plasma membrane.notebook
October 14, 2016
Structure of the Plasma Membrane
Carbohydrate Peripheral
protein
Phospholipids Cholesterol
Channel
Proteins
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plasma membrane.notebook
October 14, 2016
Peripheral Protein - involved in cell
communication.
Carbohydrate- act as ID tags to identify
cells from one another.
Channel proteins- make passage ways to
move molecules across the membrane.
Cholesterol- help to strengthen the
membrane by keeping it flexible.
Phospholipids-
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plasma membrane.notebook
October 14, 2016
Phospholipid
Polar heads are hydrophilic because they are water­
loving and attract water molecules.
Nonpolar tails are hydrophobic because they are water­
fearing and repel water molecules.
Think of a sandwich:
The polar heads are the bread, they form the outer surface of the membrane and interact with the environment. The nonpolar tails are the peanut butter and are protected from the watery environment.
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plasma membrane.notebook
October 14, 2016
Fluid Mosaic Model
The fluid mosaic model describes the arrangement of the molecules that make up the cell membrane.
2 Characteristics
Fluid­ because the phospholipids can move side to side and slide past one another.
Mosaic­ the different molecules imbedded throughout the phospholipids have different textures and patterns like mosaic tile.
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plasma membrane.notebook
October 14, 2016
Selective Permeability
Selective permeability allows some, but not all materials to cross the membrane.
Selective permeability helps to maintain homeostasis because it controls the import and export of certain molecules and ions. So, even if the ion concentration outside the cell changes drastically, the cell can survive.
Movement of molecules is determined by size and charge.
Small Polar molecules are transported across the membrane by proteins
Small Nonpolar molecules easily pass through the membrane.
Large molecules are moved in by vesicles. What is a vesicle?
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