1.7 Cellular Respiration

Question 1

What is cellular respiration?

Answer 1

A series of metabolic pathways that brings about the release of energy from a foodstuff and the regeneration of the high-energy compound adenosine triphosphate (ATP)

Question 2

What ATP composed of ?

Answer 2

Adenosine and 3 inorganic phosphate (Pi) groups

Question 3

What is stored within a ATP molecule ?

Answer 3

Energy

Question 4

When is the energy released from an ATP molecule?

Answer 4

When the bond attaching the terminal phosphate is broken

Question 5

What is the result when the bond attaching the terminal phosphate is broken?

Answer 5

Adenosine diphosphate and inorganic phosphate

Question 6

What is the energy released for give 5 examples ?

Answer 6

Cellular processes e.g. Muscle contraction
Active transport mitosis/ meiosis (to separate chromosomes)
DNA replication
Protein synthesis

Question 7

Why is ATP important?

Answer 7

it provides a means by which chemical energy is transferred from one type of reaction to another in a living cell.

Question 8

Why is there a rapid turnover of ATP molecules?

Answer 8

as cells require a constant supply of ATP molecule

Question 9

What is happening at the same time as ATP molecules are being broken down?

Answer 9

many are being regenerated from ADP and Pi

Question 10

What is phosphorylation?

Answer 10

an enzyme-controlled process where a phosphate group is added to a molecule.

Question 11

Give an example of phosphorylation?

Answer 11

when an inorganic phosphate combines with ADP to form ATP

Question 12

What are the 3 main stages respiration is divided into?

Answer 12

glycolysis
citric acid cycle
electron transport chain

Question 13

Where does glycolysis take place ?

Answer 13

cytoplasm of a cell

Question 14

What is not needed for glycolysis to occur?

Answer 14

oxygen

Question 15

Describe overall what happens in glycolysis?

Answer 15

a series of enzyme-controlled steps where glucose is broken down into pyruvate

Question 16

What is glycolysis split into and what are they called?

Answer 16

2 enzyme-controlled phases
energy investment phase
energy pay-off phase

Question 17

What is USED UP in the energy investment phase?

Answer 17

2 ATP molecules are used up per molecule of glucose

Question 18

Why are 2 ATP molecules used up?

Answer 18

2 intermediate compounds are phosphorylated (i.e. a phosphate from the breakdown of ATP is added to these compounds)

Question 19

What does the first of these phosphorylations lead to?

Answer 19

a product that can continue to a number of pathways

Question 20

What is the second phosphorylation catalysed by?

Answer 20

an enzyme called phosphofructokinase

Question 21

What kind of reaction is the second phosphorylation and what does the resulting compound only leads to ?

Answer 21

the final stage of the glycolytic pathway

Question 22

What is produced in the energy pay-off phase?

Answer 22

4 ATP

Question 23

Apart from 4 ATP being produced during the energy payoff phase what else happens?

Answer 23

dehydrogenase enzymes release hydrogen ions from some of the compounds in this part of the pathway. These hydrogen ions are picked up by a co-enzyme called NAD which in turn becomes NADH

Question 24

When will the citric acid cycle take place?

Answer 24

if oxygen is present

Question 25

What happens to the pyruvate in the citric acid cycle?

Answer 25

pyruvate is broken down into carbon dioxide and an acetyl gorup.

Question 26

What happens to the actetyl group?

Answer 26

acetyl group binds with coenzyme A to enter the citric acid cycle as acetyl CoA

Question 27

How is citrate formed?

Answer 27

when the acetyl group of acetyl coenzyme A combines with oxaloacetate.

Question 28

Where does the citric acid cycle take place?

Answer 28

the matrix of the mitochondria

Question 29

What does the highly folded inner membrane give it?

Answer 29

larger surface area

Question 30

During citric acid cycle, what do dehydrogenase enzymes do?

Answer 30

remove hydrogen ions and electrons from the respiratory substrate. These are passed to the coenzyme NAD to form NADH or FAD to form FADH2.

Question 31

What is produced and what is released during citric acid cycle?

Answer 31

ATP is produced | carbon dioxide is released

Question 32

What does an electron transport chain consist of?

Answer 32

a group of protein molecules

Question 33

Where are many of the electron transport chains found?

Answer 33

in a cell

Question 34

Where are electron transport chains found attached to?

Answer 34

the inner membrane of mitochondria called cristae

Question 35

What do NADH and FADH2 from the glycolytic and citric acid pathways do?

Answer 35

release high-energy electrons and pass them to the electron transport chains

Question 36

What do electrons begin in?

Answer 36

a high-energy state

Question 37

What happens to electrons as they flow along a chain of electron acceptors?

Answer 37

they release energy

Question 38

What is the energy from the electrons used to do?

Answer 38

pump hydrogen ions across the membrane from the inner cavity (matrix) side to the intermembrane space,where a higher concentration of hydrogen ions is maintained

Question 39

After the hydrogen ions are pumped across to the intermembrane space, what happens to the hydrogen ions?

Answer 39

they move by diffusion and this returns the flow of hydrogen ions to the matrix drives ATP synthase to synthesise ATP from ADP + Pi

Question 40

When the electrons come to the end of the electron transport chain, what do they combine with?

Answer 40

oxygen, the final electron acceptor, to form water

Question 41

What does the electron transport chain provide?

Answer 41

Most of the energy (ATP) in cellular respiration

Question 42

How much ATP is generated in aerobic respiration?

Answer 42

38

Question 43

How much ATP is generated in glycolysis?

Answer 43

2

Question 44

How much ATP is generated in the cirtric acid cycle?

Answer 44

2

Question 45

How much ATP is generated in the electron transport chain?

