Cells Membranes Flashcards
Functions of membranes within cells
Divide into different compartments, makes different functions more efficient.
Increasing surface area to make reactions more efficient.
Can form vesicles for transport within cells.
Control what goes in and out of an organelle.
How would you describe a cell membrane?
Partially permeable
What is the name given to the structure of a cell membrane?
Fluid Mosaic
What is the fluid mosaic made up of.
Phospholipids, cholesterol, proteins and glycolipids and glycoproteins.
function of phospholipids
Hydrophilic head sticking out and hydrophobic tails attract together. They form a bilayer with a very hydrophobic region in the centre. The don’t let water soluble molecules, charged, ions or polar molecules to pass through.
function of cholesterol
Fits in-between the phospholipids binding to the hydrophobic tail. Less fluid more stable, further barrier to substances. Increasing membrane stability.
function of proteins in cell membrane
Some form channels allowing small charged particles through and carrier proteins allows large charged particles through. Also act as a receptor in cell signalling.
Functions of Glycolipids and glycoproteins
Stabilises the molecule by forming hydrogen bonds with surrounding water molecules. Act as receptors in cell signalling. Also act as antigens involved in self recognition and immune response.
Effects of temperature below 0 degrees on membranes
Phospholipids don’t have as much energy, channel proteins and carrier proteins denature, increasing permeability of the membrane. Ice crystals may form and pierce the membrane, making it have a high permeability when it thaws.
Effects of temperature between 0 and 45 degrees on membranes
Can move around, membrane is partially permeable. As temp increases the permeability will increase as they have more energy.
Effects on membranes with temperature above 45 degrees
Bilayer begins to break down. Water inside cell expands putting pressure on membrane. Channel proteins and carrier proteins inside the cell denature increasing permeability.
How do cells communicate?
By signalling via messenger molecules.
Explain cell signalling.
This starts when one cell releases a messenger molecule, this molecule travels to another cell. This messenger molecule is detected by the cell because it binds to a receptor. This triggers off changes in that cell. Then a series of chemical signals are set off.
What is a cell called the responds to particular messenger molecule?
A target cell.
Why do some cells respond and others don’t?
Receptor proteins have specific shapes - only messenger molecules with specific shapes will bind to them. The shape must be complementary.
Define diffusion.
The overall net movement of particle from an area of high concentration to an area of low concentration.
What are the factors affecting the rate of diffusion?
The concentration gradient - higher the better
Thickness of the exchange surface - thinner the better
The surface area - bigger the better
What is water potential?
The likelihood of water molecules diffusing in and out of a solution.
What is the water potential of pure water in kPA?
0
How does the water potential change as you add solute?
It lowers.
What is an isotonic solution?
When the water potential is the same on both sides.
What is a hypotonic solution?
When the water potential is higher on the outside of the cell compared to inside. Water will move out of the cell.
What happens to cells in hypotonic solutions?
Animal will swell and burst and plant cells will become turgid.
What is a hypertonic solution?
A solution where the water potential is lower on the outside of the cell compared to the inside of a cell.
