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TYS Unit 7(Science Biology)

Transport in Mammals

MCQ Unit 7 ANSWERS

1)! C 6. B2)! D 7. A3)! D 8. B4)! C 9. C5)! C 10. C

11. C

Essay Qn 1a

!!Oxygenated blood coming from thelungs enters into the left atrium (A) viathe pulmonary veins [1/2]

!!Blood then enters into the left ventricle(B) due to a pressure gradient, anddue to the contraction of the leftatrium;

Essay Qn 1a

!!The left ventricle (B) then contracts,pushing blood out into the aortic arch,which carries blood to the rest of thebody;

!!Blood is prevented from flowing backinto the left atrium due to the closureof the bicuspid/mitral valve [1/2]

Essay Qn 1a

!!Deoxygenated blood returning fromthe rest of the body enters into theright atrium (D) via the vena cavae[1/2]

!!Blood then enters into the rightventricle (C) due to a pressuregradient and due to the contraction ofthe right atrium;

Essay Qn 1a

!!The right ventricle (C) then contracts,pushing blood out into the pulmonaryarteries, which carries blood to thelungs;

!!Blood is prevented from flowing backinto the right atrium due to the closureof the tricuspid valve [1/2]

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Essay Qn 3aStructure Function

Artery: Thicker layer of

muscle and elastic tissue

compared to the veins;

Withstand high pressure of

blood, elastic tissue allows

artery to recoil and pushblood along;

Veins: Thinner layer ofmuscle & elastic tissue

compared to arteries;

Pressure in the veins islower, hence this layer can

be thinner;

Veins: Semi-lunar valves

present along length of

vein, absent in mostarteries;

To prevent the backflow of

blood in veins where

pressure is lower;

Unit 7 Essay Qn 3b

Structured Qn 1a

(i)! The heart is made of muscle, whichby contracting and relaxing, help todrive the blood around the body;

(ii)! The valves prevent the backflow ofblood into the atria when theventricles are contracting;

Structured Qn 1bi

"! Blood pressure in the veins is muchlower than in the arteries, and thereis a higher tendency for backflow ofblood;

"! This backflow of blood is preventedby the presence of valves in theveins;

Structured Qn 1bii

!!They have a thin wall made of onelayer of flattened cells, whichdecreases diffusion distance forexchange of materials between theblood and surrounding cells;

!!They have pores to increase the rateof exchange of substances;

!!They are highly branched to increasethe surface area available forexchange of materials;

Structured Qn 1c

!!During an injury, platelets help in theformation of a blood clot [1/2]

!!Damaged tissues releasethromboplastin which convertsprothrombin into thrombin;

!!Thrombin converts fibrinogen intofibrin, which traps platelets and bloodcells, forming the clot [1/2]

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Structured Qn 2a

!!Red blood cells: Transport oxygen!!Platelets: Converts fibrinogen to fibrin!!Plasma: Transports soluble food

substances

!!White blood cells: Forms antibodies!!Deduct 1 mark for 1 mistake, 1/2 mark

for 2nd-3rd mistake

Structured Qn 2bi

cell surface

membrane

Structured Qn 2bii

!!Red blood cells do not have a nucleuswhile white blood cells contain nuclei[1/2]

!!Red blood cells have a circular bi-concave disc shape, while white bloodcells have an irregular shape;

!!Red blood cells contain haemoglobinin their cytoplasm and hence appearred, while white blood cells do notcontain haemoglobin and appearcolourless [1/2]

Structured Qn 2biii

!!Bi-concave disc shape increasessurface area for diffusion of oxygen inand out of RBC;

!!Absence of nucleus allows for morehaemoglobin to be packed intocytoplasm which allows RBC to carrymore oxygen;

Structured Qn 3!! (a) artery; small artery ; capillary; small vein;

vein [3]

!! (b) (i) Blood flow in arteries is fast and inspurts as it flows under high pressure [1] ;hence arterial walls are much thicker towithstand the pressure exerted on theirwalls [1]

!! (ii) Blood pressure in veins is much lowerand therefore there is a possibility ofbackflow [1] ; hence veins have valves toprevent backflow/ensure unidirectional flowand skeletal muscles around them to pushthe blood forward [1]

Structured Qn 3c

!!(i) coronary heart disease [1]!!(ii) high saturated fat diet [1] / lack of

exercise [1] / smoking [1] [Any 2]