1. iGCSE Biology Section 2 lesson 4

2. Structures and functions in living organisms
Content
Section 2
Structures and functions in living organisms
a) Levels of organisation
b) Cell structure
c) Biological molecules
d) Movement of substances into and out of cells
e) Nutrition
f) Respiration
g) Gas exchange
h) Transport
i) Excretion
j) Coordination and response

3. Lesson 4 Content f) Respiration g) Gas exchange f) Respiration
2.33 understand that the process of respiration releases energy in living organisms
2.34 describe the differences between aerobic and anaerobic respiration
2.35 write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms
2.36 write the word equation for anaerobic respiration in plants and in animals
2.37 describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.

4. Lesson 4 Content f) Respiration g) Gas exchange g) Gas exchange
2.38 understand the role of diffusion in gas exchange
Flowering plants
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis
2.40 understand that respiration continues during the day and night, but
that the net exchange of carbon dioxide and oxygen depends on the
intensity of light
2.41 explain how the structure of the leaf is adapted for gas exchange
2.42 describe the role of stomata in gas exchange
2.43 describe experiments to investigate the effect of light on net gas
exchange from a leaf, using hydrogen-carbonate indicator
Humans
2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes
2.45 understand the role of the intercostal muscles and the diaphragm in
ventilation
2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries
2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease
2.48 describe experiments to investigate the effect of exercise on breathing in humans.

5. What is gaseous exchange?
What is respiration?
What is gaseous exchange?

6. What is gaseous exchange?
What is respiration?
Respiration is the release of energy from the breakdown of glucose, by combining it with oxygen inside living cells.
What is gaseous exchange?

7. What is gaseous exchange?
What is respiration?
Respiration is the release of energy from the breakdown of glucose, by combining it with oxygen inside living cells.
What is gaseous exchange?
Gaseous exchange is the movement of gases (oxygen and carbon dioxide) into and out of an organism.

8. Respiration – two sorts
Aerobic respiration - in the presence of oxygen.
Involves the complete breakdown of glucose.
Provides more energy.
End products in animals and plants: carbon dioxide and water

9. Respiration – two sorts
Aerobic respiration - in the presence of oxygen.
Involves the complete breakdown of glucose.
Provides more energy.
End products in animals and plants: carbon dioxide and water
Anaerobic respiration - in the absence of oxygen.
Involves the incomplete breakdown of glucose.
Provides less energy.
End product in animals – lactic acid. End product in plants - ethanol

10. Glucose + oxygen  carbon dioxide + water + energy
Aerobic respiration
Glucose + oxygen  carbon dioxide + water + energy

11. Glucose + oxygen  carbon dioxide + water + energy
Aerobic respiration
Glucose + oxygen  carbon dioxide + water + energy
C6H12O O2  6CO H2O + energy

12. Glucose + oxygen  carbon dioxide + water + energy
Aerobic respiration
Glucose + oxygen  carbon dioxide + water + energy
C6H12O O2  6CO H2O + energy
What do you notice?

13. Photosynthesis
Light
6CO H2O C6H12O O2
Chlorophyll

14. Glucose
Blood capillary
Muscle cell

15. Glucose and oxygen diffuse from the blood into the muscle cell
Blood capillary
Glucose Oxygen
Muscle cell
Glucose and oxygen diffuse from the blood into the muscle cell

16. Glucose and oxygen diffuse from the blood into the muscle cell
Deoxygenated red blood cells
Blood capillary
Glucose Oxygen  Carbon dioxide + Water
Muscle cell
Glucose and oxygen diffuse from the blood into the muscle cell
Carbon dioxide and water diffuse from the muscle cell into the blood

17. Glucose and oxygen diffuse from the blood into the muscle cell
Deoxygenated red blood cells
Blood capillary
Energy
Glucose Oxygen  Carbon dioxide + Water
Muscle cell
Glucose and oxygen diffuse from the blood into the muscle cell
Carbon dioxide and water diffuse from the muscle cell into the blood
Energy is used for muscle contraction

18. Levels of Organisation
A. Cells

19. Levels of Organisation
A. Cells
Mitochondria - organelles inside the cell where cellular respiration takes place. They absorb glucose and oxygen, release the energy and then convert it into forms that are usable by the cell. Mitochondria are more numerous in active cells such as muscle cells.

