Membrane TransportMembrane Transport

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Cell or Plasma MembraneCell or Plasma Membrane

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

• Composed of Composed of double layer of phospholipids double layer of phospholipids andand proteins proteins (phospholipid bilayer)(phospholipid bilayer)

• SurroundsSurrounds outside of outside of ALL cellsALL cells• Controls what Controls what enters or leaves the cellenters or leaves the cell• Living layerLiving layer

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PhospholipidsPhospholipids• HeadsHeads contain contain glycerol & glycerol &

phosphate phosphate and are and are hydrophilic hydrophilic (attract water)(attract water)

• TailsTails are made of are made of fatty acids fatty acids and are and are hydrophobichydrophobic (repel (repel water)water)

• Make up a Make up a bilayerbilayer where where tails tails point point inwardinward toward each other toward each other

• Can Can move laterallymove laterally to to allow allow small moleculessmall molecules (O (O22, CO, CO22, & H, & H22O O to enter)to enter)

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Cell Membrane ProteinsCell Membrane Proteins

• Proteins Proteins help move help move

large moleculeslarge molecules or or aid aid in cell recognitionin cell recognition

• Peripheral proteinsPeripheral proteins are are attached on the attached on the surface (inner or surface (inner or outer)outer)

• Integral proteinsIntegral proteins are are embedded completely embedded completely through the membranethrough the membrane

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The Cell Membrane is The Cell Membrane is also referred to as the also referred to as the

Fluid Mosaic ModelFluid Mosaic Model

Molecules in cell membranes are Molecules in cell membranes are constantly moving and changingconstantly moving and changing

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Structures Of The Plasma MembraneStructures Of The Plasma Membrane• Phosphate HeadPhosphate Head: Made of a phosphate group (polar and : Made of a phosphate group (polar and

attracts water)attracts water)

• CarbohydrateCarbohydrate: Used for cell recognition: Used for cell recognition

• Membrane ProteinMembrane Protein: Transports large particles across the : Transports large particles across the cell membranecell membrane

• CholesteralCholesteral: Helps stabilize the phospholipids: Helps stabilize the phospholipids

• Lipid TailsLipid Tails: Made of fatty acids (non-polar and does not : Made of fatty acids (non-polar and does not attract water)attract water)

DiffusionDiffusion

•Movement of Movement of particlesparticles

– From highFrom high– To LowTo Low

DiffusionDiffusion

• ConcentrationConcentration: the mass of solute (what's : the mass of solute (what's being dissolved) in a given volume of solvent being dissolved) in a given volume of solvent (what’s doing the dissolving)(what’s doing the dissolving)

• EquilibriumEquilibrium: the concentration throughout a : the concentration throughout a solution is the samesolution is the same

DiffusionDiffusion• ● ● Concentration gradientConcentration gradient: the difference in : the difference in

concentration across a barrier/membraneconcentration across a barrier/membrane

• ● ● Because diffusion depends upon random Because diffusion depends upon random particle movements, substances diffuse across particle movements, substances diffuse across membranes without requiring the cell to use membranes without requiring the cell to use energy energy

OsmosisOsmosis• Movement of waterMovement of water

• From high From high to lowto low

• Across a Across a selectively selectively permeable permeable membranemembrane-selects what -selects what moves in and out moves in and out

Osmosis

Dynamic EquilibriumDynamic Equilibrium

• Equal Equal concentrations concentrations are reachedare reached– Not the same Not the same

volumesvolumes

• Continued Continued movement across movement across the membranethe membrane

• Not gain or lossNot gain or loss

OsmosisOsmosis

• ● ● Osmosis is theOsmosis is the diffusion of water diffusion of water through a selectively permeable barrier. through a selectively permeable barrier. Water will tend to move across the Water will tend to move across the membrane until equilibrium is reached, membrane until equilibrium is reached, when this occurs the two solutions will be when this occurs the two solutions will be isotonicisotonic,, the same. the same.

• ● ● When a solution is more concentrated When a solution is more concentrated with solute it is said to be with solute it is said to be hypertonichypertonic, , whereas a dilute (less concentrated) solution whereas a dilute (less concentrated) solution is said to be is said to be hypotonichypotonic..

