Aerobic And Anaerobic Respiration

Question 1

What is respiration?

Answer 1

A set of metabolic reactions that take place in the organisms and break down respiratory substances e.g glucose into smaller inorganic molecules

Question 2

What can be broken down to release energy for respiration?

Answer 2

Energy rich respiratory substrates, such as glucose or fatty acids

Question 3

Where does glycolysis occur?

Answer 3

In the cytoplasm

Question 4

Describe the process of Glycolysis

Answer 4

1. Glucose is phosphorylated using 2 ATP into hexose phosphate
2. Hexose phosphate splits into 2 triose phosphate molecules
3. Oxidation of the 2 triose phosphate molecules yield 2 ATP each by substrate level phosphorylation. Overall glycolysis has a net gain of 2 ATP
4. Dehydration releases 2 hydrogen picked up by NAD forming pyruvate

Question 5

Where does the link reaction occur?

Answer 5

In the mitochondrial matrix

Question 6

What is important to remember in the link reaction?

Answer 6

It happens when oxygen is available. Therefore, from here the processes only occur in aerobic respiration

Question 7

Describe the process of the link reaction

Answer 7

1. One carbon atom is removed from pyruvate in the form of Carbon dioxide, the enzyme decarboxylase catalyses this reaction
2. Dehydrogenation catalysed by dehydrogenase releases pairs of hydrogen atom converting NAD to reduced NAD (NAD+H)
3. The remaining 2 carbon acetate molecule combines with coenzyme A to produce acetyl coenzyme A

Question 8

How many times does the link reaction occur for each glucose molecule?

Answer 8

Twice, every glucose molecule used in glycolysis, two pyruvate and 2 acetyl CoA molecules are made

Question 9

Where does the krebs’ cycle occur?

Answer 9

In the mitochondrial matrix

Question 10

Describe the process of the Krebs cycle

Answer 10

1. Acetal CoA from the link reaction combines with oxaloacetate (4C) to form citrate (6C). CoA is released back to the link reaction to be reused
2. The 6C is decarboxylated making Carbon dioxide and a 5 carbon acid, it is also dehydrogenated to make reduced NAD
3. The 5C is further dehydrogenated and decarboxylated and ATP is released, bringing you back to 4C.
4. FAD is converted into reduced FAD via dehydrogenation
   5) The 4C can combine with Acetyl CoA and repeat

Question 11

In the Krebs cycle how many pairs of hydrogen atoms are formed and which modules do they combine with?

Answer 11

Each turn of the cycle a total of 4 pairs of hydrogen atoms are formed.
3 pairs are combined with the hydrogen carrier NAD, one pair combines with fad

Question 12

Describe the electron transport chain

Answer 12

Both coenzymes NAD and FAD carry the hydrogen atoms on to the electron transport chain
NAD feeds electrons in earlier then FAD
1) Reduced NAD passes the electrons of the hydrogen atom into the first pump of the ETC.
2) Every move along releases enough energy to actively transport a proton to the inner membrane space
3) inner membrane is impermeable,e to protons so they accumulate in the inner membrane space. This forms an electrochemical gradient.
4) They cannot go down this gradient so the only way out is through ATP synthetase. Allowing it to catalyse ATP synthesis
5) Oxygen outside the ETM is known as the final electron acceptor. Electrons and H+ ions combine to form hydrogen and then combines with oxygen to form water . If this oxygen supply stops the ETM and ATP synthesis also stops.

Question 13

Why is respiration described as a catabolic process?

Answer 13

Complex molecules are broken down into smaller, simpler molecules

Question 14

Name the 4 stages of aerobic respiration.

Answer 14

Glycolysis
Link Reaction
Krebs Cycle
Electron Transport Chain

Question 15

How does pyruvate from glycolysis enter the mitochondria ?

Answer 15

Via active transport

Question 16

How many reduced NAD and FAD does the complete oxidation of one glucose molecule yield?

Answer 16

10 reduced NAD
2 reduced FAD

Question 17

Define anaerobic respiration

Answer 17

From of cellular respiration that takes place in the absence of oxygen.
Less ATP formed than in aerobic respiration

Question 18

State the product of anaerobic respiration in animals

Answer 18

Lactic Acid

Question 19

Outline anaerobic respiration in animals

Answer 19

Only glycolysis can continue
Reduced NAD transfers the H to pyruvate, forming lactic acid

Question 20

State the products of anaerobic respiration in plants and microorganisms

Answer 20

Ethanol and carbon dioxide

Question 21

Outline anaerobic respiration in plants and microorganisms

Answer 21

1. Glycolysis occurs
2. Triose phosphate is converted to pyruvate with the release of ATP and reduction of NAD
3. Pyruvate is decarboxylated, releasing carbon dioxide and forming ethanal
4. Reduced NAD reduces the ethanal forming ethanol
5. The oxides NAD can again be reduced during glycolysis . The cycle continues

Question 22

Compare the yield in aerobic to anaerobic respiration

Answer 22

Aerobic 30/32
Anaerobic - 2

Question 23

Name 2 types of molecules that can be used as alternative respiratory substrates

Answer 23

Amino acids from proteins
Glycerol and fatty acids from lipids

Question 24

How are lipids used in respiration?

Answer 24

Fates are hydrolysed into glycerol and fatty acids
Glycerol is converted into triose phosphate for use in glycolysis
Fatty acids split into 2C acetate fragments feeding into the Krebs cycle as Acetyl CoA

Question 25

Explain how proteins are used in respiration

Answer 25

Proteins hydrolysed into amino acids
Amino group converted into urea and excreted
Residue is converted into Acetyl CoA, pyruvate or some other Krebs cycle intermediate and oxidised

Question 26

Why is the maximum yield of ATP in aerobic respiration never achieved?

Answer 26

ATP is lost due to leaky membrane
Energy is required to move pyruvate and ADP into the mitochondrial matrix