A-LevelBiologyTransport in mammals9700/23 · May/June 2020 · Q38 Marks

Fig. 3.1 is a photomicrograph of a section through two different types of blood vessels, X and Y. [Figure 3.1] Name the two types of blood vessel shown by X and Y in Fig. 3.1. X Y

(a)(i)Fig. 3.1 is a photomicrograph of a section through two different types of blood vessels, X and Y. [Figure 3.1] Name the two types of blood vessel shown by X and Y in Fig. 3.1. X Y[1]
(a)(ii)State the reasons for your identification of the type of blood vessel shown by Y in Fig. 3.1.[2]
(b)(i)Tissue fluid and lymph are formed when blood arrives in the capillary networks of body tissues. Explain why tissue fluid is more similar to blood plasma than it is to blood.[2]
(b)(ii)Explain why the tissue fluid formed after blood arrives in the capillary network has a higher concentration of amino acids than the newly formed lymph draining away from the network.[1]
(c)The trachea, bronchi and bronchioles in the gas exchange system require a supply of glucose and oxygen from the blood for the functioning of smooth muscle. Outline the function of smooth muscle in the gas exchange system.[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

[1] X = artery Y = vein ;
[2] any two from
cross section not regular / no defined shape / AW; A not circular
tunica intima smooth; A inner layer for tunica intima A not, crinkly / wavy
thin / thinner (than X) tunica media; A thin middle layer
wide lumen diameter relative to wall thickness / relatively large lumen / AW ;
tunica, externa / adventitia, as thick / thicker, than tunica media;
[2] any two from
tissue fluid and blood plasma do not have red blood cells; A blood contains red blood cells
red blood cells are too large to pass through endothelial pores;
idea of tissue fluid and blood plasma similar viscosity / blood more viscous ;
AVP; ref. to similar colour (versus blood is red)
[1] any one from
taken up by /transported into / AW, (body) cells (from tissue fluid);
used by (body) cells to, synthesise polypeptides / proteins / enzymes ;
[2] any two from
contraction and relaxation ;
changes diameter of (lumen) of, trachea / bronchus / bronchiole ;
A (contraction causes) constriction
control of air flow (in the bronchioles);
AVP; e.g. changed size of lumen during coughing / forced air out

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