Chapter 9 Respiration

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What is Respiration?
a process of oxidizing food to release energy
inside cells
Burning of Food
A demonstration of energy released from food
oxygen
food (sugar)
Burning
energy
water
carbon dioxide
food(sugar) + oxygen
carbon dioxide + water + energy (heat + light)
does not occur in living cells because the
reaction is too fast and cells would die as they
become so hot
Respiration
 reactions are catalyzed by enzymes
 main food substance which oxidized in cells is
glucose
C6H12O6 + 6O2
enzymes
6CO2 + 6H2O + energy
 as it takes place in all living cells, it is called
cellular respiration which is used to produce
energy for cells to use
Comparison of Burning
and Respiration
 Similarities
- both involve oxidative processes
- both require the use of oxygen and food and
they produce the same products of carbon
dioxide and water
- both reactions release energy
 Differences
Burning
Respiration
takes place in air
or oxygen
takes place in cells
a single-step
process
no enzymes involved
a series of
chemical reactions
controlled by
enzymes
 Differences
Burning
 energy release is
Respiration
 energy release is
vigorous and not under
slower and under
control
control
 energy is released in
 energy is released in
form of heat and light (a
form of heat and an
flame can result)
energy-rich compound
To Demonstrate Heat
Production by Respiring
Animals using a Differential
Air Thermometer
graph paper
clip
clip
A
B
stoppered
air-filled
test tube
cotton
wool
stoppered airfilled test tube
U-shaped capillary
tube filled with
coloured liquid
cotton
wool
mouse
What is the function of the clips ?
Ans: To equalize the pressure on the two sides of the
capillary tube.
graph paper
clip
clip
A
B
stoppered
air-filled
test tube
cotton
wool
stoppered airfilled test tube
U-shaped capillary
tube filled with
coloured liquid
cotton
wool
mouse
Why should the containers be wrapped in cotton wool ?
Ans: It acts as an insulator to prevent heat loss.
graph paper
clip
clip
A
B
stoppered
air-filled
test tube
cotton
wool
stoppered airfilled test tube
U-shaped capillary
tube filled with
coloured liquid
cotton
wool
mouse
Which is preferable, a capillary tube with a wide bore or one
with a narrow bore ?
Ans: A capillary tube with a narrow bore is preferred than the
wide one as it is more sensitive and will give better
results.
graph paper
clip
clip
A
B
stoppered
air-filled
test tube
cotton
wool
stoppered airfilled test tube
U-shaped capillary
tube filled with
coloured liquid
cotton
wool
mouse
What happens to the levels of the coloured liquid ?
Ans: The coloured liquid rises up the left arm of the Ushaped capillary tube.
graph paper
clip
clip
A
B
stoppered
air-filled
test tube
cotton
wool
stoppered airfilled test tube
U-shaped capillary
tube filled with
coloured liquid
cotton
wool
mouse
Why ?
Ans: Because the mouse in container B carries out
respiration to release heat energy which warms up the
air in the test tube.
To Demonstrate Heat
Production by Germinating
Seeds using Thermos Flasks
B
A
thermos flask
germinating
seeds
Seeds killed
by boiling
cotton wool
thermometer
Which thermos flask shows a higher temperature
at the end of the experiment ?
Ans: Flask A showed a higher temperature at the end of
the experiment.
B
A
thermos flask
germinating
seeds
Seeds killed
by boiling
cotton wool
thermometer
Why ?
Ans: It is because living seeds produce heat energy.
B
A
thermos flask
germinating
seeds
Seeds killed
by boiling
cotton wool
thermometer
What is the purpose of washing the seeds with a
disinfectant ?
Ans: To kill any bacteria and fungi present on the
seeds.
B
A
thermos flask
germinating
seeds
Seeds killed
by boiling
cotton wool
thermometer
It is advisable not to fill the flasks completely with
seeds. Why ?
Ans: To provide air for the seeds to respire.
B
A
thermos flask
germinating
seeds
Seeds killed
by boiling
cotton wool
thermometer
Why are the flasks supported in the upside-down
position ?
Ans: The flasks are supported in the upside-down
position because
 carbon dioxide, produced during respiration of
the living seeds, is a heavier gas and may
escape through the cotton wool.
 hot air rises up, and inverting it will ensure that
heat will not escape through the cotton wool.
 it is easier to read the thermometer as the
thermos flasks are not transparent.
To Show Production of
Carbon Dioxide by a
Respiring Animal
to suction
pump
A
B
bell jar
C
lime water
potassium
hydroxide
solution
lime water
glass plate
mouse
Why is it necessary to bubble the incoming air through
potassium hydroxide solution before it is supplied to the
mouse ?
Ans: It is used to remove carbon dioxide in the
incoming air.
to suction
pump
A
B
bell jar
C
lime water
potassium
hydroxide
solution
lime water
glass plate
mouse
Which solution changes colour at the end of the
experiment ? What does this show ?
Ans: The lime water in flask C turns milky. It is because
carbon dioxide is given off by the mouse.
To Show the Release of
Carbon Dioxide by
Germinating Seeds
thread
thread
muslin bag
seeds
(heat-killed)
germinating
seeds
moist cotton wool
A
hydrogencarbonate
indicator solution
B
Why is it necessary to wash the seeds with a disinfectant ?
Ans: It is used to kill microorganisms.
thread
thread
muslin bag
seeds
(heat-killed)
germinating
seeds
moist cotton wool
A
hydrogencarbonate
indicator solution
B
What is the function of the moist cotton wool inside the
muslin bag ?
Ans: It prevents the seeds from drying out.
thread
thread
muslin bag
seeds
(heat-killed)
germinating
seeds
moist cotton wool
A
hydrogencarbonate
indicator solution
B
What has happened to the hydrogencarbonate indicator
solution in the two tubes ?
Ans: Indicator solution in tube A turns yellow while the
indicator solution in tube B remains unchanged.
thread
thread
muslin bag
seeds
(heat-killed)
germinating
seeds
moist cotton wool
A
hydrogencarbonate
indicator solution
B
What can be concluded from this experiment ?
Ans: Carbon dioxide is released by the germinating seeds.
Uses of the Energy Released
during Respiration
Human
Other Animals
Plants
 muscle
 produce light
 keep warm
 produce sound 
contraction
in fireflies
 absorb food by 
active transport
in some birds
produce smell in
some mammals
 absorb
mineral salts
by active
transport
transport food
substances
ATP
 energy is mainly released as heat and ATP
during respiration in cells
 however, during respiration, some ATP should
be consumed first before other ATP can be
formed
 the ATP consumed is used to form other ATP
from ADP and phosphate groups
ADP + phosphate
+ energy
ATP
(from breakdown
of glucose)
 ATP is a high-energy compound while ADP is a
low-energy one
 ATP can only store energy for a short period
 ATP is made inside organelles, mitochondria,
which is scattered in the cytoplasm of a cell
Anaerobic Respiration
 respiration in human is mainly aerobic
respiration as oxygen is essential
 when oxygen is not needed during respiration,
it is called anaerobic respiration
 yeast and muscle cells are examples which
they can respire anaerobically for a short time
Alcoholic Fermentation
 without oxygen, yeast cells respire as follows:
C6H12O6
enzymes
2CO2 + 2C2H5OH
+ energy
(ethanol)
 amount of energy released anaerobically is
smaller when compared with the aerobic
method
aerobic
respiration
anaerobic
respiration
amount of energy
released
large
small
oxidation of
glucose
completely
place of
occurrence
mitochondria
partly
cytoplasm
Industrial Use of
Yeast Fermentation
alcohol produced is used for:
 brewing beer
 making wine
carbon dioxide released is used for:
 baking bread
Lactic Acid Fermentation
 extra oxygen is required for undertaking
sternuous exercise
people cannot supply enough oxygen to
muscles even they breathe faster and deeper


