Chapter 12 - Respiration

Question 1

What is aerobic respiration?

Answer 1

Respiration in plentiful supplies of oxygen

Question 2

What is anaerobic respiration?

Answer 2

Respiration where oxygen supplies are limited

Question 3

Products of aerobic respiration

Answer 3

Carbon dioxide, water and ATP

Question 4

Products of anaerobic respiration

Answer 4

Lactate and a little ATP

Question 5

What are the four stages of respiration?

Answer 5

Glycolysis
The Link reaction
The Krebs cycle
Oxidative phosphorylation

Question 6

General description of glycolysis

Answer 6

6C glucose splits into 2x 3C pyruvate

Question 7

General description of the Link reaction

Answer 7

2C Acetylcoenzyme A is formed from the 3C pyruvate

Question 8

General description of the Krebs cycle

Answer 8

ATP, FAD and NAD are produced through the oxidation and reduction of acetylcoenzyme A

Question 9

General description of oxidative phosphorylation

Answer 9

The use of electrons to synthesise ATP and water

Question 10

Where does glycolysis occur?

Answer 10

Cytoplasm

Question 11

What happens during glycolysis?

Answer 11

Two ATP molecules are hydrolysed into ADP and P
These phosphate molecules phosphorylate the glucose, making it more reactive
The glucose molecule is split into two molecules of triose phosphate
Triose phosphate is oxidised and this hydrogen reduces a hydrogen carrier called NAD
The triose phosphate molecules are converted into 2 molecules of 3C pyruvate
This process also regenerates 2 molecules of ATP

Question 12

What happens to the pyruvate during anaerobic respiration?

Answer 12

It is converted into ethanol in plants and yeast or lactate in animals using reduced NAD

Question 13

What are the overall products from glycolysis?

Answer 13

2 molecules of ATP
2 molecules of reduced NAD
2 molecules of pyruvate

Question 14

Does glycolysis require oxygen?

Answer 14

No

Question 15

What happens during the link reaction?

Answer 15

The pyruvate is oxidised to form acetate
It loses one carbon dioxide molecule and two hydrogen atoms
These hydrogen atoms are accepted by the NAD, reducing it
The 2C acetate combines with coenzyme A to form acetylcoenzyme A

Question 16

Overall equation for the link reaction

Answer 16

Pyruvate + NAD + CoA -> CO2 + reduced NAD + acetyl CoA

Question 17

How many times will the link reaction occur per glucose molecule?

Answer 17

Twice

Question 18

What are enzymes?

Answer 18

Molecules that other enzymes require in order to function

Question 19

What are the three coenzymes in photosynthesis and respiration?

Answer 19

NAD, FAD, NADP

Question 20

What are the three main functions of the Krebs cycle?

Answer 20

Breaks down macromolecules (pyruvate) into smaller ones (CO2)
The hydrogen atoms are carried to the electron transfer chain and provide energy to make ATP
Regenerates the 4C compound that combines with acetylcoenzyme A

Question 21

How many pyruvate molecules are formed per molecule of glucose?

Answer 21

2

Question 22

What is produced during the Krebs cycle and the link reaction?

Answer 22

Reduced coenzymes
One molecule of ATP
Three molecules of CO2
The yield for a single glucose molecule is double this

Question 23

What happens during the Krebs cycle?

Answer 23

Acetyl CoA combines with a 4C compound to produce a 6C compound
This 6C compound releases one CO2 molecule and hydrogen atoms to form a 5C compound
These hydrogen atoms are used to form reduced NAD
The 5C compound has another molecule of CO2 removed to form a 4C compound
This time, one molecule of reduced FAD, one molecule of ATP, and two molecules of reduced NAD are produced
The 4C compound combines with the CoA to repeat the cycle again

Question 24

How are hydrogen atoms transported to the site of oxidative phosphorylation?

Answer 24

By the coenzymes FAD and NAD

Question 25

What is the site of oxidative phosphorylation?

Answer 25

The cristae of the mitochondria

Question 26

What is oxidative phosphorylation?

Answer 26

The process by which the energy contained in the H+ ions carried by FAD and NAD is used to make ATP

Question 27

How does oxidative phosphorylation work?

