3.5.2 Respiration

Question 1

What is the benefit of aerobic respiration over anaerobic?

Answer 1

It gives more ATP

Question 2

What is the word equation for aerobic respiration?

Answer 2

Glucose + Oxygen = Carbon dioxide + Water + Energy

Question 3

What is the equation for aerobic respiration?

Answer 3

C6H12O6 + 6O2 = 6CO2 + 6H2O

Question 4

What is the purpose of respiration?

Answer 4

To provide energy

Question 5

Where does respiration take place?

Answer 5

In the mitochondria

Question 6

What are the main steps of aerobic respiration?

Answer 6

Glycolysis
Link reaction
Krebs cycle
Oxidative phosphorylation

Question 7

What is the process of glycolysis?

Answer 7

Glucose has 6 carbons
ATP adds phosphate which splits it into two 3C molecules (triose phosphate)
Hydrogen (H+) is removed from each of the triose phosphates which reduces NAD to form NADH (reduction)
Phosphate is combined with ATP to produce 2 ATP per 3C molecule (phosphorylation)
Pyruvate is the final product

Question 8

What is the process of the link reaction?

Answer 8

Starts off with pyruvate (3C)
It loses a carbon dioxide molecule
Two hydrogens are lost which are then accepted by NAD to form NADH
The 2C acetate combines with coenzyme A to form acetylcoenzyme A

Question 9

What is the overall yield of glycosis?

Answer 9

2 x ATP
2 x NADH
2 x pyruvate

Question 10

Does glycolysis require oxygen?

Answer 10

No

Question 11

What is the the overall word equation of the link reaction?

Answer 11

Pyruvate + NAD + Coenzyme A

Acetylcoenzyme A + NADH + CO2

Question 12

What is the process of the Krebs cycle?

Answer 12

Acetylcoenzyme A (2C) combines with a 4C molecule to produce a 6C molecule
Cycle starts:
The 6C molecule loses CO2 (decarboxylation) and hydrogen (to reduce NAD to form NADH) to give a 5C molecule
The 5C molecule loses a CO2 molecule, hydrogen (to reduce FAD to form RedFAD) and a molecule of ATP (substrate-level phosphorylation)
The 4C molecule can combine with a new molecule of acetylcoenzyme A to begin the cycle again

Question 13

How much reduced FAD and NAD is produced during the Krebs cycle?

Answer 13

The quantity if variable

Less RedFAD is produced because of the availability of FAD

Question 14

What are the two types of phosphorylation?

Answer 14

Oxidative and substrate level

Question 15

What is substrate level phosphorylation?

Answer 15

Where phosphate comes from the other molecules in the reaction
When the phosphate used to phosphorylate ADP comes from an intermediate molecule
The energy comes from the breaking of the phosphate bond and the interactions between

Question 16

What is oxidative phosphorylation?

Answer 16

Energy comes from the movement of electrons down the concentration gradient
Phosphate ions can come from anywhere
Involves the oxidation of RedNAD and RedFAD

Question 17

What is the chemisosmotic theory of the electron transport chain?

Answer 17

The hydrogen atoms produced during glycolysis and the Krebs cycle combine with the coenzymes NAD and FAD
NADH and RedFAD donate the electrons of the hydrogen atoms to the first molecule in the electron transport chain
Electrons pass along a chain of electron transfer chain carrier molecules in a series of oxidation-reduction reactions
The electron movement releases energy which causes the active transport of protons across the inner mitochondrial membrane and into the inter-membrane space
The protons accumulate in the inter-membrane space before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane
At the end of the chain, the electrons combine with these protons and oxygen to form water
Oxygen is therefore the final acceptor of electrons

Question 18

What are the alternative respiratory substances?

Answer 18

Lipids and proteins

Question 19

How are lipids used as respiratory substances?

Answer 19

Lipids are hydrolysed to glycerol and fatty acids
Glycerol is phosphorylated and converted to triose phosphate which enters the glycolysis pathway and subsequently the Krebs cycle
The fatty acid component is broken down into 2C fragments which are converted to acetyl coenzyme A
This then enters the Krebs cycle
The oxidation of lipids produces 2C fragments or carbohydrate and many H atoms
The H atoms are used to produce ATP during oxidative phosphorylation
This means that lipids release over double the energy of the same mass of carbohydrate

Question 20

How are proteins used as respiratory substances?

Answer 20

Protein is hydrolysed to amino acids
The amino group is then removed (deamination) before entering the respiratory pathway at different points depending on the number of carbon atoms
3C carbons are converted to pyruvate
4C and 5C become intermediates

Question 21

Which parts of aeorbic respiration can not continue when there is an absence of oxygen? Why is this?

Answer 21

The Krebs cycle and the electron transfer chain

Because soon all the FAD and NAD will be reduced

Question 22

What are the two types of anaerobic respiration?

Answer 22

In plants and some microorganisms: the pyruvate is converted to ethanol and carbon dioxide
In animals: the pyruvate is converted to lactate

Question 23

What is the word equation for anaerobic respiration in plants and some microorganisms?

Answer 23

Pyruvate + NADH = Ethanol + CO2 + Oxidised NAD

Question 24

What happens to the lactate produced during anaerobic respiration?

Answer 24

It is oxidised back to pyruvate
This can then either be oxidised further to release energy or converted into glycogen
This happens when oxygen becomes available again

Question 25

What are the negative effects of the buildup of lactate?

Answer 25

It will cause cramp and muscle fatigue

It is an acid so causes pH changes which affects enzymes

Question 26

What are the two ways in which energy from cellular respiration is derived?

Answer 26

Substrate level phosphorylation in glycolysis and the Krebs cycle
Oxidative phosphorylation in the electron transfer chain