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PANITIA BIOLOGI NEGERI KELANTAN 2007

CHAPTER 4 : CHEMICAL COMPOSITION IN THE CELL

Multiple Choice Questions:

For question 4-1 to 4-44, each question is followed by four alternative options A,B,C and D.

Choose one correct answer for each question and blacken the corresponding space in your

objective answer

4.1 : Understanding The Chemical Composition Of The Cell

1. Which of these elements is not found in large amounts in the cell ?

A. Sulphur

B. Oxygen

C. Carbon

D. Hydrogen

2.

Which compound has the characteristics listed above ?

A. Lipid

B. Water

C. Enzyme

D. Protein

3. What is the importance of nucleic acids?

A. Build cells during growth

B. Main source of energy in cells

C. Required for the synthesis of antibodies

D. Carry genetic material

4. Which of the following is not a function of water?

A. Provides a moist surface for the diffusion of gases

B. Facilitates the movement of joints

C. An insulator of heat in the body

D. Facilitates the hydrolysis of food by enzymes

4-1

Medium for chemical reactions in cell

Maintains osmotic pressure


5. The common chemical compounds in cells are

I. Carbohydrate

II. Nucleic acids

III. Cellulose

IV. Proteins

A I and II only

B. II and IV only

C. I, II and III only

D. I, II and IV only

4.2 : Understanding Carbohydrate

6. Starch is made of

A. Glucose

B. Sucrose

C. Maltose and fructose

D. Glycerol and glucose

7. What is the major function of monosaccharide in animals?

A. Regulates metabolism

B. Acts as structural material

C. Acts as food reserve

D. Releases energy

8. Which of the following is not a disaccharide?

A. Sucrose

B. Fructose

C. Lactose

D. Maltose

9. Which of the following monosaccharide combinations produces sucrose?

A. Glucose + fructose

B. Glucose + galactose

C. Fructose + galactose

D. Glucose + glucose

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10. What is the monomer of carbohydrates?

A. Glycerol

B. Nucleotide

C. Polysaccharide

D. Simple sugar

11. Plants usually store their excess carbohydrates in the form of

A. glycogen

B. starch

C. glucose

D. cellulose

12. The main carbohydrates food reserve in liver cells is

A. glucose

B. glycogen

C. lactose

D. starch

13. The formula for disaccharide is

A. C2H10O11

B. C6H12O6

C. C12H22O11

D. (C6H12O6)n

14. Which of the following are reducing sugars ?

I. Glucose

II. Fructose

III. Sucrose

IV. Lactose

A. I and II only

B. III and IV only

C. I, II and IV only

D. I, II, III and IV

4-3


15. Which of the following elements are present in carbohydrates ?

I. Carbon

II. Hydrogen

III. Nitrogen

IV. Oxygen

A. I and III only

B. I, II and IV only

C. II, III and IV only


16. Which of the following carbohydrates are examples of polysaccharides ?

I. Glycogen

II. Starch

III. Cellulose

IV. Galactose

A. I, II and III only

B. I, II and IV only



4.3 : Understanding Protein

17. Protein is made up of

A. fatty acids

B. amino acids

C. nucleic acids

D. mineral salts

18. Haemoglobin is an example of a

A. primary structure of protein

B. secondary structure of protein

C. tertiary structure of protein

D. quaternary structure of protein

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19. Amino acids are linked together to form a

A polypeptide

B. polynucleotide

C. polysaccharide

D. polyribosome

20. A dipeptide can be broken down into amino acids by the process of

A. condensation

B. heating

C. acids addition

D. hydrolysis

21. What is the type of protein structure that both enzymes and hormones have ?

A. Primary

B. Secondary

C. Tertiary

D. Quaternary

22. The process when two amino acids are joined together is called

A. hydrolysis

B. deamination

C. condensation

D. synthesis

4-5


23. Diagram 4.1 shows the molecular structure of proteins.

Figure 1

DIAGRAM 4.1

Which protein structure do X, Y and Z belong to?

