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19

3.1 Movement Of Substances Across The Across The Plasma Membrane

1. (a) Figure 4 shows the fluid-mosaic model of membrane structure.

Trial Kelantan 2010 Trial Johor 2011

No

Marking scheme

Marks

(a)

Name the component of membrane Plasma membrane

1

1

(b)

Name the

structures M

, N, X , Y and Z.

P:

Phospholipids

Bilayer (State the component of structure P) Trail Pahang 09 S: Hydrophilic head Q :

Carrier

protein

R :Pore protien Z: Hydrophobic tails

1

1

1

1

1

4

(c)

Trial Melaka 2009 Explain the main function of P

Acts as a barrier between the internal and external environment of the cell // Allows only

Specific molecules to pass through it // provide the structural basis for all cell membrane.

1

2

S

Z

Molecule P

Molecule Q

Molecule R

(2)

20

Note: All the question refer to the Diagram 1

No

Marking scheme

Marks

(d)

The Plasma membrane is said to be semi premable membrane

What is the meaning of ‘semi-preamble’ membrane Trial Kedah 2008 Negeri Sembilan 2011 A semi-permeable plasma membrane is a membrane that allows only certain substances to

Move

freely across it.

1

1

(e)

State main component of layer P Kedah Trial 2011

Lipid /Protein

1

1

(f)

(f) Explain the causes that make plasma membrane have fluidity structure [kedah2008] P1-fluidity characteristics are caused by the protein molecules which are floating in the phospholipids bilayer.

P2- the positions of the molecules also keep on changing / not fixed in the position.

1

1

2

(g)

Molecule P move across the plasma membrane follow the concentration gradient Whereas

Molecule Q move across structure X against the concentration gradient

Name the process of movement substances across the plasma membrane as shown in molecule P, Q molecule R

Molecule P: Facilitated diffusion Molecule Q: Simple diffusion /osmosis Molecule R: Active transport

1

1

1

3

(h)

Give one example of particle that move through P,Q and R Trial Wilayah Persekutuan R: Glucose /amino acid

P: Water /carbon dioxide/oxygen /small lipid soluble

Q: Natrium /Potassium

1

1

1

3

(i)

What type of passive transport occur at Q Simple diffusion

(j)

State two feature of the particle that enables it to pass through the phospholipids bilayers of the cell membrane

P1- Small

P2- Soluble to phospholipids bilayer/lipid soluble

1

(3)

21

No

Marking scheme

Marks

(k)

Explain how these molecules pass through the channel protein.

P1- Small molecule /ion move through the pore protein in the channel protein by simple diffusion

P2-The molecule are higher concentration (outside) diffuses the s\cell cause the molecule to diffuse to a lower concentration into the cell through the pore /down the concentration gradient

1

1

2

(l)

On d

iagram 2 ,draw arrow ( ) to show the movement of oxygen across the cellular component during the day time

Arrow from inside the cell to outside the cell, pass through phospholipids bilayer

1

1

(m)

Explain the answer in (b)(i)

E1-(during day time), photosynthesis occurs in cell to produce O2

E2- O2 diffuses from a higher concentration region to lower concentration region// O2

diffuses by following the concentration gradient E3- O2 is non –polar molecule /small molecule Any 3

1

1

1

3

(n)

Explain the arrangement of molecule P (Lipid) in Plasma membrane P1-Phospholipid molecule consists of two parts

P2-Hydrophilic head contact with the extracellular environment and hydrophobic tail point toward each other

P3-Phospholipid are arrange in double layer called, phospholipids bilayer

1

1

1

3

(o)

State the characteristic of phospholipid bilayer P1-it consist of hydrophilic head and hydrophobic tail

P2- Hydrophilic head contact with the extracellular environment and hydrophobic tail point toward each other

P3-not rigid or static

1

1

(4)

22

No

Marking scheme

Marks

(a)

Essay Enhancement Coner

All movements of substances have to pass through a plasma membrane. Explain why the plasma membrane is known as a semi permeable membrane

P1- it only allows the passage of certain molecules and limits the passage of other molecules. P2-It consists of two layers of phospholipids with protein molecules scattered in them P3-Molecules that can pass through the plasma membrane easily are those that can dissolve in lipid and small uncharged molecules.

P4- Molecules which cannot move through the plasma membrane but require proteins include large molecules that do not dissolve in lipid and small charged molecules.

P5 Channel protein does not require the binding of a molecule and conformational change to open.

