Lipids in Cell Membranes Flashcards
Learning outcomes
To explain the importance of membranes in cells.
To describe the structure of lipid bilayers
To list the lipid components of bilayers
To describe what is meant by membrane fluidity and its importance in cell function.
To describe how a lipid bilayer and cell membrane is formed
To understand the various ways that proteins may interact with lipids in cell membranes
What is a lipid and what are some examples?
Lipids are substances that have a low solubility in water
Examples, fats, phospholipids, sterols and some vitamins7
What do lipids do?
Sources of energy
Form membranes
Participate in cell signalling
What does a fatty acid consist of?
A carboxyl group and a hydrocarbon chain
What are the types of fatty acid?
A saturated fat when there are no carbon double bonds.
Unsaturated cis fat when there is a double bond on the hydrocarbon (hydrogens are on the same side) creating a kink in the fat
Unsaturated Trans fat when there is a double bond on the hydrocarbon (hydrogens are on different sides, not creating a kink.)
Polyunsaturated fats when there are multiple double bonds. (double bonds are always at least 3 carbon apart)
Omega fatty acid are counted how many carbons are away from the methyl to the first double bond.
What are sterols and some examples?
Sterols, also known as steroid alcohols, are a subgroup of the steroids
Examples: Bile acids, steroid hormones, vitamins and cell membranes
What are the components of a phospholipid?
A phospholipid consists of a polar head (containing usually an alcohol and a phosphate group), a glycerol backbone and fatty acid chains.
What are the three types of membrane lipids and their main features?
Phospholipids: Always have phosphate group, fatty acids and an alcohol group
Glycolipids: Consists of a Sphingosine core and a carbohydrate attached by a glycosidic bond
Sterol: A steroid with a hydroxide group
Why are phospholipids considered amphipathic?
It has a hydrophillic head and hydrophobic tail
Explain the structure of the lipid bilayer
The hydrophillic tails face away from the water and the hydrophillic tails face into the water. Having two layers of this creates a dry barrier called the lipid bilayer. The lipid bilayer is usually in a spherical shape as it is the most energetically favorable.
Describe membrane fluidity in lipid bilayers
Lipid bilayers are more fluid in unsaturated fats because the kinks give the fats more space to move around laterally. In rare occasions, a phospholipid will flip flop.
What is the composition of cholesterol?
Has a polar head group, rigid planar steroid ring structure and a more fluid hydrocarbon tail
What are lipid rafts and what is their function?
Lipid rafts are areas of high density of proteins that aren’t very fluid and move together in one unit.
Where are lipid membranes created?
Created in the ER and then go the the Golgi which process and moves the membranes to vesicles to their desired destination.
What are the types of membrane proteins?
Transmembrane, membrane associated, lipid linked and protein attached membrane proteins
