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ECZ GRADE 10 - 12 BIOLOGY SUMMARISED
NOTES (RESPIRATION) WITH EXAM QUESTIONS
AND ANSWERS
ESKULU ZM
6/15/19
0
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G10 TO
G12 BIOLOGY
(RESPIRATION) NOTES
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Content
unit 4: respiration .................................................................................................................. 2
1.1.1 Difference between aerobic and anaerobic respiration ..........................................................2
1.1.2 ATP as energy .......................................................................................................................3
1.1.3 Uses of atp in humans ...........................................................................................................3
1.1.4 Process of respiration ...........................................................................................................4
1.1.5 Experiment involved in respiration ........................................................................................7
1.2.1 Gas exchange in humans .......................................................................................................8
1.2.2 Gaseous exchange in alveolus ............................................................................................. 10
1.2.3 Tracheal System in insects ................................................................................................... 12
1.2.4 Gaseous Exchange in Fish .................................................................................................... 13
1.2.5 Breathing............................................................................................................................ 15
1.2.6 Composition of inhaled and exhaled air ............................................................................... 17
1.2.7 respiratory diseases ............................................................................................................ 18
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UNIT 4: RESPIRATION
 All cells in living organisms (both animals and plants) need energy for
carrying out all the processes. Respiration is the chemical process by
which energy is produced from food.
 This process is usually referred to as tissue respiration or cellular
respiration. There are two types of respiration: aerobic respiration and
anaerobic respiration. The word “aerobic” means that oxygen is needed
for this chemical reaction and “anaerobic” means in the absence of
oxygen.
 Both types of respiration take place in a series of small steps not in one
jump. Each small step needs its own enzymes.
1.1.1 DIFFERENCE BETWEEN AEROBIC AND ANAEROBIC
RESPIRATION
Oxygen
Water
Location
Efficiency
Example of organisms
Aerobic respiration
i.
Produced
Begin in iii. and continue
into iv.
Very good vi. ATP from 1
glucose
Most organisms
Anaerobic respiration
ii.
Not produced
In v.
Produces vii. ATP per
glucose
Yeast, certain bacteria
Exercise
Fill in the blanks above
answers
i.
Present
ii. Absent iii. cytoplasm
v. cytoplasm
vi. 36
vii. 2
iv. Mitochondria
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1.1.2 ATP AS ENERGY
 Energy from respiration is not directly used by the organisms. It is
temporarily stored in a chemical substance called adenosine triphosphate
(ATP). ATP is sometimes called “currency” of energy for the cell.
 When there is need for energy, ATP is decomposed to ADP and a phosphate
group by the action of an enzyme called ATPase
1.1.3 USES OF ATP IN HUMANS
Usage
i. __________________
ii. __________________
iii. __________________
iv. __________________
v. __________________
Regulation of body temperature
Mode of action
Heartbeat, breathing and peristalsis.
Movement of the body
Formation of peptide bonds in
proteins.
Growth, synthesis of chromosome, cell
membrane etc.
Structural change of membrane
proteins to transport
To make ionic gradient across cell
membrane of the axon by Na-K pumps
Energy released to keep body warm
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Exercise
Name the chemicals in the blanks in the table above
Answer
i.
adenosine diphosphate ii. ATP iii. Muscle contraction iv. Protein
synthesis v. cell division vi. Active transport vii. Transmission of
nerve impulses
1.1.4 PROCESS OF RESPIRATION
 The food mainly used for energy in cells is glucose.
 Respiration must not be confused with the process of breathing, which
is also sometimes called ‘respiration’.
 Cellular respiration begins with glycolysis in both types of respiration.
Glycolysis is the process by which glucose is converted to pyruvate and
small amount of energy is released.
 Glycolysis occurs in the cytoplasm of cells. A series of steps of glycolysis
can be summarized by the following equation
Glucose

2 pyurate
+
little energy (2 atp)
 Depending on the availability of oxygen, pyruvate enter one of the two
pathways that completes cellular respiration of aerobic respiration or
anaerobic respiration:
 Aerobic respiration
o Is the reactions in cells that use oxygen to break down nutrients
to release energy
o The food molecules are combined with oxygen. The process is
called oxidation and the food is said to be oxidised.
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o Aerobic respiration is given by the equation
o The reaction takes place in small steps
o Although the energy is used for the processes in the body such as
the contraction of muscle cells, building up proteins from amino
acids, cell division, active transport etc. some of it always appears
as heat.
o In ‘warm-blooded’ animals (birds and mammals) some of this heat
is retained to maintain their body temperature.
 Anaerobic respiration
o A common example is the action of yeast on sugar solution to
produce alcohol.
o The sugar is not completely oxidised to carbon dioxide and water
but converted to carbon dioxide and alcohol.