P6Channel protein allows molecules to steadily diffuse across the membrane through diffusion.

P7However a carrier protein allows specific molecules to cross the cell membrane by undergoing a conformational change upon the binding of the molecule.

P8 The conformational change opens a hole through which the molecule can enter or leave a cell.

1

1

1

1

1

1

1

1

8

(b)

The figure below shows a fluid mosaic model of the plasma membrane

Explain the functions of the structures X, Y and Z in the movement of substances across the plasma membrane

P1- Structure X allows hydrophobic molecules which can dissolve in lipids such as fatty acids, glycerol, steroid hormones, and vitamins A, D, E and K to move in and out of the cell. P2-Structure Y allows bigger molecules which do not dissolve in lipids like glucose and amino acids to move in and out of the cell.

P3-Structure Z allows small charged molecules to move in and out of the cell.

1

1

(5)

23

Simple Diffusion Trial Perak2009

No Marking scheme

Marks

(a) Define Simple diffusion? [ESSAY] P1-The net movement of molecule /ions

P2-from a high concentration to a region of lower concentration P3-down / follow the concentration gradient

P4-Untill the dynamic equilibrium is achieved

1

1

1

1

2

(b) Based on the diagram, state one example of a substance that moves across the plasma membrane. Describe the characteristic of that substances transport

P1-Fatty acid/glycerol/vitamin A/D/E/K, Steroid S1-Small, non polar

E1-They are lipid soluble /van move through the phospholipids bilayer OR P2-Carbon dioxide, water and oxygen

S2-Small uncharged molecules

E2-they are lipid soluble /can move through the phospholipids bilayer

1

1

1

1

1

1

1

2

(c) SPM Clone 2003[Essay]

Explain briefly the process illustrated in the diagram P1-The process is known as simple diffusion

P2-the concentration of potassium manganate (VII) is higher at the bottom of the beaker

P3-the potassium manganate (VII) ions move from an area of higher concentration to an area of lower concentration

P4-Until dynamic equilibrium is achieved

P5-The ions are equally distributed throughout the whole system and turn the solution purple

1

1

1

1

1

1

5

(6)

24

Osmosis

No

Marking scheme

Marks

(a)

Based on the figure, name the process

Osmosis

1

1

(b)

Define Osmosis

(The net movement) of water molecules from a lower solute concentration region to a high

solute concentration region through a semi permeable membrane

1

1

(c)

Describe what happen to the volume of the solution on both side A and side B after five

Minutes P1-Definition

P2-causing the level of solution rise on side A

1

1

2

(d)

State the molecule involved in this process

Water molecule

1

1

(e)

Describe what happen to solute concentration on side B . Explain your answer P1-The solute concentration will increase on side B

P2-Salt diffuses from side A to side B, increasing the solute concentration

P3-Water diffuses from side B to side A, reducing the amount of water and increasing the solute concentration

1

1

1

3

(f)

State the differences of the process simple diffusion and osmosis

D1-Simple diffusion involves the movement of any molecule, Osmosis involved only the movement of water molecule

D3-Simple diffusion not require a semi- permeable membrane, Osmosis occurs through a semi permeable membrane

1

1

2

(7)

25

Facillitated Diffusion Trial Johor 2011

Trial Negeri Sembilan 2011

No

Marking scheme

Marks

(a)

Based on the diagram, name the process occur

Facilitated diffusion

1

1

(b)

Name molecule X

Amino acid/glucose/small protein

1

1

(c)

Describe and explain the following:

The uptake of potassium ions by algae even that concentration of potassium ions is higher in the cell sap the external environment

E1-Water enter plant roots by osmosis

E2-The concentration of solutes is lower in the soil in than root cell

E3-Water molecule moves across the semi preamble membrane and enter the root cell

1

1

1

3

(d)

Explain how amino acid molecule are transported across the plasma membrane by the process shown in diagram 1.1

S1-Amino acid binds to a specific site on the carrier protein

S2-Carier protein changes its shape and releases the amino acid on the other side S3-The movement of amino acid is down/follow the concentration gradient

1

1

1

3

X

(8)

26

No

Marking scheme

Marks

Essay Enhancement Coner

(a)The following information is about plasma membrane.

Based on the above statement, describe how an amino acid molecule is transported across the plasma membrane into the cell.

