Cell-Surface Membrane Flashcards
(33 cards)
What does ‘plasma membrane’ refer to?
The membranes around cells and organelles.
What model is often used to describe the cell-surface membrane?
Fluid-mosaic model.
Why is the fluid-mosaic model used to describe the cell-surface membrane?
Because of the mixture and movement of the phospholipids, proteins, glycoproteins and glycolipids it is made up of.
How is the phospholipid bilayer aligned?
Due to the hydrophillic heads being attracted to water and the hydrophobic tails being repelled by water.
What does the head of the phospholipid include?
The phosphate group and glycerol molecule.
What are the tails of the phospholipid?
The fatty acid chains
Why is the phospholipid head hydrophillic?
It has a negative charge making it attracted to water.
Why is the phospholipid tail hydrophobic?
The fatty acid chains have no charge meaning they’ll repel water but will attract other lipids.
What does cholesterol do?
Restricts the sideways movement of the molecules. Thus, it decreases fluidity and increases rigidity.
What does it mean if there is more cholesterol in the membrane?
It is more rigid. This prevents water and dissolved ions from leaking out of the cell.
Where are proteins?
Embedded across the cell surface membrane.
The proteins can be either integral or peripheral. What does peripheral mean?
It doesn’t go completely through the membrane.
The proteins can be either integral or peripheral. What does integral mean?
It goes through the entire membrane.
What is the function of peripheral proteins?
They provide mechanical support or they are connected to proteins or lipids to make glycoproteins or glycolipids. They act as receptors.
What is the function of integral proteins?
They are protein carriers or channel proteins involved in the transport of molecules across membranes.
What do channel proteins do?
They form tubes that fill with water to enable water-soluble ions to diffuse through.
What do carrier proteins do?
Bind with other carrier proteins and larger molecules such as glucose and amino acids and change shape to transport them to the other side of the membrane.
What does ‘partially permeable membrane’ mean?
Only certain molecules can diffuse through by simple diffusion across the phospholipid bilayer.
What type of molecules can diffuse by simple diffusion?
Lipid-soluble molecules and very small molecules such as CO2, O2 and H2O.
What type of molecules can’t diffuse by simple diffusion?
Water soluble (polar) substances, sodium ions and large molecules such as glucose.
Where are glycolipids and glycoproteins found?
On the exterior surface.
What are glycolipids?
Lipids with polysaccharide chains attached.
What are glycoproteins?
Proteins with polysaccharide chains attached.
What does cholesterol bind to?
Phospholipid hydrophobic fatty acid tails.
