Class test 3.docx

Name: Class Test 3

Fig. 1 is a simplified diagram of the circulatory system of a human, showing gas exchange in the lungs and in respiring tissue. The partial pressures of oxygen (pO2) and carbon dioxide (pCO2) at four locations are also shown.

With reference to Figure above, explain how the differences in pO2 and pCO2 in the

alveolus and in blood enable gas exchange in the lungs and respiring tissue.

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(O/N 2010 P22 Q6 d)

Sucrose is one of the assimilates transported in the phloem sieve tubes of plants

from source to sink. Sucrase is found in sinks. ( O/N 10 P23 Q3b)

(i) Suggest the role played by sucrase in the process of unloading of sucrose at

sinks.

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(ii) Plant sink organs convert excess products of sucrose hydrolysis to storage

molecules, such as starch. Explain why these products of hydrolysis themselves

cannot be stored in plant tissue.

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Fig. 2 shows the pressure changes in the aorta, left ventricle and left atrium during once cardiac cycle.

Various points are labelled A to H.

Fig. 2

In Table 4.1, match up each statement with an appropriate letter from A to H on Fig. 2. One has been done for you.

You may use each letter once, more than once or not at all.

Table 1

statement	letter
semilunar (aortic) valve starting to open	A
atrio-ventricular (bicuspid) valve about to open
semilunar (aortic) valve about to close
atrio-ventricular (bicuspid) valve about to close
left ventricle starting to contract
both left atrium and left ventricle relaxing
minimum blood volume in left ventricle

[6]

4	Transpiration may be defined as the loss of water vapour by diffusion from a plant to its environment. Fig. 3 shows apparatus that can be used to estimate transpiration rates of a leafy shoot. Fig. 3
	(a)	(i)	State the name of the apparatus shown in Fig. 3. ...........................................................................................................................[1]
		(ii)	A student was told that any results gained by using the apparatus shown in Fig. 5.1 are not measures of the actual transpiration rate, but only give values from which transpiration can be estimated. Explain why the results gained by using the apparatus are not measures of the actual transpiration rate. ………………………………………………………………………..………… ………………………………………………………………………..………… ………………………………………………………………………..………… ………………………………………………………………………..……...[2]
	(b)	Fig. 4 shows the results gained from an experiment to compare the rates of transpiration in two species, P and Q. Both species were kept under the same conditions during the course of the experiment. Fig. 4
		Give two possible explanations for the increase in the rate of transpiration in both species P and Q over the course of the experiment. 1. ………………………………………………………………….…………..….…… …………………………………………………………………….………….……….. ………………………………………………………..……………………………...... 2. ………………………………………………………………..……….……….…… ………………………………………………………………………..….………….… ……………………………………………………………………….……………...[4]
	(c)	Various hypotheses for the mechanism of transport in phloem have been suggested. One hypothesis proposes that the movement between sources and sink occurs entirely passively by the process of mass flow. Fig. 5 shows a physical model to illustrate the principle of mass flow. Fig. 5

		Use the information in Fig. 5.3 to explain how mass flow of materials between the source and sink would be brought about. ………………………………………………………………………..…….………… ………………………………………………………………………..…….………… …………………………………………………………………..………….………… …………………………………………………………………..…………….……… …………………………………………………………………….……………….[3] [Total: 10]

The graph shows changes in blood pressure during one cardiac cycle.

What is happening to the atrium and aortic semilunar valve at X?

atrium

aortic semilunar valve

contracting

relaxing

closing

opening

closing

opening

Which features enables the aorta to withstand high pressure at ventricular systole?

collagen fibres and elastin fibres

collagen fibres and semilunar valves

elastin fibres and large lumen

semilunar valves and smooth muscle

3.Different substances, such as sucrose and amino acids, can move in different directions in the phloem sieve tubes.

Which statement explains this?

Active transport occurs in some phloem sieve tubes and mass flow in other phloem sieve tubes.

Both active transport and mass flow occur in each individual phloem sieve tube.

Mass flow occurs in both directions at once in each individual phloem sieve tube.

Mass flow occurs in different directions in different phloem sieve tubes at the same time.