LIPIDS

Question 1

lipids

Answer 1

lipids are the organic molecules which are insoluble in water.

Question 2

fatty acids

Answer 2

fatty acids are series of acids some of which are also found in lipids. fatty acids contain the acidic group COOH or carboxyl group which forms the head of the fatty acid. Fatty acids are 15 to 17 carbon atoms long.

Question 3

Tails of fatty acids

Answer 3

some have double bonds and some have single bonds. double bonds causes a kink in structure.

Question 4

Ester bond

Answer 4

a condensation reaction between glycerol and fatty acid forms an ester bond.

Question 5

Triglycerides

Answer 5

triglycerides are the most common types of lipids which contain one molecule of glycerol and three molecules of fatty acids joined together by an ester bond in a condensation reaction.

Question 6

why are triglycerides soluble in organic solvents but not in water?

Answer 6

because of the presence of the hydro carbon tails which is non polar that is no uneven distribution of an electrical charge.

Question 7

major functions of triglycerides

Answer 7

1. triglycerides are rich source of energy even than carbohydrates because of the presence of large number of carbon hydrogen bonds.
2. triglycerides are stored in a large number of places in the human body like beneath the skin and around the kidneys. Triglycerides act as an insulator against the heat loss.
3. triglycerides are also a metabolic source of water because when they are oxidised in respiration, they produce carbon dioxide and water.
4. lipids have a relatively low mass. so a large number of lipids can be stored without increasing mass and preventing movement.

Question 8

phospholipids

Answer 8

phospholipids are a special type of lipids which contains one molecule of glycerol and one of the three molecules of fatty acid is replaced by a phosphate group.

the phosphate group is hydrophilic and polar.
the hydrocarbon tails are hydro phobic.

Question 9

amphipathic?

Answer 9

phospholipids are amphipathic meaning that they have both hyfrophilic and hydrophobic parts.

as a result phospholipids can form mono layers or bilayers in water.

Question 10

phospholipids function

Answer 10

• the hydrophobic fatty acid tails create a hydrophobic core during the formation of a phospholipid bilayer which acts as a barrier to water soluble molecules.
• the hydrophilic head forms hydrogen bonds with water allowing the cell membrane to compartmentalise.

the composition of phospholipids also contribute to the fluidity of cell membranes.

Question 11

short chemical formula of fatty acids is

Answer 11

RCOOH

Question 12

Biochemical test for lipids

Answer 12

Emulsion test
- the test sample is mixed with ethanol and then swirled.
- it is then filtered using a filter paper and beaker.
- if it turns cloudy ( milky white suspension ) then it is positive.

Question 13

R groups

Answer 13

R groups are the fatty acids which could be saturated or unsaturated.