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Chapter 1 & 2Revision Worksheet 1

Questions 1 and 2 refer to the following experiment.

A dialysis tubing (semi-permeable) tied at one end with a knot is halfly filled with 2% sugar solution, and then the other end is also tied. Now one end of the tubing is immersed into a beaker of 10% sugar solution.

1 Which of the following graphs represents the result?

2 Which of the following provide(s) suitable explanation for the result obtained in the previous experiment?

(1) Sugar molecules diffuse from a region of high sugar concentration to a region of lower sugar concentration

.(2) Water molecules move from a region of higher water

potential through a semi-permeable membrane to a region of lower water potential.

(3) The turgor pressure (pressure potential, p) increases inside the dialysis tubing throughout the whole experiment.

(4) The driving force of this molecular movement is due to the water potential inside the tubing being lower than that of the surrounding solution.

A (1) only B (2) onlyC (4) only D (1) and (3) only

3 Potassium cyanide is known to hinder the usage of ATP in cell metabolism.

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If the usage of potassium cyanide had resulted in the accumulation of ions in a cell, it may be deduced that the solute normally enters by

A active transport B diffusion C osmosis D diffusion and osmosis

4 A student was asked to identify the two compounds in each of two test-tubes. The table below shows the results of the student’s tests.

Which conclusion is consistent with the results?

A Protein and sucrose had been placed in tube X B Maltose and starch had been placed in tube Y

C Maltose and sucrose had been placed in tube X D Starch and sucrose had been placed in tube Y

5 Which of the following statements is incorrect?

A Diffusion cannot take place without the cell membraneB A cell cannot reproduce itself without the nucleus.

C Active transport cannot take place without mitochondria in a cell. D A plant cell cannot retain its shape in distilled water without the cell wall.

6 The diagrams show four agar blocks which were placed in a dish and covered with a solution of a coloured stain.

Which block has the largest surface area to volume ratio and will be completely stained most rapidly?

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7 Paramecium, a fresh water unicellular animal has two contractile vacuoles for the evacuation of excess water from its body. The table below records the average time taken by a contractile vacuole to fill up and empty when the animal is immersed in three different liquids X, Y and Z.

Bathing liquid Time/s

X 189

Y 28

Z 62

Which of the following shows the correct identities of the bathing fluid?

X Y Z

A 0.3% salt solution 0.1% salt solution Water

B 0.1% salt solution Water 0.3% salt solution

C Water 0.3% salt solution 0.1% salt solution

D 0.3% salt solution Water 0.1% salt solution

8 The diagram below shows the breakdown of three types of organic molecules.

What are the identities of X, Y and Z?

X Y ZA Carbohydrates Fats ProteinsB Carbohydrates Proteins FatsC Protein Carbohydrates FatsD Proteins Fats Carbohydrates

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9 The graph shows the effect of pH on the activity of 4 different enzymes.

Which pair of enzymes includes one from the stomach and one that is not affected by pH?

A P and QB P and SC R and QD R and S

10 An investigation was carried out to study the effect of temperature on the activity of an enzyme X. The time taken for the digestion of the proteins into peptides at different temperatures is shown in the table below.

Temperature (C) Time taken for the digestion of protein into peptides (minutes)

20 7.630 4.340 1.250 4.5

Which temperature is optimum for the activity of enzyme X?

A 20CB 30CC 40CD 50C

11 Fish contains a high amount of protein. Which process enables proteins to enter the body cells?

A Active transport against a concentration gradient in the ileum.B Diffusion down a concentration gradient in the ileum.

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C Osmosis when protein dissolves in water and gets absorbed in the colon.D None of the above as proteins are too large to pass through the

membrane.12 Cylinders of potato tissue were placed in different concentrations of sugar solution.

The graph shows the percentage change in the length of the cylinders of potato tissue.

Which solution has the same water potential as the potato tissue?A 0.1 molB 0.2 molC 0.3 molD 0.6 mol

13 Figure 1 represents the action of an enzyme. The pin represents the enzyme.

Figure 1

What is represented by the inflated balloon and the fragments of the burst balloon?

Inflated Balloon Fragments of Burst BalloonA Substrate ProductB Product SubstrateC Substrate Substrate

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D Product Product

14 Three wells were cut in agar jelly, which contained starch. A different solution was placed in each well. Twelve hours later, iodine solution was added to cover the entire area of the jelly including the wells. The diagram below shows the results of the experiment.

Which solution could have given the results as shown?

