1. iGCSE Biology Section 2 lesson 1

2. The iGCSE Biology course
Content
The iGCSE Biology course
Section 1: The nature and variety of living organisms
Section 2: Structures and functions in living organisms
Section 3: Reproduction and inheritance
Section 4: Ecology and the environment
Section 5: Use of biological resources

3. The iGCSE Biology course
Content
The iGCSE Biology course
Section 1: The nature and variety of living organisms
Section 2: Structures and functions in living organisms
Section 3: Reproduction and inheritance
Section 4: Ecology and the environment
Section 5: Use of biological resources

4. 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

5. 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

6. a) Levels of organisation
Content
Lesson 1
a) Levels of organisation
2.1 describe the levels of organisation within organisms: organelles, cells, tissues,
organs and systems.

7. Lesson 1 b) Cell structure Content
2.2 describe cell structures, including the nucleus, cytoplasm, cell membrane, cell
wall, chloroplast and vacuole
2.3 describe the functions of the nucleus, cytoplasm, cell membrane, cell wall,
chloroplast and vacuole
2.4 compare the structures of plant and animal cells.

8. Levels of Organisation

9. Levels of Organisation
A. Cells

10. Levels of Organisation
A. Cells

11. Levels of Organisation
A. Cells
Animal
Cell membrane
Cytoplasm
Nucleus

12. Levels of Organisation
A. Cells
Animal
Cell membrane
Controls the passage of substances into and out of the cell.
Cytoplasm
Nucleus

13. Levels of Organisation
A. Cells
Animal
Cell membrane
Controls the passage of substances into and out of the cell.
Cytoplasm
Most chemical reactions occur here
Nucleus

14. Levels of Organisation
A. Cells
Animal
Cell membrane
Controls the passage of substances into and out of the cell.
Cytoplasm
Most chemical reactions occur here
Nucleus
Controls the activities of the cell

15. Levels of Organisation
A. Cells

16. Levels of Organisation
A. Cells
Plant
Cell membrane
Cytoplasm
Nucleus

17. Levels of Organisation
A. Cells
Plant
Cell membrane
Cytoplasm
Cellulose cell wall
Strengthens the cell
Nucleus

18. Levels of Organisation
A. Cells
Plant
Cell membrane
Cytoplasm
Cellulose cell wall
Strengthens the cell
Permanent vacuole
Contains cell sap
Nucleus

19. Levels of Organisation
A. Cells
Plant
Cell membrane
Cytoplasm
Cellulose cell wall
Strengthens the cell
Permanent vacuole
Contains cell sap
Chloroplast
Absorbs light energy to make food through photosynthesis
Nucleus

20. Comparing plant and animal cells
Found in both plant and animal cells
Found in plant cells only

21. Nucleus Cytoplasm Cell membrane Comparing plant and animal cells
Found in both plant and animal cells
Found in plant cells only
Nucleus
Cytoplasm
Cell membrane

22. Nucleus Chloroplasts Cytoplasm Cell walls Cell membrane
Comparing plant and animal cells
Found in both plant and animal cells
Found in plant cells only
Nucleus
Chloroplasts
Cytoplasm
Cell walls
Cell membrane
Permanent vacuoles

23. Specialised cells
The egg cell , or ovum, is much larger than other cells so that it can carry food reserves for the developing embryo if fertilisation takes place.

24. Specialised cells
Sperms cells have elongated tails that enable them to swim towards the egg (ovum) following ejaculation into the vagina.

25. Specialised cells
Red blood cells do not have a nucleus, so they are able to pack in more haemoglobin molecules, and so carry even more oxygen.

26. Specialised cells
Nerve cells are very elongated, and some may be over a metre in length. They carry electrical signals around the body.

27. Levels of Organisation
B Tissues
Tissues are groups of similar cells that are able to work together to carry out a specific function.

28. Levels of Organisation
B Tissues
eg. Muscle tissue
Muscle tissue is very specialised, and has the ability to contract and also to conduct electrical impulses. There are three types of muscle: smooth, skeletal and cardiac.

