the cell surface membrane Flashcards
(19 cards)
What is the purpose of the cell membrane?
Enables control of passage of substances across exchange surfaces by passive or active transport
What does the cell membrane mainly consist of?
A phospholipid bilayer and protein
What is the cell-surface membrane described as?
The fluid-mosaic model
Why is it called the fluid-mosaic model?
The phospholipid molecules in the bilayer are constantly moving giving it the fluid structure, the protein molecules are unevenly distributed throughout the membrane forming a mosaic
What is the partial permeability related to?
The type and distribution of protein and phospholipid molecules present
Which way are the hydrophilic heads oriented?
Inwards towards the cytoplasm or outwards towards the extra-cellular fluid
Which way are the hydrophobic tails oriented?
Towards each other
What can diffuse through the gaps between phospholipids?
Very small molecules
How does water pass through the phospholipid bilayer?
Through water channels by osmosis
What does the phospholipid bilayer allow to pass through it?
Lipid soluble molecules
What does the phospholipid bilayer restrict?
Water soluble ions and polar molecules
What does cholesterol provide to the membrane?
Strength and restricts the movement of phospholipids so the membrane is less fluid and less ions are lost from the cell
What does protein provide to the membrane?
Act as channels or carriers which aid the passage of water-soluble ions and polar molecules
How are carrier proteins useful?
They aid the transport of facilitated diffusion or active transport
How are channel proteins useful?
Its charge and size determines which molecules can be transported across the membrane by facilitated diffusion
How are other embedded protein molecules useful?
They are important in cell signalling and act as specific receptors for hormones and complimentary hormones will bind to its binding site
What are branched carbohydrates?
Chains that stick out from the outer surface of some membranes
What are branched carbohydrates attached to?
Lipids forming glycolipids or proteins forming glycoproteins
What is the function of glycoproteins?
They are involved in cell-cell recognition as they can act antigens therefore foreign antigens can be recognised and attacked
