Flashcards in Biological Membranes Deck (23)
What is the function of a cell surface (plasma membrane)?
They control substances leaving and entering the cell
What is meant by partially permeable?
They only allow some molecules through, non polar and small
What is contained in the fluid mosaic model?
What is a phospholipid bilayer and what is its basic function?
They form a barrier with hydrophobic tails and hydrophilic heads.
The heads face outwards and tails face inwards.
The centre of the bilayer is hydrophilic and outside is hydrophobic
What is cholesterol and what is its basic function?
It is a type of lipid
It fits between the phospholipids and gives the membrane stability.
What are the functions of glycoproteins and glycolipids?
They act as receptors for message molecules in cell signalling
They are also antigens
What factors affect membranes permeability?
Solvents and Temperature
How does increased temperature increase a membrane's permeability?
It causes the bilayer to move more meaning they phospholipids are less tightly bound together resulting in them becoming more permeable. At a high temperature they begin to break down and proteins denature.
How do solvents effects membranes permeability?
They dissolve the lipids
What is cell signalling?
Communication between cells using messenger molecules
What are membrane receptors?
Proteins within cells act as receptors. Receptor proteins have specific shapes so only messenger molecules with complementary shapes can bind to them
What is diffusion?
Diffusion is a passive process. It is the net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient.
What factors affect diffusion?
Thickness of the exchange surface
What is osmosis?
Osmosis is a passive process. It is the net moment of water molecules from a region of high water potential to a region of low water potential down a concentration gradient.
What is an isotonic solution?
When two solutions have the same water potential
What is a hypotonic solution?
When a cell is placed in a solution with a higher water potential compared to the lower water potential within the cell
What is a hypertonic solution?
When a cell is placed in a solution with a lower water potential compared to the higher water potential within the cell
What is facilitated diffusion?
Some molecules are two big or polar therefore they cant pass through the bilayer.
Carrier and channel proteins use a passive process to move particles down a concentration gradient
How do carrier proteins work?
A large molecule attaches to a carrier proteins in the membrane
The protein then changes shape
This releases the molecule on the opposite side of the membrane
How do channel proteins work?
They form pores in the membrane, this allows for smaller ions and polar molecules to diffuse through
What is active transport?
This is an active process which uses ATP. A carrier protein, the protein changes shape and this moves molecules across the membrane. ATP is used to move the solute against a concentration gradient
What is endocytosis and how does it work?
1. It transports molecules that are two large to be transported using carrier proteins.
2. Endocytosis is entering the cell
3.The cells membrane surrounds the cell, the membrane then pinches off to form a vesicle.
4. Lysosomes are then injected into the cell breaking down the substance