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o This process is called fermentation and is shown by the following
equation:
o The processes of brewing and bread-making rely on anaerobic
respiration by yeast.
o The reaction takes place in small steps and needs several different
enzymes.
o The yeast uses the energy for its growth and living activities, but
you can see from the equation that less energy is produced by
anaerobic respiration than in aerobic respiration.
o This is because the alcohol still contains a lot of energy that the
yeast is unable to use.
o Anaerobic respiration also occurs in muscles during vigorous
exercise, because oxygen cannot be delivered fast enough to
satisfy the needs of the respiring muscle cells.
o The products are different to those produced by anaerobic
respiration in yeast.
o The process is shown by the following equation:
glucose 
lactic acid
o The lactic acid builds up in the muscles and causes muscle fatigue
(cramp).
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o Anaerobic respiration is less efficient than aerobic respiration
because it releases much less energy.
1.1.5 EXPERIMENT INVOLVED IN RESPIRATION
Experiment to determine whether oxygen is taken up during respiration
 Procedure:
Boil some water to expel all the dissolved oxygen.
When cool, use the boiled water to make up a 5% solution of glucose
and a 10% suspension of dried yeast.
Place 5cm3 of the glucose solution and 1cm3 of the yeast suspension in
a test-tube and cover the mixture with a thin layer of liquid paraffin to
exclude atmospheric oxygen.
Fit a delivery tube as shown in and allow it to dip into clear limewater.
 Result:
After 10–15 minutes, with gentle warming if necessary, there should be
signs of fermentation in the yeast–glucose mixture and the bubbles of
gas escaping through the limewater should turn it milky.

Interpretation:
The fact that the limewater goes milky
shows that the yeast– glucose mixture is
producing carbon dioxide. If we assume
that the production of carbon dioxide is
evidence of respiration, then it looks as if
the yeast is respiring. In setting up the
experiment, you took care to see that
oxygen was removed from the glucose
solution and the yeast suspension, and the
liquid paraffin excluded air (including
oxygen) from the mixture. Any respiration taking place must, therefore,
be anaerobic (i.e. without oxygen).
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 Control:
It might be suggested that the carbon dioxide came from a chemical
reaction between yeast and glucose (as between chalk and acid), which
had nothing to do with respiration or any other living process. A control
should, therefore, be set up using the same procedure as before but
with yeast that has been killed by boiling. The failure, in this case, to
produce carbon dioxide supports the claim that it was a living process in
the yeast in the first experiment that produced the carbon dioxide.
1.2.1 GAS EXCHANGE IN HUMANS
 Cells are supplied with oxygen and get rid of carbon dioxide. In humans and
other mammals, oxygen is obtained from the air by means of the lungs.
 In the lungs, oxygen dissolves in the blood and is carried to the tissues by
the circulatory system.
 Characteristics of respiratory surfaces in humans
o The exchange of oxygen and carbon dioxide across a respiratory
surface, as in the lungs, depends on the diffusion of these two gases.
o The rate of diffusion increases if:
 There is a large surface area exposed to the gas
 the distance across which diffusion has to take place is small
 there is a good blood supply, and
 there is a big difference in the concentrations of the gas at two
points brought about by ventilation
o Large surface area
 The presence of millions of alveoli in the lungs provides a very
large surface for gaseous exchange.
 One layer is the alveolus wall; the other is the capillary wall.
Thus, the distance for diffusion is very short.
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o Good blood supply
 The alveoli are surrounded by networks of blood capillaries.
 The constant removal of oxygen by the blood in the capillaries
lining the alveoli keeps its concentration low.
 Therefore, diffusion gradient which favours the rapid diffusion
of oxygen from the air passages to the alveolar lining is
maintained.
 The constant delivery of carbon dioxide from the blood into
the alveoli, and its removal from the air passages by
ventilation, similarly maintains a diffusion gradient that
promotes the diffusion of carbon dioxide from the alveolar
lining into the bronchioles.
o Ventilation
 Ventilation of the lungs helps to maintain a steep diffusion
gradient between the air at the end of the air passages and the
alveolar air.
 The concentration of the oxygen in the air at the end of the air
passages is high, because the air is constantly replaced by the
breathing actions.
 Oxygen has to dissolve in the thin film of moisture before
passing across the epithelium.
o Lung structure
 The lungs are enclosed in the thorax (chest region). They have
a spongy texture and can be expanded and compressed by
movements of the thorax in such a way that air is sucked in
and blown out.
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 The lungs are joined to the back of the mouth by the windpipe
or trachea.
 The trachea divides into two smaller tubes, called bronchi
(singular = bronchus), which enter the lungs and divide into
even smaller branches.
 The branches divide further into bronchioles. These fine
branches end in a mass of little, thin-walled, pouch-like air sacs
called alveoli.
 The epiglottis stops foo from entering the air passages when
we swallow.
1.2.2 GASEOUS EXCHANGE IN ALVEOLUS
 The alveoli have thin single-cell layer elastic walls called epithelium.
 Beneath the epithelium is a dense network of capillaries supplied with
deoxygenated blood
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 This blood, from which the body has taken oxygen, is pumped from the
right ventricle, through the pulmonary artery.
 Ventilation refers to the movement of air into and out of the lungs.
Gaseous exchange refers to the exchange of oxygen and carbon dioxide.
