Cell Surface Membrane

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The Cell Surface Membrane (Plasma This chemistry allows the formation of a Cholesterol:
Membrane) Phospholipid bilayer where two layers of - Cholesterol is only found in animal
Phospholipid molecules form. cell membranes.
Cell Membrane: The hydrophobic layer is pointing towards - Found between the Phospholipid
This membrane has two main roles the interior of the membrane and the molecules.
- it separates the cell (living) from the hydrophilic is pointing towards the - Provides stability to the membrane
non-living areas inside/outside of the cell. and makes it fluid.
- controls the entry and exit of
substances Singer and Nicholson's Fluid Mosaic Modal Transport across Membranes:
(1972): The plasma membrane is SELECTIVELY
Cell Membrane Functions: Singer and Nicholson used the electron PERMEABLE which means that it only
- Provides a structural support for the microscope in 1972 to promote their theory allows certain substances through it.
cell. of the Fluid Mosaic Modal of Membranes. Substances that can pass through it include
- Controls the taking up of nutrients - The membranes are layered in a bi- oxygen, carbon dioxide and lipid soluble
and other substances needed for molecular arrangement. molecules such as glycerol.
cell operations and any removals - Membranes are described as fluid Substances that can't pass through it include
required. since they can move. ions, polar molecules and large
- Contains Glycolipids for membranes - Any components of the membrane molecules.
role in cell-cell recognition. are free to move with respect to
- Secrets chemicals. each other WITHIN THE The Intrinsic Proteins in the fluid mosaic
MEMBRANCE. help those molecules that cannot ordinarily
Structure of the Cell (Plasma) Membrane: - In the bi-layer there are two types of pass though the membrane to get into the
- Mostly contains proteins and proteins which show a dotted pattern cell.
phospholipids. on the surface.
- Phospholipids are lipids with - Extrinsic proteins ­ seen only in MORE DETAIL WILL BE PROVIDED IN
phosphate groups attached. PO4-. ONE layer of the bi-layer. THE `TRANSPORT ACROSS CELL
- Intrinsic proteins ­ large enough to MEMBRANE' SHEET!!!
Hydrophilic and Hydrophobic Portions: extend across both layers.
- The phosphate molecule has a
polar head and a non-polar tail. Molecules found in the Membrane:
- Polar molecules are water-LOVING Glycolipids and Cholesterol are also
and so attract water. (Hydrophilic). founding the layer.
- Non-polar molecules are water-
HATING and so repel water. Glycolipids/Glycoproteins:
(Hydrophobic). - Glycolipids are fats that have a
- The chemistry to the phospholipids carbohydrate polysaccharide
molecule is the key to controlling attached.
the formation of the membrane. - They are found on the outer layer of
the cell membrane or are sticking
Phospholipid Layer: out of the outer layer.
- These Glycolipids have a role in cell
signalling/cell-cell recognition.


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