1.7 — lipids: triglycerides and phospholipids

Question 1

what is a triglyceride?

Answer 1

a triglyceride is a type of lipid used as a store of energy in animals, plants and some bacteria

Question 2

what does a triglyceride consist of?

Answer 2

a glycerol backbone attached to three fatty acid tails. each fatty acid contains a hydrocarbon chain (R group) which can vary in length and may be saturated or unsaturated

Question 3

what are the features of a triglyceride that allow it to store energy efficiently? (4)

Answer 3

1. long hydrocarbon tails — their many carbon-hydrogen binds can be broken to release energy
2. low mass to energy ratio — lots of energy can be stored in a small volume
3. insoluble — they do not affect the water potential of cells as they are large and polar
4. high ratio of hydrogen to oxygen atoms — triglycerides will release water when oxidised

Question 4

how are triglycerides formed?

Answer 4

a condensation reaction between glycerol and three fatty acids, producing three water molecules due to the three bonds formed

Question 5

how are triglycerides broken down?

Answer 5

a hydrolysis reaction, forming a glycerol and three fatty acids. the reaction uses up three water molecules due to the three bonds broken

Question 6

what’s are the bonds present in a triglyceride?

Answer 6

ester bonds

Question 7

what is a phospholipid and what is it used for?

Answer 7

a phospholipid is a type of lipid used as a structural component of the cell membrane. it contains one glycerol, two fatty acids and a phosphate group

Question 8

what are the two parts in a phospholpid?

Answer 8

1. a hydrophilic head — this contains glycerol and phosphate
2. a hydrophobic tail — this contains fatty acids

Question 9

why does the phosphate group attract water?

Answer 9

it’s polar

Question 10

how do phospholipids arrange themselves and what does this form?

Answer 10

phospholipids arrange themselves into a bilayer so that the hydrophilic heads are facing out (towards the water) and the hydrophobic tails are facing in (away from the water). this created a hydrophobic centre in the bilayer so that water-soluble substances cannot pass through.

Question 11

what is the function of triglycerides?

Answer 11

to act as an energy store

Question 12

what is the function of phospholipids?

Answer 12

to act as structural components of membrane

Question 13

what number of fatty acid tails do triglycerides contain?

Answer 13

three

Question 14

what number of fatty acid tails do phospholipids contain?

Answer 14

two

Question 15

do triglycerides contian phosphate?

Answer 15

no

Question 16

do phospholipids contian phosphate?

Answer 16

yes

Question 17

are triglycerides polar?

Answer 17

no, they are non-polar

Question 18

are phospholipids polar?

Answer 18

yes, they are polar