1. People can die when they inhale gases from burning charcoal in poorly ventilated rooms. What compound is formed in the human body that leads to such deaths? (1mk)
2. Explain why blood from a donor whose blood group is A cannot be transfused into a recipient whose blood group is B. (2mks)
Blood group A has antigens A on red blood cells and antibodies b in plasma. Recipient’s blood group B has B antigens and a antibodies. When blood group A from donor is transferred ,antigen A will react with antibody a in the recipient’s blood. Clumping or agglutination of the red blood cells will take place: the clumped red blood cells block capillaries and this hinders the flow of blood and may result in death.
3. State one difference between closed and open circulatory systems. (1mk)
In a closed circulatory system, blood flow is confined to enclosed vessels while in open circulation blood is not confined to vessels but flows in cavities (sinuses) and is in direct contact with tissues.
4. a) Give an example of a phylum where all members have
i) Open circulatory system
ii) Closed circulatory system (2mks)
b) What are the advantages of the closed circulatory system over the open circulatory system? (5mks)
When blood is confined within vessels, it generates high pressure. This results in a faster rate of circulation, over long distances, ensuring efficient transportation of material e.g nutrient to all parts of the body, which renders the animals more active than those with open circulatory system.
5. Explain two ways in which mammalian erythrocytes (red blood cells) are adapted to their function (2mks)
-They contain haemoglobin, a molecule that readily combine with oxygen.
-They are biconcave discs without a nucleus, allowing more haemoglobin to be packed in cells so that each cell can carry more oxygen.
6. a) i) Name the blood vessels that link arterioles with venules. (1mk)
ii) Explain four ways in which the vessels you named in (a) above are suited to carrying out their functions. (4mks)
- Have a small diameter to increase pressure thus allow materials to diffuse out.
- They are intimately associated with tissues in order to allow exchange of materials
- They are numerous- to provide a large surface area for exchange of materials.
b) State two ways in which the composition of blood in the pulmonary arterioles differ from that in the pulmonary venules. (2mks)
i)Pulmonary arterioles contain more carbon dioxide than pulmonary venules.
ii) Pulmonary arterioles contain less oxygen than pulmonary venules.
7. Why would carboxyhaemoglobin lead to death? (2mks)
It does not dissociate easily hence leads to suffocation
8. Explain how the red blood cells of mammals are adapted for efficient transport of oxygen. (2mks)
i) They contain haemoglobin, a molecule that readily combine with oxygen.
ii) They are biconcave discs without a nucleus, allowing more haemoglobin to be packed in cells so that each cell can carry more oxygen.
9. The chart below is a summary of the blood clotting mechanism in man.
i) The blood cells represented by X
ii) Metal ion represented by Y
iii) The end product of the mechanism represented Z
10. a) How can excess bleeding result in death? (2mks)
Anemia/low blood volume/low haemoglobin leading to low oxygen, loss of nutrients and dehydration.
b) Name the process by which the human body naturally stops
c) How can low blood volume be brought back to normal? (2mks)
Transfusion, taking fluids/eating iron in foodstuff/taking iron tablets
11. a) Name one defect of the circulatory system in humans. (1mk)
- Varicose veins
b) State three functions of blood other than transport. (3mks)
- Regulate body temperature
- Regulate pH of fluids
- Regulate osmotic pressure
12. a) What prevents blood in veins from flowing backwards? (1mk)
Presence of valves
b) State two ways in which the red blood cells are adapted to their function. (2mks)
- Have biconcave shape to increase surface area for absorption of gases.
- Absence of nucleus and other organelles to increase packaging of haemoglobin.
- Presence of red pigment haemoglobin that has high affinity for oxygen.
13. State one way by which HIV/AIDS is transmitted from mother to child. (1mk)
- During birth
- Breast feeding
14. Explain how the various components of blood are adapted for their function. (20mks)
- Red blood cells have a biconcave shape, which increases the surface area for gaseous exchange. They have a thin plasma membrane, which allows rapid diffusion of gases. They contain haemoglobin, which readily combines with oxygen in areas of high oxygen tension (lungs) and releases it readily in areas of low oxygen tension (other body tissues). They have no organelles with whole internal space being filled with haemoglobin. They contain the enzyme carbonic anhydrase which help in the transport of carbon dioxide.
- Some white blood cells are phagocytic which enables them to engulf and destroy invading micro-organisms. They are also capable of amoeboid motion, which enables them to squeeze between cells of the capillary wall and into infected tissues where they proceed to engulf invading micro- 135 organisms other white blood cells called lymphocytes are able to recognize antigens of invading micro-organism and to form antibodies against them.
- Platelets are able to aggregate at the site of a damaged blood vessel forming a temporary platelet plug which stops blood loss. They also produce the substance called thromboplastin which initiates the blood clotting mechanism. - Plasma is composed mainly of water which is a solvent for a large variety of substance. This enables it to act as a medium for transport of a large number of water soluble substances. It has a high heat capacity that enables it to transport heat from highly active tissues to the rest of the body.
15. Distinguish between blood, plasma, serum, tissue fluid and lymph. (10mks)
Blood: Tissues which consist of a liquid part called plasma in which several types of cells are suspended.
Plasma: Liquid part of the blood
Serum: Plasma from which the blood clotting protein called fibrinogen has been removed. It does not clot.
Tissue fluid: Liquid part of blood without plasma proteins. It is derived from the blood by the process of ultra filtration.
Lymph: is a tissue fluid, which drains into lymphatic vessels instead of going back into the blood vessels.
16. a) A patient whose blood group is A died shortly after receiving blood from a person of blood group B. Explain the possible cause of death of the patient. (2mks)
The patient’s red blood cells have antigen A on their membrane and his 136 plasma has anti-b antibodies . The donor’s red blood cells have antigen B on their membrane and his plasma has anti-a antibodies. After transfusion, the anti-b antibodies in the patient’s plasma reacted with B antigens on the donor’s red blood cell membrane. This led to clumping together of the donor red blood cells a process called haemagglutination. This may have caused blockage of capillaries in a vital organ like the heart or brain leading to death.
b) A person of blood group AB requires a transfusion.
i) Name the blood groups of the possible donors (2mks)
ii) Give reasons for your answer in (i) above. (2mks)
He is universal recipient. His plasma’ lacks antibodies.
17. Differentiate between active immunity and passive immunity. (2mks)
Active immunity-that is produced when an animal’s body reacts to an antigen by producing antibodies.
Passive immunity- Immunity that is produced when antibodies are transferred from one individual to another.
18. Explain why a person can catch a cold several times in a year but only catches measles once in his or her lifetime. (2mks)
Antibodies formed against common cold viruses remain in the body and provide immunity for only a few days. Therefore, once a person has recovered from cold, he/she is only protected for a few days. Those antibodies formed against measles virus remain in the body and provide immunity throughout the person’s life. Therefore, once a person has recovered from measles, he or she is protected for life.
19. Most carbon dioxide is transported from tissues to the lungs within the red blood cells and not in the blood plasma. Give two advantages of this mode of transport. (2mks)
PH of blood plasma is not altered homeostasis is maintained. Within the red blood cells, there is an enzyme (carbonic anhydrate) which help in fast loading/combination and offloading/dissociation of carbon dioxide.
20. What is the importance of tissue fluid? (2mks)
Through tissues fluid, Oxygen and other food substance pass from the blood to the cells. Carbon dioxide waste substance passes from the cells to the blood through it.