P1-Amino acid is a large water soluble molecule

P2-It requires carrier protein to move across the membrane

P3-Amino acid will bind to the carrier protein which is specific to it

P4-Carrier protein will change its shape to bring the amino acid molecule across the membrane P5-Lastly the carrier protein will release the amino acid and returns to its original shape

1

1

1

1

1

(b)State the similarities and differences between passive transport (facilitated diffusion) and active transport in the movement of molecules across the cell membrane.

Similarities :

S1-Both occurs in living cells

S2-Both occurs through a semi-permeable membrane

S3-Both require carrier protein to bind with the substances ANY 2 Differences :

Facilitated diffusion Active transport

Molecules move down the concentration gradient

Molecules move against the concentration gradient

Molecules move through pore proteins or carrier proteins

Molecules move through carrier proteins only

Occurs until a dynamic equilibrium is achieved

Results in accumulation of substances in the cell or removal of substances from the cell ATP or energy is not required ATP or energy is required

Not dependent on cellular respiration Dependent on cellular respiration

Not affected by inhibitors Inhibited by inhibitors such as respiratory poisons

Each differences 1 mark

1

1

1

1

1

1

1

1

1

8

The plasma membrane is semi-permeable and allows certain substances to move across.

(9)

27

Trial Johor 2009

No

Marking scheme

Marks

(c)

Explain how molecule P move across the plasma membrane

F -Molecule P moves across the plasma membrane by facilitated diffusion P1-Molecule P is water soluble/not soluble in lipid

P2-Molecule P moves from higher concentration region to lower concentration region//against concentration gradient

P3-Molecule P binds to the specific site of the carrier protein P4-Carier protein change its shape

P5-Molecule P move through Carrier protein

( F + any 3P)

1

1

1

1

1

1

1

4

Explain how gaseous exchange occur across the alveolus

P1 : Oxygen diffuse/ moves across a( plasma membrane/through ( plasma membrane) to blood capillary

P2: From higher (oxygen ) concentration ( in alveolus )to lower concentration ( in blood capillary)

P3: On the other hand the partial pressure of carbon dioxide is lower in the air of the alveoli compared to the blood capillaries.

P4: Carbon dioxide diffuse out of the blood capillaries into the alveoli. P5 : expelled through the nose or mouth into the atmosphere

.

1

1

1

1

1

3

P

(10)

28

Active Transport Kedah Trial 2008 JUJ 2009

Trial Johor 2011 Trial Kelantan 2011

No

Marking scheme

Marks

(a)

Define active transport

Movement of molecule or ions, against the concentration gradient across plasma membrane with the help of carrier protein and energy / ATP

1

1

(b)

State the process that involved in the uptake of mineral ions

Active transport

1

1

(c)

Explain what will happen to the uptake of mineral ions by the root hair if the roots are immersed into the solution containing metabolic poisons such as cyanide.

P1-metabolic poisons stopped the cell respiration P2-no energy/ATP is produced

P3-active transported cannot occur

P4-no uptake of mineral ions by roots cell (any 3)

1

1

1

1

3

(d)

Sodium ions found to be higher in concentration outside a human cell while potassium ions is found to be higher outside the cell

Describe the process that leads to the occurrence of the above situation

P1-The carrier protein‘s opening end has active site, which are filled by the sodium ions. P2-An ATP molecule then attaches on the protein and release energy

P3-The carrier Protein \change shape (and open to the other end, Where),it release the sodium ion to outside

P4-Carier Protein Returns to its original shape and release the potassium ions

Any 3

1

1

1

(11)

29

No

Marking scheme

Marks

(e)

Explain why paramecium has to pump it’s contractile vacuole when placed in 0.25 sucrose solution

P1-0.25%sucrose solution is hypotonic to cytoplasm P2-Water diffuses into that paramecium through osmosis

P3-Excess water has to be expelled, otherwise the paramecium will burst

1

1

1

3

(f)

Paramecium will and die when placed in the 0.25% sucrose solution added with respiratory poison

Explain the above statement

P1-The poison will inhibit cellular respiration P2-No energy is produced

P3-Contractile vacuole will not work/pump P4-Excess water cannot be expelled

1

1

1

1

4

(g)

How unicellular organisms living in freshwater maintain the water balance? P1-Gaseous exchange in the alveoli occurs through diffusion

P2-The concentration of oxygen in the alveoli is higher than that of the blood capillaries surrounding the alveoli

P3-This causes oxygen to diffuses into the blood

P4-Likewise, the higher concentration of carbon dioxide in the blood capillaries causes carbon dioxide to diffuse into the blood capillaries

1

1

1

1

4

(h)

What is the important of the process in (a) to an organism

(12)

