uss module 6 chpt 9 digestion

Module 6:Wonders of My Body (II)Chapter 9 Digestion

© 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?


ObjectivesExplain 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


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

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?


ObjectivesIdentify 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 pancreasFood 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. © Copyright Star Publishing

Pte Ltd

Activity Book LinkActivity 9.1The Digestive SystemActivity 9.2The 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.© 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?


ObjectivesShow 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.© Copyright Star Publishing Pte Ltd

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.© Copyright Star Publishing Pte Ltd

Enzymes and TemperatureAt 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.


Enzymes and TemperatureDifferent 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 and TemperatureEnzymes are

destroyed by high temperatures

Enzymes destroyed by high temperatures cannot digest food


Activity Book LinkActivity 9.3What 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 LinkActivity 9.4Digestive Enzymes (Characteristics)

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?


ObjectivesDescribe 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 toconstipation.(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.


Effects of Alcohol on the LiverWhen 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.


Effects of Alcohol on the Liver

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 fibreprevents constipation

DiabetesDiabetes 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 needto check their blood sugar

levels regularly

Signs and symptoms of diabetestA 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 diabetesIf 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 LinkActivity 9.5Digestive Disorders

uss module 6 chpt 9 digestion

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