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Topic 4: Bioenergetics
Respiration
Learning Objectives:
1. Recall the equations for aerobic and
anaerobic respiration.
2. Analyse the differences between aerobic and
anaerobic respiration.
3. Explain the term metabolism.
Vocabulary
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Aerobic respiration
Anaerobic respiration
Exothermic
Endothermic
Oxygen debt (pg. 161)
Fermentation
Metabolism (pg. 165)
Mitochondria (review)
Enzymes (review)
Respiration
The process of transferring energy from
glucose, which goes on in every cell.
• Involve chemical reactions catalysed by
enzymes
• Exothermic process (releases energy)
Energy is Used To…
• Build larger molecules from smaller ones
(example: proteins are made from amino
acids)  this process also makes new cells for
growth, repair, and reproduction
• Muscle contraction (movement)
• Temperature regulation (mammals and birds)
Aerobic Respiration
• Aerobic means with oxygen
• Happens in the mitochondria
• Occurs all the time in plants and animals
Glucose + Oxygen  Carbon Dioxide + Water
C6H12O6 + 6O2  6CO2 + 6H2O
• Releases a large amount of energy
Anaerobic Respiration in Muscles
• Happens when there is not a large enough
supply of oxygen getting to the muscles.
• Happens when you need more energy than can
be supplied by aerobic respiration.
Glucose  Lactic Acid
• Releases less energy, so only useful in
“emergencies”.
Oxygen Debt
The amount of extra oxygen the body needs after
exercise to react with the build up of lactic acid
and remove it from the cells.
lactic acid + oxygen  carbon dioxide + water
• Lactic acid is poisonous (it also causes muscle
soreness) and needs to be removed.
• Breathing rate and heart rate remain high after
stopping exercise to “pay back” the oxygen debt.
Fermentation
The anaerobic respiration in yeast that
produces ethanol and carbon dioxide.
• Used in industry to produce ethanol (type of
alcohol)
glucose  ethanol + carbon dioxide
Comparing Aerobic and Anaerobic
Respiration
Is oxygen
needed?
Aerobic
Respiration
Anaerobic
Respiration
YES
NO
CO2 + Water
Lactic acid (muscles)
Ethanol + CO2 (yeast)
LARGE
SMALL
Products?
Amount of
energy?
Metabolism
The sum (total) of all the reactions that happen in a cell
or the body.
• Enzymes control the reactions in metabolism.
Examples of reactions:
• Exothermic reactions (such as breaking down large
molecules into smaller ones like in respiration) that
release energy
• Endothermic reactions (such as building large molecules
from small ones) use up energy from respiration
Summary
• http://www.bbc.co.uk/schools/gcsebitesize/scien
ce/add_aqa/respiration/aerobic_anaerobicact.sht
ml
Respiration in humans
• http://www.bbc.co.uk/education/clips/zbmd7ty
Respiration in plants
• http://www.bbc.co.uk/education/clips/z6cygk7
Writing Task
• Use all of the vocabulary terms to answer the
following essay question.
• Compare aerobic and anaerobic respiration
and explain the importance of respiration in
living things.