lipids: triglycerides and phospholipids

Question 1

are lipids soluble in water?

Answer 1

low solubility in water bit high in organic solvents e.g ethanol

Question 2

what do triglycerides form?

Answer 2

fats or oils

Question 3

how does the number of carbon atoms in a triglyceride affect melting point?

Answer 3

the more carbon atoms the higher the melting point as the intermolecular forces are stronger so more energy is needed to overcome them

Question 3

what is the structure of triglycerides?

Answer 3

made from glycerol binded by ester bonds to 3 fatty acids

Question 4

what bond is between glycerol and fatty acids?

Answer 4

ester

Question 5

how are triglycerides made? what reaction

Answer 5

made by a condensation reaction with the relase of 3 molecules of water

Question 6

how are triglycerides broken down?

Answer 6

hydrolysis reaction with the addition of 3 water molecules

Question 7

what are oils?

Answer 7

lipids with short hydrocarbon chain fatty acidsform oils which are liquid at room temp

usually contain unsaturated fatty acids

Question 8

what are fats?

Answer 8

lipids with long hydrocarbon chain fatty acids
solid at room temp

usually contain saturated fatty acids

Question 9

what is the main function of triglycerides?

Answer 9

energy storage

Question 10

why are triglycerides more efficient energy stores compared to carbohydrates?

Answer 10

due to the large ratio of energy storing carbon hydrogen bonds compared to the number of carbon atoms. this allows it to store more energy per unit of mass

fats and oils are the prefered energy store

Question 11

what are the properties of triglycerides?

Answer 11

good thermal insulators and provide mechanical protection to delicate organisms

provide buoyancy (floating) for many aquatic organisms as fat is less dense than water

hydrophobic: some animals coat their fur in oils to make them waterproof

insoluble as they are hydrophobic so triglycerides dont affect water potential

Question 12

what do all lipids contain?

Answer 12

high proportion of CH2 groups and have a low solubility in water but high in organic solvents e.g ethanol

Question 13

what is the structure of phospholipids?

Answer 13

contains a glycerol molecule
2 fatty acid chains which are hydrophobic
hydrophilic phosphate head which contains a phosphate oin

2 fatty acids bond to the glycerol by 2 condensation reactions resulting in 2 ester bonds

Question 14

how are the 2 fatty acids and glycerol bonded?

Answer 14

2 condensation reactions resulting in 2 ester bonds

Question 15

what are the properties of phospholipids?
how do they arrange themselves in water

Answer 15

when in water they are positioned so that the hydrophillic head is exposed to water and hydrophobic tails are not
phospholipid bilayer in membranes

Question 16

what does fluidity of membrane affect?

Answer 16

how easy it is for the cell membrane to move

Question 17

how does membranes having only saturated fatty acids influence fluidity?

Answer 17

those with only saturated fatty acids are the least fluid

Question 18

how does membranes having only unsaturated fatty acids influence fluidity?

Answer 18

least fluid

Question 19

what do lipids containing only saturated fatty acids usually form at room temperature? and why

Answer 19

usually form fats at room temperature

this is because fatty acid tails are straight and can pack closely together

stronger forces of attraction form so more energy is needed to break bonds and melt fat so melting point is higher

Question 20

what do lipids containing only unsaturated fatty acids usually form at room temperature? and why

Answer 20

form oils at room temp
the double bonds make fatty acid chains less straight so they link and they cant pack as closely together

so forces of attraction are weaker between the fatty acids so less energy is needed to break the nonds and melt the oil so they have a lower melting point