Answer 45

34

Question 46

What is the main substrate used in the respiratory pathway?

Answer 46

glucose

Question 47

What other substrates can be used in the respiratory pathway?

Answer 47

``` starch glycogen other sugar molecules e..g. lactose amino acids fats ```

Question 48

What are starch and glycogen examples of?

Answer 48

complex carbohydrates

Question 49

What is starch ?

Answer 49

a complex carbohydrate stored by plants

Question 50

What is glycogen?

Answer 50

a complex carbohydrate stored by animals

Question 51

What are both starch and glycogen composed of?

Answer 51

chains of glucose molecules

Question 52

What can starch and glycogen be used in?

Answer 52

respiration as they breakdown into glucose molecules

Question 53

What are fats broken down into and when?

Answer 53

glycerol and fatty acids when it is required to take part in respiration

Question 54

What is glycerol and fatty acids converted into?

Answer 54

Glycerol is converted into a glycolytic intermediate and fatty acids are metabolised into smaller fragments that enter the pathway as acetyl coA for use in the citric acid cycle

Question 55

What are proteins broken down into ?

Answer 55

amino acids by digestive enzymes

Question 56

What happens to extra amino acids that are not required for protein synthesis ?

Answer 56

they undergo deamination, forming urea and respiratory pathway intermediates

Question 57

During glycolysis, how can the enzyme phosphofructokinase be inhibited?

Answer 57

by the accumulation of ATP and/or citrate

Question 58

What is the inhibition of phosphofructokinase by the accumulation of ATP and/or citrate an example of?

Answer 58

feedback inhibition

Question 59

What does the feedback inhibition of phosphofructokinase help to do?

Answer 59

synchronise and regulate the RATE of glycolysis and the citric acid cycle.

Question 60

Why is the feedback inhibition of phosphofructokinase important to a cell?

Answer 60

it prevents the needless buildup of intermediate compounds ATP is only produced when it is required It conserves resources

Question 61

What happens to muscle cells during intense exercise?

Answer 61

they start to respire anaerobically because they do not achieve an ADEQUATE supply of oxygen from the bloodstream to support an increased level aerobic respiration.

Question 62

If there is an inadequate supply of oxygen what can neither the citric acid cycle nor the electron transport chain not do?

Answer 62

generate additional ATP; only glycolysis is able to provide more ATP.

Question 63

What does glycolysis able to generate?

Answer 63

2NADH and 2ATP from each molecule of glucose as it is broken down to pyruvate

Question 64

What happens to the pyruvate if there is an inadequate supply of oxygen?

Answer 64

it is converted to lactate and this is accompainied by the transfer of hydrogen from NADH and the regeneration of NAD.

Question 65

Why must NAD present?

Answer 65

to enable glycolysis to continue and produce more ATP

Question 66

What does a build up of lactate in muscle cells cause?

Answer 66

fatique and an oxygen debt builds up

Question 67

What happens when exercise stops?

Answer 67

energy generated by aerobic respiration is now used to convert lactate back to pyruvate

Question 68

During intense muscular activity, what do muscle cells do?

Answer 68

breakdown ATP to release energy

Question 69

What do muscle cells contain?

Answer 69

a small store of ATP, which can supply energy for only a few muscle contractions

Question 70

What is the chemical which provides much of the energy needed for intense muscular activity?

Answer 70

creatine phosphate

Question 71

What does creatine phosphate do?

Answer 71

breaks down to release energy and phosphate that is used to convert ADP to ATP at a fast rate.

Question 72

What the creatine phosphate system only support?

Answer 72

strenuous muscle activity for around 10 seconds, when the creatine phosphate supply runs out.

Question 73

When is the supply of creatine phosphate restored ?

Answer 73

when energy demands are low

Question 74

Why are skeletal muscle fibres required by the body?

Answer 74

to bring about all kinds of movemenr

Question 75

What are the 2 types of skeletal muscle fibres?

Answer 75

slow-twitch muscle fibres | fast-twitch muscle fibres

Question 76

When are slow-twitch muscle fibres most effective and why?

Answer 76

during endurance activities such as long-distance running as they can work for a long time without getting tired

Question 77

What speed do slow-twitch muscle fibres contract?

Answer 77

slowly

Question 78

What do slow-twitch muscle fibres depend on?

Answer 78

aerobic respiration to generate most of their ATP

Question 79

What number of mitochondria do slow-twitch muscle fibres have?

Answer 79

large

Question 80

When are fast-twitch muscle fibres most effective?

Answer 80

during power events such as weight-lifting

Question 81

What speed do fast-twitch muscle fibres contract?

Answer 81

quickly

Question 82

What is the length of time contraction is sustained in a fast-twitch muscle fibre?

Answer 82

short periods of time, but get tired fast, as they consume lots of energy.

Question 83

What do fast-twitch muscle fibres depend on?

Answer 83

glycolysis to generate ATP

Question 84

What number of mitochondria do fast-twitch muscle fibres have?

Answer 84

small

Question 85

What blood capillary density do fast-twitch muscle fibres have?

Answer 85

low

Question 86

What blood capillary density do slow-twitch muscle have?

Answer 86

high

Question 87

What concentration of myoglobin do fast-twitch muscle fibres have?

Answer 87

low

Question 88

What concentration of myoglobin do slow-twitch muscle fibres have?

Answer 88

high

Question 89

What is myoglobin?

Answer 89

an oxygen-storing protein present in muscle cells

Question 90

What major storage fuels are used in slow-twitch muscle fibres?

Answer 90

fats

Question 91

What major storage fuels are used in fast-twitch muscle fibres?

Answer 91

glycogen and creatine phosphate