Chapter 3 Biology form 4

8/12/2019 Chapter 3 Biology form 4

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Movement of Substances Across

Plasma Membrane


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1. In chapter 2, have learned about cell is surround bythin plasma membrane

2. Plasma membrane is composed mainly ofphospholipids and proteins.

3. In 1972, S.Singer and G. Nicolson introduced thefluid-mosaic model of the membrane structure.

4. They proposed that membrane proteins aredispersed throughout and inserted into thephospholipid bilayer.


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5. Each phospholipid molecule has :polar head give it the hydrophilic property

a pair of non-polar tail give it hydrophobic property

6. in plasma membrane, phospholipid arrange in twolayer ( bilayer)hydrophilic head of outer layer face extracellular fluid( outside

cell)

hydrophilic head of inner layer face the cytoplasmic fluid (in thecell)

7. Phospholipid bilayer :acts as a barrier which isolate the two sides of the membrane

In most cells, the phospholipid bilayer also contain cholesterol.Cholesterol help to stabilize and strengthen the plasmamembrane, making it more flexible and make it less permeable towater soluble molecule such as ions.


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7. There are various types of proteins ( eitherpartially attached to the surface or whollyembedded in the membrane ) :Pore protein

protein molecule that forms a channel or a

poreallow small water soluble molecule and ions to passthrough the membrane.

Carrier protein protein molecule that acts as a carrierhave sites that can bind to specific molecules, such asglucose molecules, before transporting them across theplasma membrane.

Glycoprotein membrane protein that have carbohydratesattach to them


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P:

N: O:


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1. Impermeable prevent the passage of all

molecule.2. Semi-permeable/ selectively permeable

some substances can move across themembrane freely while other cannot.

3. Plasma membrane is semi-permeable .4. Factor that determine the passing of

molecule:Size

Polarity of molecule


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5. Since phospholipid bilayer form the major part ofplasma membrane lipid soluble molecule (fatty acid andglycerol)can pass phospholipid bilayer freely.

6. Non polar molecule ( O2, CO2)- also can move easily

7. Hydrophobic tails prevent polar molecule (H2O) passing

through them but H2O still can move across theplasma membrane because the molecule are small enoughto slide between the phospholipid bilayer or movethrough the pores(pore protein) .

8. Large water-soluble molecule (glucose, amino acid)cannot move through the hydrophobic region of plasmamembrane unless aided by carrier proteins.


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Permeable to: Impermeable to:Small non-polar molecule :Fatty acids, vitamins, glycerol,

vitamin A,D,E,K and steroid.

Water, carbon dioxide and oxygen

Large polar moleculeGlucose, amino acids, nucleic

acid

Ion ( charged): H+,Na+,K+,Cl-, Ca2+

These substances cannot pass easilythrough the plasma membrane and

require help of carrier protein andcellular energy.


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Types:

Concentration

Gradient :

Energy :

Name

of process:

Substances

transported:

Movement of substancesacross the plasma

membrane

Passive transport Active transport

Down concentrationgradient

Against concentration

gradient

Not require Required

SimpleDiffusion

OsmosisFacilitatedDiffusion

1. Oxygen2. Carbon

dioxidemolecules

Watermolecules

1. Glucose2. Amino

acid3. Mineral

ion

Active transport

1. Mineral ions2. Amino acids


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Activetransport

Passivetransport


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Lets watch video of passive and

active transport
http://c/Users/User/Desktop/Passive%20%20%20Active%20Transport.flvhttp://c/Users/User/Desktop/Passive%20%20%20Active%20Transport.flvhttp://c/Users/User/Desktop/Passive%20%20%20Active%20Transport.flvhttp://c/Users/User/Desktop/Passive%20%20%20Active%20Transport.flv


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1.Simple

Diffusion

3. Osmosis

2. Facilitated

Diffusion


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Going down concentration gradient until anequilibrium is achieved.

Simple diffusion is a physical process that

can be observed in liquid and gases.

1.Simple Diffusion

Is net movement of molecules or ions from a region ofhigher concentration to a region of lower concentration.


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Eg: place a drop of dye into beaker of water.

Dye and water molecules move in all direction.

Area dye are dropped : higher concentration of dyemolecules these molecules move from the area of higherconcentration to area with fewer dye molecules.

This process continues until reached dynamic equilibrium(evenly dispersed) / concentration is the same in all

regions.


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2.

Similar to simple diffusion but it only involveswater molecules.

2.Osmosis

net movement of water moleculesfrom aregion of higher water concentration tolower water concentrationthrough semi-

permeable membrane.

Higher water concentration = low solute

concentration in water

Lower water concentration = high soluteconcentration water


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Molecules which are not soluble in lipids: ions,amino acids, nucleic acids, amino acids cannotpass through the phospholipid bilayer of theplasma membrane.

This substances pass through the membrane byfacilitated diffusion with the aids of :

carrier proteinPore protein.

3.Facilitated Diffusion


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Carrier protein :Can only combine with specific molecule .eg: glucose molecules

can only bind with specific carrier protein for glucose.Function by binding to the moleculesCarrier protein then change the shape to allow the molecules

to pass through to the other side of the membrane.Net movement is always down a concentration gradient.


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Pore protein :Form pores or channelsIons ( small dissolved particles, eg: Na+,K+, Ca2+)

- can diffuse across plasma membrane.


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The movement of molecules or ions against theconcentration gradient across the plasmamembranes.

Require:energy ( ATP) to transport the molecules or ions.carrier protein


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The effect of hypotonic, hypertonic andisotonic solutions on animal and plant cells.

