Lipids

Question 1

Definition of lipids

Answer 1

Lipids are macromolecules and all contain carbon, hydrogen and oxygen. They include Triglycerides, Phospholipids and Cholesterol.

Question 2

Definition of Macromolecule

Answer 2

Its a very large, organic molecule

Question 3

Describe lipids solubility

Answer 3

Lipids are insoluble in water because they are not polar therefore they don’t attract water molecules, but do dissolve in alcohol.

Question 4

Definition of Triglycerides

Answer 4

They have one molecule of glycerol with three fatty acids attached to it.

Question 5

How are Triglycerides synthesised?

Answer 5

They’re synthesised by the formation of an ester bond between each fatty acid and the glycerol molecule.

Question 6

Definition of Glycerol

Answer 6

they have three carbon atoms. It is an alcohol, which means it has free -OH groups. There are 3 -OH groups.

Question 7

What bonds and how many bonds do an Triglycerides have?

Answer 7

it has three ester bonds

Question 8

How is each ester bond formed?

Answer 8

by a condensation reaction

Question 9

Whats the process called in which Triglycerides are synthesised

Answer 9

esterification

Question 10

Describe fatty acids

Answer 10

They have long ‘tails’ made of hydrocarbon. The tails are ‘hydrophobic’ therefore are insoluble in water.

Question 11

Definition of saturated fatty acids

Answer 11

saturated fatty acids don’t have any double bond between their carbon atoms in their hydrocarbon tails. They fatty acid is ‘saturated’ with hydrogen.

Question 12

Definition of unsaturated fatty acids

Answer 12

Unsaturated fatty acids have at least one double bond between carbon atoms, which causes chain to kink

Question 13

Definition of phospholipid

Answer 13

molecule consisting of glycerol, two fatty acids and one phosphate group

Question 14

Definition of cholesterol.

Answer 14

Cholesterol has a hydrocarbon ring structure attached to a hydrocarbon tail. the ring structure has a polar hydroxyl (OH) group attached to it.

Question 15

What are the main two functions of Triglycerides

Answer 15

Energy source and energy store

Question 16

explain Triglycerides been an energy source

Answer 16

its mainly used as energy storage molecules. Triglycerides can be broken down in respiration to release energy and generate ATP.

Question 17

explain Triglycerides been an energy store

Answer 17

> Good for storage because the long hydrocarbon tails of the fatty acids contain lots of chemical energy - load of energy is released when they’re broken down. Because of these tails, lipid contain about twice as much energy per gram as carbohydrates.
They are insoluble in water, they can be stored without affecting the water potential of the cell.

Question 18

Function of phospholipid

Answer 18

They make up phospholipid bilayer

Question 19

Describe the phospholipid bilayer

Answer 19

Phospholipid head are hydrophilic and their tails are hydrophobic so they form a double layer with their heads facing out towards the water on either side.

Question 20

Describe the centre of of the bilayer

Answer 20

The centre of the bilayer is hydrophobic, so water-soluble substances can’t easily pass through it - the membrane acts as a barrier to those substances.

Question 21

Function of cholesterol

Answer 21

It help strengthen the cell membrane by interacting with the phospholipid bilayer.

Question 22

Describe the structure of cholesterol and advantage of it.

Answer 22

Cholesterol has a small size and flattened - this allow cholesterol to fit in between the phospholipid molecules in the membrane. They bind to the hydrophobic tails of the phospholipid, causing them to pack more closely together. this helps to make the membrane less fluid and more rigid.