Membrane Structure Flashcards
What is the width of the cell membrane?
5nm
What are the main functions of the cell membrane?
- Control what enters and exits the cell.
- Maintains the difference in ion concentration across the membrane
- Participates in joining and interaction with neighbouring cells.
What lipids are found in the membrane?
Phosphoglycerides, sphingolipids and sterols.
What do sterols have connected to their polar heads?
A rigid steroid ring.
How does cholesterol affect the membrane?
Stiffens it.
What kind of lipids form micelles?
Single tailed lipids.
What kind of lipids form bilayers?
Double tailed lipids.
Why did the membrane take the structure of a sphere?
As a planar bilayer would leave the edge lipid exposed which is unfavourable.
How do unsaturated hydrocarbon chains on lipids affect the cell membrane?
The phospholipids pack less tightly and so the membrane is more fluid.
What are rafts?
Areas of the membrane with an increased concentration of proteins.
What are examples of ligand binding receptors?
Hormone receptors and growth factor receptors.
Where do adhesion molecules form contact?
On neighbouring cells.
What is the function of adhesion molecules?
To regulate cell shape, growth and differentiation.
What is the function of pores and channels?
To allow water/ions to pass through the lipid bilayer.
What is the function of carrier proteins?
To couple with molecules in facilitated diffusion.
What is the function of pumps?
They use energy from ATP hydrolysis to drive transport of substances against their concentration gradient.
What do the short carbohydrate chains on the membrane allow the cell to do?
Identify other cells.
What allows bending of the bilayer?
Proteins
What does cell adhesion result from?
Interactions between proteins or carbohydrates.
What is homotypic cell adhesion?
The same type of molecule binds on each membrane.
What is heterotypic cell adhesion?
Different molecules bind on each cell.
What are the three types of cell junctions?
Tight junctions, desmosomes and gap junctions.
What is the function of tight junctions?
To prevent substances moving between cells and cell migration.
What is the function of desmosomes?
To hold cells tightly together but still allows substances to move in the extracellular matrix.
What is the function of gap junctions?
They run between pores and allow substances to pass between cells.
What is the function of integrin?
To allow epithelial cells to attach to the extracellular matrix.
