Anaerobic respiration

Question 1

What is the net gain of ATP molecules in anaerobic respiration?

Answer 1

2 ATP molecules per glucose molecules respired

Question 2

What are the two types of anaerobic respiration?

Answer 2

1. Alcoholic fermentation

2. Lactate fermentation

Question 3

What is alcoholic fermentation?

Answer 3

• Occurs in yeasts and some plant cells
• To keep glycolysis going there must be a supply of NAD
• Pyruvate produced is decarboxylated to ethanal (pyruvate carboxylase)
• CO2 is produced
• Ethanal reduced to ethanol (alcohol dehydrogenase) by accepting hydrogen from NADH, oxidising it back to NAD
• NAD can then accept hydrogen in conversion of TP to pyruvate to keep glycolysis going so ATP can be produced

Question 4

What is lactate fermentation?

Answer 4

• Occurs in mammals
• Pyruvate converted to lactic acid (lactate dehydrogenase)
• Conversion involves accepting hydrogen from reduced NAD, oxidising it back to NAD
• NAD then can accept hydrogen in conversion of triose phosphate to pyruvate so glycolysis can continue producing ATP
• Lactic acid converted back to glucose in liver by Cori cycle
• Lactic acid causes fall in pH and will lead to proteins denaturing which is why it cannot occur indefinitely
• Respiratory enzymes and muscle filaments are made from protein and would cease to work if the pH got too low

Question 5

How to investigate anaerobic respiration rates?

Answer 5

• Mixture of yeast and glucose solution in a conical flask
• Add bung with gas syringe connected
• Measure volume of CO2 produced per unit time
• Ensure oxygen doesn’t get into mixture by putting liquid paraffin on top of it
• Rate of CO2 production will be equal to rate of respiration

Question 6

Bacterial adaptations to low oxygen environments:

Answer 6

-Different groups of bacteria evolved to use nitrate ions, sulphate ions and carbon dioxide as final electron acceptors in place of oxygen

Question 7

Mammalian biochemical adaptations to low oxygen environments:

Answer 7

-Greater concentrations of haemoglobin and myoglobin, especially in muscles used in swimming, delaying onset of anaerobic metabolism
Whales have a higher tolerance to lactic acid so can respire anaerobically much longer without suffering tissue damage
-Greater tolerance for CO2 levels. Have a very effective blood buffering system that prevents a catastrophic rise in pH

Question 8

Mammalian physiological adaptations to low oxygen environments:

Answer 8

• Many diving mammals have a modified circulatory system
• When diving peripheral vasoconstriction occurs, so blood is shunted to heart, brain and muscles
• Heart rate drops, causing bradycardia
• Reduces energy demand of heart
• Whales exchange 80-90% of air in the lungs when they breathe so have more oxygen to use

Question 9

Mammalian physical adaptations to low oxygen environments:

Answer 9

• Streamlining to reduce drag due to friction from water when swimming, reducing energy demand during diving
• Limbs of marine mammals are ‘fin shaped’ to maximise the efficient use of energy in propulsion