20. Why anaerobic respiration?
If it is so inefficient compared with aerobic respiration, why do cells bother?
Sometimes our muscles are working so hard that the lungs and bloodstream cannot deliver oxygen fast enough, so the muscles must respire anaerobically.
This can lead to a build up of lactic acid in the muscle.

21. Why anaerobic respiration?
If it is so inefficient compared with aerobic respiration, why do cells bother?
A lactic acid build-up in muscles can result in cramp, an unpleasant and often painful sensation caused by muscle contraction or over-shortening.

22. Why anaerobic respiration?
If it is so inefficient compared with aerobic respiration, why do cells bother?
In order to break down the lactic acid the body needs more oxygen  OXYGEN DEBT

23. Why anaerobic respiration?
If it is so inefficient compared with aerobic respiration, why do cells bother?

24. Anaerobic respiration in plants

25. Anaerobic respiration in plants
Glucose  ethanol carbon dioxide + energy

26. Anaerobic respiration in plants
Glucose  ethanol carbon dioxide + energy
C6H12O6  2C2H5OH CO2

27. Anaerobic respiration in plants
Glucose  ethanol carbon dioxide + energy
C6H12O6  2C2H5OH CO2
In plants, anaerobic respiration (respiration without oxygen) is known as fermentation. This process is commonly used to our advantage in the production of beer and ales, and wine.

28. Aerobic v Anaerobic

29. Aerobic v Anaerobic AEROBIC ANAEROBIC
A very efficient method of producing energy.
Inefficient (incomplete breakdown of glucose) – releases 1/20th energy compared to aerobic.

30. Aerobic v Anaerobic AEROBIC ANAEROBIC
A very efficient method of producing energy.
Inefficient (incomplete breakdown of glucose) – releases 1/20th energy compared to aerobic.
Occurs during normal daily activity.
Produces energy much faster over a short time period. Eg. sprinting

31. Aerobic v Anaerobic AEROBIC ANAEROBIC
A very efficient method of producing energy.
Inefficient (incomplete breakdown of glucose) – releases 1/20th energy compared to aerobic.
Occurs during normal daily activity.
Produces energy much faster over a short time period. Eg. sprinting
Produces energy more slowly than anaerobic.
Build-up of waste products eventually stops the muscle from working

32. Lesson 4 Content f) Respiration g) Gas exchange g) Gas exchange
2.38 understand the role of diffusion in gas exchange
Flowering plants
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis
2.40 understand that respiration continues during the day and night, but
that the net exchange of carbon dioxide and oxygen depends on the
intensity of light
2.41 explain how the structure of the leaf is adapted for gas exchange
2.42 describe the role of stomata in gas exchange
2.43 describe experiments to investigate the effect of light on net gas
exchange from a leaf, using hydrogen-carbonate indicator
Humans
2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes
2.45 understand the role of the intercostal muscles and the diaphragm in
ventilation
2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries
2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease
2.48 describe experiments to investigate the effect of exercise on breathing in humans.

33. What is gaseous exchange?
What is respiration?
Respiration is the release of energy from the breakdown of glucose, by combining it with oxygen inside living cells.
What is gaseous exchange?
Gaseous exchange is the movement of gases (oxygen and carbon dioxide) into and out of an organism.

34. What is gaseous exchange?
Gaseous exchange is the movement of gases (oxygen and carbon dioxide) into and out of an organism.
Gaseous exchange is brought about by the actions of the breathing system (also referred to in some textbooks as the respiratory system)

35. The Breathing System

36. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing

37. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.

38. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Rib muscles - the intercostals. Raise and lower the rib cage

39. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage

40. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage
Diaphragm – a sheet of muscle used in the mechanism of breathing

41. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage
Right bronchus – a branch of the trachea
Diaphragm – a sheet of muscle used in the mechanism of breathing

42. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage
Bronchiole - a smaller branch of the bronchus
Right bronchus – a branch of the trachea
Diaphragm – a sheet of muscle used in the mechanism of breathing

43. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage
Bronchiole - a smaller branch of the bronchus
Right bronchus – a branch of the trachea
Alveoli - clusters of grape-like air sacs where gas exchange takes place
Diaphragm – a sheet of muscle used in the mechanism of breathing

