3.5 - Lipids

Question 1

What elements do lipids contain?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What is the structure of triglycerides?

Answer 2

One glycerol molecule and three fatty acids

Question 3

What type of reaction occurs during the interaction of the hydroxyl groups?

Answer 3

Esterification ( a condensation reaction )

Question 4

What bonds are formed between the fatty acids and the glycerol molecule?

Answer 4

Ester bonds - The triglyceride molecule looks like an ‘E’, E for Ester bonds

Question 5

What is the reverse of an esterification reaction and what is added to perform this?

Answer 5

A hydrolisis reaction, and water molecules are supplied to the triglyceride to break it down.

Question 6

What is the difference between a saturated fat and an unstaurated fat?

Answer 6

Saturated fats have NO double bonds between the carbon atoms, because all the carbon atoms form a maximum number of bonds with the hydrogen atoms.

Unstaurated fats DO have double bonds between some of the carbon atoms.

Question 7

What are the properties of saturated fats due to their structure?

Answer 7

Saturated fats have NO double bonds between the carbon atoms.
This means they are a straight chain molecule and therefore they can be densely packed together, allowing for them to be solid at room temp.

Question 8

What are the properties of unsaturated fats due to their structure?

Answer 8

Unsaturated fats DO have double bonds between some of the carbon atoms.

This causes the molecule to bend and therefore they cannot pack so closely together.

This makes them a liquid at room temp rather than a solid, they are therefore oils rather than fats.

Question 9

What do the terms monounsaturated and polyunsaturated mean?

Answer 9

Monounsaturated means that the molecule has ONE carbon double bond.

Polyunsaturated means that the molecule has MULTIPLE carbon double bonds.

Question 10

What elements do phospholipids contain?

Answer 10

Phosphorus, carbon, hydrogen, and oxygen

Question 11

What is the negatively charged ion that aids in cell membrane formation, nucleic acid and ATP formation, and bone formation?

Answer 11

PO4^3-

Question 12

What does the ion PO4^3- do in the body?

Answer 12

Aids in cell membrane formation, nucleic acid and ATP formation, and bone formation

Question 13

What makes the phosphate ions soluble in water?

Answer 13

They have extra electrons and therefore are negatively charged, sonthey are soluble in water.

Question 14

How is a phospholipid formed?

Answer 14

One of the fatty acid chains in a triglyceride molecule is replaced with a phosphate group to make a phospholipid.

Question 15

What end of the phospholipid is hydrophyllic?

Answer 15

The charged head.

Question 16

What end of the phospholipid is hydrophobic?

Answer 16

The non-polar tails.

Question 17

What does it mean by a ‘phospholipid bilayer’?

Answer 17

Means that phospholipids, due to their hydrophobic and hydrophillic nature, can split an aqueous environment from the cytosol in the cells.

Question 18

What is the function of cholesterol in the body?

Answer 18

It regulates the fluidity of the cell membrane.

Question 19

What are the functions of lipids in living organisms?

Answer 19

• Membrane formation
• Hormone production
• Waterproofing, eg in bird feathers or plant leaves

Triglycerides in particular:

• Thermal insulation
• Cushioning for vital organs
• Buoyancy for aquatic animals, eg whales
• Long term energy storage

Question 20

How do you identify lipids?

Answer 20

By an emulsion test

1. Sample is mixed with ethanol
2. Solution is mixed with water and then shaken
3. If a white precipitate forms on top of the solution, the test is positive, if not, the test is negative.

Question 21

What are triglycerides and phospholipids?

Answer 21

Macromolecules