The Cell MembraneThe Cell Membrane

Animal CellAnimal Cell

Plant CellPlant Cell

Prokaryotic Cell: BacteriaProkaryotic Cell: Bacteria

Important FactsImportant Facts Lipid bi-layerLipid bi-layer Embedded proteinsEmbedded proteins Encloses the cytoplasmEncloses the cytoplasm

Organelles and Cytosol (liquid)Organelles and Cytosol (liquid) Separates inside of cell from outside Separates inside of cell from outside

environmentenvironment

Semi-PermeableSemi-Permeable Controls what enters and leaves the cellControls what enters and leaves the cell Allows some things in and keeps others outAllows some things in and keeps others out

Also known as “Also known as “plasma membraneplasma membrane””

Cell Membrane StructureCell Membrane Structure

Fluid-like structureFluid-like structure Not stiff or rigidNot stiff or rigid

Phospholipids and proteins can Phospholipids and proteins can drift/move arounddrift/move around

Proteins form patterns that look like a Proteins form patterns that look like a mosaicmosaic

Fluid Mosaic ModelFluid Mosaic Model Current description for the membraneCurrent description for the membrane

Cell Membrane StructureCell Membrane Structure

Cell Membrane StructureCell Membrane Structure

Bi-layer made up Bi-layer made up of lipids and of lipids and proteinsproteins PhospholipidsPhospholipids

Special lipids Special lipids made of made of one one glycerol, two glycerol, two fatty-acidsfatty-acids and and a a phosphatephosphate

Phospholipid StructurePhospholipid Structure

Phospholipid StructurePhospholipid Structure

Properties of Water ReviewProperties of Water Review Water is a Water is a polar polar moleculemolecule

Partially positively charged Partially positively charged (hydrogen)(hydrogen)

Partially negatively Partially negatively charged charged (oxygen)(oxygen)

Water molecules are Water molecules are attracted to other attracted to other moleculesmolecules

-+

+

So polar molecules stick together and So polar molecules stick together and repel away non-polar moleculesrepel away non-polar molecules

Properties of Water Properties of Water ReviewReview

Since water is a polar molecule the opposite charges on other molecules help them stick together!!

Phospholipid StructurePhospholipid Structure ““Polar Heads”Polar Heads” HydrophilicHydrophilic

““water loving”water loving”

Phosphate part is Phosphate part is attracted to waterattracted to water

Polar heads point to Polar heads point to watery parts of the watery parts of the cellcell CytoplasmCytoplasm Outside EnvironmentOutside Environment

Phospholipid StructurePhospholipid Structure ““Non-Polar Tails”Non-Polar Tails” HydrophobicHydrophobic

Doesn’t like waterDoesn’t like water Fatty-acids (lipid) Fatty-acids (lipid)

repels waterrepels water

Non-Polar tails point Non-Polar tails point towards each other towards each other in the center of the in the center of the membranemembrane Between the two Between the two

layers layers

Bi-Layer ArrangementBi-Layer Arrangement

The cytoplasm of the cell is an “aqueous” or The cytoplasm of the cell is an “aqueous” or “watery” environment.“watery” environment.

How do the phospholipids arrange How do the phospholipids arrange themselves?themselves?

Remember….hydrophilic Remember….hydrophilic and hydrophobic and hydrophobic

areas.areas.

Bi-Layer ArrangementBi-Layer Arrangement

Hydrophilic Hydrophobic

Bi-Layer ArrangementBi-Layer ArrangementHydrophilic

Hydrophobic

Membrane ProteinsMembrane Proteins Transmembrane ProteinsTransmembrane Proteins

Embedded in the cell membraneEmbedded in the cell membrane Exposed to both the inside and outside of the cellExposed to both the inside and outside of the cell

Peripheral ProteinsPeripheral Proteins Attached to the external or internal surface of the Attached to the external or internal surface of the

membranemembrane Channel ProteinsChannel Proteins

Help move materials into and out of the cellHelp move materials into and out of the cell Cell MarkersCell Markers

Carbohydrate chains that identify cell typesCarbohydrate chains that identify cell types EnzymesEnzymes

Assist in chemical reactionsAssist in chemical reactions Speed up and lower activation energySpeed up and lower activation energy

Membrane ProteinsMembrane Proteins

Transmembrane Protein

Peripheral Protein

Channel Protein

Cell Marker Protein

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Section 7-3

Figure 7-12 The Structure of the Cell Membrane

The Cell MembraneThe Cell Membrane