bab 3 biology form 4

7/30/2019 bab 3 biology form 4

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BIOLOGY: CHAPTER 3

MOVEMENT OF SUBSTANCES

ACROSS THE PLASMA

MEMBRANE


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ARE YOU READY TO GO TROUGH THEMEMBRANE PLASMA???

READY1,2,3.!


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C:\Users\se7en\Downloads\The PlasmaMembrane(240p_H.263-MP3).flv
http://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flvhttp://c/Users/se7en/Downloads/The%20Plasma%20Membrane(240p_H.263-MP3).flv


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The Fluid-Mosaic Model of the plasma membrane

was proposed by S. Singer and G. Nicolson in 1972.

They proposed that membrane proteins are dispersed

throughout and inserted into the phospholipidbilayer.

Pictured as "mosaic" because it has various protein

molecules embedded in the phospholipid bilayer.

The membrane is "fluid" cause the proteins andphospholipid molecules drift laterally in the

membrane.


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Two parts in each phospholipid molecule:(i) a polar head which is hydrophil ic (' keenof water ' )(i i ) a pair of non-polar fatty acid tai ls which

are hydrophobic ('hate of water ' ).

Phospholipids are arranged in bilayer =

phospholipid bilayer.


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Types of proteins embedded :

(i ) pore proteins : has a pore to provide apassage for solutes to pass through the

plasma membrane.

(i i ) carr ier proteins :acts as a carr ier to

carry molecules across the plasma

membrane.


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Passive transport is the movement of

substances across the plasma membrane

from a region ofHIGH concentration to aregion ofLOWERconcentration, that is

going down a concentration gradient until

a dynamic equilibrium achieved.

2. Therefore, this process does not require

energy.


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Substances move across the plasma

membrane down the concentration gradient

through three different ways:

(a) lipid bilayer(b) carr ier protein(c) pore protein


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Substances move freely either

through

(a) simple diffusion(b) osmosis

(c) facil i tated diffusion (with the help ofcarr ier proteins or pore proteins)


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1. Molecules diffuse across the plasmamembrane down the concentration gradientthrough the phospholipid bilayer until dinamic

equilibrium achieved.

2. Substances involved:(i) small uncharged polar molecules : oxygen,carbon dioxide, water. Example: exchange ofgases between the alveolus and bloodcapillaries.


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Osmosis is the diffusion of water molecules through the

plasma membrane or semi-permeable membrane.

2. The net movement of water molecules is from a regionofLOW SOLUTE CONCENTRATION (high water

concentration/dilute solution) to a regiON OF HIGH

SOLUTE CONCENTRATION through a semi-permeable

membrane.

3. Example: the absorption of water by root hairs of a

plant where the soil has a higher water concentration than

the cytoplasm in the root hairs.


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1. Refers to the movement of hydrophilic molecules or ions across the

plasma membrane with the help of transport proteins:

(i) transported by binding at the binding sites of carrier proteins

(examples: larger uncharged polar molecules like glucose and aminoacids). Then carrier proteins change their shapes. After the process, the

carrier proteins return back to their original shapes.

(ii) through the pores of pore proteins (examples: small charged molecules

like mineral ions).

2.


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Examples : transportation of moleculeswhich are not soluble in lipids such asglucose, amino acids and mineral ions

through the villus at the ileum.


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(i)Facilitateiffusionthrough a carrierprotein

(i i) Facil itated diff usion through a pore

protein


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Similarities between Simple Diffusion and Facilitated Diffusion

Down the concentration gradient (From high concentration to

low concentration)

No energy is required


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Movement of molecules or ions against theconcentration gradient acroSs the plasma

membrane.

Requires BOTH carrier proteins and the expenditureof energy to transport the molecules or ions. The

energy for active transport usually comes from ATP

(adenosine triphosphate)which is generated during

respiration in the mitochondria.


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The carrier protein has an active site which binds to

the particular molecule or ion and another activesite which binds to the ATP.

The carrier protein changes shape when thephosphate group from the ATP binds to it.

Usually, active transport results in the accumulationof or elimination of molecules or ions from the cells.

Carrier proteins act as pumps.


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CONTINUE WITH MOVEMENT OFSUBSTANCES ACROSS PLASMA

MEMBRANE IN EVERYDAY LIFE

bab 3 biology form 4

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