Uss module 6 chpt 9 Digestion

Module 6:
Wonders of My Body (II)
Chapter 9 Digestion
1© Copyright Star Publishing Pte Ltd

Chapter 9 Digestion
9.1 Why is Digestion Important?
9.2 How does the digestive system
work?
9.3 How does the body speed up
digestion?
9.4 Health Issues Related to Digestion?

Objectives
 Explain why digestion is necessary for
most food in order for our body to use
food for energy, growth and repair

Why do we need food?
 Food is important to us. We need food for
various reasons:
(a) To provide ourselves with energy to carry
out daily activities
(b) For growth and repair of injured body
parts
(c) To keep us healthy
 Food contains nutrients, water and dietary
fibre.
 The nutrients in our food are carbohydrates,
fats, proteins, mineral salts and vitamins
© Copyright Star Publishing Pte Ltd 4

Our body requires all types of nutrients to
grow and stay healthy.

Why must food be digested?
 Food that we eat may contain large
molecules that are insoluble.
 They are too large to enter the
bloodstream and cannot be carried to
all parts of the body. Some examples of
such foods are carbohydrates,
proteins, and fats.
 The body cannot make use of food as
it is. Food needs to be digested into
simpler forms.

Why must food be digested?
 When food is digested, large,
insoluble food molecules are
broken down into smaller, soluble
molecules which can enter the
bloodstream and be carried to all
parts of the body to be used.

Only digested food molecules can enter
the bloodstream

What happens during
digestion?

Chapter 9 Digestion
work?
digestion?

Objectives
 Identify the main organs and the
associated organs of the digestive
system (mouth, gullet, stomach, small
intestine, large intestine, rectum, anus,
salivary glands, pancreas, gall bladder
and liver) and state their functions

Parts of the digestive system

Digestive organs and their functions

The liver, gall bladder and pancreas
 Food does not pass through the liver,
gall bladder and pancreas, but these
organs play important roles in the
digestion of food.

Liver
 The liver produces a greenish-yellow liquid
called bile, which is stored in the gall
bladder.

Bile
 Bile does not contain enzymes so it
cannot digest food.
 It breaks up large fat droplets into
smaller fat droplets. This makes it
easier for enzymes to digest fats in the
small intestine.

Functions of the liver
 Other functions of the liver include:
(a) Storing excess glucose
(b) Breaking down excess proteins in
our diet into urea, which is removed
in our urine
(c) Breaking down harmful substances
such as alcohol and drugs into
harmless substances in a process
known as detoxification.

Gall bladder
 The gall bladder stores bile produced
by the liver and releases it into the small
intestine.

The gall bladder
 The gall bladder releases bile into the
small intestine and bile enters the
small intestine via the bile duct.
Activity Book Link
Activity 9.1
The Digestive
System
Activity 9.2
The Digestion
Process

Pancreas
 The pancreas
releases enzymes
that help increase
the rate of
digestion.
 Pancreatic
enzymes are
carried to the small
intestine via the
pancreatic duct.

Chapter 9 Digestion
work?
digestion?

Objectives
 Show an understanding that digestive
enzymes are important in helping to
speed up the rate of digestion and that
they require optimum temperature and
pH to work efficiently
 Interpret data on the effect of pH and
temperature on the rate of protein
digestion enzymes

Specificity of Enzymes
 Enzymes have many properties.
 Each enzyme only digests a specific type of
nutrient.
 For example, an enzyme that digests carbohydrates
cannot digest fats or proteins.
enzymes digest only specific molecules

Enzymes and Temperature
 Enzymes are affected by temperature.
 Enzymes operate at an optimum temperature.
 They do not work well or stop working when
temperatures are too low or too high.

 At low temperatures, the enzyme is
less active and the rate of reaction is
low.
 As temperature increases, enzymes
become active and the rate of enzyme
reaction increases.
 Enzymes are the most active at the
optimum temperature. The rate of
enzyme reaction is the highest.