30

3.2 The movement of substances across the plasma membrane in everyday life Plant Cell

In an experiment, the palisade mesophyl cell is immersed in distilled water for a certain period of time Trial SBP 2012

Trail Johor 2011

Type of solution Question & Marking Scheme

Solution A

Trail Johor 2011

(a) Based on the diagram, name the term use to describe the following/State the properties of the following solution/state the type of solution

Hypotonic/’hypotonic solution

(b) State the condition of the cell in the following solution Turgid

(c) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component

F1- This cellular component/ plasma membrane is pushed against the cell wall F2-The distilled water /solution is hypotonic to the cell sap

E1-Distilled water is hypotonic to the cell sap // cell sap hypertonic to

distilled

water

E2- Water molecule diffuses into the cell by osmosis E3-Vacuole Expand /swell up

E4- the cell are highly turgid /Any 3

Solution C (a) Based on the diagram, name the term use to describe the following/State the properties of the following solution/ state the type of solution

Hypertonic/Hypertonic solution

(b) State the condition of the cell in the following solution

Flaccid

(c) Name a physical process of plant cell in solution C

Plasmolysis

(d) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component

P1-The …solution is hyper tonic to cell sap

P2-Water molecule diffuses out of the large central vacuole by osmosis P3-the plasma membrane pull away from the cell wall

(13)

31

Type of solution Question & Marking Scheme

Solution B (a) Based on the diagram, name the term use to describe the following/State the properties of the following solution/ state the type of solution

Isotonic/ Isotonic solution

(b) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component

P1-the solution outside the cell is isotonic to the cell sap P2-Water diffuse in and out the cell at equal rate

P3-the cell maintain its shape/not change P4- no plant cell shrinks /.any 3

A plasmolysed plant cell become turgid when immersed in distilled water

No

Marking scheme

Marks

(a)

What process does the plant cell experienced?

depalsmolysis

1

1

(b)

Explain your answer

P1-plasmolysed cell can become turgid again by immersing in a hypotonic solution P2-water molecule diffuses in and the cell become turgid again

1

1

2

(c)

Draw a labeled diagram of the condition of palisade mesophyl cell after being immersed in the distilled water

D- The shape of the cell must be rectangular The cell wall is drawn with double line The vacuole must be large

L-Label vacuole

Reject other shape of the cell

1

1

2

(14)

32

Animal Cell

Trial Kelantan SPM

Type of solution

Question& Marking scheme

Solution M

State what your observe( / ) before P1 Normally get 1 marks Eg.P1-raw egg is floating

(a) Name a physical process that causes the changes in erythrocyte cells L and M. Haemolysis

(b) What are the characteristics /properties of the solutions used to soak :/ state the type of solution(must have word SOLUTION)

Hypotonic

(c

) State the condition of the cell

Crenated

(c) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component/ Explain what happen on the red blood cells in solution M/Explain the phenomena(state the phenomena)

P1-the solution is hypertonic to the red blood cell P2-Osmosis occur

P3-Water molecule diffuses in the cells P4-the cell start to swell and eventually burst P5-Haemolysis occur

P6-cytoplasmic fluid of red blood cells cause the solution change into clear red ANY 3

Solution K

State what your observe( / ) before

P1

Normally get 1 marks

(a) What are the characteristics /properties of the solutions used to soak :state the type of solution

Isotonic

(b) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component/ Explain what happen on the red blood cells in solution/ Explain the phenomena(state the phenomena)

P1-the solution outside the cell is isotonic to the cell sap P2-Water diffuse in and out the cell at equal rate

P3-the cell maintain its shape/not change P4- no red blood cell shrinks /burst ANY 3

(15)

33

No

Marking scheme

Marks

(a)

Use a tick (/) in the correct column to identify solution L and solution M

Name of solution Distilled water 10% salt solution

Solution L /

Solution M /

Explain why paramecium has to pump its contractile vacuole when placed in 0.25 sucrose solution

P1-0.25%sucrose solution is hypotonic to cytoplasm P2-Water diffuses into that paramecium through osmosis

P3-Excess water has to be expelled, otherwise the paramecium will burst

1

1

1

1

1

2

3

(b)

Cells P is mixed with detergent. The detergent dissolves lipids.

After 10 minutes, the mixture is examined under a microscope; no cells P were seen but the mixture turn red and cloudy.

Explain why?