29. Levels of Organisation
C Organs
Organs consist of groups of tissues working together to perform specific functions.

30. Levels of Organisation
C Organs
eg. the Heart
The heart is a muscular organ found in all animals with a circulatory system. It is composed mostly of cardiac muscle and connective tissue, but also nervous tissue and blood.

31. Levels of Organisation
D Organ system
An organ system is a group of organs that work together to perform a certain task.

32. Levels of Organisation
D Organ system
eg. the Digestive system
The digestive system consists of numerous organs, including the stomach and liver. It digests food and enables it to be absorbed into the blood stream.

33. Levels of Organisation
A. Cells
B. Tissues
C. Organs
D Organ system

34. c) Biological molecules
2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol
2.7 describe the tests for glucose and starch
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site
2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH
2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.
Lesson 1
c) Biological molecules

35. Biological molecules
To maintain a healthy body we need to eat the right amount of food and also the right types of food.

36. Biological molecules
Our diet needs to contain sufficient and balanced quantities of carbohydrates, proteins and lipids.

37. Biological molecules
carbohydrates

38. Biological molecules
carbohydrates
Carbon C

39. Biological molecules
carbohydrates
Carbon C
Hydrogen H

40. Biological molecules
carbohydrates
Carbon C
Hydrogen H
Oxygen O

41. Biological molecules carbohydrates Carbon C H Oxygen O
Hydrogen H
Oxygen O
Eg. glucose, C6H12O6

42. Biological molecules carbohydrates Sugar Starch Cellulose
Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose.
Sugar gives us energy, so we call it an energy food.
Starch
Cellulose

43. Biological molecules carbohydrates Sugar Starch Cellulose
Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose.
Sugar gives us energy, so we call it an energy food.
Starch
Starch is found particularly in bread, potatoes and cereals.
Starch is a storage molecule, but it does provide us with energy.
Cellulose

44. Biological molecules carbohydrates Sugar Starch Cellulose
Different foods contain different kinds of sugar. Eg fruit contains fructose or glucose. Lactose is in milk. Table sugar is sucrose.
Sugar gives us energy, so we call it an energy food.
Starch
Starch is found particularly in bread, potatoes and cereals.
Starch is a storage molecule, but it does provide us with energy.
Cellulose
Cellulose is found in plant cell walls
It is a structural molecule, and supports the plant cell.

45. Biological molecules Fats
Fats also contain C, H and O, but relatively less O. Fats occur in both plant and animal foods.
Fats – solid at room temperatures.
Oils - liquid at room temperatures.

46. Biological molecules Fats
Fats also contain C, H and O, but relatively less O. Fats occur in both plant and animal foods.
Fats – solid at room temperatures.
Oils - liquid at room temperatures.
Fats also give us energy. They also provide insulation in humans and other mammals, and are energy stores.

47. Biological molecules Proteins
Proteins contain C, H and O, and also some nitrogen (N) and a little suplhur (S).
Proteins are found in milk, eggs, meat and fish.

48. Biological molecules Proteins
Proteins contain C, H and O, and also some nitrogen (N) and a little suplhur (S).
Proteins are found in milk, eggs, meat and fish.
Proteins are needed for growth and body-building (muscles and skin), and they are also used to make enzymes.

49. Biological molecules

50. Biological molecules
Simple sugars Starch / glycogen

51. Biological molecules
Fatty acids, glycerol Fats, oils (lipids)

52. Biological molecules
Amino acids Proteins

53. Food tests
Glucose
Benedict’s Test

54. Food tests Glucose Positive result: Benedict’s Test BLUE GREEN YELLOW
ORANGE
BRICK RED

55. Food tests
Starch
IodineTest

56. Food tests
Starch
IodineTest

57. ENZYMES

58. ENZYMES
Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things.

59. ENZYMES
Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things.
What are the features of enzymes?

60. ENZYMES
Enzymes are biological catalysts – they speed up the rate of chemical reactions going on inside living things.
What are the features of enzymes?
Enzymes are globular proteins
Every enzyme has an area called its active site
Enzymes are specific
Enzymes are affected by temperature and pH

