lipids⭐️

Question 1

what does saturated mean?

Answer 1

there are no c=c double bonds and the molecule has as many hydrogen atoms as possible

Question 2

what does unsaturated mean?

Answer 2

there is at least one c=c double bond therefore contains fewer hydrogen atoms than is maximally possible

Question 3

what is a triglyceride?

Answer 3

formed by the joining of one molecule of glycerol to three fatty acids through three condensation reactions, forming ester bonds

Question 4

what are the characteristics of lipids?

Answer 4

soluble in organic solvents, insoluble in water, all have C. H and O

Question 5

what are the roles of lipids?

Answer 5

source of energy- when oxidised, lipids release twice the amount of energy as the same mass of carbohydrate.
waterproofing- insoluble in water so provides waterproofing in plants and animals.
insulation- slow conductor of heat so reduced heat loss. electrical insulator for myelin sheath (nerves)
protection- around organs

Question 6

what are the role of triglycerides?

Answer 6

key role in respiration and energy source due to its insolubility and high carbon to hydrogen ratio

Question 7

what is a phospholipid?

Answer 7

a glycerol with two fatty acids and one phosphate group binded to it, joined via a condensation reaction

Question 8

what is the role of phospholipids?

Answer 8

create a phospholipid bilayer in cell membranes as the hydrophobic tails and hydrophilic heads allow them to arrange themselves away from the direction of the water

Question 9

what are the properties of triglycerides?

Answer 9

low mass to energy ratio- good storage molecules because much energy can be stored in a small volume.
high ratio of energy storing carbon-hydrogen bonds to carbon atoms- excellent source of energy.
large, non polar molecule so insoluble in water- doesnt affect osmosis in cells or water potential
high ratio of hydrogen to oxygen atoms so release water when oxidised- provide a source of water to desert animals

Question 10

name the group represented by COOH

Answer 10

carboxylic acid

Question 11

describe the test for the presence of lipid in a liquid food sample

Answer 11

dissolve the sample in water. add ethanol and shake to dissolve. white milky emulsion

Question 12

explain the arrangement of phospholipids in the cell surface membrane

Answer 12

phospholipids are polar molecules, fatty acid tail repels the water, meaning its hydrophobic, and phospholipid heads are hydrophilic, so attract water, therefore create a bilayer

Question 13

whats the function of phospholipids?

Answer 13

they form a hydrophobic barrier around cells, polar phospholipids arrange themselves into a bilayer.
they are also responsible for cell recognition, the phospholipid heads combine with carbohydrates to form glycolipids

Question 14

What is the structure of a triglyceride?

Answer 14

Triglycerides are made from a glycerol molecule and three fatty acids. The fatty acids form ester bonds with the glycerol through condensation reactions. Fatty acids vary in length and whether they have double bonds between carbon atoms (unsaturated) or not (saturated)

Question 15

How does the structure of a triglyceride effect its function?

Answer 15

• source of energy due to many carbon - hydrogen bonds
• storgae due to low mass to energy ratio
• do not affect osmosis due to large, insoluble nature
• source of water due to high number of hydrogen to oxygen atoms which can release water when oxidised

Question 16

Why are triglycerides good for energy storage?

Answer 16

Long hydrocarbon trails of fatty acids contain lots of chemical energy so lots of energy released when they’re hydrolysed.
They’re insoluble so don’t affect water potential. Triglycerides clump together as insoluble droplets in cells as the fatty acids are hydrophobic, so face inwards.