lipids

Question 1

what are lipids?

Answer 1

large class of molecules that are all hydrophobic

Question 2

what are the different functions of lipids?

Answer 2

1. long term energy storage
2. protection against heat loss (insulation)
3. protection against physical shock
4. protection against water loss
5. major component of membranes (phospholipids)

Question 3

what are the three groups of lipids?

Answer 3

fats, steroids and phospholipids

Question 4

what are fats?

Answer 4

1. built by bonding one glycerol molecule, an alcohol, and three fatty acid molecules
2. the final molecule is called a triglycerol

Question 5

how are fatty acids bonded to the glycerol molecule?

Answer 5

dehydration reactions bond fatty acids to the glycerol molecule and the bonds that are formed are called ester linkages

Question 6

what can fatty acids, and the triglycerols, that they are a part of can be classified as?

Answer 6

1. saturated - only single bonds between C atoms in the hydrocarbon chain, the maximum number of H atoms are present in the hydrocarbon chain.
2. unsaturated - one or more double bonds are present between C atoms in the hydrocarbon chain. every C atom involved in a double bond has one fewer H atoms attached to it than a saturated C atom.
   -> monounsaturated : only one carbon double bond
   -> polyunsaturated : two or more carbon double bonds

Question 7

what are phospholipids?

Answer 7

• main component of cell membranes (vital for life)
• made up of two fatty acid chains bonded to a glycerol molecule, and a phosphate group attached to a charged glycerol molecule.

Question 8

what forms the head of the phospholipid?

Answer 8

the phosphate group, charged or polar group, and the glycerol.

Question 9

why is the phospholipid’s head hydrophilic but the tails hydrophobic?

Answer 9

• hydrophilic head; charged group
• hydrophobic tails; large number of nonpolar bonds in the hydrocarbon chain.
  this forms a phospholipid bilayer in water.

Question 10

what are steroids?

Answer 10

• made up of four fused carbon rings attached to a variable group bonded to one end of the rings, forming a structure known as a tetracyclic structure.
• cholesterol is a type of steroid, and is a common component of cell membranes and myelin.