1. • Living organisms respire because they need
energy to sustain life.
• Energy that is needed for organisms to move, grow,
excrete and reproduce, is obtained through the
consumption of food.
• To use the energy available in food, living things
need to breakdown the food substances.
• The breakdown of food substances to produce
energy in living cells is called respiration.
Why respire?
10.1 Why do We Respire?
2. What is aerobic respiration?
• It is the breakdown of food substances in the presence
of oxygen.
• It results in the production of a large amount of energy
• Carbon dioxide and water are also produced in the
process.
• The word equation for aerobic respiration:
+
glucose + oxygen
carbon
dioxide + water
10.1 Why do We Respire?
large
amount
of energy
3. What happens during exercise and why?
• Muscles contract vigorously to enable movement.
• Respiratory rate and heart rate increase to enable
more oxygen to reach the muscles.
• If the increased oxygen intake is not able to meet the
oxygen demand, an oxygen debt results and
anaerobic respiration takes place to provide the
energy required.
• Anaerobic respiration results in the accumulation of
lactic acid in the muscle cells.
10.1 Why do We Respire?
4. What happens during exercise and why?
• Lactic acid accumulation can cause fatigue and
muscular pains.
• Lactic acid has to be broken down via aerobic
respiration.
• Once lactic acid is removed, our muscles recover.
10.1 Why do We Respire?
5. What is anaerobic respiration?
• It is the breakdown of food molecules in the
absence of oxygen.
• It releases less energy than aerobic respiration.
• Lactic acid is produced in the process.
• The chemical equation for anaerobic respiration
in humans:
10.1 Why do We Respire?
+
glucose lactic acid
small amount
of energy
6. Human gas exchange system
nasal passage
larynx
pharynx
The fringe of hair and the
mucous layer on the walls
of the nasal passage
trap dust and foreign
particles.
Human Gas Exchange System
10.2
external nostril
7. Human gas exchange system
Human Gas Exchange System
10.2
epithelium enlarged
transverse section
of trachea
8. gland cell
ciliated cell
cilia
mucus
produced
by gland
cell
The inner surface of the
trachea is covered by a
membrane called the
epithelium. The epithelium
consists of:
• Cells that contain cilia.
Cilia sweep the trapped
particles and bacteria up
the bronchi and trachea,
into the pharynx.
• Gland cells produce
mucus that trap dust
particles and bacteria.
Human Gas Exchange System
10.2
9. nasal passage
larynx
pharynx
trachea
lung
Within the lungs, the bronchial
tubes divide repeatedly to form
bronchioles.
Bronchioles end in cluster of air
sacs called alveoli.
bronchiole
cluster of alveoli
bronchus
UR
L
Human gas exchange system
Gas Exchange in Humans
10.3
10. How is the alveoli adapted for
efficient gas exchange?
• The numerous alveoli in the lungs increase
the surface area for gas exchange.
The alveoli are the site of
gas exchange.
Human Gas Exchange System
10.2
11. • The wall of each alveolus is
only one cell thick to provide
a short diffusion distance for
gases.
• The alveolar surface is coated
with a thin film of water. This
allows gases to dissolve in it.
• The alveoli are well-supplied
with blood capillaries to
maintain a constant
concentration gradient of
oxygen and carbon dioxide.
blood vessel
from heart blood vessel
to heart
air in and out
capillary
network
alveolar
wall
capillary
wall
thin film
of water
The alveoli
Human Gas Exchange System
10.2
12. CO2
O2
inhaled oxygen
carbon dioxide
to be exhaled
capillary
alveolus
Gas exchange in the alveolus
deoxygenated
blood (carbon
dioxide rich)
oxygenated blood
(transported to the
heart and enters the
systemic circulation)
UR
L
Human Gas Exchange System
10.2
13. Gas exchange in the alveolus
Human Gas Exchange System
10.2
• Blood entering the lungs has:
– lower concentration of oxygen; and
– higher concentration of carbon dioxide than
the air in the alveolus (inspired air).
• Carbon dioxide from the blood diffuses into the
alveolus and this carbon dioxide will be
channelled out of the lungs via expiration.
14. Gas exchange in the alveolus
Human Gas Exchange System
10.2
• The air in the alveolus contains a higher
concentration of oxygen than the blood entering
the lungs.
• The oxygen in the alveolus diffuses into the
blood in the capillaries and is transported to the
heart where it is pumped throughout the body.
15. + O2
- O2
Haemoglobin
Oxyhaemoglobin
How oxygen is transported
Oxygen molecules bind to
haemoglobin (Hb) in red blood
cells to form oxyhaemoglobin.
+
High O2 concentration
Low O2 concentration
haemoglobin oxygen oxyhaemoglobin
Human Gas Exchange System
10.2
16. Nicotine
• addictive
• makes blood clot more
easily
• increases blood pressure
• increases the risk of heart
diseases
Carbon monoxide
• decreases the ability of red
blood cells to transport oxygen
• increases the rate at which fats
are deposited on the inner
arterial walls
• Narrows the lumen of arteries
and increases blood pressure
Tar
• Increases risk of lung cancer
• paralyses the cilia lining in air
passages
• reduces the efficiency of
gaseous exchange
Irritants
(e.g. formaldehyde, hydrogen
cyanide)
• paralyse the cilia lining in air
passages
• increase the risk of chronic
bronchitis and emphysema
10.3
Effects of Cigarette
Smoke on Human Health
17. Chronic bronchitis
In chronic bronchitis:
• The epithelium lining the air
passages is inflamed.
• There is excessive mucus
secretion.
• The cilia lining the air passages
are paralysed, leading to dust
particles trapped and cannot be
removed.
• The blocked airways cause
breathing difficulties.
• This results in frequent coughing
to clear the blocked air passages
over secretion
of mucus
cilia paralysed and
unable to remove
mucus
10.3
Effects of Cigarette
Smoke on Human Health
18. healthy
lungs
diseased
lungs
In emphysema:
• The partition walls of alveoli
break down due to violent
coughs.
• The lungs lose their elasticity
and become inflated with air.
• This reduces the surface area
available for gaseous
exchange.
• This causes breathing
difficulties
damaged
partition
walls
partition
walls
between
alveoli
Emphysema
10.3
Effects of Cigarette
Smoke on Human Health
