Cell Membrane
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Transcript of Cell Membrane
Cell Membrane
What cells have a cell membrane…• ALL cells have a cell membrane!– Prokaryotic and Eukaryotic
Cell Membrane’s Job…• Forms a boundary between a cell and the
outside environment• Controls the passage of materials into and out
of a cell
What is the cell membrane made of?
• A double layer of phospholipids–Hydrophilic Heads-”water loving”-are
exposed to water inside and outside the cell–Hydrophobic Tails-”water fearing”-
cannot be exposed to water
Phospholipid
The cell membrane also has…
• Molecules embedded within the phospholipid layers– Cholesterol molecules-provide strength for
membrane– Proteins-help materials cross the membrane– Carbohydrates-attach to membrane proteins and
serve as identification tags
Cell Membrane Structurecell membrane carbohydrate
chain
protein
protein channelcholesterolprotein
Fluid Mosaic Model
• Describes the arrangement of the molecules that make up the cell membrane
• Cell membrane is flexible, not rigid.• The phospholipids in each layer can move
from side to side and slide past each other.
http://youtu.be/Rl5EmUQdkuI
Property of the Cell Membrane
• Selective Permeability (semipermeable)–Cell membrane allows some, but not
all, materials to cross into or out of the cell.–Enables cell to maintain homeostasis
Concentration-number of particles present in a solution
Which side, outside or inside, has the highest/lowest concentration?
How do molecules move across the cell membrane?
• Several different ways molecules will move.– Some ways require the cell to use energy and
some do not.• How a molecule moves across the membrane
depends on:– Size – Polarity– Concentration inside the cell vs. outside the cell
Examples of materials moving across the cell membrane…
• Small nonpolar molecules move easily across the membrane
• Small polar molecules are transported via proteins
• Large molecules are moved in vesicles