Respiration & Gas Exchange | Cambridge IGCSE Biology

This IGCSE Biology presentation explains respiration and gas exchange, covering the differences between aerobic and anaerobic respiration, the structure of the respiratory system, gas exchange in the lungs, and the role of diffusion. Learn about the effects of exercise on breathing, how smoking affects the lungs, and how respiration provides energy for cells. A perfect study resource for Cambridge IGCSE students preparing for exams!

1. FOR IGCSE BIOLOGY(0610)
GAS EXCHANGE
RESPIRATION &

2. Introduction
•Energy is needed for cellular respiration
•Food is in the source of energy for human
•Oxygen is needed to release this energy from food
•Respiration is the process by which the body obtains and
utilises oxygen and eliminates carbon dioxide
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3. The three process of respiration
in human
Process Mode of action
Breathing Involves external respiratory system to
take in O
2 and release CO
2
Internal
respiration
Exchange of substances between
capillaries and cells
Cellular
respiration
Release of energy from food
substances in living cells
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4.  the release of energy from food substances in all living cell
Comparison of aerobic and anaerobic respiration

CELLULAR RESPIRATION
Aerobic Anaerobic
Oxygen Present Absent
Energy from breakdown
of food
Large amount Relatively small
Location Begins in cytoplasm and
continues into the mitochondria
In cytoplasm
Efficiency  Very good
 36 molecules of ATP
from 1 glucose molecule
 Inefficient
 2 molecules of ATP
from 1 glucose
molecule
Example of organismAll organisms and some yeastYeast, bacteria, seals and
whales ( animals that dive
deep into the ocean)
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5. Aerobic Respiration
Uses of energy Mode of action
Muscle contraction For muscular contractions, cardiac muscles and
peristalsis
Protein synthesis Formation of peptide bonds
Cell division Growth, synthesis of chromosomes, cell membrane, etc.
Active transport Transport of substances across a concentration gradient
Growth New protoplasm, and in metabolic processes
Transmission of nerve
impulse
Along the axon, and for the transport of sodium ions out
Regulation of body
temperature
Energy released to keep the body warm
C
6H
12O
6 + 6O
2 6CO
2 + 6H
2O + ENERGY
Uses of aerobic respiration in human
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6. Anaerobic Respiration
Types Mode of action
Alcoholic fermentation (in
plants)
• Incomplete breakdown of sugar to release
energy
• Glucose → ethanol + CO
2 + energy (2 ATP)
• Economically important, e.g. in bread making,
brewing of beer and wine
Lactic acid fermentation (in
man and animal)
{ Some bacteria causes milk to turn sour and
form yoghurt
{ The bacteria feeds on sugar
{ Glucose → lactic acid + energy (2 ATP)
Anaerobic respiration and its uses
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7. Anaerobic respiration and its uses
Types Mode of action
During rigorous muscular
activity
¶During strenuous activity, breathing is not
enough to provide O
2 for respiration
¶Muscles experience a shortage of O
2,
causing formation of lactic acid
¶Accumulation of lactic acid causes
muscular cramp and fatigue
¶Muscle experiences O
2 debt during
periods of anaerobic respiration
¶Rapid breathing helps to repay the debt
by increasing O
2 in the muscles, thus
converting lactic acid back to glucose
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8. GASEOUS EXCHANGE IN MAN
•Lungs are the main respiratory organ in human
•They lie in the upper chest cavity
•Lungs are divided into section called lobes
•Air enters through nostril, into nasal passages,
pharynx, larynx, trachea, bronchi and bronchioles
before entering the alveoli
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9. Components of respiratory organs and its function
Organs Function
Nostrils Projecting nasal hairs filter out dust and debris
Nasal cavity üDivided by septum
üLined with ciliated epithelium
üBlood vessels below epithelium warms the air
Pharynx § Both air and food passage
§ Warms, moistens and filters air
Glottis Guarded by epiglottis (elastic flap at entrance of trachea)
Larynx Has vocal cord
Trachea ÆCylindrical tube with rings of cartilage to provide
support
ÆLayer of cilia and mucus – secreting cells
ÆTraps debris and sweeps it upwards towards
the mouth
ÆDivided to form two bronchi
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11. Components of respiratory organs and its functions
Organs Function
Lung JRich in blood supply, site of gaseous exchange
JLeft lung has two lobes
JRight lung is bigger, with three lobes
Bronchus Divided into smaller tubes called bronchioles
Plural membraneEncloses each lung
Diaphragm TMuscular tissue attached to thoracic cavity