Well 1 Well 2 Well 3A Amylase + acid Amylase Boiled amylaseB Amylase + acid Boiled amylase AmylaseC Amylase Amylase + acid Boiled amylaseD Amylase Boiled amylase Amylase + acid

15 Typical protein molecule isi formed by an amino acid chain.ii formed by a condensation reaction with peptide bonds.iii formed by combining amino acids and simple sugars.iv made of coiled chains of amino acids linked together by weak hydrogen

bonds.

A i and iiB ii and iiiC i and ivD ii and iv

16 If Mary places an animal cell in pure water, which of the following will happen?A Water molecules will move out of the cell, so the cell will shrink and die

from the lack of water.B There will be no change.C Water molecules will move into the cell and it will swell and may burst.D All the cell’s energy will be used to prevent the movement of water

molecules into the cell.

17 Which of the following activities or properties reveals the protein nature of enzymes?

A Enzymes catalyse chemical reactions.B Enzymes remain unchanged during chemical reactions.C Enzyme reactions decrease rapidly at high temperatures.

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D Enzymes are inactivated at low temperatures.

18 A piece of food was crushed and a little water was added to it. Then the meshed food was squeezed to get a solution from it. The solution was tested as follows:

Tests ResultsBoiled with Benedict’s solution for 3 – 5 minutes Orange-red pptTreated with sodium hydroxide and copper (II) sulphate Blue solutionIodine solution added Blue-black

colourationMixed with alcohol and added a few drops of water White emulsion

What types of food substances were present in that piece of food?A Glucose, starch and oilB Glucose, protein and oilC Protein, starch and oilD Protein, sucrose and oil

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Section B

1. The diagram below shows an apparatus set up to investigate the rate of water loss and the rate of water uptake by a green plant. The weight of the apparatus was recorded at the start of the investigation and again after 24 hours. The scale on the measuring cylinder was used to read the volume of the water before and after the 24 hour period.

The table below shows the results after the investigation.

i. Calculate the decrease in mass of the apparatus per hour, over the 24 hour period. Show your working

ii. Calculate the volume of water absorbed by the plant per hour, over the 24 hour period. Show your working.

iii. Given the density of water is 1g/cm3, calculate the mass of water absorbed by the plant per hour, over the 24 hour period.

iv. Based on your knowledge of how water moves up a plant, explain why your answers to parts (i) and (iii) are quite similar.

v. Why is the amount of water absorbed by the roots not equal to the amount of water loss by the plant?

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2. Figure 1 shows a complex formed between an enzyme and its substrate.

a) What is represented by the amino acids that have been coloured black? b) Name a property of enzymes that is represented in this diagram.

c) Sketch a graph to represent the change in the rate of enzymatic reaction when the enzyme is salivary amylase and pH is increased to 12 on the pH scale.

d) Use the information in the diagram and your own knowledge to explain why increasing the concentration of carbon dioxide does not increase the rate of photosynthesis.

3. The following is the result of an experiment investigating the action of enzyme on

starch.

Temperature of water

bath (o C)

Rate of reaction (relative amount of sugar formed

per minute)

10 10.0

20 33.0

30 48.5

40 54.5

50 46.5

60 34.0

70 17.0

a) Using a suitable scale, draw a graph to show the relationship between the rate of reaction and the temperature.

Substrate

Amino acids of the enzyme

Figure 1

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b) Describe and explain the relationship shown by the curve drawn in a)

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Answers

Section A1. A B B D A

6. A D B A C

11. D C A A D

16. C C A

Section B1.(i) Rate of decrease = (185g – 171g)/ 24h

= 0.58g/hr

(ii) Rate of water absorbed= (80 – 64)cm3/24h = 0.67 cm3/hr

(iii) Mass of water absorbed = 0.67g/hr

(iv) Water vapour is lost through the stomata via transpiration.This create a suction force called transpiration pull which pulls water from the roots.Water that is lost will be replaced by transpiration.

(v) Water absorbed is used for photosynthesis.Water is retained for turgidity.

2. a) Active site (1m) b) Enzyme / substrate specificity (1m)

c) Bell shape curve (1m) axis label (1m)d) There is limited amount of enzymes (1m). Active sites of enzymes are fully occupied with carbon dioxide (1m), therefore

increasing the amount of carbon dioxide will not increase the rate of photosynthesis because enzymes are the limiting factor.

3. Axes – correct label each [1m]Points – at least 5 correctly plotted [1m]Curve – joining up the points plotted [1m]b) Rise in temperature increases rate of reaction.[1m]Optimum at 40oC [1m]High temperature increases the kinetic energy of enzyme and substrate[1m] , thus they are more active and higher chance of collision. [1m]Lowers the activation energy [1m]Rate of reaction decreases beyond 40oC as enzymes start to get denatured as enzymes are protein [1m] in nature and high heat changes its 3D configuration, losing its active sites to fit the substrates. [1m]