1. Hypotonic cair

2. Hypertonic pekat

3. Isotonic sama


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1. In comparing 2 solutions with different soluteconcentration :

Hypotonic solution(less)- solution with lowerconcentration of solutes/ higher waterconcentration than the cell / larutan cair

Hypertonic solution (more) solution with higherconcentration of solutes/ lowerwaterconcentration than the cell/ larutan pekat

Isotonic solution( equal) solution which theconcentration of solutes are equal inside andoutside the cell / kepekatan bahan larut sama.


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Larutan yang mempunyai kepekatan bahan larut yang rendah ,kepekatan molekul air yang tinggi- larutan cair.

Example : 0.15 M sodium chloride solution ,0.50 M sodiumchloride solution ,distilled water (air suling ) Distilled water is hypotonic solution because has lower solute

concentration and higher water concentration.

Larutan yang mempunyai kepekatan bahan larut yang tinggi,kepekatan molekul air yang rendah- larutan pekat.

Example : 30 % sucrose solution, 5% sucrose solution , distilledwater.

30 % sucrose solution is hypertonic because it has highersolute concentration and lower water concentration.


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Larutan yang mempunyai kepekatan bahan larut dan kepekatanmolekul air yang sama dengan sitoplasma sel.

Example : 30 % sucrose solution, 5% sucrose solution , distilledwater.5 % sucrose is isotonic because 30 % sucrose solution is

hypertonic solution, and distilled water is hypotonic solutions.


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1. Solution with lower concentration of solutes/ higher water

concentration than the cell.2. Since the concentration of water is higher outside the cell,the water molecule move from outside into the cell.

3. As a result, the cell gain water , the cell swell

Animal cell ( red blood cell)

1. If an animal cell such as redblood cell is immersed in ahypotonic solution, watermolecules is diffuse intothered blood cells by OSMOSIS

2. The RBC gain water & SWELL&finally BURST(pecah) becauseno cell wall.

3. The red blood cells are said to

undergo HAEMOLYSIS


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Plant cell

1. When a plant cell is placed in ahypotonic solution, water

molecules is transported intothe cell by OSMOSIS.

2. The vacuoles gain water,EXPANDSand exerts pressureoutwards on the cell wall.

3. It caused the plant cell tobecome TURGID.


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1. solution with higherconcentration of solutes/ lowerwater

concentration than the cell.2. Since the concentration of water is higher within the cell, the

water molecules from inside to the outside of cell.

3. As a result, the water leaves the cell, the cell shrink.

Animal cell ( red blood cell)

1. If RBC immersed in hypertonic solution,the solution outside the cell is moreconcentrated than the inside.

2. Water molecules diffuse out of the cellsby OSMOSIS.

3. Cells loses water to external environment.

4. RBC will SHRINKand plasma membraneCRINKLES UP.

5. This process calledCRENATION.


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Plant cell

1. When a plant cell is placed in a hypotonicsolution, the solution outside the cell is

more concentrated than the inside.

2. Water molecules DIFFUSE OUT of thecells by OSMOSIS.

3. Vacuole and cytoplasm LOSE WATER tothe surrounding and SHRINK.

4. The cell become FLACCIDand causeplant to WILD( layu)

5. The PLASMA MEMBRANE PULLS AWAYfrom the cell wall.

6. This process called PLASMOLYSIS.

7. However , if the plasmolysed plant cellimmersed in hypotonic solution, it willbecome turgid again.

8. This process called DEPLASMOLYSIS


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Plant cell in hypertonic

solutions
http://c/Users/User/Desktop/SPM%20Biology%20%20Types%20of%20Solution%20-%20Hypertonic.flvhttp://c/Users/User/Desktop/SPM%20Biology%20%20Types%20of%20Solution%20-%20Hypertonic.flvhttp://c/Users/User/Desktop/SPM%20Biology%20%20Types%20of%20Solution%20-%20Hypertonic.flvhttp://c/Users/User/Desktop/SPM%20Biology%20%20Types%20of%20Solution%20-%20Hypertonic.flv


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1. solution which the concentration of solutes are equal inside

and outside the cell.2. There is no net movement of water moleculeacross the plasma

membrane.

3. water molecules flow across the membrane at the same rateinboth direction.

4. The shapeof animal cell (RBC) and plant cell REMAINCONSTANT.

Animal cell ( Red blood cell ) Plant cell


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1. 5 % sucrose solution, 30 % sucrose solution, 0.1 % sucrose solution,

Complete it :

Hypotonic solution : ____________

Hypertonic solution :____________

Isotonic solution : ______________


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2. Which of the following onion cells were

immersed in a hypertonic solution?

3. Naming the process:_____________


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4. The diagram shows diffusion through a partiallypermeable membrane.

What are X and Y?

X Y

A Sucrose solution 20% Distilled water

B Distilled water Distilled waterC Sucrose solution 20% Sucrose solution 20%

D Distilled water Sucrose solution 20%


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5. The diagram below shows a strip of potato after it hasbeen soaked in solution P.

What is solution P?______________________


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The concept of osmosis and diffusion can beapplied in preservation of food.

1.

Preservation with salt The salt solution is hypertonic to the tissue of fish. Water molecules leaves the fish tissue and enter

the salt solution by osmosis. The cell become dehydrated and cell crenate. Without water, bacteria can not grow in fish tissue. At the same time, bacterial cell crenate. The preserved fish do not decay so soon and can

last longer.


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2. Preservation with sugar solution . Fruits such as rambutans and lychee can be

preserved by soaking them in concentrated sugarsolution .

The sugar solution is hypertonic to the cell sap inthe vacuoles of the fruits cells.

As a result, water leaves the fruits.

Chapter 3 Biology form 4

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