61. ENZYMES
Commonly named by adding the ending “-ase” to the substrate molecule being acted upon.
Eg. sucrase works on sucrose, lipase works on lipose.
A few enzymes are known by common names, eg. pepsin, trypsin

62. ENZYME ACTION Enzyme e.g. Sucrose Glucose + Fructose Sucrase
Substrate Product
Enzyme
e.g. Sucrose Glucose + Fructose
Sucrase

63. ENZYME ACTION
Binding site

64. ENZYME ACTION

65. ENZYME ACTION

66. Enzymes and Temperature
Time (minutes)
Temperature (oC) 10 20 30 40 50 60
An experiment was carried out to investigate how temperature affects the rate at which an enzyme converts starch into sugar.

67. Enzymes and Temperature
Time (minutes)
Temperature (oC) 10 20 30 40 50 60
The results are shown in this table. A black circle means that there is still starch present. An orange dot means that there is no starch present.

68. Enzymes and Temperature
Temperature (oC) 10 20 30 40 50 60
Time taken for starch to disappear (min.)
Plot a graph with temperature along the x-axis (across) and time up the y-axis.
What can you conclude about this investigation? How does temperature affect the action of enzymes.
Find out what ‘denatured’ means. How does it apply to this investigation?

69. Lesson 1 d) Movement of substances into and out of cells
2.12 understand definitions of diffusion, osmosis and active transport
2.13 understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport
2.14 understand the importance in plants of turgid cells as a means of support
2.15 understand the factors that affect the rate of movement of substances into
and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient
2.16 describe experiments to investigate diffusion and osmosis using living and
non-living systems.

70. Movement of substances into and out of cells.

71. Movement of substances into and out of cells.
Diffusion
Osmosis
Active transport

72. What is diffusion?
Spray air freshener in the corner of a room

73. What is diffusion?
Particles spread out in all directions

74. What is diffusion?
Eventually the particles occupy the whole room

75. What is diffusion?
Other examples of diffusion include:
Smell of frying bacon from a kitchen
Leaking of air from inside a balloon
Sugar dissolving in a cup of tea

76. What is diffusion?
Diffusion is the movement of particles from areas of high concentration to areas of low concentration until they are evenly spread. Diffusion depends upon the random movement of particles.

77. What is diffusion?
Diffusion is the movement of particles from areas of high concentration to areas of low concentration until they are evenly spread. Diffusion depends upon the random movement of particles.
Diffusion is slower in liquids than in gases because liquid particles are not as free to move as gas particles.

78. Diffusion in living organisms

79. Diffusion in living organisms
Food
oxygen

80. Diffusion in living organisms
Food
oxygen
Out:
Carbon dioxide
Waste products

81. Diffusion in living organisms
Eg. movement of oxygen in Amoeba

82. Diffusion in living organisms
Eg. movement of oxygen in Amoeba
High oxygen concentration
Low oxygen concentration

83. Diffusion in living organisms
Eg. movement of oxygen in Amoeba
High oxygen concentration
Low oxygen concentration
Oxygen will move from a high concentration outside the cell to a lower concentration inside the cell. It is moving from high to low – i.e. down a concentration gradient.

84. Diffusion in living organisms
Where diffusion occurs in living organisms, the surfaces across which gases are exchanged are often specialised by having LARGE SURFACE AREAS to increase the rate at which diffusion can occur.
Eg. alveoli in the lungs provide a huge surface area for the exchange of oxygen and carbon dioxide.

85. What is osmosis?

86. What is osmosis?
Osmosis is:
a special type of diffusion
it is the diffusion on water molecules from an area of high water concentration to an area of lower water concentration through a partially permeable membrane.

