IGCSE BIOLOGY

2.  the process of providing or obtaining the
food necessary for health and growth.
 proper nutrition for growth and
maintenance, and to provide energy for work
and vital functions.

3.  There are two main types of nutrients:
 1) MACRONUTRIENTS - include
carbohydrate, protein, and fat.
 2) MICRONUTRIENTS - are vitamins and
minerals , and these are extra molecules
that cells need to make energy.

4.  A balanced diet is one that
gives your body the
nutrients it needs to function
correctly.
 The 7 components of a
balanced diet are
Carbohydrates, Proteins,
Fats, Vitamins, Minerals,
Fibre and Water.

5.  Each component carries out one or more of
three basic functions :
 1) To provide energy- mainly the role of
carbohydrates and fats. Proteins are used for
energy only if they are in excess of requirements for
growth, development, repair and replacement.
 2) To allow growth and repair- of body cells.
Protein provide a source of amino acids, for cells to
make their own proteins.
 3)To regulate the body’s metabolism – vitamins
and minerals are needed in small quantities to help
regulate the body’s metabolism.

6.  Energy required for body
functions is the basal
metabolic rate (BMR).
 BMR- number of calories
required to keep your body
functioning at rest.
 Adult – 7000 kJ per day
 Varies from person to
person

7.  Depends of age, sex and activity
 children need more energy due to the fact they
have a high metabolic rate
 Young children weigh less that adults but may have
a higher BMR per kilogram per day because they
are still growing.
 Need more protein per unit of body mass because
they are still developing.
 Older people have lower BMR.
 Women have more fat content than men, fat tissue
has a lower metabolic rate than muscle ,so women
have a lower BMR than men.

8.  Provides more energy per gram than carbs
or protein.
 2 types of fat:
 1) Saturated Fat - type of dietary fat. It is
one of the unhealthy fats, along with
trans fat. Comes from animals.
 2) Unsaturated Fat - is a fat or fatty acid in
which there is at least one double bond
within the fatty acid chain. Fats that comes
from fish and plants.

9.  Saturated fat in the died may
increase the concentration of
cholesterol in our blood.
 Cholesterol – is a chemical
made in the liver and found in
the blood.
 High concentrations of
cholesterol in the blood are
linked to a narrowing of the
arteries, an increased risk of
developing high blood
pressure and heart disease.

10.  Two types of unsaturated fats :
 1) Monounsaturated fats - has little effects
on blood cholesterol.
 1) Polyunsaturated fats – may help reduce
cholesterol concentrations which will help
reduce heart disease.

11.  Diets in different parts of the world vary
 Carbohydrates :
 include sugar and starch, which provide us with a ready
source of energy that is easily respired.
 Carbohydrates are classified into three subtypes-
 1) Monosaccharide- any of the class of sugars (e.g.
glucose) that cannot be hydrolysed to give a simpler
sugar.
 2) Disaccharides- is the sugar formed when two
monosaccharide (simple sugars) are joined by glycosidic
linkage.
 3) Polysaccharides-a carbohydrate (e.g. starch, cellulose,
or glycogen) whose molecules consist of a number of
sugar molecules bonded together.

12.  Protein:
 To grow and develop, it need protein
to make new cells.
 You digest protein into amino acids
and then use these to make your
own proteins.
 There is 20 different types of amino
acids and your body must have all of
these to make its own protein.
 Cell membranes and cytoplasm
contain a high amount of proteins.

13.  Fats:
 Long-term energy store
 Stored under your skin and around your heart
and kidneys.
 Good thermal insulators, cut down heat loss.
 Gives buoyancy to marine animals.
 Water:
 Makes up two-thirds of your body mass.
 Vital for survival.
 Needed for chemical reactions to take place
in the body.
 Waste chemicals are passed out our body in
solutions in the urine and water in our sweat
cools us down.

14.  Vitamins and Minerals:
 Needed in small amounts.

15.  Fibre:
 Dietary fibre or roughage comes from plants.
 Mainly cellulose from plant cell walls.
 Although it can’t be digested, it is an important
part of the diet.
 Fibre adds bulk to the our food. Doesn't provide
energy.
 The muscles of the gut wall need something to
push against. Fibre helps the movement of food
in the alimentary canal by peristalsis, so
preventing constipation.
 Absorbs poisonous wastes from bacteria in our
gut
 High fiber diets lowers the concentrations of
cholesterol in the blood.
 Reduced the rick of heart disease and bowel
cancer.

16.  What happens if we eat too much?
 If you eat more food then you need, your body stores the
extra as fat.
 Energy intake – is the energy you get in your food in a
day in proteins, carbohydrates and fats.
 Energy output – in the energy your body uses in a day.
 If energy intake in more than energy output, then fat is
stored in the body and body mass increases.
 Risk of being over weight or even obese.
 People with low BMR are more likely to become over
weight.

17.  Obesity :
can be caused by a high intake of fatty
foods and refined foods containing a lot a
of added sugar plus the effects of too little
exercise.
Major causes of obesity include-
1) High intake if fatty foods and refined
foods containing a lot of added sugar.
2) Too little exercise.
3) Social or emotional stress, leading to
‘comfort eating’.
 Are more exposed to heart disease,
high blood pressure, diabetes caused by
high blood sugar and arthritis(worn
joints).

