2005 T7 GEP ANS.doc 1

Maris Stella High School Class (Index No.): ____ ( ) Secondary 4 Biology Name: ___________________ GEP Term 3 Lesson 1: Topic 5 Date: _____________

Transport In Man MS

1. Transport in Mammals: Question 1 a. Draw two large labeled diagrams to show the structure of a red cell and a white

cell in mammalian blood.

b. Describe the functions of these two cells. Red blood cells: Transport oxygen

- Contains haemoglobin in cytoplasm that binds reversibly to oxygen - Absence of nucleus allows for more haemoglobin to be carried - Biconcave disc shape increases surface area for the diffusion of oxygen

White blood cells: Immune system, fight infection

- Phagocytes ingest foreign particles - Lymphocytes produces antibodies

c. Name the fluid part of blood and describe its composition and functions.

Plasma composition: Water, digested food (eg. Amino acids, glucose), hormones, minerals, vitamins, bicarbonate ions, urea, plasma proteins (eg. Fibrinogen, prothrombin) Function: Transport medium, carries materials, allows for clotting

Maris Stella High School Essay Questions: Answers Secondary 4 Biology Topic 5

2009 T5 GEP Answers.doc 2

2. Transport in Mammals: Question 2 a. Why is a circulatory system necessary in mammals and not in lower animals such

as Amoeba? In unicellular organisms like the Amoeba, , no part of protoplasm of the organism is far away from the body surface, allowing oxygen, waste materials to diffuse in and out quickly. For complex multi-cellular organisms like mammals, many cells in the centre of the body are far away from the environment, and the process of diffusion alone cannot bring enough oxygen and food to those cells nor remove waste products fast enough. A circulatory system is needed to carry materials from one part of the body to another.

b. What is the advantage to mammals of having capillaries which are narrow,

repeatedly branched and thin-walled? Narrow and repeatedly branched capillaries: Increases surface area to volume ratio, to increase rate of diffusion/transfer of materials between the blood and body cells. Branching also increases total cross-sectional area, lowering the blood pressure and slowing the flow of blood, allowing for exchange of materials. Thin-walled capillaries increases rate of diffusion of materials.

c. Explain briefly how the blood defends the body against disease organisms. White blood cells: Phagocytes ingest foreign particles that may cause disease, while lymphocytes produce antibodies which, 1. Neutralize toxins that may be produced by disease organisms. 2. Cause agglutination of foreign particles, eg. bacteria, which are then ingested by

the phagocytes. 3. Allow foreign particles to be easily ingested by the phagocytes.

3. Transport in Mammals: Question 3 The composition of blood is affected by the organs through which it circulates. Describe the changes that occur as blood passes through: a. The kidneys

Decrease in levels of oxygen, urea, nitrogenous waste materials, mineral salts, water. Increase in levels of carbon dioxide.

b. The pancreas

Increase in levels of insulin (if levels of glucose are higher than usual). Increase in levels of glucagon (if levels of glucose are lower than usual). Increase in levels of carbon dioxide, decrease in levels of oxygen.

c. The wall of the small intestine

Increase in levels of digested food (glucose, monosaccharides, amino acids). Decrease in levels of oxygen, increase in levels of carbon dioxide.

Maris Stella High School Essay Questions: Answers Secondary 4 Biology Topic 5

2009 T5 GEP Answers.doc 3

4. Transport in Mammals: Question 4 a. Describe the part played by each of the following in maintaining the circulation of

the blood: (i) The heart: Acts as the pump to drive blood around the body (ii) The blood vessels: Carries blood to all parts of the body and maintains a closed

loop system, directs blood flow in the body (iii) The muscles of the limbs: The muscles exert a pressure on the veins carrying

blood back to the heart, aiding in the movement of blood

b. Outline the functions of the circulatory system. Transport of substances around the body, such as digested food, oxygen, waste materials like urea and carbon dioxide. (Blood has a protective/immune function: Phagocytes that ingest foreign particles, lymphocytes that produce antibodies, platelets that help in the clotting of blood when there are cuts/damaged tissue.)

5. Transport in Mammals: Question 5 a. What is meant by a double (dual) circulation?

Blood passes through the heart twice: from main circulation to the body cells (systemic circulation) to the heart, then to the lungs and back to the heart (pulmonary circulation) before the cycle repeats itself.

b. How do the two parts of a double circulation differ from one another?

Pulmonary circulation: Links heart to lungs, lower pressure, slower blood flow. Pulmonary arteries carry deoxygenated blood from the heart to the lungs, and oxygenated blood returns to the heart via the pulmonary veins. Systemic circulation: Links heart to other parts of body, higher pressure. Arteries branching from aortic arch carry oxygenated blood to the rest of the body, and veins carry deoxygenated blood from the body back to the heart.

c. Describe how the circulatory system (i) Helps to stop bacteria from entering a cut in the skin

Damaged tissues of the cut release thrombokinase, which converts prothrombin to thrombin (in presence of calcium ions and Vitamin K). Thrombin converts soluble fibrinogen into insoluble fibrin threads which form a meshwork which entangle blood cells, forming a clot. The clot seals the cut, preventing bacteria from entering the bloodstream.

(ii) Deals with bacteria which may have entered the cut Bacteria which enter the blood are destroyed by antibodies (produced by the lymphocytes) which coat/cause agglutination of the bacteria, making ingestion by phagocytes easier. Antibodies may also neutralize the toxins produced by the bacteria.