AS Biology. Foundation. Cell membranes and Transport1 CELL MEMBRANES and TRANSPORT.

AS Biology. Foundation. Cell AS Biology. Foundation. Cell membranes and Transportmembranes and Transport

11

CELL MEMBRANESCELL MEMBRANESandand

TRANSPORTTRANSPORT


22

The CellThe Cell


33

Cell membraneCell membrane All living things are surrounded by a membrane.All living things are surrounded by a membrane.A cell membrane is also known as plasma A cell membrane is also known as plasma membrane.membrane.Controls exchange of materials such as nutrients Controls exchange of materials such as nutrients and waste between cells and their environment.and waste between cells and their environment.Has other important functions for example to Has other important functions for example to enable cells to receive hormones.enable cells to receive hormones.

To understand the function of anything in biology, To understand the function of anything in biology, you must study the structure first!you must study the structure first!


44

Cell Membranes from Opposing Cell Membranes from Opposing Neurons (TEM x436,740). Neurons (TEM x436,740).

}} cell cell membranemembrane

7nm wide7nm wide

Cell membrane Cell membrane {{

Nerve cellNerve cell

Nerve cellNerve cell

Gap between Gap between cellscells


55

HYDROPHILIC heads HYDROPHILIC heads (water liking)(water liking)-Attracted to the -Attracted to the water water

called POLARcalled POLAR

HYDROPHOBIC tails HYDROPHOBIC tails (water fearing)(water fearing)-Not attracted to -Not attracted to the waterthe water

called NON-POLARcalled NON-POLAR

Cell membranes are made Cell membranes are made of PHOSPHOLIPIDsof PHOSPHOLIPIDs

A PhospholipidA Phospholipid


66

A phospholipidA phospholipidHYDROPHILIC HEADHYDROPHILIC HEADAt the other end of the phospholipid is a At the other end of the phospholipid is a

phosphate group and several double phosphate group and several double bonded oxygens. The atoms at this bonded oxygens. The atoms at this end of the molecule are not shared end of the molecule are not shared equally. This end of the molecule has equally. This end of the molecule has a charge and is attracted to water. It a charge and is attracted to water. It is POLARis POLAR

HYDROPHOBIC TAILSHYDROPHOBIC TAILSThe two long chains coming off of the The two long chains coming off of the

bottom of this molecule are made up bottom of this molecule are made up of carbon and hydrogen. Because of carbon and hydrogen. Because both of these elements share their both of these elements share their electrons evenly these chains have no electrons evenly these chains have no charge. They are NON POLAR. charge. They are NON POLAR. Molecules with no charge are not Molecules with no charge are not attracted to water; as a result water attracted to water; as a result water molecules tend to push them out of molecules tend to push them out of the way as they are attracted to each the way as they are attracted to each other. This causes molecules with no other. This causes molecules with no charge not to dissolve in water. charge not to dissolve in water.

3D model of 3D model of a a PhospholipidPhospholipid


77

A Phospholipid BilayerA Phospholipid BilayerPhospholipids can form: Phospholipids can form:

BILAYERSBILAYERS

-2 layers of -2 layers of phospholipids withphospholipids with

hydrophobic tails hydrophobic tails protected inside by protected inside by the hydrophilic heads.the hydrophilic heads.

The PHOSPHOLIPIDThe PHOSPHOLIPIDBILAYER is the basicBILAYER is the basicstructure of structure of

membranes.membranes.


88

Fluid mosaic modelFluid mosaic model

Cell membranes also contain proteins within the phospholipid bilayer.Cell membranes also contain proteins within the phospholipid bilayer.This ‘model’ for the structure of the membrane is called the:This ‘model’ for the structure of the membrane is called the:

FLUID MOSAIC MODELFLUID MOSAIC MODELFLUID- because individual phospholipids and proteins can move FLUID- because individual phospholipids and proteins can move

around freely within the layer, like it’s a liquid.around freely within the layer, like it’s a liquid.MOSAIC- because of the pattern produced by the scattered protein MOSAIC- because of the pattern produced by the scattered protein

molecules when the membrane is viewed from above.molecules when the membrane is viewed from above.


99

Cell Membranes from Opposing Cell Membranes from Opposing Neurons (TEM x436,740). Neurons (TEM x436,740).