muscle need to produce energy anaerobically
by breaking down glucose into lactic acid
C6H12O6
enzymes
2C3H6O3 + energy
 lactic acid will cause muscle fatigue and muscle
cramps if they are allowed to accumulate
 a large amount of oxygen is needed to break
down the accumulated lactic acid into carbon
dioxide and water or turn to glycogen in liver for
storage so we pant after doing exercise
 the amount of oxygen required to get rid of lactic
acid is called oxygen debt
To Show Anaerobic
Respiration of Germinating
Seeds in Oil
germinating seeds
gas
wire gauze
paraffin oil
syringe
at the start
after two days
hydrogencarbonate
indicator solution
Does the boiling tube contain a gas after 2 days?
Ans: Yes.
germinating seeds
gas
wire gauze
paraffin oil
syringe
at the start
after two days
hydrogencarbonate
indicator solution
What happens to the hydrogencarbonate indicator
solution when the gas is bubbled through it?
Ans: The solution turns yellow.
germinating seeds
gas
wire gauze
paraffin oil
syringe
at the start
after two days
What is the gas produced?
Ans: It is carbon dioxide.
hydrogencarbonate
indicator solution
germinating seeds
gas
wire gauze
paraffin oil
syringe
at the start
after two days
hydrogencarbonate
indicator solution
What can be learned about the respiration of germinating
seeds from this experiment?
Ans: Germinating seeds can respire anaerobically and
release carbon dioxide in the absence of oxygen.
To Show Production of
Ethanol and Carbon Dioxide
during Fermentation of
Glucose by Yeast
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
Why is it important to boil the glucose solution?
Ans: This drives off any dissolved oxygen.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
Why must the glucose solution be cooled down before
yeast is added?
Ans: It is because yeast would be killed when hot.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
What is the function of liquid paraffin?
Ans: It prevents the mixture from coming into contact
with air.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
What has happened to the hydrogencarbonate indicator
solution?
Ans: The hydrogencarbonate indicator solution has
changed from red to yellow.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
What does this show?
Ans: This shows that yeast can respire anaerobically to
produce energy.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
What has happened to the reading of each thermometer?
Ans: The reading of the thermometer of the experimental
set-up rises.
thermometer
thermos
flask
liquid
paraffin
yeast in glucose
solution which has been
previously boiled and hydrogencarbonate
indicator solution
then cooled down
At the end of the experiment, what new substance would
you expect to find in the glucose solution containing living
yeast?
Ans: We can find alcohol in it.
Comparison of Aerobic and
Anaerobic Respiration
 Similarity
 Sugar is broken down to release energy
 ATP is made
 Both are controlled by enzymes
 Differences
aerobic
respiration
anaerobic
respiration
oxygen
requirement
essential
nil
oxidation of
sugar
complete
oxidation
energy
released
large
amount
incomplete
oxidation
small
amount
end
products
occurrence
aerobic
respiration
anaerobic
respiration
inorganic:
CO2 and H2O
organic:
ethanol or
lactic acid
in most
living cells
in lower organisms
(e.g. bacteria and
yeast) and
vertebrate muscles
Differences between
Respiration and Photosynthesis
aerobic
respiration
photosynthesis
produces carbon
dioxide and water
requires carbon
dioxide and water
energy is
released
energy (light)
is absorbed
an oxidative
process
a reductive
process
aerobic
respiration
a breaking down
process
occurs in all
living cells at
all times
occurs in
mitochondria
photosynthesis
a synthetic process
occurs in green
plants only when
light is available
occurs in
chloroplasts
~ END ~

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