24. Which of the following are functions of proteins ?

I. Formation of some hormones

II. Enzyme production

III. Tissue repair and building body substances

IV. Energy production

A. I and II only

B. I, II and III only



25. Which of the following elements are found in proteins?

I. Carbon

II. Nitrogen

III. Sulphur

IV. Phosphorus

A. I and II only

B. III and IV only



4-6

X Y Z

A.

B.

C.

D.

Tertiary

Primary

Secondary

Quaternary

Quaternary

Secondary

Primary

Tertiary

Primary

Tertiary

Quaternary

Secondary

X Y Z


26. Which of the following statements are true about essential amino acids?

I. They cannot be synthesised by human body from other compounds.

II. They must be taken in with food.

III. They include lysine and valine

IV. They are derived from other amino acids.

A. I and II only

B. III and IV only


D. I, II and III only

4.4 : Understanding Lipid

27. Among the elements in the cell, which are found in lipid ?

A. Carbon, nitrogen and oxygen

B. Carbon, hydrogen and oxygen

C. Carbon, hydrogen and sulphur

D. Carbon, nitrogen and phosphorus

28. How many fatty acids chains are in a phospholipids molecule ?

A. One

B. Two

C. Three

D. Four

30. A lipid is formed by condensation of

A. Amino acids and glucose

B. Amino acids and glycogen

C. Fatty acids and glycogen

D. Fatty acids and glycerol

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31. Which of the following are lipids ?

I. Steroids

II. Triglycerides

III. Oils

IV. Waxes

A. I and II only

B. I, II and III only



32. Saturated fats

I. contain fatty acids which do not have double bonds between the carbon.

II. contain fatty acids with double bonds between the carbon atoms.

III. are liquid at room temperature.

IV. have a higher content of cholesterol

A. I and IV only

B. II and III only

C. I, III and IV only

D. II, III and IV only

33. Which of the following is not true about the difference between saturated fats and

unsaturated fats ?

Saturated fat Unsaturated fat

A. Of animal origin Of vegetable origin

B. Usually in solid form or almost solid at

room temperature

Usually in liquid form at room

temperature

C.They are found in butter and cheese

They are found in most vegetable

products and oils

D. They have one or more double

bonds between their carbon atoms.

They do not have double bonds

between their carbon atoms

34. Diagram 4.2 shows a structure of one lipid molecule.

4-8


DIAGRAM 4.2

The part labelled Q represents

A. phosphate

B. glycerol

C. fatty acids

D. amino acids

35. Lipid is needed to form P while cellulose is needed to form Q. What are P and Q ?

Compound P Compound Q

A. Protoplasm Cell wall

B. Plasma membrane Cell wall

C. Cell wall Protoplasm

D Cell wall Plasma membrane

4.5 : Understanding Enzyme

36. Enzymes are made up of

A. carbohydrate

B. proteins

C. lipids

D. dietary fibres

37. Which of the following is not true about general characteristic of enzyme?

A. Enzyme action is specific

B. Active at temperatures exceeding 60oC

C. Sensitive to changes in pH

D. Accelerates the rate of biochemical reactions

38 Diagram 4.3 shows a stained shirt being washed by detergent containing pepsin at

4-9

QQ


20oC. The result was obtained after 1 hour interval.

DIAGRAM 4.3

The shirt of the same material was repeatedly washed at 37oC. Which of the following

shows the result after 1 hour?

B.

D.