Answer 27

Reduced NAD and FAD are oxidised, losing a hydrogen atom in the process. This atom splits into protons and electrons The electron from these molecules is donated to the first carrier in the electron transfer chain In a series of redox reactions, this electron is passed through the carrier molecules, each at a lower energy level to the last. The energy released by this process is used to actively transport protons into the inter-membranal space The protons accumulate here and diffuse back into the matrix of the mitochondria through ATP synthase molecules embedded in the wall At the end of the transport chain, protons, electrons and O2 combine to form water. Oxygen is the final acceptor of these electrons

Question 28

What is the important function of oxygen?

Answer 28

It acts as the final acceptor of the electrons and so keeps the process moving

Question 29

Why is energy released from ATP gradually?

Answer 29

The electron moves along the transfer chain and gradually loses energy at each level, rather than in one go

Question 30

How many ATP molecules can be made from one glucose molecule?

Answer 30

32

Question 31

How are proteins used for respiration?

Answer 31

First, they are hydrolysed into amino acids Then they are deaminised to remove the amino group They enter the respiratory pathway at different points depending on the number of carbon atoms they contain - 3C compounds are converted to pyruvate and 4 or 5 C compounds are converted to intermediates in the Krebs cycle

Question 32

how are lipids used for respiration?

Answer 32

Hydrolysed into glycerol and fatty acids Glycerol phosphorylated and converted to TP which enters glycolysis Fatty acids converted to 2C acetyl coenzyme A, which is used in the Krebs cycle

Question 33

Why do lipids release much more energy than carbohydrates?

Answer 33

Oxidising lipids produces many hydrogen atoms which are used in oxidative phosphorylation to produce ATP

Question 34

What two processes can't take place without oxygen?

Answer 34

The Krebs cycle and the electron transfer chain

Question 35

Why can the Krebs cycle and the electron transfer chain not take place without oxygen?

Answer 35

There is no FAD and NAD - it will all be reduced. This means that the H+ produced during the Krebs cycle won't be taken up by the molecules so the enzymes stop working

Question 36

What is the only process that doesn't require oxygen?

Answer 36

Glycolysis

Question 37

What must occur for glycolysis to continue happening?

Answer 37

Pyruvate and hydrogen must be removed constantly

Question 38

How is NAD regenerated?

Answer 38

The H+ is removed from reduced NAD and donated to pyruvate

Question 39

Why is it important that NAD is regenerated?

Answer 39

There is only a tiny supply of NAD in cells as it is and without regenerating NAD, the hydrogen produced during glycolysis won't be absorbed, so glycolysis stops

Question 40

What is pyruvate converted to during anaerobic respiration in microorganisms?

Answer 40

Ethanol and CO2

Question 41

What is pyruvate converted to during anaerobic respiration in animals?

Answer 41

Lactate

Question 42

How is ethanol produced?

Answer 42

During anaerobic respiration in yeast, the pyruvate loses a CO2 molecule and gains a hydrogen atom

Question 43

What is the equation for the production of ethanol?

Answer 43

Pyruvate + reduced NAD -> ethanol + oxidised NAD + CO2

Question 44

What happens during strenuous exercise?

Answer 44

Oxygen is used up more rapidly than it is supplied leading to an oxygen debt

Question 45

How is lactate produced during anaerobic respiration?

Answer 45

NAD from glycolysis accumulates when oxygen is in short supply. To overcome this, pyruvate takes two hydrogen atoms from the reduced NAD to form lactate and oxidised NAD

Question 46

What is the equation for the production of lactate?

Answer 46

Pyruvate + reduced NAD -> lactate + oxidised NAD

Question 47

What will happen after the oxygen debt is repaid?

Answer 47

Lactate is oxidised to re-form pyruvate

Question 48

Why is lactate bad?

Answer 48

It is acidic so affects enzymes | Causes cramp and muscle fatigue

Question 49

Where is lactate removed from the body?

Answer 49

The liver

Question 50

How is ATP produced during anaerobic respiration?

Answer 50

Glycolysis - pyruvate is used up so neither the Krebs cycle nor the electron transfer chain can use it