Lipids

Question 1

What are lipids?

Answer 1

Lipids are organic molecules mainly made up of two main types of lipids: triglycerides and phospholipids

Question 2

What are the monomers of triglycerides?

Answer 2

Monomers of triglycerides are glycerol and fatty acids

Question 3

What are triglycerides

Answer 3

Triglycerides are non - polar hydrophobic molecules

Question 4

What are triglycerides composed of?

Answer 4

Triglycerides are composed of three fatty acids attached to a glycerol molecule

Question 5

How are triglycerides formed?

Answer 5

Triglycerides are formed from three separate condensation reactions that occur between the glycerol molecule and the three fatty acids, forming three water molecules as waste

Question 6

What type of bond is formed from the condensation reaction in triglycerides?

Answer 6

Triglycerides form ester bonds

Question 7

What is the two ways fatty acids can vary?

Answer 7

Fatty acids can vary in length and fatty acid chain type. Fatty acid chains can be saturated and unsaturated

Question 8

What is a saturated fatty acid chain?

Answer 8

A saturated fatty acid consists of no double bonds within their hydrocarbons

Question 9

What is a polyunsaturated fatty acid?

Answer 9

A fatty acid chain consisting of two or more double bonds between the hydrocarbons

Question 10

What is an unsaturated fatty acid? What are the two different types?

Answer 10

An unsaturated fatty acid contains at least one or more double bonds within their hydrocarbons.

The two possible types of hydrocarbon are mono or poly - unsaturated fatty acids

Question 11

What is a monounsaturated fatty acid?

Answer 11

A fatty acid consisting of one double bond between the hydrocarbons

Question 12

Name some structural features of triglyceride that result in some of its properties

Answer 12

1. Triglyceride has a large ratio of energy storing carbon - hydrogen atoms. Which results in a lot of energy being stored in the molecule
2. Triglycerides are long and hydrophobic, making them insoluble - do not affect water potential and do not cause osmotic water uptake
3. Triglycerides are a metabolic water source. When they are oxidised water is released, allowing it to act as source of water for animals in the desert

Question 13

Where does the ester bond form in triglycerides?

Answer 13

An ester bond forms between the hydroxyl group (-OH) on glycerol and the carboxyl group -(COOH) of the fatty acid

Question 14

What is the difference between polyunsaturated fatty acids and monounsaturated fatty acids?

Answer 14

Monounsaturated fatty acids have only one double bond between their hydrocarbons and polyunsaturated fatty acids have two or more double bonds between their hydrocarbons

Question 15

How is the ester bond formed in phospholipids?

Answer 15

Two fatty acids bond to the glycerol molecule through two condensation reactions to form the two ester bonds

Question 16

What are phospholipids composed of?

Answer 16

Phospholipids are composed of a glycerol molecule, a phosphate group and two fatty acid chains

Question 17

Name some structural features of phospholipids that result in some of its properties

Answer 17

1. Phospholipids are polar molecules. This means that in an aqueous environment, phospholipid molecules form a bilayer within a cell surface membrane
2. The hydrophilic heads of phospholipid molecules help to hold at the surface of the cell surface membrane
3. The phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell - surface membrane

Question 18

What are the fatty acid chains described as?

Answer 18

Hydrophobic

Question 19

Describe the hydrophillic head

Answer 19

The hydrophilic head repels fats and attracts water since it is charged

Question 20

Why are the fatty acid chains described as hydrophobic?

Answer 20

The fatty acid chains repel water but will attract fats, mixing with them

Question 21

Why is the head of the phospholipid called hydrophilic?

Answer 21

The head is called hydrophilic because of the negative charge on the phosphate group

Question 22

What do phospholipids form?

Answer 22

Phospholipids form a phospholipid bilayer membrane structure

Question 23

How are phospholipids positioned in water?

Answer 23

In water, phospholipids have their hydrophilic heads facing the water and their tails facing each other so they are not exposed to the water

Question 24

What are the similarities between phospholipids and triglycerides?

Answer 24

1. Both contain a glycerol molecule
2. Both may be attached to a mixture of saturated, monounsaturated and polyunsaturated fatty acids
3. Both contain the elements carbon, hydrogen and oxygen
4. Both are formed by condensation reaction