The Plasma Membrane and Cell Wall (Team 4)

7/27/2019 The Plasma Membrane and Cell Wall (Team 4)

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Cell Membrane

The cell membrane is a layerthat protects the cellnucleus and cytoplasm, hasa thickness of 8 nm. Cell

membrane wrappedorganelles within the cell.The cell membrane is alsoa means of transportation

for the cell entrance andexit of substances thatare needed and not neededby the cell.


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The chemical composition of

the membraneMembrane contains:- Lipid bilayer membrane structure andframework serves as a barrier ('barrier')which restrict the movement of moleculesrandomly

- Protein- Carbohydrate binding to lipids(glycolipids) or perotein (glycoprotein)

copyright cmassengale


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Structure of the CellMembrane



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Phospholipids

Cholesterol

Proteins(peripheral and integral)Carbohydrates (glucose)

Membrane Components


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copyright cmassengale 6

2. Model Robertson (1950)Robertson using electronmicroscopy, revealed that cellmembranes are composed of three

layers of dark light of the size ofeach 2 nm - 3.5, so that the entiremembrane measuring 7.5 nm. Indescribing the concept in the lipidlayer as two sheets of lipid, calledlipid hidrofilik that the tangent tothe layer of protein molecules.


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1. Davson & Danielli (1954)

Membrane lipid bilayer structure

which is interspersed withglobular proteins across themembrane and there is also a

protein on the surface of theouter and inner membranes.


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3.Singer & Nicholson (1972)Mosaic model / 'fluid mozaic'

Plasma membrane lipid bilayerconsisting of residing in a state of

fluid and can move laterally within themembrane structure of the dynamicinteraction of the temporary orsemipermanent.

Mosaic proteins are distributeddifferently with lipid particles do notform a continuous layer. Proteins cancross the membrane phospholipids, or

are at the edge of the cell


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FLUID- because individual phospholipids and

proteins can move side-to-side within thelayer, like its a liquid.MOSAIC- because of the pattern produced by

the scattered protein molecules when the

membrane is viewed from above.

FLUID MOSAIC MODEL


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Types of Transport AcrossCell Membranes



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DIFFUSION

Diffusion is a PASSIVEprocess which means noenergy is used to make

the molecules move,they have a naturalKINETIC ENERGY

Molecules move from

area of HIGH to LOWconcentration throughtthe membran plasma ornot


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Diffusion of Liquids


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Diffusion through aMembrane

Cell membrane

Solute moves DOWN concentration gradient (HIGH to

LOW)


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Diffusion of H2O Across A

Membrane

High H2O potential

Low solute concentration

Low H2O potential

High solute concentration


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Osmosis

Osmosis is the movementof solvent molecule

through a selectivelypermeable membrane.theprinciple of osmosis : fromthe dilute (hipotonis) to

the more concentrated(hypertonic). Osmosis willstop if concentration isisotonic.

Diffusion across a membrane

Semipermeablemembrane


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Example :1. Sign in and increase the mineral water into

bodys trees. The water content in the soil has agreater solvent (hypotonic) than in thevessel, so that the water enters the xylem / cellplant.

2. If a plant cell is placed in hypertonic conditions(high solute or solvent low), then the cell willshrink ( plasmolisis) because the cell fluid outinto the hypertonic solution.

3. Sea water is hypertonic to the cells of thehuman body, so drink sea water it causesdehydration.

4. The potatoes were put in salt water willexperience shrinkage.


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Types of Transport Proteins

Channel proteins are embeddedin the cell membrane & have apore for materials to cross

Carrier proteins can change

shape to move material fromone side of the membrane tothe other


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Active Transport

Requires energy orATP

Moves materials fromLOW to HIGH

concentration

AGAINSTconcentration gradient


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Active transport

Examples: PumpingNa+ (sodium ions)

out and K+

(potassium ions) inagainst strong

concentrationgradients.Called Na+-K+ Pump


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Endocytosis Pinocytosis

Most common form of endocytosis.

Takes in dissolved molecules as a vesicle.


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Pinocytosis

Cell forms aninvagination

Materialsdissolve inwater to bebrought into cell

Called CellDrinking


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Endocytosis Phagocytosis

Used to engulf large particles such asfood, bacteria, etc. into vesicles

Called Cell Eating


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ExocytosisThe opposite of endocytosis is exocytosis. Large

molecules that are manufactured in the cell arereleased through the cell membrane.

Inside Cell Cell environment


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Present in plant cells andbacterial cellsFunction: provide suport

and protection to the cellmembraneThere are pores in thecell walls to facilitate the

exchange of materialoutside of the material inthe cellMade of cellulose

Cell Wall


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Prokaryotic Cell Wall Eukaryotic Cell Wall

Cells without a nucleus and other

membrane-bound organelles

Cells with a nucleus & membrane

bound organelles

Have a simple DNA, slimmercontain the couple of basa

nukleotida, in form of sirkuler

Have a complex DNA, more amountcontaining couple of basa

nukleotida, so that have to befurled protein histon

Have a single chromosome Have a chromosome more than oneProcess the regulasi sintesis

protein more simple

Process the regulasi sintesis

protein more complexProcess the transkipsi andtranslasi can be happened bysimultan

Process Transkipsi in the nucleus

and process translasi in the

sitoplasma, Both cannot walk

concurrently

Differences Of Prokaryotic Cell Wall and Eukaryotic Cell Wall

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The Plasma Membrane and Cell Wall (Team 4)