ATP synthase is an enzyme that synthesises ATP from ADP and Pi. The energy for this comes from the flow of H+ ions.

Question 36

What happens to the hydrogen ions and the electrons at the end of the electron transport chain?

Answer 36

The hydrogen ions and electrons combine with oxygen to form water.

Question 37

Compare the amount of ATP generated when oxygen is not available to the amount generated when oxygen is present.

Answer 37

Much more ATP is generated when oxygen is present. Glycolysis generates 2 ATP (net). Oxygen is not needed for this. When oxygen is present 36 ATP are generated through the citric acid cycle and the electron transport chain.

Question 38

What happens to pyruvate in animal cells when oxygen is not present?

Answer 38

Fermentation takes place in the cytoplasm. This involves the pyruvate being converted to lactate in a reversible reaction.

Question 39

What happens to pyruvate in plant cells when oxygen is not present?

Answer 39

In plants and yeast, ethanol and carbon dioxide are produced in an irreversible reaction.

Question 40

Why is the generation of ATP so important to cells?

Answer 40

ATP is used to transfer energy to cellular processes which require energy.