Summative Practice Chapter 9 – Question 7 (Form 4 Biology Textbook Exercise and Answer)

Question 7:
(a) Explain why a diet rich in fats is not good for health.

(b) Suggest suitable types of food for someone who wants to reduce weight and reduce the risk of contracting cardiovascular disease. Explain your answer.

(c) Explain the processes of starch digestion, absorption and assimilation in the human body.

A diet rich in fat is not good for health for the following reasons:

• A diet with a high content of fat and oily foods may cause high blood pressure and lead to cardiovascular diseases.

• Excess fat will be deposited in the arterial walls (atherosclerosis) causing blocked arteries.

• The lumen of the artery becomes narrow. This will make it difficult for blood to flow. The condition will increase blood pressure (hypertension).

• If the arterial lumen that becomes narrow is the coronary artery (artery in the heart), this may cause a heart attack due to the lack of oxygen supply to the cardiac muscles.

• If the cholesterol hardens and clogs the coronary artery, heart attack or coronary thrombosis (lack of oxygen supply to the heart) may occur, resulting in damage to parts of the heart. This can turn fatal if pumping of the heart stops.

• Excess cholesterol may also lead to gallstone formation.

• Foods with less carbohydrates and fats. Less carbohydrate will be converted to fats.

• Foods with less fats and cholesterol. Less cholesterol will be deposited on the arterial walls blocking the arteries. Blood flow in the heart will also not be blocked.

• The hydrolysis of starch by salivary amylase produces maltose. Next, the hydrolysis of maltose by maltase produces glucose. The final product of starch is glucose. Glucose is absorbed through the ileum epithelial cells and then absorbed into the blood circulatory system through blood capillaries.

• Glucose is then transported by the hepatic portal vein to the liver.

• Assimilation occurs in the liver. Depending on the body’s needs, glucose in the liver is oxidised, excess glucose is converted into glycogen to be stored in the liver or changed to fats to be transported to other body parts for storage.

• From the liver, some of the glucose is carried in the blood circulatory system to the heart and then pumped to the whole body.

• In body cells, glucose is oxidised to yield energy, water and carbon dioxide.

• Energy is used for chemical processes in the cell, for example, muscle contraction and protein synthesis. Excess glucose is stored in the muscles.

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