Terms in this set (56)

The cell membrane regulates what enters and leaves the cell and also protects and supports the cell
Cells are surrounded by a barrier known as the cell membrane
All cells contain a cell membrane that regulates what eners and leaves the cell and also protects and supports the cell
The composition of nearly all cell membranes is a double layered sheet called a lipid bilayer which gives the cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings
Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water

Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water
The fatty acid portions of such a lipid are hydrophobic or water hating while the opposite end of the molecule is hydrophilic meaning water loving.
When such lipids are mixed with water their hydrophobic fatty acid tails cluster together while their hydrophobic fatty acid tails cluster together while their hydrophilic tails are attracted to water this forms a lipid bilayer.
The head groups of lipids in a bilayer form an oily layer inside the membrane from which water is excluded.
Most cell membranes contain protein molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins
Because the proteins embedded in the lipid bilayer can move around and float among the lipids and because so many different kinds of molecules make up the cell membrane scientists call it a fluid mosaic
Some of the proteins form channels and pumps that help to move material across the cell membrane
Many of the carbohydrate molecules act like chemical identification cars allow individual cells to identify with one another.
Although many substances can cross biological membranes some are too large or to strongely charged to cross the lipid bilayer.
If a substance is able to cross a membrane the membrane is said to be permeable to it
A membrane is impermeable to substances that cannot pass across it
Most biological membranes are selectively permeable meaning that some substances can pass across and some can't these membranes can also be called semipermeable.
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