P1- Detergent dissolves the lipid in the plasma membrane. P2- Plasma membrane disintegrate/destroyed

P3- Cytoplasm (of red blood cell) mix into the solution P4- Cell P is haemolysed AYN 3

1

1

1

1

3

Type of solution

Question& Marking scheme

Solution L

Trial Kedah 2008

State what your observe( / )before

P1

Normally get 1 marks

(a) Name a physical process that causes the changes in erythrocyte cells L and M.

/

state the type of solution

crenation

(b) What are the characteristics /properties of the solutions used to soak :// state the type of solution(must have word SOLUTION)

Hypertonic

(c) State the condition of the cell Haemolysed

(c) Explain the effect of the following solution to plant cell/ Explain what will happen to this cellular component/ Explain what happen on the red blood cells in solution L/ Explain the phenomena(state the phenomena)

P1-The solution is hypertonic to the red blood cell P2-Water molecule diffuses out of the cells by osmosis P3-creanation occurs

(16)

34

Trial Kedah 2008 Trial Kedah 2010

No

Marking scheme

Marks

(a)

Graph in Diagram 1.2 shows the percentage of red blood cells that are burst or shrink when placed in salt solution of different concentration.

Based on the graph given, state the concentration which is isotonic to blood plasma.

0.45 g/100 cm3

1

1

(b)

Explain your answer in (b)(ii).

Both percentage of haemolysis of red blood cells and percentage of crenation of red blood

Cells

are zero (0%).

1

1

(c)

Comment on the osmotic pressure at Q.

F:

The osmotic pressure inside the red blood cells is equivalent to its environment. P2 : Amount of water moving in and out of the cells are the same,

P3 : therefore the size and structure of the red blood cells does not change

1

1

(17)

35

Trial Kedah 2010

No

Marking scheme

Marks

(a)

Name the process that causes the level of sucrose solution in the capillary tube change.

Osmosis

1

1

(b)

Explain the process

P1-Sucrose solution is hypertonic /more concentrated

P2-water diffuse from distilled water into the sucrose solution

P3-the level of sucrose solution in the capillary tube stop rising at the equilibrium stage/the concentration inside and outside the visking tube is the same /the amount of water diffuse into and out from the visking tubing is the same

1

1

1

3

(c)

A laboratory test shows that at the end of the experiment, the distilled water in the beaker did not consist of sucrose

Explain why

F-sucrose molecule is too large

E-The visking tubing is a semi-

permeable

membrane/which only allow certain substances to pass through

1

1

2

(c)

The red blood cell in solution Z is replaced with a plant cell Does the plant cell burst as the red blood cell did

Explain why F - No

P1-plant cell consist of cell wall P2-cell wall made up of cellulose

1

1

(18)

36

Trial Johor 2010

A strip of mustard green stem was placed in different of concentrations of sucrose solution

Type of solution Question& Marking scheme

Solution A (a) State the type solution A, when compared to the cell mustard Hypotonic Solution

(b) Explain why do the strips placed in solution J and solution L curved

F1-the strips in solution J curved outward /toward the epidermis/epidermis layer P1-(Cortex) cells / (parenchyma) cell becomes turgid ‘longer because

water diffuses into the cell /protoplasm/cytoplasm by osmosis P2- Epidermal cells have a layer of cuticle on the outside

P3- Which resist/ restrict the entry of water (and retain its normal size) Any 2

Solution B (a) State the type solution B, when compared to the cell mustard Isotonic Solution

c)

State the solution which has osmotic concentration nearest to the cell sap

of mustard green

Solution B

(ii) Explain your answer(c) (i)

P1-The strip in solution B remain straight

P2-because the (cortex/ Parenchyma) cell have not increase in turgidity /flaccidity //no change in size / remain the same

(19)

37

Type of solution Question& Marking scheme

Solution C 2008 (a) State the type solution c, when compared to the cell mustard Hypertonic solution

(b) Explain why do the strips placed in solution J and solution L curved as shown

F1

– the strip in solution L curved inward /toward the cortex/parenchyma layer

P1-

Water diffuses out of the cytoplasm /protoplasm /cell sap of the (cortex ) cell / (Parenchyma) cells will shrink

P2

- The cytoplasm and /or the vacuole of the cell will shrink

(d) Draw and labeled diagram of the condition of one of the mustard green cells after being immersed in solution A, B, C for 20 minutes

D-Correct drawing -With vacuole

-Doubled- line cell wall

-Plasma membrane pulled away with some parts attached to the cell wall( totally detached from the cell wall is not accept)

