Section 3: Cells and Respiration

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Section 3 Cells and Respiration
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3.1 Where do plants and animals get their energy?
glucose
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3.1 Measuring Energy in Food
A food calorimeter can be used to determine the
energy content of different foods.
4.2 kilojoules (kJ) is the quantity of energy
needed to raise the temperature of 1 litre of
water by 1 oC.
Food calorimeter
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3.1 Respiration and the role of Enzymes
Respiration is a chemical process in which energy
is released from food molecules in cells.
The main source of energy in the cell is glucose.
The chemical energy stored in glucose is released
by a series of enzyme-controlled reactions called
respiration.
More info on Respiration
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3.1 What is the energy used for?
Some of the energy produced in cells is released
as heat during respiration, however most is used
for cellular activities such as - movement
(muscle contraction), - growth (cell
division), - communication between cells
(transmission of nerve impulses).
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3.1 Summary of energy release in cells
glucose
controlled by enzymes
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3.2 ATP
Adenosine triphosphate (ATP) is an important
substance found in living cells. It is formed
using the energy released during the respiration
of glucose.
An ATP molecule is made of an adenosine group
joined to three inorganic phosphate (Pi) groups.
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3.2 ADP
ATP is made in cells from the related molecule,
adenosine diphosphate (ADP).
An ADP molecule is made of adenosine joined to
only TWO inorganic phosphate (Pi) groups.
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3.2 Formation of ATP
Energy released during respiration is used to
form ATP. ATP acts as a energy storage molecule
within the cell. The chemical reaction that joins
an inorganic phosphate onto ADP to make ATP is
controlled by an enzyme.
Pi

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3.Formation of ATP
Pi

enzyme
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ATP
ADP Pi
Energy released from the breakdown of glucose is
used to synthesise ATP from ADP Pi. The energy
from ATP can be used by the cell as an energy
source when required.
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3.3 Aerobic Respiration
Aerobic respiration is the release of energy from
food in cells using oxygen.
Glycolysis is the breakdown of glucose resulting
in the formation of pyruvic acid.
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3.3. Overview of Aerobic Respiration
series of enzyme-controlled reactions
series of enzyme-controlled reactions
requires oxygen
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3.2 Breakdown of Pyruvic Acid
series of enzyme-controlled reactions
requires oxygen
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3.3. Production of ATP during glycolysis
glucose
2 ADP 2 Pi
2 ATP
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3.3. Production of ATP during breakdown of
pyruvic acid
36 ADP 36 Pi
In the presence of oxygen
36 ATP
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3.3 Total production of ATP during aerobic
respiration
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3.4 Anaerobic Respiration in Animals
In the absence of oxygen, glucose cannot be
broken down into carbon dioxide and water.
Therefore, glucose is only partly broken down and
only a few molecules of ATP are released.
More info on Anaerobic respiration
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3.4 Anaerobic Respiration in Animals
glucose
Glycolysis takes place, as in aerobic respiration
In the absence of oxygen, pyruvic acid is
converted to lactic acid
lactic acid
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3.4 Production of ATP during anaerobic
respiration
glucose
2 ADP Pi
2 ATP
No ATP molecules are formed.
lactic acid
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3.4 Production of ATP during anaerobic
respiration
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3.4 Effect of lactic acid on the muscles

• Muscle fatigue is caused as lactic acid builds up
  in the muscle cells and has two effects on the
  muscles
• Lactic acid causes the muscles to ache
• Lactic acid causes the muscles to contract
  with less power

More info on muscle fatigue
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3.4 Effect of lactic acid on the muscles
After anaerobic exercise stops, a period of
recovery is needed. During the recovery period,
the breathing rate and depth of breathing
continue at a higher level than normal to enable
the body to obtain enough oxygen.
The oxygen is used to convert lactic acid back
into pyruvic acid.
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3.4 Anaerobic Respiration in Animals
glucose
pyruvic acid
lactic acid
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3.4 Anaerobic Respiration in Plants and Yeast
Budding Yeast
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3.4 Anaerobic Respiration in Plants and Yeast
glucose
2 ADP Pi
2 ATP
No ATP molecules are formed.
ethanol
carbon dioxide

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3.6 Uses of Respiration in Yeast
Why is anaerobic respiration in yeast of
commercial value?
What type of organism are they?
FUNGI
BEER, BREAD
What causes yeast to change from one type of
respiration to another?
yeast
What food do they obtain their energy from?
GLUCOSE
What happens when yeast cells are budding?
LACK OF OXYGEN
REPRODUCING
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3.5 Comparing Aerobic and Anaerobic Respiration