Transport Across the Transport Across the Plasma MembranePlasma Membrane

OverviewOverview

Certain substances must move into Certain substances must move into the cell to support metabolic the cell to support metabolic reactionsreactions

Some materials must be moved out Some materials must be moved out of the cell because they have been of the cell because they have been produced as cellular wasteproduced as cellular waste

The Plasma Membrane is responsible The Plasma Membrane is responsible for regulating these materialsfor regulating these materials

FluidsFluids

Intracellular Fluid (ICF) – fluid Intracellular Fluid (ICF) – fluid contained within cells (cytosol)contained within cells (cytosol)

Extracellular Fluid (ECF) – fluid Extracellular Fluid (ECF) – fluid outside the body cellsoutside the body cells– Interstitial Fluid – fluid between cellsInterstitial Fluid – fluid between cells– Plasma – fluid in blood vesselsPlasma – fluid in blood vessels– Lymph – fluid in lymphatic vesselsLymph – fluid in lymphatic vessels

SolutionsSolutions

Solute – any substance dissolved Solute – any substance dissolved in a fluidin a fluid– Solutes in the body include gases, Solutes in the body include gases,

nutrients and ionsnutrients and ions Solvent – the fluid in which Solvent – the fluid in which

something is dissolvedsomething is dissolved– Water serves as the solvent in the Water serves as the solvent in the

bodybody

ConcentrationsConcentrations

Concentration – the amount of Concentration – the amount of solute in a solutionsolute in a solution

Concentration Gradient – the Concentration Gradient – the difference in concentration difference in concentration between 2 areasbetween 2 areas– Molecules can move “up” or “down” Molecules can move “up” or “down”

a concentration gradienta concentration gradient

Passive ProcessesPassive Processes

A substance moves down a A substance moves down a concentration gradient through concentration gradient through the membrane using only its own the membrane using only its own energy of motion (no ATP)energy of motion (no ATP)– Include Diffusion and OsmosisInclude Diffusion and Osmosis

DiffusionDiffusion

The movement of a substance from The movement of a substance from one place to another due to the one place to another due to the substance’s kinetic energy.substance’s kinetic energy.

The net movement of particles is The net movement of particles is from an area of high from an area of high concentration to an area of lower concentration to an area of lower concentration until equilibrium is concentration until equilibrium is reachedreached

Simple DiffusionSimple Diffusion

Substances diffuse through the Substances diffuse through the membrane by passing right through membrane by passing right through the lipid bilayerthe lipid bilayer– EX – oxygen, carbon dioxide, nitrogen, EX – oxygen, carbon dioxide, nitrogen,

fatty acids, steroids, vitamins, waterfatty acids, steroids, vitamins, water OR substances can pass though a OR substances can pass though a

channel in an integral proteinchannel in an integral protein– EX - ionsEX - ions

Ion ChannelsIon Channels

Most membrane channels are ion Most membrane channels are ion channelschannels

Allow specific type of ion to pass Allow specific type of ion to pass by simple diffusion through a by simple diffusion through a channel’s porechannel’s pore

Gated Channels – moves in one Gated Channels – moves in one direction to let substances in and direction to let substances in and the other to let substances outthe other to let substances out

Facilitated DiffusionFacilitated Diffusion

An integral protein assists a SPECIFIC An integral protein assists a SPECIFIC substance across the membrane.substance across the membrane.

The substance binds to a transporter on The substance binds to a transporter on one side of the membrane and is one side of the membrane and is released on the other side after the released on the other side after the transporter undergoes a change in transporter undergoes a change in shapeshape

DOES NOT REQURE CELLULAR ENERGY DOES NOT REQURE CELLULAR ENERGY (no ATP = Passive)(no ATP = Passive)

**This is how glucose enters the cell**This is how glucose enters the cell

OsmosisOsmosis

The net movement of water The net movement of water through a selectively permeable through a selectively permeable membranemembrane

Water moves from high WATER Water moves from high WATER concentration to low WATER concentration to low WATER concentration or..concentration or..

From low SOLUTE concentration From low SOLUTE concentration to high SOLUTE concentrationto high SOLUTE concentration

Osmotic PressureOsmotic Pressure

The pressure a solution The pressure a solution containing solute particles that containing solute particles that cannot pass through a membrane cannot pass through a membrane exerts on that membrane.exerts on that membrane.

Depends on the concentration of Depends on the concentration of the solute particles – the higher the solute particles – the higher the concentration, the higher the the concentration, the higher the osmotic pressureosmotic pressure

Isotonic SolutionIsotonic Solution

Contains the same concentration Contains the same concentration of solutes as the cellof solutes as the cell– Cell maintains it’s shape and volumeCell maintains it’s shape and volume

Hypotonic SolutionHypotonic Solution

Has a lower concentration of Has a lower concentration of solutes than the cellsolutes than the cell– Net movement of water into the cell Net movement of water into the cell

will cause it to swell and eventually will cause it to swell and eventually burstburst This is called hemolysis in red blood This is called hemolysis in red blood

cellscells

Hypertonic SolutionHypertonic Solution

Concentration of solutes is Concentration of solutes is greater than the cellgreater than the cell– Net movement of water out of the Net movement of water out of the

cell will cause the cell to lose cell will cause the cell to lose volume, and shrinkvolume, and shrink This is called crenationThis is called crenation

Concentration of BloodConcentration of Blood

The concentration of the salt in the The concentration of the salt in the blood is 0.9% NaClblood is 0.9% NaCl

Isotonic Solution Isotonic Solution (Normal Saline)(Normal Saline) = 0.9% = 0.9% NaClNaCl

Hypotonic Solution < 0.9% NaClHypotonic Solution < 0.9% NaCl Hypertonic Solution > 0.9% NaClHypertonic Solution > 0.9% NaCl

Check Point – Answer Check Point – Answer these questions in your these questions in your notesnotes What are the 2 types of fluids in the body?What are the 2 types of fluids in the body? What is a solute?What is a solute? In which direction is the net flow of In which direction is the net flow of

molecules in diffusion?molecules in diffusion? What is the difference between simple and What is the difference between simple and

facilitated diffusion?facilitated diffusion? How do ions get into/out of the cell?How do ions get into/out of the cell? What osmotic pressure?What osmotic pressure? What will happen to a red blood cell if it is What will happen to a red blood cell if it is

placed in a solution with a concentration placed in a solution with a concentration of 0.3%NaCl?of 0.3%NaCl?