39. The active site of an enzyme is

A. specific to its substrate

B. identical to the active sites of other enzymes

C. complementary to its substrate

D. denatured at the end of a chemical reaction

40. Which of the following statements regarding enzymes is true?

A. All enzymes in living organisms have an optimum temperature of 37°C.

B. Enzymes increase the activation energy for the reactions they catalyses.

C. Enzymes are denatured at 0°C.

D. Enzymes function as organic catalysts.

41. Which organelle is involved in the production of extracellular enzymes ?

4-10

After 1 hour

A

B

C

D


A. Golgi apparatus

B. Mitochondrion

C. Chloroplast

D. Smooth endoplasmic reticulum

42. Which of the following is correct about the types of enzymes produced for P and Q?

P Q

A

B

C

D

Intracellular

Extracellular

Intracellular

Extracellular

Extracellular

Intracellular

Intracellular

Extracellular

43. A suitable enzyme that can be used for these activities is

A. cellulase

B. protease

C. zymase

D. amylase

4-11

P – enzymes which are synthesised in the cell but secreted from the cell to work externallyQ – enzymes which are synthesised and retained in the cell for use of the cell itself

Remove germ from wheat Separate agar from seaweed


44. Diagram 4.4 shows the mechanism of enzyme action. Which property of enzyme is

shown in the diagram?

A. Enzyme structure is denatured by extremes of pH.

B. Temperature affects the rate of enzyme reaction.

C. Enzyme reaction is non-specific.

D. Structure of enzyme remains unchanged at the end of the reaction.

Structured Items

4-12

DIAGRAM 4.4


Answer all questions. Write your answer in the spaces provided in the question paper

4.1: Understanding The Chemical Composition Of The Cell

4.2: Understanding Carbohydrate

Structured Items

Answer all questions. Write your answer in the spaces provided in the question paper

4.1: Understanding The Chemical Composition Of The Cell

4.2: Understanding Carbohydrate

(1) Diagram 4.4 shows the structures of 3 examples of polysaccharides P, Q and R.

DIAGRAM 4.4

(a) Identify the molecules labeled P, Q and R.

P : Starch

Q : Glycogen

R : Cellulose

[3 marks]

(b) Where can the molecules be found

P : in the cell wall of plant cells

Q : Chloroplast

R : Liver cells

[3 marks]

(c) Structure P can be broken down into a simpler form by a process. What is the

4-13


process involved?

Hydrolysis

[1 mark]

(d) (i) State one similarity in the 3 polysaccharides

A polymer formed by the glucose monomer

(ii) What is the main difference between structures P and Q?

P (starch) is food storage in plant cells while Q (glycogen) is

food storage in animal cells.

[2 marks]

(e) Sucrose and lactose are examples of disaccharides that can be formed from

condensation of monosaccharide. What are the monosaccharide that form

Sucrose : Glucose and fructose

Lactose : Glucose and galactose

[2 marks]

(f) Briefly describe how to test for the presence of reducing sugar in an unknown

sample of food.

Food sample is heated with Benedict’s solution and a brick-red

precipitate is

formed.

[1 mark]


4-14


2. Diagram 4.5 shows the organelle involved during the synthesis and secretion of

protein in animal cell.

DIAGRAM 4.5

(a) Name the organelles labeled X, Y and Z.

X: Golgi apparatus

Y: Ribosomes

Z: Secretory vesicle

[3 marks]

(b) State the function of X and Y

X: processing, packaging and transporting centre of the synthesised

proteins.

Y: the site of protein synthesis

[2 marks]

(c) Molecule P is produced from the protein excreted by the cell.

(i) What is the type of structure shown by the molecule?

4-15

Molecule P

X

Y

Z


Quarternary structure

(ii) Give one example of the structure mentioned in c(i).

Haemoglobin

[2 marks]

(d) (i) Proteins are made from amino acids, name two types of amino acids

involved.

Essential amino acids

Non essential amino acids

[2 marks]

(ii) Briefly, explain the meaning of the answer in d(i).

Essential amino acids are the amino acids that can be synthesised

by the body

Non essential amino acids are the amino acids that cannot be

synthesised by the body.

[2 marks]


4-16


3. Diagram 4.6 shows the structure of a lipid molecule.

DIAGRAM 4.6

(i) Name the parts X and Y.

