lipids

Question 1

what’s the molecular formula of glycerol?

Answer 1

C3H8O3

Question 2

is glycerol soluble in water?

Answer 2

yes

Question 3

why is glycerol soluble in water?

Answer 3

because of its polar OH group

Question 4

are fatty acids soluble in water?

Answer 4

no, fatty acids are hydrophobic

Question 5

why are fatty acids hydrophobic?

Answer 5

because of the abundance of non-polar C-H bonds

Question 6

how are triglycerides formed?

Answer 6

a condensation reaction. an ester linkage (-COO) is formed between the OH group of glycerol and the COOH group of the fatty acid

Question 7

how does increasing hydrocarbon chain length affect the melting point of fats?

Answer 7

the melting point of fats increases

longer hydrocarbon chain = more extensive hydrophobic interaction = more thermal energy required to break bonds = higher melting point

Question 8

how does increasing degree of unsaturation of fatty acid tails affect the melting point of fats?

Answer 8

the melting point of fats decreases when the number of C=C bonds increases

more C=C bonds = more kinks in fatty acid tails = molecules unable to pack closely = less extensive hydrophobic interactions = less thermal energy required to break bonds = lower melting point

Question 9

why are triglycerides more efficient energy stores than carbohydrates?

Answer 9

triglycerides have a greater number of carbon atoms per unit mass than carbs. upon oxidation, triglycerides release a larger amount of energy than carbs

1g of fat releases more than 2x as much energy as 1g of carbs

Question 10

why do triglycerides release more water when they are oxidised during cellular respiration compared to carbs?

Answer 10

triglycerides have 2x more hydrogen atoms per unit mass than carbs, so more water is released during cellular respiration

Question 11

why do triglycerides not affect water potential of cells?

Answer 11

C-H bonds are non-polar, making triglycerides hydrophobic, so no associated water molecules are stored along with triglycerides, so triglycerides have no extra weight due to water of hydration

absence of water in triglycerides keeps animal’s body mass at a minimum to facilitate locomotion

Question 12

why can triglycerides slide under pressure?

Answer 12

hydrocarbon tails are non-polar so weak hydrophobic interactions occur, thus triglycerides can slide

Question 13

how are phospholipids formed?

Answer 13

2 fatty acids are linked to the glycerol by an ester linkage while the phosphate group is linked to the third OH group of the glycerol by a phosphoester linkage

Question 14

how do fats aid buoyancy of aquatic animals?

Answer 14

triglycerides have a lower molecular weight than water per unit volume so they are less dense than water

Question 15

what are phospholipids made up of?

Answer 15

1 glycerol
2 fatty acids
1 negatively-charged phosphate group

additional small molecules may be linked to the phosphate group.

Question 16

why are phospholipids amphipathic?

Answer 16

hydrocarbon tail (made up of 2 fatty acids) is non-polar hence hydrophobic
hydrophilic head (made up of phosphate group and its attachment) is polar and has an affinity for water

Question 17

describe the micelle

Answer 17

a small, spherical droplet consisting of a phospholipid monolayer. the hydrophilic heads are on the outside, in contact with the aqueous environment, while the hydrocarbon tails are restricted to the water-free interior

dn memo just know

Question 17

describe the bilayer

Answer 17

2 lipid monolayers combine, forming a 2D sheet. the hydrophilic heads are exposed to the polar exterior while the hydrophobic tails are in contact with those of neighbouring molecules but excluded from water

dn memo just know

Question 18

describe the liposome/vesicle

Answer 18

formed when a lipid bilayer folds back on itself, forming a hollow sphere. by doing so, bilayer sheets avoid exposing their hydrophobic edge regions, achieving maximal stability and creating a separate aqueous compartment

Question 19

what are glycolipids made up of?

Answer 19

2 fatty acids
1 short carbohydrate chain
1 glycerol
NO phosphate

Question 20

how are glycolipids formed?

Answer 20

a glycosidic bond joins the carbohydrate chain to the OH group of glycerol