IGCSE Biology GCSE Biology

Here you will find the answers to the 'in-text' questions which occur in IGCSE Biology (2nd edition) and GCSE Biology (3rd edition) by D. G. Mackean, published by Hodder Education, London, UK.

Chapters: | Index | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 |

Chapter 12. The blood circulatory system


Page 109

1. a White cells can vary their shape. They have a nucleus. They do not contain haemoglobin.
    b They are an important part of the immune system They can produce antibodies which
    combat foreign substances which get into the bloodstream. Some of them can ingest bacteria
    or damaged cells and other unwanted particles. White cells do not carry oxygen.
2. The lungs.
3. In all the living, respiring cells of the body.
4. If oxyhaemoglobin was a stable compound it would not readily break down to release its
    oxygen where needed.
    If a diet is deficient in iron an adequate supply of haemoglobin cannot be produced. Cellular
    respiration would be reduced and the person would be anaemic.

Page 111

1. a Both ventricles pump blood into the arteries.
    b The bicuspid, tricuspid and semi-lunar valves prevent blood flowing the wrong way.
2. c Atria contract.
    e Blood enters ventricles.
    b Ventricles contract.
    g Tri- and bicuspid valves close.
    a Blood enters arteries.
    f Semi-lunar valves close.
    d Ventricles relax.
   (You could start with d).
3. a The ventricles have to pump blood all round the body. The atria have only to pump blood
    into the ventricles.
    b The left ventricle has to pump blood all round the body (apart from the lungs). The right
    ventricle has to pump blood only to the lungs.
4. The pulmonary veins are not shown.
5. If the heart valves do not function properly, some of the blood in the arteries can flow back
    into the heart, so less blood is delivered to the body. This means that less oxygen reaches the
    muscle cells and this impairs vigorous activity.

Page 114

1. a Left Atrium.
    i Left ventricle.
    c Aorta.
    b Vena cava.
    f Right atrium.
    h Right ventricle.
    e Pulmonary artery.
    d Lungs.
    g Pulmonary vein.
2. The pulmonary artery carries deoxygenated blood.
    The pulmonary vein carries oxygenated blood.
3. a Veins return blood to the heart. Arteries carry blood away from the heart.
    b Veins are wider than arteries, less elastic with thinner walls and less muscle tissue.
    Some of them have valves in their linings.
4. a Capillaries have ‘walls’ only one cell thick compared with the thick, muscular walls of
    arteries and the thinner walls of veins. Capillaries are much smaller than veins or arteries. The
    capillary walls allow exchange of oxygen, carbon dioxide and digested food substances
    with the tissues.
    b Capillaries penetrate all the tissues of the body and supply them with food and oxygen.
    Arteries deliver blood to the capillaries and veins collect blood from the capillaries but do not
    exchange substances with the tissues.
    5. Blood pressure is needed to circulate blood round the body. It is a normal function of a
    healthy blood circulatory system. Usually when people say they suffer from ‘blood pressure’
    they mean a level of pressure which exceeds the normal range, i.e. ‘high blood pressure’.

Page 115

1. Lymph consists of water, plasma proteins, salts (as ions), white blood cells and antibodies.
    The lymphatics leaving the alimentary canal may contain lipid droplets.
2. The fat molecule has not been digested to fatty acids and glycerol so it will enter a lacteal in a
    villus rather than a capillary. The lacteals empty their contents into lymphatic vessels which
    eventually join up to form a lymphatic duct. The duct empties its contents into the left
    subclavian vein which joins the vena cava before entering the left side of the heart. The left
    ventricle will pump blood round the body and some of it will reach the liver in the hepatic
    artery.
3. B lymphocytes (‘memory cells’) are retained in the lymph nodes. These cells produce
    antibodies which attack bacteria and other harmful cells. The spleen produces lymphocytes
    and antibodies. It removes bacteria from the blood. These are all immunological reactions.

Page116

1. a) gain b) lose
(i) Kidneys carbon dioxide oxygen, glucose, water, urea, excess salts
(ii) Lungs oxygen glucose, carbon dioxide, water vapour
(iii) Active muscle carbon dioxide oxygen, glucose

Page 120

1. The phagocytes ingest harmful bacteria, the lymphocytes produce antibodies which act against
    these bacteria.
2. The inoculation promotes the production of antibodies against a disease. The body is ready to
    ‘fight’ the disease organisms when they arrive.
    It is too late to do this once the disease organisms are present. The body will start making its
    own antibodies but it will take time for them to build up to an effective level.
3. a Examples of diseases controlled by active immunity are measles, mumps, rubella, diphtheria
    and flu.
    b An example of a disease controlled by passive immunity is tetanus.
4. The ‘universal donor’ is a group O person. The red cells have neither A or B antigens on their
    surface and cannot be clumped by anti-A or anti-B antibodies.
5. If a person’s blood is clumped by the anti-B serum he could be group B or group AB. If the
    blood fails to clump in anti-A serum, he cannot be group AB and must be Group B.

Page 122

1. a Maintain a good level of regular exercise, reduce your stress levels..
    b Don’t smoke, avoid an excess of fatty foods.
2. a If 95% of patients needing leg amputation are smokers there is clearly a correlation.
    b Smoking cannot cause leg amputation but it might lead to conditions in which amputation
    becomes necessary.
    c Smoking is one of the causes of atheroma. If the atheroma occurs in the leg and cannot be
    treated, it may necessitate amputation. (In fact there are many ways of treating atheroma in the
    leg. Amputation is necessary only in extreme cases).
3. a Vigorous exercise increases the demand for oxygen and glucose for the higher rates of
    respiration. These are met by increasing the blood flow which delivers these two substance
    more rapidly to the muscles.
    An increased respiration rate in active muscles produces CO2 which is removed by the faster
    blood flow.
    The arterioles supplying the muscle will widen and so increase the amount of blood reaching
    the muscle. Increased ventilation in the lungs will hasten the supply of oxygen and the
    removal of excess CO2.
    b Stored glycogen in the muscles and liver will be converted to glucose. Lipids will be
    released. The body temperature will rise leading to vasodilation in the skin and sweating (See
    p. 138).
    Levels of pyruvic and lactic acids may rise (See p. 20).
    c The raised heart rate will increase the blood flow to all parts of the body, not just the
    muscles.
 4. The first injection stimulates the lymphocytes in the immune system to produce antibodies
    specific to the antigen in the vaccine. Some of the B lymphocytes are ‘memory’ cells. When
    the second injection is received, the memory cells reproduce very rapidly and raise the level of
    antibodies.

Downloads
Download the answers in PDF format below
Section 1, Chapters 1-5
Section 2, Chapters 6-9
Section 3, Chapters 10-12
Section 3, Chapters 13-17
Section 3, Chapters 18-20
Section 4, Chapters 21-24
Section 5, Chapters 25-27
Section 5, Chapters 28-29
Section 6, Chapters 30-34
Section 6, Chapters 35-37
Section 7, Chapters 38-39
Section 8, Chapters 40-41


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