Cell Membrane Structure / Function and Cell Transport Ms. Kim Honors Biology

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Cell Membrane Structure / Function and Cell Transport Ms. Kim Honors Biology. Cell membrane. The Cell Membrane. Thin, flexible, surround all cells Controls the traffic of molecules into and out of the cell (school doors/fence/security guards) - PowerPoint PPT Presentation

Transcript of Cell Membrane Structure / Function and Cell Transport Ms. Kim Honors Biology

Slide 1

Cell Membrane Structure/ Function and Cell TransportMs. KimHonors Biology

Cell membrane

The Cell MembraneThin, flexible, surround all cellsControls the traffic of molecules into and out of the cell (school doors/fence/security guards)Takes in substances & takes out the cells wasteAllows substances through by either passive transport (no energy) or active transport (energy required!)3Overview of CellMembraneThe plasma (cell) membrane the boundary that separates living cell from its nonliving surroundings Also called the phospholipid bilayer Structure of Plasma MembraneMade of phospholipidsPhosphate head and 2 fatty acid chains are the tailArranged in a bilayerHeads (polar) hydrophilicTails (nonpolar) hydrophobicRoots:Phospho- polar phosphate groupLipid- non-polar fatBi- twoLayer- sheet or quantity covering a surface



Membrane movement animationPolar heads love water & dissolve.Non-polar tails hide from water.Carbohydrate cell markersFluid Mosaic Model of the cell membrane

8The phospholipid bilayer is a selectively permeable membrane. It is semi-permeable.Only allows certain substances to cross it more easily than others.Selective Permeability: Allows some materials, but not all, to cross throughSmall, non-polar, hydrophobic, neutral molecules can pass easily through membraneAlthough polar, water is SO small that it can move through the cell membrane.

Selective Permeability Small polar molecules must pass through proteins

Large molecules must be moved with vesicles

Membrane Proteins and Their FunctionsA membraneIncludes different proteins embedded in the fluid lipid bilayerFUNCTION:Help move molecules and ions across the membraneThey help cells communicate between the cells internal and external environments2 major types of membrane proteinsIntegralPermanently attached to the membrane Are often transmembrane found throughout the entire bilayerPeripheral Are appendages loosely bound to the surface of the membraneOnly found outside of the bilayer


Cholesterol stabilizes (stiffens) the membraneIntegrates between phospholipidsWithout cholesterol, cell membranes would be too fluid, not firm enough (very mushy).Cholesterol also helps maintain the fluidityAlso helps separate the phospholipids so that the fatty acid chains cant come together and crystallize.Therefore, cholesterol helps prevent extremeswhether too fluid, or too firmin the consistency of the cell membrane.Present in animal cell membranesAbsent in bacteria and most plants where the cell wall provides stability

CholesterolWhy have Carbohydrates on Cell Membrane proteins?Cell-cell recognitionIs a cells ability to distinguish one type of neighboring cell from anotherIts their ID tag

Carbs found on the outside for identificationGlycolipids and Glycoproteins serve as recognition sites for other cells

Carbohydrates (Oligosaccharides)GlycoproteinGlycolipids2 different types membrane carbohydratesGlycolipids Carbohydrates covalently attached to lipids GlycoproteinsCarbohydrates covalently attached to proteins (most abundant)

Fluid Mosaic ModelDescription of arrangement of molecules that make up the cell membraneCell Membrane is flexible, not rigidPhospholipids can move from side to side and slide past each otherVariety of molecules studding the membrane is similar to arrangement of tiles with different textures and patterns

Know this picture!16http://www.dnatube.com/video/360/Fluid-Mosaic-Model