The Plasma The Plasma MembraneMembrane

and and Cellular Cellular

TransportTransport

Maintaining a BalanceMaintaining a Balance

Maintain Maintain HOMEOSTASIS:HOMEOSTASIS: internal balanceinternal balance

Selective Selective permeabilitypermeability: allows : allows some materials to pass some materials to pass through membrane through membrane while rejecting others.while rejecting others.

Fluid-Mosaic ModelFluid-Mosaic Model This description is of a This description is of a plasma plasma

membranemembrane that is made up of molecules that is made up of molecules that are that are free to flow among one anotherfree to flow among one another..

The The kindskinds and and arrangementsarrangements of of proteinsproteins and and lipidslipids vary from one membrane to vary from one membrane to another and give each type of membrane another and give each type of membrane specific specific permeabilitypermeability properties. properties.

Structure of the Plasma MembraneStructure of the Plasma Membrane

Two-layered structure:Two-layered structure:– Lipid bilayerLipid bilayer

Made of Made of lipidlipid molecules withmolecules with proteinprotein molecules in the molecules in the lipid lipid layerlayer..

PROTEINSPROTEINS aid in the aid in the movement of materials movement of materials through the through the membrane.membrane.

Structure of the Plasma MembraneStructure of the Plasma Membrane The Lipids have two fatty The Lipids have two fatty

acids attached to acids attached to glycerolglycerol and a and a phosphate groupphosphate group (phospholipid).(phospholipid).

The The Polar “head”Polar “head” of a of a Phospholipid molecule Phospholipid molecule contains a polar contains a polar phosphorus groupphosphorus group, and , and two “two “tailstails” are long, ” are long, nonpolar nonpolar carbon chainscarbon chains..

Structure of the Plasma MembraneStructure of the Plasma Membrane

Structure of the Plasma MembraneStructure of the Plasma Membrane F = Phospholipid bilayerF = Phospholipid bilayer

PhospholipidPhospholipid– D = Hydrophilic D = Hydrophilic

head head– E = Hydrophobic E = Hydrophobic

tails tails

I = CholesterolI = Cholesterol

ProteinsProteins– J = transportJ = transport

G = Cytoskeletal G = Cytoskeletal filamentsfilaments

A = Carbohydrate chainA = Carbohydrate chainC = CarbohydrateC = Carbohydrate

GlycolipidGlycolipid GlycoproteinGlycoprotein

Proteins of the Plasma MembraneProteins of the Plasma Membrane

1) 1) Transport ProteinsTransport Proteins

2) 2) Receptor ProteinsReceptor Proteins

1)1) Transport ProteinsTransport Proteins

Channel ProteinsChannel Proteins – – channel for lipid channel for lipid insoluble molecules insoluble molecules and ions to pass freely and ions to pass freely throughthrough

Carrier ProteinsCarrier Proteins – bind – bind to a substance and to a substance and carry it across carry it across membrane, change membrane, change shape in processshape in process

2)2) Receptor ProteinsReceptor Proteins

– – Bind to chemical Bind to chemical messengers (Ex. messengers (Ex. hormones) which hormones) which sends a message into sends a message into the cell causing the cell causing cellular reactioncellular reaction

• Materials must move Materials must move in and out of the cell in and out of the cell through the plasma through the plasma membrane.membrane.

• Some materials Some materials move between the move between the phospholipids.phospholipids.

• Some materials Some materials move through the move through the proteins.proteins.

How do materials move into and How do materials move into and out of the cell?out of the cell?

Plasma Membrane TransportPlasma Membrane Transport

• Molecules move across the plasma Molecules move across the plasma membrane by:membrane by:

What are three types of What are three types of passive transport?passive transport?

1)1) DiffusionDiffusion

2)2) Facilitated DiffusionFacilitated Diffusion

3)3) OsmosisOsmosisATP energy is ATP energy is notnot

needed to move the needed to move the molecules through.molecules through.

Passive Transport 1: DiffusionPassive Transport 1: Diffusion

• Also called Also called Brownian Motion: Brownian Motion: random random motion of molecules.motion of molecules.

• Molecules can move directly through the Molecules can move directly through the phospholipids of the plasma membranephospholipids of the plasma membrane

What is Diffusion?What is Diffusion?

• Diffusion is the net movement of molecules from a high Diffusion is the net movement of molecules from a high concentration to a low concentration until equally distributed.concentration to a low concentration until equally distributed.

• Diffusion rate is related to temperature, pressure, state of Diffusion rate is related to temperature, pressure, state of matter, size of concentration gradient, and surface area of matter, size of concentration gradient, and surface area of membrane.membrane.

Dynamic Equilibrium:Dynamic Equilibrium:

a continuous movementa continuous movement

of molecules, but noof molecules, but no

change in concentration.change in concentration.

Concentration GradientConcentration Gradient

The difference in The difference in concentration of a concentration of a substance across a substance across a space.space.

Passive Transport 2: Facilitated Passive Transport 2: Facilitated DiffusionDiffusion

• Molecules can move through the Molecules can move through the plasma membrane with the aid of plasma membrane with the aid of transport proteinstransport proteins

This is called …This is called …

What is Facilitated Diffusion?What is Facilitated Diffusion?

• Facilitated diffusion Facilitated diffusion is the net movement is the net movement of molecules from a of molecules from a high concentration to high concentration to a low concentration a low concentration with the aid of with the aid of channel or carrier channel or carrier proteinsproteins..

Passive Transport 3: OsmosisPassive Transport 3: Osmosis

• Water Molecules can move directly Water Molecules can move directly through the phospholipids of the through the phospholipids of the plasma membraneplasma membrane

This is called …This is called …

What is Osmosis?What is Osmosis?