18.  How to lose weight ?
 1) eat less high-energy foods
 2) more exercise
 A sensible approach to slimming should
combine : a balanced diet
a gradual increase in
exercise
setting a target

19.  Constipation:
 Caused by a diet lacking in roughage(fibre).
 Soft foods do not stimulate the muscles to
contract as effectively as the harder, indigestible
food that form roughage.
 If the movement is slow it causes constipation.
 A diet containing fruit and vegetables contain
lots of roughage; these are best foods to relieve
constipations.

20.  People can survive many weeks with food
provided that they have water. This is because
during periods of starvation, the body draws
upon its stores of carbohydrate, fat and protein
for energy, but there are no stores upon water.
 During starvation BMR is reduced.
 The body uses stored fat ,then it breaks down
protein in the muscles to use a source of
energy- leading to muscle wasting and an
emaciated appearance.

21.  Worldwide, the most common form of under nutrition is Protein
Energy Malnutrition (PEM)- lack of dietary energy and protein.
 In its worst form it can lead to kwashiorkor or marasmus.
 Kwashiorkor : a condition resulting from inadequate protein
intake. Early symptoms include fatigue, irritability, and lethargy.
As protein deprivation continues, one sees growth failure, loss
of muscle mass, generalized swelling (edema), and decreased
immunity. A large, protuberant belly is common.
 Marasmus : undernourishment causing a child's weight to be
significantly low for their age. Symptoms are very low body
mass; thin arms and legs; little muscle or fat; wizened, old
looking face

22.  In both cases, children are in danger and feeding
should involve frequent serving of small quantities
of food. This is because PEM causes cell of the
pancreas and intestine to die, so fewer digestive
enzymes are secreted and the surface area for
absorption if digested food is reduced.
 Dietary survey of poor communities in developing
nations have shown that , which should be used for
growth and development, is used for a source of
energy– this shows that just how much of proteins
is being lacking off.

23.  Nutrient needs :
 Vitamin C - is necessary for the growth, development and repair
of all body tissues. It's involved in many body functions,
including formation of collagen, absorption of iron, the immune
system, wound healing, and the maintenance of cartilage,
bones, and teeth.
 Lack of vitamin C can cause scurvy.
 Scurvy - symptoms of deficiency include weakness, feeling tired
and sore arms and legs. Without treatment, decreased red
blood cells, gum disease, changes to hair, and bleeding from the
skin may occur.

24.  Vitamin D – Is needed for the small intestine to
absorb calcium in bone cells
 Lack of vitamin D can cause Rickets or
Osteomalacia.
 Rickets - People with rickets may have weak and
soft bones, stunted growth, and, in severe cases,
skeletal deformities.
 Osteomalacia - a disease characterized by the
softening of the bones caused by impaired bone
metabolism primarily due to inadequate levels of
available phosphate, calcium, and vitamin D, or
because of resorption of calcium.

25.  Iron is needed to make hemoglobin, which is found is red blood cells.
 Hemoglobin is a protein combined with. It is needed to carry oxygen around
the body.
 If there is lack of iron , it causes anaemia.
 an adult needs about 16 mg of iron each day.
 Girls need to make sure they have enough iron in their diet as they start to
menstruate.
 The lack of iron lead to a reductions in the number of red blood cells.
 General symptoms of anaemia may include:
 extreme tiredness (fatigue)
 lack of energy (lethargy)
 breathlessness.
 feeling faint.
 headaches.
 pale skin.
 noticeable heartbeats (palpitations)

26.  During the passage of food in the alimentary canal, a number of
different processes can be identified.
 1) Ingestion : is the taking of substances into the body through
the mouth.
 2) Digestion : is the breaking down of large insoluble molecules
into small soluble molecules so that they can pass through the
gut wall into the blood.
 3) Absorption : is the movement of small food molecules and
ions through the wall of the intestine into the blood.
 4) Assimilation : is the movement of digestive food molecules
into the cells of the body where they are used, becoming part of
the cells.
 5) Egestion : is the passing out of food that has not been
digested of absorbed, as faeces through the anus.

27.  Digestion occurs mechanically and chemically.
 This happens in the alimentary canal , or gut, which
together with the liver and pancreas form your digestive
system.
 When food is digested it is absorbed through the wall of
the small intestine into the blood.
 Before the food molecules and insoluble; they will not
dissolve , therefore cannot get through the wall of the
small intestine
 Small food molecules are soluble. They will dissolve so
they can get through the wall of the small intestine into the
blood and the lymph, which is another body fluid that
absorbs and transports fat.

28.  Mechanical Digestion : involves physically breaking the
food into smaller pieces. Mechanical digestion begins in
the mouth as the food is chewed. Muscular contractions of
the stomach continue the process. In the small intestine ,
large globules of fat are broken into smaller globules by
emulsification by bile.
 Emulsification - is defined as a process of dispersing
one liquid (containing the bioactive compounds) in a
second immiscible liquid, by applying electrostatic, or
hydrophobic, or hydrogen bonding interactions between
the bioactive compounds and an encapsulating material .

29.  Chemical Digestion : involves breaking down
the food into simpler nutrients that can be used
by the cells. Chemical digestion begins in the
mouth when food mixes with saliva.
 There are three types of enzymes in the
alimentary canal are : proteases, carbohydrates
and lipases.
 Each type of food molecule need a specific
enzyme because they have different shapes.

30.  Amylase breaks down starch molecules to glucose
molecules
 Protease breaks down protein molecule to amino acids.
 Lipase breaks down fats to fatty acids and glycerol.

31. Thank you