} } Phospholipid Phospholipid BilayerBilayer

7nm wide7nm wide


1010

Movement of selected Movement of selected molecules across the cell molecules across the cell

membrane membrane


1111

Methods of Transport Methods of Transport Across MembranesAcross Membranes

1. Diffusion1. Diffusion

2. Osmosis2. Osmosis

3. Facilitated Diffusion3. Facilitated Diffusion

4. Active Transport4. Active Transport


1212

Methods of Transport Methods of Transport Across MembranesAcross Membranes

1.1. Diffusion -passive transport - no Diffusion -passive transport - no energy expendedenergy expended2. Osmosis - Passive transport of water2. Osmosis - Passive transport of water

across membrane across membrane3.3. Facilitated Diffusion - Use of proteins to Facilitated Diffusion - Use of proteins to carry polar molecules or ions acrosscarry polar molecules or ions across4.4. Active Transport- requires energy to Active Transport- requires energy to transport molecules against a transport molecules against a concentration gradient – energy is concentration gradient – energy is in the form of ATPin the form of ATP


1313

DiffusionDiffusion

Movement of molecules from Movement of molecules from an area of high concentration an area of high concentration to an area of low to an area of low concentration.concentration.

Movement from one side of a Movement from one side of a membrane to another, un-membrane to another, un-facilitatedfacilitated


1414

Diffusion


1515

SolutionsSolutions Solutions are made of solute Solutions are made of solute

and a solventand a solvent Solvent - the liquid into which Solvent - the liquid into which

the solute is poured and the solute is poured and dissolved. We will use water as dissolved. We will use water as our solvent today.our solvent today.

Solute - substance that is Solute - substance that is dissolved or put into the dissolved or put into the solvent. Salt and sucrose are solvent. Salt and sucrose are solutes.solutes.


1616

Osmosis


1717

Tonicity is a relative Tonicity is a relative termterm

Hypotonic SolutionHypotonic Solution - One solution - One solution has a lower concentration of has a lower concentration of solute than another.solute than another.

Hypertonic SolutionHypertonic Solution - one solution - one solution has a higher concentration of has a higher concentration of solute than another.solute than another.

Isotonic SolutionIsotonic Solution - both solutions - both solutions have same concentrations of have same concentrations of solute.solute.


1818

Plant and Animal Cells put into various solutions


1919

Types of Transport


2020

Diffusion LabDiffusion Lab

We are using dialysis tubing We are using dialysis tubing as the cell membrane - It is as the cell membrane - It is selectively permeableselectively permeable

The solute is either the eosin The solute is either the eosin starch solution or the sugar starch solution or the sugar solutionsolution

What is the solvent?What is the solvent?


2121

Membrane PermeabilityMembrane Permeability SoluteSolute is eosin-starch-chloride solution is eosin-starch-chloride solution SolventSolvent is Water is Water IndicatorIndicator for presence of starch is IKI for presence of starch is IKI Starch is made of amylose and Starch is made of amylose and

amylopectin – amylopectin is insolubleamylopectin – amylopectin is insoluble Iodine is not very soluble in water, but Iodine is not very soluble in water, but

with KI it forms a Iwith KI it forms a I33-- (triiodine ion) (triiodine ion)

which is soluble. which is soluble. II33

-- combines with the amylose and the combines with the amylose and the starch molecule turns blue-black.starch molecule turns blue-black.


2222

Test for StarchTest for Starch

Elmhurst College Website


2323

Test for Chloride ionsTest for Chloride ions

Indicator for presence of chloride Indicator for presence of chloride ions is silver nitrate, AgNOions is silver nitrate, AgNO33

A white precipitate, AgCl, forms if A white precipitate, AgCl, forms if chloride is present.chloride is present.


2424

Test for Sulfate ionsTest for Sulfate ions

Indicator for the presence of Indicator for the presence of sulfate ions is Barium chloride, sulfate ions is Barium chloride, BaClBaCl Barium sulfate, BaSOBarium sulfate, BaSO44 - forms a - forms a

white precipitatewhite precipitate BaCl + NaSOBaCl + NaSO4 4 ----> BaSO----> BaSO44 + NaCl + NaCl


2525

Living CellsLiving Cells

Fern gametophytes are used to Fern gametophytes are used to see result of putting live cells in see result of putting live cells in solutions of varying tonicitysolutions of varying tonicity


2626

OsmosisOsmosis

We will make an osmometer to We will make an osmometer to see osmosissee osmosis

Sugar solution in a dialysis tube Sugar solution in a dialysis tube is used to simulate a cell is used to simulate a cell membrane.membrane.

Various concentrations of solute Various concentrations of solute may be used around the room.may be used around the room.


2727

Moving amoebaMoving amoeba

Date post:	21-Dec-2015
Category:	Documents
Upload:	alexander-nash
View:	251 times
Download:	0 times

AS Biology. Foundation. Cell membranes and Transport1 CELL MEMBRANES and TRANSPORT.

Documents