44. The Breathing System
Trachea – surrounded by rings of cartilage to stop it collapsing
Ribs – these protect the contents of the thorax. There are 12 pairs of ribs in both men and women.
Left lung
Rib muscles - the intercostals. Raise and lower the rib cage
Bronchiole - a smaller branch of the bronchus
Right bronchus – a branch of the trachea
Alveoli - clusters of grape-like air sacs where gas exchange takes place
Diaphragm – a sheet of muscle used in the mechanism of breathing

45. Alveolus (plural alveoli)
Where oxygen and carbon dioxide move between the lungs and the blood stream.

46. Bronchiole
Alveolus
There are millions of alveoli in each lung, very close to blood capillaries

47. 1. Deoxygenated blood flow from the tissues, rich in carbon dioxide
Bronchiole
Alveolus 1
1. Deoxygenated blood flow from the tissues, rich in carbon dioxide

48. Bronchiole
Alveolus 2
2. Carbon dioxide diffuses out of the blood stream into the alveoli, and then into the bronchiole

49. Bronchiole
Alveolus 3
3. Oxygen diffuses from the bronchiole into the alveoli and then into the red blood cells.

50. Bronchiole 4
Alveolus
4. Oxygenated blood now leaves the alveoli and carries oxygen to the tissues.

51. Features of the alveoli:

52. Features of the alveoli:
1. A very large, moist surface area.

53. Features of the alveoli:
A very large, moist surface area.
An excellent capillary blood supply

54. Features of the alveoli:
A very large, moist surface area.
An excellent capillary blood supply
Very thin cell membrane separating blood and lung

55. Ventilation INHALATION = taking air into the lungs
EXHALATION = removing air from the lungs

56. Ventilation IN OUT Nitrogen 79% Oxygen 21% Oxygen 16%
Carbon dioxide 0.04%
Carbon dioxide 4%

57. Ventilation BREATHING IN Rib cage moves upwards and outwards.
Overall effect: volume of the thorax increases, pressure decreases, so air is drawn IN
Diaphragm moves downwards and becomes flatter.

58. Ventilation BREATHING OUT Rib cage moves downwards and inwards.
Overall effect: volume of the thorax decreases, pressure increases, so air is pushed OUT
Diaphragm moves upwards and becomes dome shaped.

59. Lesson 4 Content f) Respiration g) Gas exchange g) Gas exchange
2.38 understand the role of diffusion in gas exchange
Flowering plants
2.39 understand gas exchange (of carbon dioxide and oxygen) in relation to respiration and photosynthesis
2.40 understand that respiration continues during the day and night, but
that the net exchange of carbon dioxide and oxygen depends on the
intensity of light
2.41 explain how the structure of the leaf is adapted for gas exchange
2.42 describe the role of stomata in gas exchange
2.43 describe experiments to investigate the effect of light on net gas
exchange from a leaf, using hydrogen-carbonate indicator
Humans
2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes
2.45 understand the role of the intercostal muscles and the diaphragm in
ventilation
2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries
2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease
2.48 describe experiments to investigate the effect of exercise on breathing in humans.

60. Leaf adaptations Cross section through a leaf
Inter-cellular air spaces
Lower epidermis – note the presence here of stomata (tiny pores surrounded by guard cells).

61. Leaf adaptations Cross section through a leaf
Lower epidermis – note the presence here of stomata (tiny pores surrounded by guard cells).

62. Leaf adaptations Cross section through a leaf
Oxygen is absorbed and carbon dioxide is released direct from cells to air spaces during respiration.

63. Gaseous exchange in plants
6CO H2O  C6H12O O2
C6H12O O2  6CO H2O

64. Gaseous exchange in plants
PHOTOSYNTHESIS!
6CO H2O  C6H12O O2
RESPIRATION!
C6H12O O2  6CO H2O

65. +
Oxygen production
12 midnight
12 mid-day
12 midnight -
Time of Day

66. +
Oxygen production
12 midnight
12 mid-day
12 midnight -
Time of Day

67. +
Oxygen production
12 midnight
12 mid-day
12 midnight -
Time of Day

68. +
Oxygen production
12 midnight
12 mid-day
12 midnight -
Time of Day

69. +
Oxygen production
12 midnight
12 mid-day
12 midnight -
Time of Day

70. + - Time of Day Oxygen production photosynthesis 12 midnight
12 mid-day
12 midnight -
respiration
Time of Day

71. + - Time of Day Oxygen production Compensation point
12 midnight
12 mid-day
12 midnight -
Time of Day

72. End of Section 2 Lesson 4 In this lesson we have covered: Respiration
Gaseous exchange