Substances needed by the cellsSubstances needed by the cells WaterWater OxygenOxygen Nutrient Nutrient

– GlucoseGlucose– Amino acidAmino acid– Mineral Mineral – Fatty acidFatty acid– VitaminVitamin

The substances have to move across the The substances have to move across the membranemembrane

Substances to be eliminate from Substances to be eliminate from the cellsthe cells

Carbon dioxideCarbon dioxide Urea Urea ToxinToxin

Fluid Mosaic ModelFluid Mosaic Model

1972 - Singer and Nicolson called the 1972 - Singer and Nicolson called the membrane a membrane a “Fluid Mosaic Model”.“Fluid Mosaic Model”.

Mosaic:Mosaic: different proteins embedded different proteins embedded in in the phospholipids. the phospholipids.

Fluid:Fluid: proteins and phospholipids proteins and phospholipids can can move freely in the move freely in the membrane.membrane.

Components of a phospholipid Components of a phospholipid bilayer.bilayer.

1.1. phospholipidsphospholipids

2.2. proteins - proteins - enzymes, receptors, enzymes, receptors, transport.transport.

3.3. glycolipidsglycolipids

4.4. glycoproteinsglycoproteins

5.5. carbohydratescarbohydrates

6.6. cholesterolcholesterol

Plasma MembranePlasma Membrane

Boundary that separates the Boundary that separates the living cellliving cell from it’s from it’s non-livingnon-living surroundings. surroundings.

Phospholipid bilayerPhospholipid bilayer AmphipathicAmphipathic - having both: - having both:

hydrophilic headshydrophilic heads

hydrophobic tailshydrophobic tails ~8 nm thick~8 nm thick PhospholipidPhospholipid

Controls trafficControls traffic into and out of the cell into and out of the cell with with phospholipidsphospholipids and and transport transport proteinsproteins..

Selectively permeableSelectively permeable >>> semi-permeable>>> semi-permeable

Transport proteinTransport protein

What is Selective Permeability?What is Selective Permeability?

The The propertyproperty of of biological membranesbiological membranes which allows some substances to cross which allows some substances to cross more easily than others.more easily than others.

Transport ProteinsTransport Proteins

Transports Transports moleculesmolecules or or ionsions across across biological membranesbiological membranes

Two types:Two types:– Carrier proteinsCarrier proteins– Pore proteinsPore proteins

Through phospholipids layer:Non polar molecules = Oxygen. Carbon dioxide, water , lipid soluble molecules

By pore – proteins : water soluble molecules and ions

By carrier- proteins and energy : ions.

By carrier- proteins : glucose, amino acids.

Passive transport:Passive transport: NONO energyenergy is expended.is expended.– Simple diffusion Simple diffusion – gases, – gases, – Osmosis – water Osmosis – water

facilitated diffusionfacilitated diffusion: : type of type of passive transportpassive transport which uses which uses transport transport proteins. proteins. – – glucose and amino acidglucose and amino acid

Active transport Active transport ::– Using carrier protein and energy – ionsUsing carrier protein and energy – ions

DiffusionDiffusion

The net movement of a substance (molecules) down a concentrationconcentration gradientgradient from an area of highhigh conconcentrationcentration to an area of lowlow concentrationconcentration.

Facilitated diffusionFacilitated diffusion Allows diffusion of large, membrane insoluble Allows diffusion of large, membrane insoluble

compounds such as sugars and amino acids compounds such as sugars and amino acids Does not require energy (passive) Does not require energy (passive) Highly Selective Highly Selective Substance binds to transport protein Substance binds to transport protein Fully reversible - molecules may enter the cell Fully reversible - molecules may enter the cell

and leave the cell through the transport protein. and leave the cell through the transport protein. Particles move from areas of high concentration Particles move from areas of high concentration

to areas of low concentration. to areas of low concentration. Movement rate of particles will saturate Movement rate of particles will saturate

– Maximum rate limited by number of transporters Maximum rate limited by number of transporters – Once all transporters are operating at 100%, an increase Once all transporters are operating at 100%, an increase

in concentration will not increase rate in concentration will not increase rate

Active TransportActive Transport Movement across membrane with an Movement across membrane with an

energy cost (usually against concentration energy cost (usually against concentration Used to pump specific compounds in or Used to pump specific compounds in or

out of the cell out of the cell Requires energy to overcome the Requires energy to overcome the

concentration gradient or to allow a large concentration gradient or to allow a large or charged particle to cross membrane or charged particle to cross membrane

Requires specific carrier proteins Requires specific carrier proteins – The energy requirement distinguishes active The energy requirement distinguishes active

transport from facilitated diffusiontransport from facilitated diffusion

OsmosisOsmosis

The movement of The movement of waterwater across across selectively permeable membranesselectively permeable membranes..

The The waterwater moves from a moves from a low low concentration area concentration area to to high high concentration areaconcentration area

Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

Hypotonic solutionHypotonic solution

Less soluteLess solute More waterMore water Compare to cytoplasm of the cellCompare to cytoplasm of the cell

Hypertonic solution Hypertonic solution

More soluteMore solute Less waterLess water Compare to cytoplasm of the cellCompare to cytoplasm of the cell

Isotonic solutionIsotonic solution

Equal concentration compare to Equal concentration compare to cytoplasm of the cellcytoplasm of the cell

Hypertonic Solution: • Solute concentration of solution higher than cell

• More dissolved particles outside of cell than inside of cell

• Hyper = more (think hyperactive); Tonic = dissolved particles • Water moves out of cell into solution

• Cell shrinks

Hypotonic Solution: • Solute concentration of solution lower than cell

• Less dissolved particles outside of cell than inside of cell • Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles • Water moves into cell from solution • Cell expands (and may burst)

Isotonic Solution: Solute concentration of solution equal to that of cell

No net water movement

Why the use of excess fertilizer caused

wilting in plant?

Explain these preservation process