lipids, triglycerides and phospholipids

Question 1

what do lipids contain?

Answer 1

carbon, hydrogen and oxygen. They contain hydrocarbons

Question 2

what is the most common type of lipid

Answer 2

a triglyceride

Question 3

what do lipids exist as?

Answer 3

fats, oils and waxes

Question 4

describe the structure of triglycerides

Answer 4

one molecule of glycerol with 3 fatty acids attached to it These have long tails of hydrocarbons

Question 5

what is the basic structure of a fatty acid?

Answer 5

a carbon atom which links to glycerol, a variable R group that is the hydrocarbon tail, a double bond O and a HO

Question 6

what does hydrophobic mean? what part of a triglyceride is hydrophobic?

Answer 6

Water repelling, the tails are hydrophobic which makes lipids insoluble in water

Question 7

how are triglycerides formed?

Answer 7

3 fatty acid chains attach to a glycerol molecule through condensation reaction. Since there are 3 OH molecules from the fatty acids, 3 water molecules are released. The bond between the fatty acid chain and glycerol is an ester bond.

Question 8

what is a saturated fatty acid?

Answer 8

No double bonds in between hydrogen and carbon in the r group

Question 9

what is an unsaturated fatty acid?

Answer 9

at least one double bond in between in the hydrocarbon chain

Question 10

what are some properties and uses of fatty acids?

Answer 10

used for storage, the long hydrocarbon tails release a lot of energy when broken down. They’re insoluble as the tails are hydrophobic so they don’t affect water potential

Question 11

what are phospholipids?

Answer 11

the lipids found in cell membranes

Question 12

describe the structure of phospholipids

Answer 12

they are similar to triglycerides except one fatty acid molecule is replaced by a phosphate group. The group is hydrophobic and the FA tails are hydrophilic.

Question 13

what do phospholipids do?

Answer 13

they make up the bilayer of cell membranes. The heads are hydrophilic and the tails are hydrophobic so they form a double layer with the heads facing out towards the water on each side. The centre is hydrophobic so water soluble substances can’t pass through it easily

Question 14

what is the test for lipids?

Answer 14

1. add 2cm3 of sample to 5cm3 of ethanol
2. shake to dissolve any lipids
3. add 5cm3 of distilled water and shake
4. a milky white emulsion will form if a lipid is present

Question 15

describe what happens in the test for lipids?

Answer 15

A milky white emulsion will form if a lipid is present, if not, it will remain clear

Question 16

describe the difference between the structure of a triglyceride molecule and a phospholipid molecule?

Answer 16

in a phospholipid, one of the fatty acids is substituted by a phosphate group