3.3 Plasma Membranes Flashcards
Plasma membranes are found on the…
Outside of every cell and control what enters and leaves the cell
The basic structure of the membrane is made up of molecules called…
Phospholipids
A phospholipid is a…
Glycerol molecule with a phosphate group and two fatty acids attached to it
The fatty acids are made up of…
Carbon and hydrogen only (no charge)
Insoluble in wate
The fatty acid chains form the ‘tail’ of the molecule which is…
Hydrophobic
The phosphate group is…
Charged and it is soluble in water
The phosphate and glycerol form the ‘head’ of the molecule. Because it is water soluble is is said to be…
Hydrophilic
In a membrane the phospholipids pack together to form a double layer or a …
Bilayer
The ‘heads’ face the..
Outside of the membrane so that they are in contact with water (which surrounds all cells, as well as in the cytoplasm)
The ‘tails’ are found in the…
Middle of the membrane away from the water
Lipid-soluble molecules can…
pass through the phospholipid bilayer
Oxygen, carbon dioxide and water molecules pass…
Between the phospholipids because they are very small
Scattered among the phospholipids are many different…
Proteins
Some of the proteins pass all the way through the phospholipid, so are called…
Intrinsic proteins
Intrinsic proteins can act as…
Carriers to transport water-soluble substances across the membrane
Others are enzymes
Some proteins are found in only one of the phospholipid layers so these are called…
Extrinsic
Extrinsic proteins give…
Mechanical support to the membrane or act as cell receptors
Some of the proteins have carbohydrate chains attached to them, called…
Glycoproteins
Glycoproteins act as…
Antigens, allowing cells to recognise each other
Also act as recognition sites for hormones
Carbohydrate may also attach to the phospholipids forming…
Glycolipids
Scattered among the phospholipids are…
Cholesterol molecules - keeps the membrane stable
The way the molecules are arranged in a membrane is by…
The fluid-mosaic structure
The membrane is fluid because the…
Phospholipid heads move around within their layer
The mosaic appearance is due to…
The floating protein molecules among the phospholipid heads
