A sample of human blood was put in a test tube and allowed to spin in a centrifuge. The components of the blood sample were clearly separated.
(a) List the four main components of blood that would be in the test tube.
(b) Name the component of the blood that: (i) would form the top layer in the test tube, (ii) destroys pathogens; (iii) is biconcave in shape (iv) would be relatively low in a haemophilic condition (v) is produced in the bone marrow: (vi) is a thrombocyte; (vii) is nucleated.
(c) Mention three chemical substances transported by the blood component named in 1(b)(i).
(d) List four diseases associated with blood.
(e) Explain briefly why a disease of the blood could be dangerous.
(a) Four main components of blood
- Plasma
- Red blood cells (erythrocytes)
- White blood cells (leucocytes)
- Platelets (thrombocytes)
(b) Naming the component described
- (i) Forms the top layer in the test tube - plasma (it is the lightest and stays on top after spinning).
- (ii) Destroys pathogens - white blood cells.
- (iii) Is biconcave in shape - red blood cells.
- (iv) Would be relatively low in a haemophilic condition - platelets.
- (v) Is produced in the bone marrow - red blood cells.
- (vi) Is a thrombocyte - platelets.
- (vii) Is nucleated - white blood cells.
(c) Three chemical substances transported by plasma (the component in b(i))
- Digested food substances such as glucose and amino acids.
- Excretory waste such as urea (and carbon dioxide as hydrogencarbonate).
- Hormones (also dissolved mineral salts and antibodies).
(d) Four diseases associated with blood
- Anaemia
- Leukaemia
- Sickle-cell anaemia
- Haemophilia (also thrombosis)
(e) Why a disease of the blood could be dangerous
Blood circulates throughout the whole body and performs vital functions such as transporting oxygen, food, hormones and waste, defending the body against disease, and clotting to prevent excessive bleeding. A disease of the blood therefore affects the entire body at once: it can reduce the supply of oxygen and nutrients to the tissues, weaken the body's defence against infection, prevent proper clotting so that a person may bleed to death, and, because the affected blood reaches every organ, the disorder spreads quickly and can be fatal.
