Respiration

Question 1

Why is build up of lactic acid in the muscle cells bad?

Answer 1

Lactate causes a fall in pH which may stop the muscles from contracting due to reduced enzyme activity. This is due to interference with hydrogen bonding in tertiary structure

Question 1

Where is the cori cycle and what is its role?

Answer 1

convert lactic acid back to pyruvate. This takes place in the liver. It uses oxygen hence oxygen debt

Question 2

Why does anaerobic respiration produce a much lower yield of ATP than aerobic respiration?

Answer 2

There is no lik reaction, krebs cycle or oxidative phosphorylation

Question 3

Why can lactate fermentation be described as being ‘less wasteful’ than alcoholic fermentation?

Answer 3

Because it can be reversed, the pyruvate can then be used in aerobic respiration

Question 4

What are the two enzymes involved in alcoholic fermentation?

Answer 4

Pyruvate decarboxylase and ethanol dehydrogenase

Question 5

Is alcoholic fermentation reversible?

Answer 5

No. Ethanol is not broken down, even if oxygen becomes available again. It accumulates in cells and can rise to toxic concentrations

Question 6

What molecule links the metabolism of three types of macromolecule?

Answer 6

Acetyl CoA links protein, glucose (carbohydrates) and fats

Question 7

How do fatty acids enter the krebs cycle?

Answer 7

they are broken down into two acetyl CoA molecules. Hydrogen is released, picked up by FAD and NAD and fed into the ETC

Question 8

Why might desert animals respire fat?

Answer 8

Longer fatty acids chains have more hydrogen atoms so more (metabolic) water is produced

Question 9

What is a limitation of respiring fat?

Answer 9

If the carbon chain is long there are more carbon atoms so more CO2 produced. Muscles have a limited blood supply and if they respired fat not glucose they would produce more CO2 than could be removed quickly enough

Question 10

Why is more ATP produced from respiring a longer fatty acid chain?

Answer 10

There are more hydrogen atoms so more FAD and NAD reduced so more ATP produced. This is why tissues with a rich blood supply, such as the liver, respire fat

Question 11

How do proteins enter the krebs cycle?

Answer 11

Protein is hydrolysed to constituent amino acids which are deanimated at the liver (amino group converted to urea and excreted), residue is converted to acetyl CoA, pyruvate or another krebs cycle intermediate and oxidised

Question 12

What is a respiratory quotient?

Answer 12

ratio of the voumes of oxygen absorbed and carbon dioxide given off in respiration

Question 13

What are the respiratory quotients for Carbohydrates, protein and fat?

Answer 13

Carbohydrate= 1
protein= 0.9
fat= 0.7

Question 14

What would have no RQ?

Answer 14

Lactate pathway

Question 15

In a respirometer, what appartus is used to measure the change in liquid level?

Answer 15

A manometer

Question 16

What do you use in a respirometer to remove CO2?

Answer 16

Potassium or Sodium hydroxide

Question 17

How do you measure volume of CO2 released by germinating seeds?

Answer 17

First Measure volume of oxygen absorbed using the normal set up of the respirometer. Then replace the sodium hydroxide with water (so CO2 is no longer absorbed) and record the change in liquid level in the manometer.
Volume of CO2= volume O2- change in liquid level