lipids

Question 1

main characteristic of lipids

Answer 1

insoluble in water but soluble in organic solvents

Question 2

what do lipids consist of

Answer 2

carbon
hydrogen
oxygen ( much less than hydrogen )

Question 3

difference between fat and oil

Answer 3

• lipid in solid state at 20℃ is fat
• lipid in liquid state at 20℃ is oil

Question 4

what are simple lipids?

Answer 4

made out of fatty acids with various alchohols
* fats - esters of fatty acids with glycerol
* waxes - esters of fatty acids with complex alchohol

Question 5

what are compound lipids?

Answer 5

made out of lipid + non lipids
* Phospholipid = lipid + alchohol + phosphate

Question 6

structure of glycerol

Answer 6

alchohol with 3 carbons, each bearing a hydroxyl (-OH) group

Question 7

structure of fatty acids

Answer 7

• consists of a hydrocarbon chain with a carboxyl (-COOH) group
• hydrocarbon chains is chain of carbon atoms to which hydrogen atoms are attached
• may be saturated or unsaturated

Question 8

details about saturated fatty acids

Answer 8

• general formula RCOOH , where R is a hydrocarbon chain made entirely out of single C-H and C-C bonds
• does not contain carbon-carbon double bonds
• has the maximum number of hydrogen atoms possible
• more solid at room temperature than unsaturated fatty acids
• produced by animals

Question 9

details about unsaturated fatty acids

Answer 9

• contains carbon - carbon double bonds
• double bonds causes kinks in the hydrocarbon chain
• more than 1 double bond - polyunsaturated
• low melting point because fatty acid chain bends at the double bonds (kinks) , prevents fat molecules from aligning closely with one another, hence usually liquid at room temperature
• produced by plants

Question 10

what makes triglyceride

Answer 10

1 molecule of glycerol + 3 fatty acid molecules

Question 11

how is triglyceride formed

Answer 11

each hydroxyl (-OH) group in glycerol reacts with carboxyl (-COOH) group in fatty acid, in which the condensation reaction removes 1 molecule of water to form an ester bond.

Question 12

functions of lipids

Answer 12

• triglycerides store energy
• good thermal insulator
• protect deliacte organs
• component of cell membrane
• low density, increases buoyancy of organism

Question 13

test for lipids

Answer 13

Ethanol emulsion test

1. add 2cm³ of ethanol to 2 drops of the test subtance in a test tube. Mix well. (grind solid subtances)
2. decant the ethanol into another test tube containing 2cm³ of water
3. Mix well and observe for cloudiness

present –> white emulsion formed when water was added

absent –> stayed clear when water was added