X : Glycerol

Y : Fatty acids

[2 marks]

(b) (i) What is the chemical reaction P that takes place to form the bonds

between X and Y?

Condensation

[1 mark]

(ii) What is product Q formed during this reaction?

Water

[1 mark]

(c) (i) What is the structural difference between a phospholipid molecule and

the lipid molecule shown in the figure above?

Phospholipids molecule has 2 fatty acids in its structure while the

lipid molecule has 3 fatty acids in its structure

[1 mark]

(ii) What is the function of phospholipids in cells?

Phospholipids is important to build the plasma membrane

[1 mark]

(d) One of the main types of lipid is fat.

(i) State two types of fat

4-17


Saturated fat (example is butter)

Unsaturated fat (example is oils)

[2 marks]

9ii) State two differences between the types of fat named in d(i).

Condition of saturated fats at room temperature is solid while

condition of unsaturated fats at room temperature is liquid.

Saturated fats contain cholesterol while unsaturated fats usually

do not contain cholesterol.

[2 marks]

(e) Explain why a daily intake of a diet rich in fats is bad for health.

Rich in cholesterol

Causes cardiovascular diseases

[2 marks]


4. Diagram 4.7 shows the organelles involved in the production of extracellular enzymes.

DIAGRAM 4.7

(a) Name the organelles labeled T and U.

T : Nucleus

4-18

S

T

R

U


U : Mitochondrion

[2 marks]

(b) State the function of organelle labeled R

Transport protein synthesised by ribosome to Golgi apparatus

[1 mark]

(c) Using an example and place produced, explain the term of extracellular

enzyme.

Example is lipase

Produced by the pancreas and transport to the duodenum

Extracellular enzyme is an enzyme which is synthesised in the cell but

secreted from the cell to work externally.

[3 marks]

(d) Based on the organelles shown in Diagram 4.7, explain how extracellular

enzymes are produced.

Proteins are synthesised in the ribosome

Rough endoplasmic reticulum transports the protein using transport

vesicle to the Golgi apparatus.

Golgi apparatus modifies proteins to become enzymes which are

secreted out from the cell

[3 marks]

(e) Diagram 4.8 shows the action of an enzyme and its substrate.

4-19


DIAGRAM 4.8

Explain the mechanism of enzyme action.

The enzyme has an active site

The substrate molecule binds to the active site of the enzyme to form an

enzyme-substrate complex

The enzymes catalyses the substrate to become products

The hypothesis for enzyme reaction is called ‘lock and key’ hypothesis.

[Max : 3 marks]

5. Diagram 4.9 shows a graph represent the effect of temperature on the rate reaction of

enzyme P.

DIAGRAM 4.9

(a) What is the optimum temperature for enzyme P ?

40oC

[1 mark]

(b) Describe the effect of different temperature on the rate of enzyme reaction.

At low temperature, the enzyme is inactive and the rate of reaction is low.

4-20

Temperature (oC)


The rate of reaction doubles with every 10oC rise in temperature.

At optimum temperature, the enzyme is very active and the rate of

reaction is at maximum.

At temperatures above 40oC, the enzyme becomes inactive and the rate of

reaction decreases rapidly.

At a higher temperature (60oC), the enzyme is denatured and the reaction

stopped.

[max: 4 marks]

(c) Enzymes are widely used in the household & industries. Explain how enzymes

act in :

(i) Helping to cook meat.

Using protease, to tenderise meat, so easy to cook

(ii) Extracting agar from seaweed

Using cellulase,to digest the cell wall of seaweeds, to extract

sugar

[4 marks]

(d) State three factors besides temperature that affect the enzymes activity.

pH value

concentration of enzyme

concentration of substrate

[3 marks]

Essay Items

4-21


Answer all questions

4.1 : Understanding The Chemical Composition Of The Cell

4.2 : Understanding Carbohydrate



1.

