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Flashcards in Biological Membranes Deck (23)
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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?

Phospholipid bilayer
Carrier protein
Channel protein


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?

Concentration gradient
Thickness of the exchange surface
Surface area


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


What is exocytosis and how does it work?

1. It transports molecules that are two large to be transported using carrier proteins.
2. Exocytosis is leaving the cell
3. The golgi apparatus packages the molecules into vesicles and then they move towards the plasma membrane
4. The vesicles fuse with the membrane and then release the contents to the outside of the cell