• OsmosisOsmosis: diffusion of : diffusion of WATERWATER molecules through a membrane molecules through a membrane from an area of from an area of higherhigher water water concentration to concentration to lowerlower water water concentration.concentration.

Osmosis in actionOsmosis in action• What will happen in the What will happen in the

U-tube if water freely U-tube if water freely moves through the moves through the membrane but glucose membrane but glucose can not pass?can not pass?

• Water moves from side with Water moves from side with high concentration of water to high concentration of water to side with lower concentration side with lower concentration of water. Movement stops of water. Movement stops when osmotic pressure when osmotic pressure equals hydrostatic pressure.equals hydrostatic pressure.

Osmosis and TonicityOsmosis and Tonicity

Tonicity refers to the total solute Tonicity refers to the total solute concentration of the solution outside the concentration of the solution outside the cell.cell.

What are the three types of tonicity?What are the three types of tonicity?1)1) IsotonicIsotonic

2)2) HypotonicHypotonic

3)3) HypertonicHypertonic

IsotonicIsotonic Solution in which the concentration of Solution in which the concentration of water (solvent) water (solvent)

outside the cell outside the cell is the is the same same as the concentration as the concentration inside inside the cellthe cell..

What will happen to a cell placed in an Isotonic solution?What will happen to a cell placed in an Isotonic solution? The cell will have no net movement of water and will stay The cell will have no net movement of water and will stay

the same size.the same size. Ex. Blood plasma has high concentration of albumin Ex. Blood plasma has high concentration of albumin

molecules to make it isotonic to tissues.molecules to make it isotonic to tissues.

Hypotonic (Hypotonic (Less ConcentrationLess Concentration)) Solution in where concentration of water (solvent) outside Solution in where concentration of water (solvent) outside

the cell is the cell is higherhigher than the concentration inside the cell. than the concentration inside the cell.

What will happen to a cell placed in a Hypotonic solution?What will happen to a cell placed in a Hypotonic solution? The cell will gain water and swell.The cell will gain water and swell. If the cell bursts, then we call this If the cell bursts, then we call this lysislysis. (Red blood cells = . (Red blood cells =

hemolysis)hemolysis) In plant cells with rigid cell walls, this creates In plant cells with rigid cell walls, this creates turgorturgor

pressure.pressure.

Hypertonic (More Concentrated)Hypertonic (More Concentrated) Solution in which concentration of water (solvent) Solution in which concentration of water (solvent)

outside the cell is outside the cell is lowerlower than the concentration than the concentration inside the cell.inside the cell.

What will happen to a cell placed in a Hypertonic What will happen to a cell placed in a Hypertonic solution?solution?

The cell will lose water and shrink. The cell will lose water and shrink. In plant cells, the central vacuole will shrink and In plant cells, the central vacuole will shrink and

the plasma membrane will pull away from the cell the plasma membrane will pull away from the cell wall causing the cytoplasm to shrink called wall causing the cytoplasm to shrink called plasmolysis.plasmolysis.

Review TonicityReview Tonicity

What will happen to a red blood cell in a hypertonic What will happen to a red blood cell in a hypertonic solution?solution?

What will happen to a red blood cell in an isotonic solution?What will happen to a red blood cell in an isotonic solution? What will happen to a red blood cell in a hypotonic solution?What will happen to a red blood cell in a hypotonic solution?

1) Active Transport1) Active Transport2) Exocytosis2) Exocytosis3) Endocytosis3) Endocytosis

– PhagocytosisPhagocytosis– PinocytosisPinocytosis

What are three types of What are three types of Active transport?Active transport?

ATP energy is ATP energy is requiredrequired to move to move the molecules the molecules through.through.

Active TransportActive Transport Molecules move from areas of low Molecules move from areas of low

concentration to areas of high concentration concentration to areas of high concentration with the aid of ATP energy.with the aid of ATP energy.

The Importance of Active TransportThe Importance of Active Transport Bring in essential moleculesBring in essential molecules Rid cell of unwanted molecules (Ex. Rid cell of unwanted molecules (Ex.

sodium from urine in kidneys)sodium from urine in kidneys) Maintain internal conditions different Maintain internal conditions different

from the environmentfrom the environment Regulate the volume of cells by Regulate the volume of cells by

controlling osmotic potentialcontrolling osmotic potential Control cellular pHControl cellular pH Re-establish concentration Re-establish concentration

gradients to run facilitated diffusion. gradients to run facilitated diffusion. (Ex. Sodium-Potassium pump and (Ex. Sodium-Potassium pump and Proton pumps)Proton pumps)

Active Transport 2: Active Transport 2: Exocytosis (Exo – out) Exocytosis (Exo – out)

Movement of large Movement of large molecules bound in molecules bound in vesicles vesicles out ofout of the cell the cell with the aid of ATP with the aid of ATP energy. Vesicle fuses energy. Vesicle fuses with the plasma with the plasma membrane to eject membrane to eject macromolecules.macromolecules.

Ex. Proteins, Ex. Proteins, polysaccharides, polysaccharides, polynucleotides, whole polynucleotides, whole cells, hormones, mucus, cells, hormones, mucus, neurotransmitters, wasteneurotransmitters, waste

Active Transport 3: Active Transport 3: Endocytosis (Endo – In)Endocytosis (Endo – In)

Movement of large Movement of large molecules molecules intointo the cell the cell by engulfing them in by engulfing them in vesicles, using ATP vesicles, using ATP energy.energy.

Two types of Two types of Endocytosis:Endocytosis:– PhagocytosisPhagocytosis– PinocytosisPinocytosis