(a) Explain the importance of organic compounds like carbohydrate and protein in

a cell. [10 marks]

Explain the importance of organic compounds like carbohydrate and

protein in a cell.

CARBOHYDRATE

- Carbohydrates consist of carbon, hydrogen and oxygen molecules

- In plants carbohydrates are stored as to provide energy to cells

- In animals, carbohydrates are stored as glycogen to provide

energy in

human and animals tissues

- Cellulose forms the cell wall of plant cells.

(4 marks)

PROTEIN

- Proteins consist of carbon, hydrogen, oxygen and nitrogen

4-22

There are several components in cells which form organic and inorganic

compounds. Organic compounds normally found in cells are carbohydrate,

proteins, lipids and nucleic acids. Each compound plays an important role in

the cell.


molecules.

- Some proteins have sulphur and phosphorus

- Build new cells for growth, replacing dead cells and renew the

damaged tissue.

- A component in plasma membrane in the form of carrier protein

and

pore protein.

- Required in the synthesis of enzyme, antibodies and hormone.

- Build haemoglobin for oxygen transport.

- Form structural component such as keratin (skin), collagen

(bones)and myosin (muscle tissue) [max : 6 marks]

(b) (i) Name two types of nucleic acids found in living cells. [2 marks]

- DNA (deoxyribonucleic acids)

- RNA (ribonucleic acids)

(ii) Compare and contrast

saturated fats and unsaturated fats

Saturated fats Comparisons Unsaturated fats

Single bond

between the carbon

atoms

Type of bond

Double bond

between the carbon

atoms

SolidCondition at room

temperatureLiquid

Contain cholesterol Cholesterol levelUsually not contain

cholesterol

Animal

E.g. : like butterCould be found in

Plant / vegetables

oils

E.g. : palm oil

Essential amino acids and non essential amino acids [8 marks]

Essential amino Comparisons Non essential

4-23


acids amino acids

Cannot be

synthesised by the

body

Synthesis by the

body

Can be synthesised

by the body

Obtained from the

dietDerived from

Are derived from

other amino acid

9 amino acidsNumber of amino

acids11 amino acids

First class protein

from animal protein

Type of protein

produced

Second class

protein from plant

protein


2. (a) (i) What is an enzyme?

Enzymes are biological catalysts which can speed up biochemical

reactions in the cell without themselves being changed at the end

of the process. [2 marks]

(ii) Explain the characteristics of enzymes from the ‘lock and key’

hypothesis

There are two characteristics of enzymes from the ‘lock and key’

hypothesis :

- Enzyme reactions are highly specific.

- Enzymes have specific sites (active sites) to bind with a

specific substrate and catalyse the substrate to form

products.

- Enzymes remain unchanged at the end of the reaction.

- Enzymes are not destroyed by reactions they catalysed and

can be used again [4 marks]

(iii) Describe how an enzyme-controlled reaction is affected by pH. - Most enzymes can only function within a certain range of

pH

4-24


- For example,

- optimal pH for pepsin is about 2

- optimal pH for trypsin is about 8

- optimal pH for amylase is about 7

- extremes in pH result in denaturation of the enzyme (hence

decreasing the rate of reaction) [4 marks]

(b) Enzymes can be extracted and separated from cells in order to be used. Explain how

the enzymes can be used in daily life and industry. [10 marks ]

P1- detergents are mixed an enzyme / bioenzyme

P2- which will digest the stain

P3- speed up the cleaning process

P4- the enzyme (protease) is used in the leather industry

P5- to tenderize the leather /to remove hair from hides /skinning of fish in food

industries.

P6- lactobacillus bacteria produces enzymes to convert the lactose into

lactic acids

P7- Lactic acids is used in making yogurt

P8- Plant origin enzymes are used in food industry

P9- example lipase is used in the ripening of cheese

P10- amylase is used in the processing of fruit juice / to convert starch to sugar

in the making of syrup

4-25