3.2.3 Transport across cell membranes Flashcards
(9 cards)
What model is used to describe plasma membranes?
Fluid mosaic model
Why do we call the model referring to plasma membrane the ‘fluid mosaic model’?
It is a mosaic of phospholipids, proteins, cholesterol and carbohydrates. This gives the membrane a fluid character
The plasma membrane is selectively permeable. What does this mean?
The membrane allows some materials to freely enter or leave the cell/organelle, while other materials cannot move freely
What is the structure of a phospholipid?
A molecule consisting of glycerol, 2 fatty acids and a phosphate-linked head group
What is the normal thickness of a phospholipid bilayer?
5-10 nm
What 3 factors can influence the permeability of cell membranes?
pH, solvent concentration, temperature
How does pH affect the permeability of cell membranes and how can we control it?
pH affects the the protein structure in the cell membrane. Buffer solutions can be used to control the pH
How does solvent concentrations affect the permeability of cell membranes and how can we control it?
The more easily the phospholipid bilayer is dissolved, the more permeable the membrane is. It can be controlled by using the same solvent at the same concentration for each trial.
How does temperature affect the permeability of cell membranes and how can we control it?
Higher temperatures increase the fluidity of the membrane increasing its permeability. It can be controlled by using a water bath to keep the temperature constant.
