IGCSE Biology

1. Respiration

2. LO:
• State the uses of energy in the body of
humans: muscle contraction, protein
synthesis, cell division, active transport,
growth, the passage of nerve impulses and
the maintenance of a constant body
temperature
• State that respiration involves the action of
enzymes in cells

3. LO:
• Define aerobic respiration as the chemical
reactions in cells that use oxygen to break down
nutrient molecules to release energy
• State the balanced chemical equation for aerobic
respiration as
C6 H12 O6 + 6O2 → 6CO2 + 6H2 O
• Investigate the uptake of oxygen by respiring
organisms, such as arthropods and germinating
seeds
• Investigate the effect of temperature on the rate
of respiration of germinating seeds

4. LO:
• Define anaerobic respiration as the chemical
reactions in cells that break down nutrient
molecules to release energy without using
oxygen
• State the balanced chemical equation for
anaerobic respiration in the microorganism yeast
as C6 H12 O6 → 2C2 H5 OH + 2CO2
• State that anaerobic respiration releases much
less energy per glucose molecule than aerobic
respiration

5. LO:
• State that lactic acid builds up in muscles and
blood during vigorous exercise causing an
oxygen debt
• Outline how the oxygen debt is removed
during recovery

6. LO: define the term respiration
• the set of chemical reactions that break down
nutrient molecules in living cells to release
energy
• Definition: respiration is the release of energy
from food substances, and goes on in all living
cells
• respiration involves the action of enzymes in
cells

7. Energy
= capacity for doing work
- Needed for life
- Source of energy = sun
- Energy conversions:
- First conversion = photosynthesis
- Second conversion = respiration

8. • Growth (proteosynthesis) – protein synthesis
• Maintenance of a constant body temperature
• Active transport
• Cell division
• Movement – muscle contraction
• The passage of nerve impulses

9. LO: Know the form of energy found in human body
Adenosine triphosphate
• Small packet of energy which can drive the
reactions in a cell
• Short-term store of energy

10. LO: Define aerobic respiration ;State the balanced chemical equation
for aerobic respiration
• the release of a relatively large amount of energy
in cells by the breakdown of food substances in
the presence of oxygen
• chemical reactions in cells that use oxygen to
break down nutrient molecules to release energy
• Takes place in mitochondria
• Some energy is lost as heat

11. LO: Define anaerobic respiration; state the word equation
• the release of a relatively small amount of energy
by the breakdown of food substances in the
absence of oxygen
Word equation:
• in muscles during hard exercise
glucose → lactic acid
• microorganism yeast
glucose → alcohol + carbon dioxide

12. LO: State the balanced chemical equation for anaerobic
respiration in the microorganism yeast as
• balanced chemical equation for anaerobic
respiration in the microorganism yeast
C6 H12 O6 → 2C2 H5 OH + 2CO2
• Glucose alcohol and carbon dioxide

15. • Anaerobic respiration releases
much less energy per glucose
molecule than aerobic
respiration!!!

16. LO: State that lactic acid builds up in muscles and blood during
vigorous exercise causing an oxygen debt
• Lactic acid produced by muscles during
anaerobic respiration is carried out of the
muscles in the blood
• It is transported to the heart, liver and kidneys
and is oxydated to pyruvate
• Heart, liver and kidneys need extra oxygen to
get rid of the lactic acid, provided by the deep
fast breathing that follows hard exercise

17. • HOMEWORK:
• Pages 52-53 Describe the role of anaerobic
respiration in yeast during brewing and bread-
making.