Respiration

Question 1

Define respiration

Answer 1

Respiration is the process where glucose is broken down to release energy in the form of ATP, in all living cells

Question 2

Define aerobic respiration

Answer 2

Aerobic respiration is the breakdown of glucose in the presence of oxygen with the release of 38 ATP molecules

Question 3

What happens when oxygen is present

Answer 3

• 2 pyruvate molecules formed during glycolysis will enter the mitochondrion
• Pyruvate molecules are completely oxidised into carbon dioxides and water
• Each pyruvate molecule yields 18 ATP molecules

Question 4

Define glycolysis

Answer 4

Glycolysis is sugar splitting, where 1 glucose molecule is broken down to form 2 pyruvate molecules and 2 ATP molecules

Question 4

Where does glycolysis occur

Answer 4

Cytosol

Question 4

What are the products of aerobic respiration

Answer 4

• 6 water molecules
• 6 carbon dioxide molecules
• 38 ATP molecules

Question 5

What are the reactants in aerobic respiration

Answer 5

• 1 glucose molecule
• 6 oxygen molecules

Question 6

Define anaerobic respiration

Answer 6

Anaerobic respiration is the breakdown of glucose in the absence of oxygen, resulting in the release of less energy than aerobic respiration

Question 7

What happens when oxygen is absent

Answer 7

• Pyruvate molecules formed in glycolysis will not enter the mitochondrion
• Pyruvate is converted into either lactic acid or ethanol and carbon dioxide, which are removed as metabolic waste products

Question 8

What is alcoholic fermentation

Answer 8

• Pyruvate converted into ethanol and carbon dioxide
• Occurs in yeast
• Used in production of beer and bread

Question 9

What is lactic acid fermentation

Answer 9

• Pyruvate converted into lactic acid
• Occurs in human muscle cells, bacteria and fungi
• Used in production of cheese and yoghurt

Question 10

What is the chemical equation for lactic acid fermentation

Answer 10

C6H12O6 –>
2C3H6O3+ATP

Question 10

What is the chemical equation for aerobic respiration

Answer 10

C6H12O6+6O2 –>
6CO2+6H2O+ATP

Question 11

Can aerobic and anaerobic respiration occur at the same time

Answer 11

YES

Question 12

What is the chemical equation for alcoholic fermentation

Answer 12

C6H12O6 –>
2C2H5OH+2CO2+ATP

Question 13

What are the uses of ATP in the human body

Answer 13

• Muscle contraction
• Protein synthesis
• Cell division
• Active transport
• Growth
• Passage of nerve impulses
• Maintenance of constant body temperature

Question 14

Describe production of lactic acid in muscles during vigorous exercise

Answer 14

• During vigorous exercise, muscles first respire aerobically
• Breathing and heart rate increase
• But there is a limit to breathing and heart rate
• Hence there is insufficient oxygen to meet the needs of muscles
• Muscle cells must also respire anaerobically
• Extra energy released by anaerobic respiration supplements the energy released by aerobic respiration, allowing muscles to continue contracting
• Lactic acid builds up in muscle cells due to anaerobic respiration
• An oxygen debt is incurred, and soon the build up of lactic acid will overwhelm muscle cells

Question 15

Describe the recovery period

Answer 15

• Breathing and heart rate continues to be high for some time
• This provides ‘extra’ oxygen needed to repay the oxygen debt
• Lactic acid is removed from muscles and transported to liver
• Some lactic acid is oxidised to release energy
• This energy is used to convert remaining lactic acid to glucose
• Oxygen debt is repaid when all lactic acid is converted to glucose