 Different enzymes have different
optimum temperatures. For instance,
enzymes found in our bodies work best
at body temperature, 37°C.
 Above the optimum temperature,
activity decreases as temperature
increases.
 At higher temperatures, the enzyme is
destroyed and is not able to digest food.

 Enzymes are
destroyed by high
temperatures
 Enzymes
destroyed by high
temperatures
cannot digest
food
Activity Book Link
Activity 9.3
What is the Optimum Temperature
for Starch Digestion?

Enzymes and pH
 Different enzymes work well at different pH.
 Enzymes found in the stomach work best in
acidic conditions (pH 2), while enzymes in our
small intestine work best in slightly alkaline
conditions (pH 8).
Activity Book Link
Activity 9.4
Digestive Enzymes
(Characteristics)

Chapter 9 Digestion
work?
digestion?
9.4 Health Issues Related to
Digestion?

Objectives
 Describe the effects of excessive
alcohol consumption on the liver (e.g.
damaged liver, liver cancer)
 Outline how constipation may occur
and suggest how to prevent them
 State how the diet and activity level of
a diabetic person can be changed to
control his/her blood glucose level

How does our diet and lifestyle affect
our health?
 Drinking too much alcohol, a diet high in
fat and low in dietary fibre, and a lack of
exercise can be harmful to our health:
(a) Drinking too much alcohol can cause
liver damage.
(b) A lack of dietary fibre in our diet leads to
constipation.
(c) A diet high in fat and sugar may result
in obesity, which can lead to diabetes.

Effects of Alcohol on the Liver
 Alcohol is found in alcoholic drinks such as beer and
wine.
 Beer, wine and champagne are some common
alcoholic beverages.

 When a person drinks alcohol, it
enters the bloodstream through the
stomach wall and is brought to the
liver to be broken down into
harmless substances.
 Too much alcohol can cause liver
damage. Once damaged, the liver
cannot return to its original healthy
condition.

 Drinking too much alcohol over a period of time
damages liver cells.
 This reduces the liver’s ability to break down harmful
substances. Over time, this can lead to liver
hardening, which will result in liver failure and even
liver cancer.

Ways to prevent alcohol addiction

Constipation
 Constipation is having difficulty in clearing
faeces from the anus.
 Constipation may occur because the faeces
are too hard and dry and cannot move
smoothly through the large intestine.

Constipation
 A diet lacking water and dietary fibre may cause
constipation.
 Dietary fibre solidifies the faeces and retains water
in the faeces so that they can move easily through
the large intestine.
 This reduces the time needed for the undigested
food to pass out of the body through the anus.

How do we prevent constipation?
 In order to prevent
constipation, we
should consume
food rich in
dietary fibre and
water.
 Fruits, vegetables
and cereals are
good sources of
dietary fibre.
eating food high in fibre
prevents constipation

Diabetes
 Diabetes is a condition
in which the amount of
glucose in the blood
cannot be controlled.
 Diabetes may be
(a) inherited from
parents
(b) caused by an
unhealthy lifestyle
and diet high in
sugar and fats
people with diabetes need
to check their blood sugar
levels regularly

Signs and symptoms of
diabetest
 A diabetic person may experience the
following signs and symptoms:
(a) Frequently need to urinate
(b) Feel thirsty
(c) Tend to have a very good appetite
(d) Feel tired
(e) Experience blurred vision
(f) Pass out urine that is high in sugar,
which attracts ants

Effects of diabetes
 If left untreated, a diabetic person
may risk:
(a) Uncontrolled infections of open
wounds on body surfaces, for
example a cut on the skin
(b) Blindness if there is bleeding in
the eye

How can we control diabetes?
 Diabetes can be controlled by
(a) injecting insulin before meals
(b) controlling the diet by reducing
the amount of carbohydrates
eaten
(c) exercising regularly to maintain a
healthy weight.
Activity Book Link
Activity 9.5
Digestive Disorders

Uss module 6 chpt 9 Digestion

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