Cell Membranes Flashcards
What is a phospholipid?
A lipid made from two fatty acid chains attached to a phosphate head.
How are the tail and head different?
The tail is hydrophobic and the head is hydrophilic.
Why do phospholipids form bilayers?
Because of their polar nature and the way they interact with water. The heads are towards the water and the tails face away from it.
What is the function of phospholipids?
Allow lipid soluble substances to enter and exit the cell
Prevent water soluble substances from entering and exiting the cell.
Which molecules find it the easiest to pass through?
Small non polar molecules like CO2 and O2
What do the proteins that occur on the surface of the bilayer do?
They act as mechanical support to the membrane and act with glycolipids to make cell receptors for hormones.
What proteins span the bilayers width?
Protein channels and carrier proteins. (intrinsic proteins)
What do protein channels do?
They form water filled tubes and allow water soluble molecules to pass through.
What do carrier proteins do?
Bind to ions like glucose and amino acids and change shape to move the molecules across the membrane.
What is the function of protein in the membranes?
Provide structural support
Act as channels
Allow active transport through the membrane.
Form cell surface receptors
What does cholesterol do?
Add strength and rigidity to the membranes by pulling together the fatty acid tails and limiting their movement.
Prevent leakage
Make the membranes less fluid at higher temperatures
What are glycoproteins?
Proteins with a carbohydrate chain attached.
Why is it called a fluid mosaic model?
Fluid - phospholipids in the bilayer
Mosaic - appearance of the proteins
Difference between simple and facilitated diffusion?
Simple - molecules move directly through the bilayer
Facilitated - move down their concentration gradient through channel proteins/carrier
Factors affecting rate of diffusion?
Surface area Concentration gradient Thickness Temperature Size of molecules
