Cell membrane structure Flashcards
(22 cards)
What is the fluid mosaic model?
Describes the structure of the plasma membrane as a mosaic of phospholipids, cholesterol, proteins, and carbohydrates. This gives the membrane a fluid character.
What does the plasma membrane do?
It defines the borders of cells and most organelles. It is partially permeable.
What does a ‘partially permeable’ membrane mean?
The membrane allows some materials to freely enter or leave the cell, while other materials cannot move freely
What is a phospholipid?
A molecule consisting of glycerol, two fatty acids and a phosphate-linked head group
How are these phospholipids arranged?
The molecules arrange themselves into a bilayer, around 10nm thick. The hydrophilic phospholipid head faces outward and the hydrophobic fatty acid tails face inwards.
What is cholesterol?
A lipid that sits with phospholipids in the core of the membrane
What does cholesterol do to the membrane?
Cholesterol molecules make the membrane more rigid, helping to maintain the shape of animal cells
Which part makes up the ‘fluid’ part of the fluid mosaic model?
The phospholipid bilayer
What part makes up the ‘mosaic’ part of the fluid mosaic model?
The various proteins, carbohydrate and lipid molecules that punctuate membranes
What are membrane bound proteins?
Large molecules embedded in the bilayer. They can form open pores that allow the diffusion of large molecules across the bilayer.
What is an example of a membrane bound protein?
ATP-synthase, which catalyses the production of ATP during oxidative phosphorylation on the inner mitochondrial membrane
What are glycolipids and glycoproteins?
Proteins and lipids in cell membranes which have carbohydrate chains attached to them
What is the function of many glycolipids and glycoproteins?
They can form hydrogen bonds with water molecules surrounding the cell, helping to stabilise the membrane
What is the function of other glycolipids and glycoproteins?
Act as cell signalling receptors and have active binding sites for communication molecules such as hormones and drugs
What happens when these receptors bind to a target molecule?
The glycomolecule undergoes a conformational change and initiates a chain of reactions known as a cascade that can lead to a cell-level response to the binding of certain signalling molecules
What factors influence the permeability of cell membranes?
Temperature
Solvent concentration
pH
How does temperature influence the permeability of the cell membrane?
Higher temperatures increase the fluidity of the membrane, increasing its permeability
How can you control the temperature of a cell membrane?
Using a water bath can help keep temperature constant
How does solvent concentration influence the permeability of the cell membrane?
The more easily the phospholipid bilayer is dissolved, the more permeable the membrane is
How can you control the solvent concentration of a cell membrane?
By using the same solvent at the same concentration for each trial
How does pH influence the permeability of the cell membrane?
pH affects the protein structure in the cell membrane
How can you control the pH of a cell membrane?
Buffer solutions can be used to control the pH