OsmosisOsmosis

Isotonic SolutionsIsotonic Solutions• Iso- equalIso- equal

• No change in concentrationsNo change in concentrations– Water still movesWater still moves– Same amount of water moves in as moves outSame amount of water moves in as moves out

• Both sides of membrane are the sameBoth sides of membrane are the same

Hypertonic SolutionHypertonic Solution• Hyper- OverHyper- Over

• Out side of cellOut side of cell– More dissolved substanceMore dissolved substance– Less waterLess water

• Water moves out of cellWater moves out of cell

Hypotonic SolutionHypotonic Solution

• Hypo- underHypo- under

• Out side of cellOut side of cell– Less dissolved substanceLess dissolved substance– More waterMore water

• Water moves into cellWater moves into cell

Passive TransportPassive Transport

• Cell uses no energyCell uses no energy

• From high to lowFrom high to low

Concentration

gradient

Plasma

membrane

Facilitated DiffusionFacilitated Diffusion

• Type of passive Type of passive transporttransport

• Use transport Use transport

proteinsproteins– Channel proteinsChannel proteins– Carrier proteinsCarrier proteins

• Changes shapeChanges shape

• From high to lowFrom high to low

Facilitated DiffusionFacilitated Diffusion

• ● ● During facilitated diffusion molecules that During facilitated diffusion molecules that would not normally be able to cross through the would not normally be able to cross through the membrane, such as glucose, diffuse across the membrane, such as glucose, diffuse across the membrane through selected protein channels. membrane through selected protein channels.

• It is dependent upon the concentration gradient It is dependent upon the concentration gradient because it does not require the cell to expend because it does not require the cell to expend any energy.any energy.

Active TransportActive Transport

• Cell uses energyCell uses energy• Against concentration Against concentration

gradientgradient– From low to highFrom low to high

• Carrier ProteinsCarrier Proteins– Molecule binds with carrier Molecule binds with carrier

proteinprotein– Energy then used to change Energy then used to change

shapeshape– Molecule released on other Molecule released on other

sideside– Carrier protein returns to Carrier protein returns to

original shapeoriginal shape

Active TransportActive Transport

• ●●The movement of material across a membrane The movement of material across a membrane and against a concentration gradient is calledand against a concentration gradient is called active transportactive transport. .

• Like facilitated diffusion this is carried out by Like facilitated diffusion this is carried out by protein channels in the membrane called protein channels in the membrane called transport proteins, however in this form of transport proteins, however in this form of diffusion energy is expended in the process of diffusion energy is expended in the process of “pumping” the material “uphill” against the “pumping” the material “uphill” against the gradient.gradient.

Molecule tobe carried

Moleculebeing carried

Energy

Active Transport

Large Particle TransportLarge Particle Transport

• ●● EndocytosisEndocytosis is the process of taking is the process of taking material into the cell by means of enfolding's, material into the cell by means of enfolding's, or pockets, of the cell membrane. The pocket or pockets, of the cell membrane. The pocket or enfold, once it has surrounded the molecule, or enfold, once it has surrounded the molecule, then closes and breaks off from the membrane then closes and breaks off from the membrane forming a vacuole. Two examples of forming a vacuole. Two examples of endocytosis are endocytosis are phagocytosisphagocytosis (cell eating) (cell eating) and and pinocytosis pinocytosis (cell drinking). (cell drinking).

• ● ● ExocytosisExocytosis works the opposite of works the opposite of endocytosis. It is a vacuole with material endocytosis. It is a vacuole with material designated to leave the cell which joins with designated to leave the cell which joins with the cell membrane then releases its material the cell membrane then releases its material outside of the cell. outside of the cell.

Large Particle Transport Large Particle Transport (Exocytosis and (Exocytosis and

Endocytosis)Endocytosis)

Large Particle TransportLarge Particle Transport

• Not through Not through membranemembrane

• Requires energyRequires energy

• Exocytosis- outExocytosis- out

Large Particle TransportLarge Particle Transport

• Endocytosis- inEndocytosis- in

Types of EndocytosisTypes of Endocytosis

Pinocytosis: liquid (into) Phagocytosis: Solid Pinocytosis: liquid (into) Phagocytosis: Solid (into)(into)