IGCSE BIOLOGY

SECTION 2 LESSON 3
 Content

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

Lesson 2 2.15 describe the process of photosynthesis and

understand its importance in the conversion of
light energy to chemical energy
2.16 write the word equation and the balanced
e) Nutrition chemical symbol equation for photosynthesis
2.17 understand how varying carbon dioxide
concentration, light intensity and temperature
affect the rate of photosynthesis
2.18 describe the structure of a leaf and explain
how it is adapted for photosynthesis
2.19 understand that plants require mineral ions
for growth and that magnesium ions are needed
for chlorophyll and nitrate ions are needed for
amino acids
2.20 describe experiments to investigate
photosynthesis, showing the evolution of
oxygen from a water plant, the production of
starch and the requirements of light, carbon
dioxide and chlorophyll
 Content
Humans

Lesson 3 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Types of nutrition
AUTOTROPHS –organisms that can
produce complex organic compounds
from simple inorganic molecules.
They are the PRODUCERS in a food
chain.

HETEROTROPHS – organisms that

cannot produce their own food, but
acquire complex organic molecules by
consuming plants or other animals.
 Biological molecules

Our diet needs

to contain
sufficient and
balanced
quantities of
carbohydrates,
proteins and
lipids.
 Biological molecules
carbohydrates
Different foods contain Sugar gives us
different kinds of sugar.
Eg fruit contains fructose energy, so we call
Sugar or glucose. Lactose is in it an energy food.
milk. Table sugar is
sucrose.

Starch

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

Starch is found Starch is a storage

particularly in molecule, but it does
Starch bread, potatoes provide us with
energy.
and cereals.

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

Starch is found Starch is a storage

particularly in molecule, but it does
Starch bread, potatoes provide us with
energy.
and cereals.
Cellulose is found It is a structural
in plant cell walls molecule, and
Cellulose supports the plant
cell.
 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.
 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.
 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.
 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.
 Components of our diet
Minerals: contain certain elements essential for
the proper functioning of our bodies.
 Components of our diet
Minerals: contain certain elements essential for
the proper functioning of our bodies.

Needed for Occurs in Deficiency

hardening foods such as results in
Calcium our bones milk, cheese rickets
and teeth. and fish
 Rickets

Rickets is a softening of bones

in children due to deficiency or
impaired metabolism of vitamin
D, magnesium, phosphorus or
calcium, potentially leading to
fractures and deformity.
Rickets is among the most
frequent childhood diseases in
many developing countries.
 Components of our diet
Minerals: contain certain elements essential for
the proper functioning of our bodies.

Needed for Occurs in Deficiency

hardening foods such as results in
Calcium our bones milk, cheese rickets
and teeth. and fish

Present in Occurs in a Deficiency

haemoglobin, number of results in
the red foods, anaemia
Iron pigment in especially
blood used to liver and
carry oxygen kidneys
 Anaemia

Anaemia is a decrease in
the number of red blood
cells in the blood, meaning
that less oxygen can be
carried by the blood to
various organs and
tissues,. The main
symptoms are tiredness
and lethargy.
 Components of our diet
Vitamins: a collection of organic substances
needed in small quantities in the body. Their
overall function is to help control the chemical
reactions taking place in the body.
 Components of our diet
Vitamins: a collection of organic substances
needed in small quantities in the body. Their
overall function is to help control the chemical
reactions taking place in the body.

Important for Found in fish Deficiency

our eyes – liver oil, and makes it
Vitamin A helps protect carrots. difficult to
their surfaces see in dim light
 Components of our diet
Vitamins: a collection of organic substances
needed in small quantities in the body. Their
overall function is to help control the chemical
reactions taking place in the body.

Important for Found in fish Deficiency

our eyes – liver oil, and makes it
Vitamin A helps protect carrots. difficult to
their surfaces see in dim light

Needed for Found in citrus Deficiency

strong gums fruits, green results in
Vitamin C vegetables and scurvy
blackcurrants
 Scurvy

Scurvy can result in

swollen gums, severe pain
in joints, shortness of
breath, and blurred
vision.
 Components of our diet
Vitamins: a collection of organic substances
needed in small quantities in the body. Their
overall function is to help control the chemical
reactions taking place in the body.

Necessary for Occurs in fish Deficiency

bones to take liver oil, and results in
up calcium can be made in rickets.
Vitamin D salts the skin
provided
sunlight is
present.
 Components of our diet
Fibre is necessary for a healthy balanced diet,
but the body can’t absorb it. It helps our
digestive system to process food and absorb
nutrients. It helps your bowel to pass food by
making stools soft and bulky. It helps prevent
constipation.
Fibre is found in foods such as brown rice, oats,
wholegrain breads and cereals.
 Components of our diet
Water makes up more
than two-thirds of the
weight of the human
body. It serves as a
lubricant, helps
regulate body
temperature, prevents
and relieves
constipation. Without
enough water we can
become dehydrated.
The human digestive system
(also known as the alimentary canal)

From mouth to anus

The human digestive system
The human digestive system

In digestion, large
insoluble molecules
are broken down
into smaller
soluble particles
that can be
absorbed into the
bloodstream.
The human digestive system

Mouth – mechanical
chewing of the food.
Salivary glands
produce the enzyme
amylase which begins
breaking down
polysaccharides into
simpler sugars.
The human digestive system