87. What is osmosis?
A partially permeable what ……… ?

88. What is osmosis?
A partially permeable what ……… ?
Membrane!

89. What is osmosis?
A partially permeable what ……… ?
Membrane!

90. A partially permeable what ……… ? Membrane!
What is osmosis?
A partially permeable what ……… ?
Membrane!
Higher water concentration (fewer solute particles)
Lower water concentration (more solute particles)

91. A partially permeable what ……… ? Membrane!
What is osmosis?
A partially permeable what ……… ?
Membrane!
Higher water concentration (fewer solute particles)
Lower water concentration (more solute particles)

92. What is osmosis?
Water particles will continue to move until there are equal numbers of water molecules on both sides of the membrane.
Higher water concentration (fewer solute particles)
Lower water concentration (more solute particles)

93. What is osmosis?
More concentrated solution inside
WATER
WATER
Less concentrated solution outside (more DILUTE)
WATER
WATER
In root hair cells water moves from the surrounding soil into the cell by osmosis, along a concentration gradient

94. Dialysis tubing containing sugar solution
Osmosis experiments
Dialysis tubing containing sugar solution

95. Osmosis experiments Dialysis tubing containing sugar solution
Placed in pure water
Dialysis tubing containing sugar solution
Water enters by osmosis, tubing swells up

96. Osmosis experiments Dialysis tubing containing sugar solution
Placed in pure water
Dialysis tubing containing sugar solution
Placed in concentrated sugar solution
Water enters by osmosis, tubing swells up
Water leaves by osmosis, tubing shrivels up

97. Osmosis experiments
Weighed potato chip

98. Water enters by osmosis, potato chip weighs more
Osmosis experiments
Placed in pure water
Weighed potato chip
Water enters by osmosis, potato chip weighs more

99. Osmosis experiments Weighed potato chip Placed in pure water
Placed in concentrated sugar solution
Water enters by osmosis, potato chip weighs more
Water leaves by osmosis, potato chip weighs less

100. What is Active Transport?

101. What is Active Transport?
Active transport is moving substances against a concentration gradient.

102. What is Active Transport?
Active transport is moving substances against a concentration gradient.
Imagine trying to push a trolley up a hill

103. What is Active Transport?
Active transport is moving substances against a concentration gradient.
Imagine trying to push a trolley up a hill
It will require
ENERGY!

104. What is Active Transport?
Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required.

105. What is Active Transport?
Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required.
Root hair cell with a high concentration of nitrate ions.
Soil with a lower concentration of nitrate ions.

106. What is Active Transport?
Similarly, when substances are moved into a cell where there is already a higher concentration, then ENERGY from respiration will be required.
Root hair cell with a high concentration of nitrate ions.
Energy will be used to ‘pull’ nitrate ions from the surrounding soil into the cell
Soil with a lower concentration of nitrate ions.

107. What is Active Transport?
Active transport also occurs in the human body. For example, in the kidneys, sugar is recovered back into the blood by transporting it against a concentration gradient.

108. Factors affecting the movement of substances

109. Factors affecting the movement of substances
Surface area to volume ratio
Temperature
Concentration gradient

110. Factors affecting the movement of substances
Surface area to volume ratio
The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs
Temperature
Concentration gradient

111. Factors affecting the movement of substances
Surface area to volume ratio
The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs
Temperature
As temperature increases, particles gain kinetic energy. They therefore move faster, and so diffusion, osmosis and active transport all occur at a faster rate.
Concentration gradient

112. Factors affecting the movement of substances
Surface area to volume ratio
The bigger the surface area compared to the volume, the faster the rate of movement of substances – eg. the lungs
Temperature
As temperature increases, particles gain kinetic energy. They therefore move faster, and so diffusion, osmosis and active transport all occur at a faster rate.
Concentration gradient
The bigger the concentration difference, for example inside and outside of the cell, the faster substances will move – think about a steeper hill?

113. End of Section 2 Lesson 1 In this lesson we have covered:
Levels of organisation
Cell structure
Biological molecules
Movement of substances into and out of cells