Cell Membrane Cell Membrane StructureStructure

BUBBLES!!

MUST wear goggles at ALL times! NO taking straw out of the dish! NO drinking/ inhaling bubble fluid THIS IS an EXPERIMENT!!! You can have fun, but ALL usual

lab safety RULES APPLY!

Questions to think about: Can anything pass through the

bubble without breaking it? Can one bubble divide to become

several bubbles? Can several bubbles merge to form

one- how? Can a drop of water pass through a

bubble without popping it? Does it look like the surface of the

bubble moves? How can you tell?

Bubble Summary!

A bubble is a lipid monolayer!! How does a bubble model the

fluid nature of a cell membrane? What is the structure of the

membranes of our cells?

Key words to know!Key words to know!

HydrophilicHydrophilic HydrophobicHydrophobic Cell MembraneCell Membrane Fluid Mosaic Fluid Mosaic

ModelModel PhospholipidPhospholipid CholesterolCholesterol

DiffusionDiffusion OsmosisOsmosis Selectively Selectively

PermeablePermeable Passive TransportPassive Transport Active TransportActive Transport

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Learning Objectives1. Describe the fluid mosaic model of

membrane structure and explain the reasons for its structure.

2. Outline the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins in membranes.

3. Outline the roles of the plasma membrane, and the roles of membranes within cells.

Cell MembranesCell Membranes

AKA Plasma membraneAKA Plasma membrane What are the functions of the cell What are the functions of the cell

membrane?membrane? How does its structure allow it to How does its structure allow it to

carry out its functions?carry out its functions?

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Cell (plasma) MembraneCell (plasma) Membrane Encloses the cell’s Encloses the cell’s

contentscontents Selectively Permiable- Selectively Permiable-

regulates which regulates which particles (nutrients, particles (nutrients, wastes) can enter and wastes) can enter and exit the cell.exit the cell.

Cell communication Cell communication recognitionrecognition

Cell Membranes:

Every cell is enclosed by a double layer of phospholipids.

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Cell Membrane StructureCell Membrane Structure

Building blocks are phospholipids… Building blocks are phospholipids… – Lipid with a phosphate group in place of one Lipid with a phosphate group in place of one

fatty acid chain.fatty acid chain.– Phosphate Phosphate headhead is is hydrophilichydrophilic, fatty acid , fatty acid tail is tail is

hydrophobichydrophobic..

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Phospholipids have Split Phospholipids have Split Personalities!Personalities!

HYDROPHOBIC tails (the fatty acid

portion)- HATE water!!

HYDROPHILIC heads (phosphate

group)- LOVE water!!

Phospholipid BilayerPhospholipid Bilayer

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PropertiesProperties of Cell of Cell MembranesMembranes Phospholipids act as a barrier to

most water soluble substances... (“water and oil don’t mix”)

What is a mosaic?What is a mosaic?

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Fluid Mosaic ModelFluid Mosaic ModelPhosopholipids, Phosopholipids, cholesterol cholesterol and and proteinsproteins

form a mosaic (pattern) within the cell form a mosaic (pattern) within the cell membranemembrane

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Why call it a Fluid Mosaic Why call it a Fluid Mosaic Model? Model?

FLUID- phospholipids and some FLUID- phospholipids and some proteins move around freely proteins move around freely within the layerwithin the layer

MOSAIC- the pattern produced by MOSAIC- the pattern produced by scattered protein molecules in the scattered protein molecules in the membrane.membrane.

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Visualizing structure Visualizing structure and functionand function http://www.youtube.com/watch?v

=Rl5EmUQdkuI&feature=fvwp&NR=1&safe=active

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Functions of Proteins in Cell Functions of Proteins in Cell MembraneMembrane

Proteins act as channels for substances to

move in or out of cell.

Some act as membrane enzymes in

chemical reactions.

Glycoproteins act as receptors for cell

communication and recognition.

Function of Function of Cholesterol In Cell Cholesterol In Cell

MembraneMembrane Cholesterol (a lipid) is found Cholesterol (a lipid) is found

between the phospholipid between the phospholipid molecules in the cell membrane.molecules in the cell membrane.

Help maintain stability of the Help maintain stability of the membrane…not too fluid, not too membrane…not too fluid, not too rigid.rigid.

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Functions of components of Functions of components of cell membranescell membranes

ComponentComponent Description Description FunctionFunction

1. Phospholipids1. Phospholipids

2. Proteins2. Proteins

3. Cholesterol3. Cholesterol