1) Respiration is the process by which organisms break down glucose to release energy. There are two types: aerobic respiration, which requires oxygen, and anaerobic respiration, which does not. 2) Aerobic respiration fully breaks down glucose, releasing the most energy as carbon dioxide and water. Anaerobic respiration only partially breaks down glucose when oxygen is absent, producing less energy and molecules like lactic acid. 3) In humans, anaerobic respiration occurs in muscles during intense exercise when oxygen demands outpace supply, leading to lactic acid buildup. Yeast undergoes anaerobic fermentation, producing ethanol and carbon dioxide.

1. CHAPTER 7 :
RESPIRATION
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2. 2

3.  State that all living processes require energy
 Identify the main substrate for producing energy
 State the two types of respiration
 Explain what cell respiration is
 Explain the energy production from glucose during the
process of aerobic respiration
 State the conditions leading to anaerobic respiration in
cells
 Explain the process of anaerobic respiration in human
muscles
 Write the chemical equations for aerobic & anaerobic
respiration
 Compare & contrast aerobic respiration with anaerobic
respiration
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4.  All organisms require energy to carry out all
living processes  growth (cell division),
reproduction (meiosis), response (transmitting
impulses), movement (contraction of muscle),
breathing, digestion & excretion (synthesis of
proteins, hormones, lipids & enzymes)
 RESPIRATION : the metabolic process in
which organic molecules broken down to
simpler products with the release of
chemical energy for other living processes.
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5.  Occurs in two stage :
 External respiration – a mechanical process that
maintains a continuous exchange of gases between the
respiratory surfaces of an organisms & its environment
 Internal respiration (cellular respiration) – the
biochemical process in which energy is made available to
all living cells
 The main substrate : glucose (obtain from digestion of
carbohydrates & photosynthesis)
 Occurs in mitochondria & cytoplasm of cells
 Involves a series of reactions controlled by enzymes
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6. TYPES OF RESPIRATION
 AEROBICRESPIRATION
 ANAEROBIC RESPIRATION
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7. AEROBIC RESPIRATION
 The breaking down of glucose in the
presence of oxygen to release chemical
energy
 Oxygen is required to oxidise the glucose
to produce CO2, H2O & energy
 The glucose is completely oxidised to
release all the chemical energy in the
glucose
 Occurs in mitochondria & cytoplasm of
cells
 Slowly occurs & in stages controlled by
enzymes.
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8.  The energy is released in stages & in small
amounts
 Some chemical energy released in changed to
heat energy while the rest of the chemical
energy released is stored in a form of ATP, a
carrier of chemical energy
 ATP can e regenerated by combining inorganic
phosphate (P) to ADP using the chemical energy
obtained from the oxidation of food
 ATP ↔ ADP + P + energy
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9.  When body cells need energy, ATP
molecules will be hydrolysed to yield
energy, a molecule energy & an inorganic
phosphate
 Energy from ATP can be used to carry out
biological process
Glucose + oxygen  carbon dioxide + water + energy
C6H12O6 + 6O2  6CO2 + 6H20 + 38 ATP (2898 kJ)
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10. A N A E R O B IC
R E S P IR A T IO N
 A type of cell respiration which occurs in
the absence of oxygen to release energy
 Glucose is not completely broken down 
not all energy in glucose is released
 Some of the energy in glucose is stored in
the product of anaerobic respiration  2
ATP is released
 Occurs in cytoplasm
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11. ANAEROBIC RESPIRATION IN HUMAN
MUSCLES
 Occurs during vigorous exercise @ vigorous activities
(100m sprint).
 Oxygen need to be transported fast enough to the
muscles for rapid cell respiration. Will enable the
release of sufficient energy for the vigorous muscle
activity.
 The breathing rate & heart rate are increased to
supply more oxygen quickly to the muscles for rapid
muscular contraction
 Still insufficient  have to carry out anaerobic
respiration to release energy
C6H12O6 2C3 H6O3 + 2 ATP (150 kJ)
Glucose Lactic acid Energy
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12.  Lactic acid accumulates in the muscles
causing muscular ache (cramp)
 An OXYGEN DEBT incurred because the
maximum rate of oxygen used is less than
the oxygen supplied
 Oxygen is pay off by rapid breathing
continues after the vigorous activity to
obtain sufficient oxygen
 The oxygen will break down the lactic acid
to carbon dioxide, water & energy
oxygen
Lactic acid carbon dioxide + water + energy
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13. ANAEROBIC RESPIRATION IN YEAST
 Yeast carries out both aerobic & anaerobic respiration
 Anaerobic respiration in yeast cells called
fermentation.
 Yeast secretes the enzyme zymase which hydrolyses
glucose in the absence of oxygen to form ethanol,
carbon dioxide & energy
C6H12O6 2C2H5OH + 2CO2 + 210 kJ
Glucose Ethanol carbon dioxide energy
 The enzyme zymase secreted by the yeast speeds up
the fermentation process
 The product of fermentation as CO2 is used as a raising
agent in aking bread while ethanol is used to produce
alcoholic drinks such as wine.
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14. COMPARISON BETWEEN AEROBIC
RESPIRATION & ANAEROBIC RESPIRATION
AEROBIC RESPIRATION ANAEROBIC
RESPIRATION
Presence of oxygen Absence of oxygen
Large amount of energy (38 Less energy (2 ATP @ 150
ATP @ 2898 kJ) kJ/210 kJ
Produce CO2 & water Produce lactic acid or ethanol
Completely broken down of Glucose not completely broken
glucose down
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