Sug Ans Ch03e

Certificate Biology - New Mastering Basic Concepts

Suggested answers Ch 3

Suggested answers The University of Cambridge Local Examinations Syndicate/Midland Examining Group bears no responsibility for the example answers to questions taken from its past question papers which are contained in the textbooks.

Chapter 3

Cell activities and organization

Reinforce and test your learning (p.65) 1

a b c d e f g

T F F T T T F

Some enzymes work outside cells. Enzymes are made of proteins.

Muscles and bones are tissues.

1m 1m 1m 1m 1m 1m 1m

2

As water has a higher water potential than the cell contents, it moves across the differentially permeable membrane into the cells by osmosis. 1m As the cell membranes of red blood cells are thin and not surrounded by cell walls, some cells burst as more and more water enters. When the cells burst, the red pigment is released. It makes the water red. 2m

3

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At 2-minute intervals, take a drop of the mixture from the tube with a dropper. Add it to an iodine drop on a spot plate. Record the time taken until the blue-black colour disappears. Title and correct choice of axes Correct labelling of axes with units Correct plotting and joining of all points

1m 1m 1m 1m 1m 1m

At 15 oC, the movement of enzyme and substrate molecules was low. The frequency of collision was low and the time for digestion was thus longer. 1m As the temperature increased, the movement of molecules increased and thus the rate of collision increased. Therefore the time for digestion decreased with the increase of temperature from 15 oC to 50 oC. 1m When the temperature increased to above 50 oC, the shape of some of the enzyme molecules changed and they could not catalyze the digestion of starch. 1m The time for digestion thus became longer with temperature rose as more and more enzyme molecules were denatured by the high temperature. 1m

 Oxford University Press 2003

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Certificate Biology - New Mastering Basic Concepts

4

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b c

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Suggested answers Ch 3

In test tube A, distilled water had a higher water potential than the red blood cells. 1m Water entered red blood cells by osmosis. 1m All red blood cells burst and haemoglobin was released into the water. 1m In test tube C, concentrated saline had a lower water potential than the red blood cells. 1m Water did not enter the cells and they did not burst. 1m Dilute saline had a higher water potential than some of the red blood cells. 1m Only some red blood cells burst and so a smaller amount of haemoglobin was released. 1m I would take some fluid from tube A and some solid matter from the bottom of tube B and observe them under a microscope. 1m The fluid from tube A should contain no intact cells but the solid matter that from tube B should contain some. 1m Sea water has a lower water potential than that of the cytoplasm. 1m Too much water may leave the cells and the animals will die. 1m Cardiac muscle 1m Circulatory system 1m Leaf 1m Transport system 1m

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With the development of tissues, organs and systems, different kinds of cells with specific functions are required. 1m Cells need to be specialized into distinctive shapes and structures to carry out different functions. 1m There can be division of labour among the different tissues, organs and systems so that various body activities can be carried out at optimum conditions. 1m

Examination papers Multiple-choice questions (p.66) 1

A

2

C

3

C

4

B

 Oxford University Press 2003

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