TSeparates thoracic cavity from abdominal cavity
TThoracic cavity changes volume to assist in
breathing
Bronchiole {Connects directly to alveoli
{Widens and narrows during breathing
Alveoli ØAir sacs with thin wall with a moist surface
ØA network of blood capillaries covers the alveoli
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12. Process of breathing
inspiration expiration
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13. Comparison of inspiration and expiration
Inspiration Expiration
J External intercostal muscle
contracts
J Increase in volume of thoracic
cavity
J Ribs swing upwards and
outwards
J Diaphragm contracts, flattens
down
J An increase in thoracic cavity
volume reduces air pressure in
the cavity and lungs. Gases
expand to fill the available space,
creating a partial vacuum. This
forces air into the lungs.
ü Internal intercostal muscle
contracts
ü Reduction in volume of thoracic
cavity
ü Ribs swing downwards and
inward
ü Diaphragm is relaxed and
elevated
ü A reduction in the volume of
thoracic cavity increases air
pressure. This forces air out of
the lungs to equalise the
pressure of the lungs with the
atmosphere.
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14. Alveolar Pressure Changes
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15. Comparison of composition inhaled and exhaled air
Inhaled air Exhaled air
Oxygen 21% 17%
Carbon dioxide < 0.1% 4%
Nitrogen 79% 79%
Temperature Room temperature 37°C
Moisture Variable 100%
Dust Variable Absent
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16. Control of Breathing
•The respiratory center is located in the lower
medulla oblongata
•The stimulus for the respiratory center is the
presence of CO
2
•When CO
2 level increases, breathing rate increases
as well
•During anxiety or anger, the hormone adrenaline
increases metabolic rate and breathing
•If the levels drop, it inactivates the respiratory
center. This could lead to death.
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18. Adaptations of alveoli and blood
capillaries for exchange of gases
Adaptation Mode of action
Network of blood capillaries For transport of gases to and from
alveoli
Large surface area Allows for increased rate of diffusion
Moist surface of alveoli Allows gases to dissolve before
diffusion occurs
Concentration gradient Increased rate of diffusion
Distance between alveoli and blood
capillaries
Short distance increases rate of
diffusion
Wall of alveoli and blood capillariesOne cell thick : faster diffusion
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20. Internal Respiration
•This is the exchange of gases between blood and
body tissues
•Carbon dioxide is carried as carbamino
haemoglobin or bicarbonate ions
Hb + CO
2 → carbamino haemoglobin
CO
2 + H
2O → H
2CO
3
H
2CO
3 → H
+
+HCO
3
-
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21. Passage of Gases
Oxygen Carbon dioxide
During inspiration, O
2
diffuses across the alveolus
During expiration, CO
2 is
expelled with water vapour from
the lungs
It enters the blood streamThere is a higher concentration
of deoxygenated blood in this
area
98% combines with blood to
form oxyhaemoglobin
It is carried in the blood as
bicarbonate ions and carbamino
haemoglobin
< 2% enters the plasma It diffuses out of capillary into
the alveoli
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24. Pulmonary Volumes
•Tidal volume
•Volume of air inspired or expired during a normal
inspiration or expiration
•Inspiratory reserve volume
•Amount of air inspired forcefully after inspiration of
normal tidal volume
•Expiratory reserve volume
•Amount of air forcefully expired after expiration of
normal tidal volume
•Residual volume
•Volume of air remaining in respiratory passages and
lungs after the most forceful expiration
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25. Pulmonary Capacities
•Inspiratory capacity
•Tidal volume plus inspiratory reserve volume
•Functional residual capacity
•Expiratory reserve volume plus the residual volume
•Vital capacity
•Sum of inspiratory reserve volume, tidal volume, and expiratory
reserve volume
•Total lung capacity
•Sum of inspiratory and expiratory reserve volumes plus the tidal
volume and residual volume
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26. Spirometer and Lung Volumes/Capacities
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27. Respiratory System Functions
•Gas exchange: Oxygen enters blood and carbon dioxide
leaves
•Regulation of blood pH: Altered by changing blood
carbon dioxide levels Carbonic acid Buffer system
•Sound production: Movement of air past vocal folds
makes sound and speech
•Olfaction: Smell occurs when airborne molecules drawn
into nasal cavity
•Thermoregulation: Heating and cooling of body
•Protection: Against microorganisms by preventing entry
and removing them
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