L-Correct Labels -Plasma /cell membrane -vacuole

(20)

38

Wilting of plant Trial Terrenganu 2010

No

Marking scheme

Marks

(a)

Name the process that is occurs in the diagram

Osmosis

1

1

(b)

What is the factors that affects that direction in (a)(i)

Relative concentration (of solute) inside and outside the cell

1

1

(c)

Give an explanation what will happen to the plant of there is no water

P1-soil become hypertonic

P2-water molecule diffuses out of the root cell by osmosis

P3-the plant cell become flaccid

P4-the plant become wilt

1

1

1

1

5

(d)

Explain the condition of plant after being spread with excess fertilizers

P1-excess fertilizers cause the soil becomes hypertonic

P2-water diffuses out from (cell) via osmosis

P3-palnt cell loses water and cells are plasmolysed

P4-hence plant wilt

1

1

1

1

3

(e)

A Chemical substance inhibits the respiration process in the root hairs cells of the plant.

Explain the effect to the transport of the mineral ions into the root hair cells of the plant

P1: The cell unable to produce energy // energy is not generated

P2: Active transport does not occur.

P3: Thus, mineral ions cannot be transported into the cell. /any 2

1

1

(21)

39

No

Marking scheme

Marks

(f)

Explain how water move to structure T xylem tissue

P1-The cell sap of the root hair is hypetonic to the soil water P2-So, water diffuses into root hairs by osmosis

P3-The entry o dater dilutes cell sap of root hairs // cell sap of root hairs become hypotonic compared to the cell sap of spongy mesophyll cell

P4- water diffuses into spongy mesophyll cell /o these adjacent cells which become more diluted themselves, so osmosis continues across the S

P5-the continuous flow of water in S creates a force known as root pressure to push water into xylem

1

1

1

1

1

4

Essay enhancement coner

Diagram A Diagram B

No

Marking scheme

Marks

(a)

Diagram A shows a well –watered plant .diagram B shows the same plants have not been watered for week. Based on biological knowledge, explain what happens to the plants in diagram A and B

Diagram A

P1-The soil solution is hypotonic to the cell sap o the plants cell P2-water diffuses into the cell by osmosis

P3-Vacoule expand/swell up //cytoplasm to press outwards against the cell wall P4-Cell becomes turgid, supporting the plant upright

Diagram B

P1-The soil solution becomes hypotonic to the cell sap of the plant cell P2-water diffuses out from the cell by osmosis

P3-Vacoule/cytoplasm shrink//plasma membrane pull away from the cell wall P4-the plasmolysed/flaccid cells causing the plant to wilt

1

1

1

1

1

1

1

1

8

(22)

40

Food Preservation Trial Negeri Sembilan

No

Marking scheme

Marks

(a)

Explain the concept of osmosis in the preservation of mango

P-The addition of preservatives such as concentrated

salt/ sugar solution makes the

surrounding solution hypertonic to the cell sap of the mango

S1-Causing water to diffuse out from the cucumber cell by osmosis

S2-The dehydrated condition of the mango prevent the growth of bacteria and fungi S3-Causes water to diffuse out the bacteria /fungi

S4-Bacteria/fungi dehydrates and dies ANY 3

1

1

1

1

1

1

3

Essay enhancement corner Trial Pahang 2011

No

Marking scheme

Marks

(a)

Explain how natural preservation can preserves the cucumber for a long per

iod of time

P1-Immersed in salt and sugar solutions

P2-Solution outside of the food is hypertonic compared to the cytoplasm P3-Water in the food diffuse out by osmosis

P4-The cells in the food become dehydrated P5-microoraganism/bacteria/fungi lose water

P6-these conditions are not favorable for the growth of microorganism

1

1

1

1

1

1

1

6

(23)

41

No

Marking scheme

Marks

(b)

Diagram 3.1.2 and 3.1.3 show two types of food which can be preserved.

Diagram 3.1.2 Diagram 3.1.3

Explain how vinegar and concentrated salt solution can be used in the food preservation. P1-Vinegar is acidic and has low pH

P2-This prevent the growth of microorganisms in mangoes P3-The mangoes can be preserved to last longer

P4-Concentrated salt solutions hypertonic to the tissue of fish P5-Water diffuse out of fish cell by osmosis

P6-Water also diffuse out of bacteria cell to the surroundings P7-The bacteria cells become plasmolysed

P8-This prevent the growth of bacteria which cause food spoilage

1

1

1

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1

1

1

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1

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References

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