2.4 Respiration

• Meaning of respiration
• Aerobic and anaerobic respiration; oxygen debt
• Respiratory substrates and the respiratory quotient
• Factors affecting respiration
• Economic importance of anaerobic respiration in industry and at home

• explain the meaning of respiration in living things
• describe aerobic and anaerobic respiration in living things
• relate the respiratory quotient to the type of substrate and respiration
• explain factors affecting respiration in living things
• describe the economic importance of anaerobic respiration
• acknowledge the significance of respiration in living things

“Why do your legs ache after running hard, and why do you keep panting after you stop?”

“How does the same process make both bread and beer?”

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1. Respiration with and without oxygen
   40 min · 2 practice tasks · quiz
   How cells release energy from food, what happens when oxygen runs short, and why you keep panting after a race.
2. Respiratory quotient and the uses of fermentation
   40 min · 2 practice tasks · quiz
   A number that reveals what a cell is burning, and the industry built on yeast.
3. Why respiration never stops
   40 min · 2 practice tasks · quiz
   The jobs energy pays for, why plants respire in daylight, and why sitting still is not free.
4. Investigating aerobic respiration
   40 min · 2 practice tasks · quiz
   How germinating seeds show that living cells release heat and carbon dioxide, and why boiled seeds are the control.
5. What changes the rate of respiration
   40 min · 2 practice tasks · quiz
   Temperature, oxygen, water, substrate and activity, and why damp stored grain heats up.
6. Fermentation at home and in industry
   40 min · 2 practice tasks · quiz
   Baking, mala, silage, biogas and biofuel as one process turned to Kenyan uses, plus a yeast practical.