Respiration

Question 1

What is respiration?

Answer 1

A set of metabolic reactions that take place in organisms and break down respiratory substances like glucose into smaller inorganic molecules, like water and carbon dioxide.
It is linked to the synthesis of ATP.

Question 2

Why is respiration described as a catabolic process?

Answer 2

Because complex molecules are broken down into smaller, simpler molecules.

Question 3

Why do organisms need to respire?

Answer 3

-It produces ATP for a variety of processes
-Releases heat energy for thermoregulation

Question 4

Define aerobic respiration

Answer 4

Cellular respiration that takes place in the presence of oxygen and produces CO2, water and ATP.

Question 5

Name the 4 main stages of aerobic respiration

Answer 5

glycolysis, link reaction, Krebs cycle, electron transport chain.

Question 6

What is substrate level phosphorylation?

Answer 6

Reactions which involve the direct generation of ATP from ADP without using the respiratory chain. This involves the enzyme-catalyzed transfer of a phosphate group from an organic molecule to ATP.

Question 7

Outline the stages of glycolysis.

Answer 7

1. Glucose is phosphorylated to hexose diphosphate by 2 ATP molecules.
2. Hexose biphosphate splits into two 3-carbon sugars
3. Each of these molecules is oxidized to 2 pyruvate.
   Net gain of 2 reduced NAD and 2 ATP per glucose molecule.

Question 8

Where does glycolysis occur?

Answer 8

In the cytoplasm

Question 9

How does pyruvate from glycolysis enter the mitochondria?

Answer 9

Via active transport.

Question 10

What molecule is produced during anaerobic glycolysis from the reduction of pyruvate?

Answer 10

lactate

Question 11

What is the link reaction?

Answer 11

The process which forms Acetyl CoA from pyruvate for use in the citric acid cycle.

Question 12

Describe the link reaction

Answer 12

1. one molecule of pyruvate is oxidatively decarboxylated and dehydrogenated to make acetate.
2. this is then combined with Coenzyme A to produce acetyl CoA

Question 13

Write an equation to summarize the link reaction

Answer 13

pyruvate + NAD + CoA - acetyl CoA + reduced NAD + CO2

Question 14

where does the link reaction occur?

Answer 14

In the mitochondrial matrix

Question 15

What is the Krebs cycle?

Answer 15

A series of oxidation-reduction reactions in the matrix of the mitochondria in which acetyl coenzyme A is oxidised, generating reduced NAD, reduced FAD, ATP and carbon dioxide

Question 16

What is the function of the Krebs cycle?

Answer 16

It is a means of releasing energy from carbon bonds to provide ATP, reduced NAD and reduced FAD (with the release of CO2)

Question 17

Where does the Krebs cycle occur?

Answer 17

In the mitochondrial matrix

Question 18

What is a decarboxylation reaction?

Answer 18

A reaction which removes one carbon and 2 oxygen atoms from a molecule in the form of a molecule of CO2

Question 19

Briefly outline the process of the Krebs cycle

Answer 19

A series of enzyme catalysed reactions that oxidize Acetyl CoA and produce many reduced cofactors through dehydrogenation reactions.

Question 20

What is a dehydrogenation reaction?

Answer 20

A reaction where hydrogen is removed from a molecule.

Question 21

What are the products of the Krebs cycle?

Answer 21

1 ATP (produced by substrate level phosphorylation)
3 reduced NAD
1 reduced FAD
2 CO2

Question 22

What is the electron transport chain?

Answer 22

A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reactions, releasing energy in the form of ATP.

Question 23

What is ATP synthase?

Answer 23

Enzyme found in the inner mitochondrial membrane which catalyses the formation of ATP from ADP and inorganic phosphate, using energy from chemiosmosis H+ ions.

Question 24

Define chemiosmosis

Answer 24

The passive diffusion of protons down a concentration gradient across a partially permeable membrane used in oxidative phosphorylation.

Question 25

How does chemiosmosis produce ATP during aerobic respiration?

Answer 25

-Protons flow down their concentration gradient into the mitochondrial matrix via ATP synthase
-ATP synthase phosphorylates ADP to form ATP as protons flow through it.

Question 26

Why is oxygen known as the terminal electron acceptor?

Answer 26

Oxygen accepts the electrons at the end of the electron transport chain to form water.

Question 27

Describe the role of reduced NAD and reduced FAD in the electron transport chain

Answer 27

They are a source of electrons and protons.

Question 28

How many ATP are produced per oxidized NAD in aerobic respiration?

Answer 28

3

Question 29

How many ATP are produced per oxidized FAD in aerobic respiration?

Answer 29

2

Question 30

What happens to lactate after a period of anaerobic exercise?

Answer 30

It is transported in the blood to the liver where it’s converted (under aerobic conditions) back to pyruvate and then to glucose.

Question 31

What is the respiratory quotient QR?

Answer 31

A ratio of the CO2 production and the oxygen uptake of an organism. It can be used to determine what class of biomolecule is being used as the primary respiratory substrate.

Question 32

How is the respiratory quotient (RQ) calculated?

Answer 32

RQ= CO2 produced / O2 consumed