Theory question 101
Transport in AnimalsA 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.
Show the model answer
(a) Plasma; red blood cells (erythrocytes); white blood cells (leucocytes); platelets (thrombocytes).
(b)(i) Plasma. (ii) White blood cells. (iii) Red blood cells. (iv) Platelets (clotting factors). (v) Red blood cells (also white cells and platelets). (vi) Platelets. (vii) White blood cells.
(c) Any three: digested food (glucose, amino acids); hormones; urea; mineral salts; carbon dioxide (as hydrogencarbonate); antibodies; vitamins; plasma proteins.
(d) Any four: anaemia; sickle cell anaemia; leukaemia; haemophilia; malaria; hepatitis B; HIV/AIDS; septicaemia.
(e) Blood flows to every part of the body and carries oxygen, food and defence cells; a disease of the blood can spread quickly to all organs and stop vital transport and defence, threatening life.
Plasma is the lightest component, so it settles on top after spinning.