 The diagram above shows how oxygen reaches the red blood cells and how
carbon dioxide escapes from the blood. The oxygen combines with the
haemoglobin in the red blood cells, forming oxyhaemoglobin.
 The capillaries carrying oxygenated blood from the alveoli join up to form
the pulmonary vein, which returns blood to the left atrium of the heart.
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 From here it enters the left ventricle and is pumped all around the body, so
supplying the tissues with oxygen.
1.2.3 TRACHEAL SYSTEM IN INSECTS
 Many insects are terrestrial, that is, they live on land. Like all other
terrestrial animals, insects face a problem of water loss, which can lead to
dehydration.
 To prevent dehydration, insects are covered by a waterproof waxy cuticle,
which is called chitin.
 While offering protection against dehydration, the cuticle also acts as a
barrier to gaseous exchange.
 Openings to the atmosphere are found in the cuticle of the thorax and
abdomen.
 These openings are called spiracles. Spiracles allow air to pass in and out of
the insect body.
 Spiracles are directly connected to a network of fine tubes traversing whole
insect body called trachea (singular = trachea).
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 Trachea thus permeates through the insect body and end in the tissue as
very tiny tubes called tracheoles. The tracheoles are the sites for gaseous
exchange in insects.
1.2.4 GASEOUS EXCHANGE IN FISH
 Fish obtain oxygen from water in form of dissolved air by using the gills
located in the gill chamber.
 The gills are covered and protected by a semi-circular flap called
operculum. Each gill is made of filamentous outgrowths called gill
filaments.
 The gill filaments provide a large surface area for gaseous exchange.
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 Events in gaseous exchange in fish:
Step
1
2
3
4
5
Mouth
Volume of mouth
and pharynx
Operculum
Pressure in gill
chamber
Water
Inspiration
Open
Increase
Expiration
Close
Decrease
Close
Decrease
Open
Increase
Enter
Come out
Exercise
Fill the blanks in the diagrams above
Answers:
1. 2. 3. 4. 5.
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1.2.5 BREATHING
 Breathing refers to the movement of air into and out of the lungs, which is
brought about by changes in the volume of the thorax, or chest.
 These changes are caused by the action of two muscles, the diagram and
intercostal muscles.
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Step
1.a
1.b
2.a.
2.b.
External Intercostal muscles
Internal Intercostal muscles
Diaphragm
Movement of ribs
3.
4.
Volume of thorax
Lungs
When inhaling
Contract
Relax
Flatten
Upwards and
outwards
Increase
Expand
When exhaling
Relax
Contract
Elevate
Downwards and
inwards
Decrease
Reduce
 The outside of the lungs and the inside of the thorax are lined with a
smooth membrane called the pleural membrane.
 This produces a thin layer of liquid called pleural fluid, which reduces the
friction between the lungs and the inside of the thorax.
 The diagrams below show the mechanisms during breathing
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1.2.6 COMPOSITION OF INHALED AND EXHALED AIR
 Differences in composition of inspired and expired air are shown in the
table below
Inhaled
Oxygen
Carbon dioxide
Nitrogen
i.
iii.
v.
%
%
%
Exhaled
ii.
iv.
vi.
 The lining of the alveoli is coated with a film of moisture in which the
oxygen dissolves. Some of this moisture evaporates into the alveoli and
saturates the air with water vapour.
 The exhaled air contains more water vapour than the air you breathe in.
 The presence of water vapour in expired air is easily demonstrated by
breathing onto a cold mirror: condensation quickly builds up on the glass
surface.
 The exhaled air is warmer as well, so in cold temperate climates you lose
heat to the atmosphere by breathing.
Exercise
Fill in the blanks in the table above
answers:
i. 21 ii. 17 iii. 0.03
iv. 4 v.79 vi. 79
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1.2.7 RESPIRATORY DISEASES
 The following are diseases that affect the respiratory system
Name
Bronchitis
Pleurisy
Pneumoconiosis
Pneumonia
Tuberculosis
Emphysema
Influenza
Silicosis
Lung cancer
Cause
Inflammation of the bronchial tubes, leading to excess
mucus in bronchi.
Inflammation of the plural membranes
Inflammation of lungs due to, asbestos or silica dust etc.
Infection of the lungs by bacteria or viruses
Infection of the lungs by bacteria
Destruction of walls of the aveoli e.g caused by smoking,
leading to smokers cough
Infection of the respiratory passages by viruses
Prolonged inhaling of dust
Growth in walls of the bronchial tubes caused by smoking
etc.
 Smoking causes many respiratory diseases as well as coronary. Harmful
substances in tobacco are nicotine, tar, carbon monoxide, etc.
 Some substances are known as cancer-inducing chemicals called carcinogen.
This affects not only smokers but also the people in the same room. The
people are called “passive smokers”.
 The following are the harmful effects of smoking.
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QUESTIONS
1.
3.
4.
2.
5.
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6.
9.
7.
10.
8.
answers
1. C
2. A 3. D 4. C
5. B
6. D 7. D 8. A 9. D 10. B
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