These revision notes refer to AQA AS Biology Chapter 3.5
The cell surface membrane is another name for the cell membrane or plasma membrane.
- It surround the cell boundary between the cell cytoplasm and the environment (this is where there is different conditions inside and outside of the cell).
The Fluid Mosaic Model
Why is this called the fluid-mosaic model?
Fluid - The Molecules move relative to one another
Mosaic - means being made up of different substances, in this case proteins and phospholipids.
How do substances pass through a cell membrane?
(a very common exam question)
- the phospholipids form a bilayer
- the phospholipids are arranged with hydrophilic heads on the outside and hydrophobic tails on the inside
- There are two types of proteins, some are passing through and some are confined to one layer
- There are other molecules present, for example: cholesterol or glycoproteins
- substances are moved DOWN the concentration gradient (from a high to low concentration)
- water and ions move through the channel proteins
- lipid soluble molecules are passed between the phospholipids
- carrier proteins are involved in facilitated diffusion.
The cell surface membrane is another name for the cell membrane or plasma membrane.
- It surround the cell boundary between the cell cytoplasm and the environment (this is where there is different conditions inside and outside of the cell).
The Fluid Mosaic Model
Why is this called the fluid-mosaic model?
Fluid - The Molecules move relative to one another
Mosaic - means being made up of different substances, in this case proteins and phospholipids.
How do substances pass through a cell membrane?
(a very common exam question)
- the phospholipids form a bilayer
- the phospholipids are arranged with hydrophilic heads on the outside and hydrophobic tails on the inside
- There are two types of proteins, some are passing through and some are confined to one layer
- There are other molecules present, for example: cholesterol or glycoproteins
- substances are moved DOWN the concentration gradient (from a high to low concentration)
- water and ions move through the channel proteins
- lipid soluble molecules are passed between the phospholipids
- carrier proteins are involved in facilitated diffusion.
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