2.7 Respiration

REVISION NOTES

IGCSE Edexcel Biology

2.7 Respiration

2.7.1 Understand how the process of respiration produces ATP in living organisms

Respiration:

Exothermic reaction
Continuously occurs in living cells
Glucose and oxygen is produced

Energy is released from glucose in the form of ATP (adenosine triphosphate)

2.7.2 Identify the sources and describe the functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, the mineral ions calcium and iron, water and dietary fibre as components of the diet

ATP provides energy for the cells:

Immediate source of energy
A high energy molecule

ATP is used for:

Chemical reactions
Grow and repair cells
Muscle contraction for:
- Movement
- Digestion
- Breathing
Regulating body temperature
Build large molecules from smaller molecules

2.7.3 Describe the differences between aerobic and anaerobic respiration

Aerobic respiration:

Requires oxygen
Completely breaks down glucose
Large amounts of energy can be released
Products are CO2 and H2O

Anaerobic respiration:

Does not require oxygen
Incomplete breakdown of glucose
Relatively smaller amounts of energy released
Products in animals: Lactic acid
Products in plants and yeast: Ethanol and CO2

2.7.4 Describe the structure and function of the human alimentary canal, including the mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine (colon and rectum) and pancreas

2.7.5 Understand how food is moved through the gut by peristalsis

Anaerobic respiration in animals:

Glucose is broken down into lactic acid
Exercising at high intensities:
- Demand for energy and oxygen in our muscles increases
Oxygen levels drop:
- Glucose is broken down without oxygen
- Production of lactic acid
Incomplete breakdown of glucose:
- Energy stored in the bonds of lactic acid molecules
Only a small amount of energy is released
Oxygen debt is the amount of energy required to break down lactic acid build up

Anaerobic respiration in plants:

- Glucose broken down into:

Ethanol

Carbon dioxide

Some plants and yeast can respire without oxygen
Anaerobic respiration in yeast is called fermentation

2.7.6 Practical: investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms

Production of carbon dioxide practical:

Add 5cm3 of hydrogencarbonate indicator into 3 boiling tubes
Add a layer of cotton to the boiling tubes
Add 5 germinating seeds to test tube A
Add 5 boiled/dead seeds to test tube B
Leave test tube C empty
Seal each tube using a rubber bung
Observe the colour of the indicator after 2 hours

- Tube A should turn yellow:
  - Presence of carbon dioxide produced by the respiring seed
- Tube B should stay orange:
  - Dead seeds do not respire
  - Do not produce carbon dioxide
- Tube C should stay orange:
  - No living cells that can respire

Set up two flasks, one with dead seeds and one with germinating seeds
Add cotton wool to seal the neck of each flask
Use a thermometer to measure the initial temperature of the seeds in each flast
Measure temperature again after 5 days

- Flask A with the germinating seed:
  - Increase in temperature due
  - Heat produced during respiration
- Flask B:
  - Stay at room temperature
  - Seeds are not respiring thus not producing heat