lipids

Question 1

describe what lipids are

Answer 1

lipids are fats and oils
fats are solid at room temperature
oils are liquid at room temperature

Question 2

what elements are lipids made of?

Answer 2

• C, carbon
• H, hydrogen
• O, oxygen
• sometimes P (if phospholipids)

Question 3

what are triglycerides composed of?

Answer 3

• glycerol
• 3 fatty acids

Question 4

structure of triglycerides

Answer 4

H ** O ** ester bond
| ||
H - C - O - C - R
| O
| ||
H - C - O - C - R
| O
| ||
H - C - O - C - R
|
H

Question 5

what kind of reaction is the formation of a triglyceride molecule?

Answer 5

a condensation reaction, since (3) water molecules are released and the bonds formed are called ester bonds.

Question 6

what are the two types of fatty acids?

Answer 6

• unsaturated, the fatty acid has one or more carbon-carbon double bonds in its structure
• saturated, the fatty acid has no carbon-carbon double bonds in its structure and all of the C atoms are fully ‘saturated’ with H atoms

Question 7

explain why triglycerides containing unsaturated fatty acids tend to be liquid at room temperature?

Answer 7

the carbon-carbon double bonds in unsaturated fatty acids makes a kink in the chain, it means the molecules do not pack together so tightly and so the intermolecular forces are weaker as a result

Question 8

what are the properties of triglycerides

Answer 8

triglycerides are non-polar molecules because of their long hydrocarbon chains, this means that they are insoluble in water

Question 9

what are the functions of triglycerides?

Answer 9

• source of energy/long term energy storage. more dense isn’t used till we’ve used all glucose and glycogen
• used as insulation, poor conductor of heat
• used as a layer of protection for the organs below
• waxy cuticle to prevent water loss through osmosis
• insoluble

Question 10

whats the structure of phospholipids?

Answer 10

they are composed of glycerol, phosphate and fatty acids

Question 11

how is the structure of a phospholipid different to the structure of a triglyceride?

Answer 11

the 3rd fatty acid on a triglyceride is replaced by a phosphate

Question 12

properties of a phospholipid

Answer 12

• a polar, hydrophilic head (which interacts with water)
• a non-polar hydrophobic tails (which does not interact with water)

Question 13

whats the functions of a phospholipid?

Answer 13

• phospholipids are the main component of cell membranes, since the inside of the cell is an aqueous solution and so is the outside of the cell, the phospholipids arrange themselves into a phospholipid bilayer

Question 14

whats the test for lipids?

Answer 14

emulsion test
add ethanol, add water and shake
if lipids are present a white cloudy emulsion will appear