Oesophagus (also
known as the gullet).
Passes food down
from the mouth to the
stomach by a process
known as peristalsis.
 Peristalsis

Rings of muscle
around the
oesophagus
effectively ‘squeeze’
food towards the
stomach, as you
would with
toothpaste in a
tube.
The human digestive system

Stomach – more
mechanical digestion
happens here. The
stomach produces the
enzyme protease, and
also hydrochloric acid
which kills bacteria,
and this acid also
provides the ideal
conditions for
protease.
The human digestive system

Pancreas – produces
many enzymes,
including amylase,
protease and lipase.
The human digestive system

Small intestine – can

be over six metres
long. Digested food is
absorbed here into
the blood stream.
The surface area of
the small intestine is
greatly increased by
the presence of small,
finger-like projections
called villi (villus).
Villi
The human digestive system

Large intestine – as
the fibre and other
undigested material
passes along the large
intestine, water is
absorbed from it, so it
becomes more solid.
This solid matter then
passes on to the
rectum where it is
stored as faeces.
 The human digestive system

The Liver – produces a

substance known as
bile, which is stored in
the gall bladder
before it is released
into the small
intestine.

Bile has 2 functions:

 The human digestive system

The Liver – produces a

substance known as
bile, which is stored in
the gall bladder
before it is released
into the small
intestine.

Bile has 2 functions:

1. It neutralises the acid
from the stomach, producing
more alkaline conditions.
 The human digestive system

The Liver – produces a

substance known as
bile, which is stored in
the gall bladder
before it is released
into the small
intestine.

Bile has 2 functions:

2. It emulsifies fats – i.e. it
breaks large drops of fat
into small droplets to
increase their surface area,
so enzymes can work faster.
Pause time!
 Definitions
Ingestion

Digestion

Absorption

Assimilation

Egestion
 Definitions
This is the process of taking in food
Ingestion substances through the mouth.

Digestion

Absorption

Assimilation

Egestion
 Definitions
This is the process of taking in food
Ingestion substances through the mouth.

This is the mechanical and chemical

Digestion breakdown of food into smaller, more
soluble, components.

Absorption

Assimilation

Egestion
 Definitions
This is the process of taking in food
Ingestion substances through the mouth.

This is the mechanical and chemical

Digestion breakdown of food into smaller, more
soluble, components.
This is the process of taking soluble food
Absorption through the wall of the small intestine by
diffusion into the blood stream.

Assimilation

Egestion
 Definitions
This is the process of taking in food
Ingestion substances through the mouth.

This is the mechanical and chemical

Digestion breakdown of food into smaller, more
soluble, components.
This is the process of taking soluble food
Absorption through the wall of the small intestine by
diffusion into the blood stream.
This is the process whereby absorbed
food is altered chemically by the liver or
Assimilation chemical substances before being utilised
by the cells of the body.

Egestion
 Definitions
This is the process of taking in food
Ingestion substances through the mouth.

This is the mechanical and chemical

Digestion breakdown of food into smaller, more
soluble, components.
This is the process of taking soluble food
Absorption through the wall of the small intestine by
diffusion into the blood stream.
This is the process whereby absorbed
food is altered chemically by the liver or
Assimilation chemical substances before being utilised
by the cells of the body.
This is the process where solid undigested
Egestion food material is removed from the
digestive system via the anus.
 Biological molecules

Simple sugars Starch / glycogen

 Biological molecules

Fatty acids, glycerol Fats, oils (lipids)

 Biological molecules

Amino acids Proteins

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

Substrate Product

Enzyme

e.g. Sucrose Glucose + Fructose

Sucrase
Enzyme summary
Salivary Gland -
produces amylase which
breaks down
carbohydrates (such as
starch) into simple
sugars (eg. glucose)
Enzyme summary

Stomach – produces
protease which breaks
down proteins into
amino acids
Enzyme summary

Pancreas – produces
amylase (carbohydrates
 sugars), protease
(proteins  amino
acids), lipase (fats 
fatty acids + glycerol)
Enzyme summary

Small intestine – produces

amylase (carbohydrates 
sugars), protease (proteins
 amino acids), lipase (fats
 fatty acids + glycerol)
Enzyme summary
One more thing ………….
Maltase, thought to be
produced by the walls
of the small intestine,
converts the
disaccharide maltose
(formed by the action
of amylase on starch)
into the simple sugar
glucose.
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 Content
Humans

Lesson 1 2.21 identify sources and describe functions of

carbohydrate, protein, lipid (fats and oils), vitamins A,
C and D, the mineral ions calcium and iron, water and
dietary fibre as components of the diet
e) Nutrition 2.22 describe the structures of the human alimentary
canal and describe the functions of the mouth,
oesophagus, stomach, small intestine, large intestine
and pancreas
2.23 understand the processes of ingestion, digestion,
absorption, assimilation and egestion
2.24 explain how and why food is moved through the
gut by peristalsis
2.25 understand the role of digestive enzymes, to
include the digestion of starch to glucose by amylase
and maltase, the digestion of proteins to amino acids
by proteases and the digestion of lipids to fatty acids
and glycerol by lipases
2.26 understand that bile is produced by the liver and
stored in the gall bladder, and understand the role of
bile in neutralising stomach acid and emulsifying
lipids
 End of Section 2 Lesson 3

In this lesson we have covered:

Nutrition – human