lipids

Question 1

describe the solubility of lipids in different solvents

Answer 1

insoluble in water but soluble in organic solvents

Question 2

components of lipids? what is the general formula of lipids?

Answer 2

carbon, hydrogen, oxygen
unlike carbohydrates, there is no fixed structure

therefore, if the formula is not in the form of carbohydartes, its more likely a lipid

Question 3

state the difference between oils and fats

Answer 3

fat: lipid at solid state at 20°C
oil: lipid at liquid state at 20°C

Question 4

state the difference between simple and compound lipids

Answer 4

simple: made up of fatty acids with various alcohols
compound: has lipid and non-lipid components

Question 5

give an example of a simple and compound lipid, including what they are composed of

Answer 5

simple: fats/triglyceride, esters of fatty acids with glycerol

compound: phospholipid, lipids made up of fatty acids + alcohol + phosphate

Question 6

what is triglyceride composed of?

Answer 6

glycerol + 3 molecules of fatty acids

Question 7

describe and sketch the structure of glycerol

Answer 7

alcohol with three carbons, each bearing a hydroxyl group (-OH)
structure

Question 8

describe fatty acids

Answer 8

• consists of hydrocarbon chain and carboxyl group (-COOH)
• may be saturated / unsaturated

Question 9

describe the structure of saturated fatty acids

Answer 9

• general formula: RCOOH, where R is a hydrocarbon chain made entirely of single C-H and C-C bonds
• hydrocarbon chain does not does not contain any carbon-carbon double bond and contains the maximum number of hydrogen atoms possible

Question 10

describe the state of fats with high content of saturated fatty acids at room temperature, and state what living organisms always produces saturated fats

Answer 10

• solid at room temperature, higher melting point
• animals

Question 11

describe the structure of unsaturated fatty acids

Answer 11

• contains carbon-carbon double bonds, which causes kink(s) in hydrocarbon chain
• if a fatty acid has more than one double bond, it is polyunsaturated

Question 12

a) describe AND explain the state of fats with high content of unsaturated fatty acids at room temperature
b) state what living organisms always produces unsaturated fats

Answer 12

a)
- liquid at room temperature, lower melting point
- because fatty acid chain bends at double bonds, preventing fat molecules from aligning closely with one another.

b)
- plants (expect tropical oils like palm/coconut oil)

Question 13

describe the composition of one molecule of triglyceride, and hence the condensation reaction in lipids

Answer 13

• one molecule of triglyceride consists of 3 fatty acid molecules and one molecule of glycerol
• each hydroxyl group (-OH) in the glycerol molecule reacts with the carboxyl group (-COOH) of a fatty acid. in this reaction, one molecule of water is removed and an ester bond is formed between glycerol and one fatty acid

Question 14

what are the functions of lipids? (at least 4 points)

Answer 14

1. triglyceride serves as a form of storage of energy (higher energy value and harder to hydrolyse as compared with starch / glycogen -> long term storage)
2. good thermal insulator to prevent excessive heat loss
3. shock absorbant and protects delicate organs from mechnical shock
4. releases metabolic water when hydrolysed
5. low density substance that improves buoyancy of organisms
6. major component of cell membrane
7. electrical insulation and act as a component of myelin sheath surrounding nerve cells

Question 15

describe the test for lipids

Answer 15

1) add 2cm3 of ethanol to two drops of the test substance in a test tube. mix well.
OR grind the solid test substance and add..(same).. allow any solid particles to settle
2) decant the ethanol into another test tube containing 2cm3 of water
3) mix well and observe for cloudiness

expected results (standard):
homogeneous solution formed when ethanol was added

lipids absent: solution remained homogeneous when water was added
lipids present: white emulsion was formed when water was added

Question 16

draw the condensation / hydrolysis reaction of triglyceride

Answer 16

answer

Question 17

draw a saturated and unsaturated fatty acid

Answer 17

answer