Transport in Humans

Question 1

what does plasma contain (4 points)

Answer 1

• mainly water
• blood cells
• excretory products (e.g. urea, amino acids)
• substances (nutrients, hormones)

Question 2

what is the main function of red blood cells (erythrocytes)

Answer 2

to transport oxygen from lungs to other parts of the body

Question 3

what are the 4 adaptations of red blood cells

Answer 3

1) contains haemoglobin (purplish-red)
- combines reversibly with oxygen
- haemoglobin binds to oxygen in lungs (high oxygen conc.) to form oxyhaemoglobin (bright red)
- oxyhaemoglobin releases oxygen in tissues (low oxygen conc.) to tissue cells for cellular respiration

2) biconcave shape
- increases surface-area-to-volume ratio, increasing rate of oxygen diffusion in and out of the cell

3) enucleate
- makes more space available for haemoglobin (NOT OXYGEN)

4) flexible
- can change into bell-shaped structure to move easily through narrow capillaries

Question 4

what are the 2 functions of white blood cells (leucocytes)

Answer 4

1) phagocytes engulf and destroy pathogens like bacteria (phagocytosis)

2) lymphocytes produce antibodies which can:
- recognise and destroy pathogens
- cause pathogens to clump together for easy ingestion by phagocytes
- neutralise toxins produced by bacteria

*phagocytes have lobed nucleus, lymphocytes have large round nucleus
*lymphocytes produced by bone marrow

Question 5

what is the function of platelets (thrombocytes)

Answer 5

converts fibrinogen to fibrin threads, which entangle with red blood cells to form blood clots that seal wounds

*contains enzyme (thrombin) that catalyses this conversion
*cytoplasm fragments (spiky small thing)
*fibrinogen soluble, fibrin threads insoluble

Question 6

what are antigens

Answer 6

special proteins found on surface of red blood cells (or bacteria)

Question 7

what are the types of antigens (on red blood cell) and antibodies (in plasma) in different blood groups?

Answer 7

group A:
- antigen A, antibody b

group B:
- antigen B, antibody a

group AB (universal acceptor):
- antigen A and B, no antibodies

group O (universal donor):
- no antigens, antibodies A and B

Question 8

what is another term for clumping of blood

Answer 8

agglutination

Question 9

what is the function of arteries

Answer 9

transports blood away from the heart at high pressure

Question 10

what is the function of veins

Answer 10

transports blood back to the heart at low pressure

Question 11

what is the function of capillaries

Answer 11

facilitate exchange of substances between blood and tissue cells in body

*mainly by diffusion

Question 12

describe the 2 adaptations of arteries

Answer 12

1) thick muscular and elastic walls
- to withstand high pressure of blood flowing within
- elasticity allows artery wall to stretch and recoil, helps push blood in spurts along artery, giving rise to the pulse

2) contraction and relaxation of arterial walls
- when artery constricts, lumen becomes narrower and less blood flows through per unit time
- when artery dilates, lumen becomes wider and more blood flows through per unit time

Question 13

describe the 3 adaptations of veins

Answer 13

1) one-way valves
- prevents backflow of blood

2) thin muscular and elastic walls
- transports blood back to the heart at low pressure and velocity, more smoothly and slower than arteries

3) contractions of skeletal muscles
- compresses vein and helps push blood along more quickly

Question 14

describe the 3 adaptations of capillaries

Answer 14

1) partially permeable, one-cell thick walls
- provides short diffusion distance for higher rate of diffusion

2) tiny and numerously branched
- increases surface area for exchange of substances
- increases total cross-sectional area of blood vessels, lowering blood pressure and slowing down blood flow for more time for exchange of substances

3) continuous blood flow in capillaries
- maintain steep concentration gradient