y3.2: respiration 💁‍♀️

Question 1

what is respiration？

Answer 1

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

Question 2

what is aerobic respiration?

Answer 2

The breakdown of glucose (glycolysis) in the presence of oxygen with the release of 38 ATP molecules. Carbon dioxide and water are released as waste products.

Question 3

What is glycolysis?

Answer 3

1 glucose molecule is broken down to form 2 molecules of pyruvate and 2 ATP molecules.

Question 4

Mode of action of mitochondrion in aerobic respiration

Answer 4

2 molecules of pyruvate enter the mitochondrion where they are completely oxidised into carbon dioxide and water to yield 18 ATP molecules each.

Question 5

Overall equation for aerobic respiration (word and symbols)

Answer 5

Glucose + oxygen => carbon dioxide + water + 38 ATP
C6H12O2 + 6 O2 => 6 H2O + 38 ATP

Question 6

Uses of energy in the body of humans

Answer 6

ATP is required for
- muscle contraction
- protein synthesis
- cell division
- active transport
- growth
- passage of nerve impulses
- maintenance of a constant body temperature

Question 7

what is anaerobic respiration?

Answer 7

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

Question 8

process of anaerobic respiration in humans

Answer 8

glycolysis takes place in the cytosol to yield 2 molecules of pyruvate and 2 molecules of ATP. in the absence of oxygen, pyruvate does not enter the mitochondria. instead, pyruvate is converted into lactic acid, which is removed as a metabolic waste product. (lactic acid fermentation)

Question 9

process of anaerobic respiration in yeast

Answer 9

glycolysis takes place in the cytosol to yield 2 molecules of pyruvate and 2 molecules of ATP. in the absence of oxygen, pyruvate is converted into ethanol and carbon dioxide, which are removed as metabolic waste products. (alcoholic fermentation used to make bread!)

Question 10

overall equation for anaerobic respiration (word and symbols, humans and yeast)

Answer 10

humans: glucose => lactic acid + ATP (small amount)
C6H12O6 => 2C3H6O3 + ATP (small amount)

yeast: glucose => ethanol + carbon dioxide + ATP (small amount)
C6H12O6 => C2H5OH + 2CO2 + ATP (small amount)

Question 11

why does anaerobic respiration take place during exercise?

Answer 11

• during vigorous muscular contractions, muscle cells first respire aerobically
• breathing rate and heart rate increases to take in and transport oxygen to the muscles at a faster rate. however, there is a limit to the increase in rate of breathing and heartbeat. hence, there is insufficient oxygen to meet the needs of vigorous muscular contractions
• in such cases, muscle cells also respire anaerobically to supplement the energy released by aerobic respiration to allow the muscles to continue contracting

Question 12

why does the body become tired after exercising for long periods of time?

Answer 12

• when anaerobic respiration occurs, there is a build-up of lactic acid in muscle cells and the cells incur an oxygen debt
• lactic acid concentrations build up in the muscles, and may become high enough to cause muscular fatigue. the body then needs to recover :<

Question 13

describe the recovery period after exercise

Answer 13

• after exercise, breathing rate continues to be high for some time to provide extra oxygen to repay the oxygen debt
• lactic acid is removed from muscle cells and transported to the liver
• in the liver, some of the lactic acid is oxidised to release energy
• this energy is used to convert the remaining lactic acid back to glucose
• when all the lactic acid has been converted back into glucose, the oxygen debt is repaid
• glucose is transported back to muscle cells