PHGY 170: Learning Outcomes Assignment 6
1. Describe the four major classes of lipids found in the plasma membrane. (4)
Phospholipids
● Composed of 4 major components; a head group, phosphate group, glycerol, and a fatty
acid tail.
● The head group and fatty acid tails vary in structure leading to diverse phospholipids.
● Head group: attaches to the phosphate group, its chemical properties determine where
the phospholipid ends up in the membrane.
● Phosphate group: hydrophilic charged component.
● Glycerol: a three carbon chain with three hydroxyl groups, the backbone of the
phospholipid.
● Fatty acid tail: two long hydrocarbon chains that vary in composition and bond number,
they attach to the glycerol backbone.
Cholesterol
● Major component in animal tissues.
● Has a hydroxyl group on one ring.
● Ring interacts with the surface of the membrane.
● The rest of the molecule interacts with the lipid part of the membrane.
Glycolipids
● Have a sugar group attached to the lipid but no phosphate group.
● Involved in cell signalling.
● One type: fatty acids attached to sugar moieties.
● Other types: sphingosine, glycerol backbone.
Sphingomyelin (SM)
● Looks like a phospholipid but has a different backbone - sphingosine.
● Components; phosphocholine, head group, sphingosine, and a fatty acid.
● Common in myelin sheaths which wrap around the axons of nerve cells.
2. Define the fluid mosaic model and describe the macromolecules that form lipid rafts.
(2)
Fluid Mosaic model: the concept that there are multiple components to the plasma membrane,
not just the lipid bilayer. Lipids are able to move freely in the membrane and do so rapidly. One
phospholipid can move from one side of a cell to the other in just a few seconds.
Lipid Raft: a cluster made up of:
1. Describe the four major classes of lipids found in the plasma membrane. (4)
Phospholipids
● Composed of 4 major components; a head group, phosphate group, glycerol, and a fatty
acid tail.
● The head group and fatty acid tails vary in structure leading to diverse phospholipids.
● Head group: attaches to the phosphate group, its chemical properties determine where
the phospholipid ends up in the membrane.
● Phosphate group: hydrophilic charged component.
● Glycerol: a three carbon chain with three hydroxyl groups, the backbone of the
phospholipid.
● Fatty acid tail: two long hydrocarbon chains that vary in composition and bond number,
they attach to the glycerol backbone.
Cholesterol
● Major component in animal tissues.
● Has a hydroxyl group on one ring.
● Ring interacts with the surface of the membrane.
● The rest of the molecule interacts with the lipid part of the membrane.
Glycolipids
● Have a sugar group attached to the lipid but no phosphate group.
● Involved in cell signalling.
● One type: fatty acids attached to sugar moieties.
● Other types: sphingosine, glycerol backbone.
Sphingomyelin (SM)
● Looks like a phospholipid but has a different backbone - sphingosine.
● Components; phosphocholine, head group, sphingosine, and a fatty acid.
● Common in myelin sheaths which wrap around the axons of nerve cells.
2. Define the fluid mosaic model and describe the macromolecules that form lipid rafts.
(2)
Fluid Mosaic model: the concept that there are multiple components to the plasma membrane,
not just the lipid bilayer. Lipids are able to move freely in the membrane and do so rapidly. One
phospholipid can move from one side of a cell to the other in just a few seconds.
Lipid Raft: a cluster made up of:
