2.2 Lipids

Question 1

What are organic solvents?

Answer 1

Solvents containing carbon, such as ethanol

Question 2

What atoms are lipids made of ?

Answer 2

Carbon, hydrogen and oxygen. Like carbohydrates, but they have a higher proportion of hydrogen and lower proportion of oxygen.

Question 3

What are lipids? Are they soluble or insoluble?

Answer 3

A diverse group of compounds that are insoluble in water but soluble in organic solvents

Question 4

Why are lipids a good energy sources?

Answer 4

They contain twice the amount of energy as carbohydrates

Question 5

Where are lipids stored?

Answer 5

Adipose tissue (fat)

Question 6

What is adipose tissue used for?

Answer 6

Layers of fat around organs provide protection, such as around your kidneys. Fat can also provide warmth by reducing heat loss under skin.

Question 7

When are fatty acids produced?

Answer 7

When fats in our food/diet are broken down

Question 8

What are fatty acids used for?

Answer 8

They are essential for many things, for instance they are used in plasma membranes

Question 9

If a fatty acid is monounsaturated what does it have?

Answer 9

It contains one double bond

Question 10

If a fatty acid is polyunsaturated what does it have?

Answer 10

It contains many double bonds

Question 11

What does it mean if a fatty acid is saturated?

Answer 11

It means it contains no double bonds

Question 12

What molecules do fatty acids contain?

Answer 12

Carbon and hydrogen molecules

Question 13

What type of chains do saturated fatty acids form and what does this mean about their attractions?

Answer 13

They form straight chains, consequently molecules can line up closely forming strong attractions between all molecules

Question 14

Due to strong attractions what do saturated fatty acids have, and why?

Answer 14

They have high melting points as a lot of energy is needed to overcome the attractions

Question 15

What state are saturated fatty acids at, at room temperature?

Answer 15

They tend to be solid at room temperature

Question 16

What are triglycerides and what are they used for?

Answer 16

The are a type of lipid used for energy storage, insulation and protection.

Question 17

Where are triglycerides found?

Answer 17

In fatty tissues under skin and layers of fat surrounding organs to provide protection

Question 18

What does a triglyceride consist of?

Answer 18

A glycerol backbone and 3 fatty acids

Question 19

Are triglycerides soluble or insoluble in water?

Answer 19

They are insoluble

Question 20

What reaction occurs to form a triglyceride and what bond is formed?

Answer 20

• a condensation reaction (water is lost)

* an ester bond is formed

Question 21

What is another name for this process?

Answer 21

Esterification

Question 22

What does the structure of a phospholipid consist of?

Answer 22

A phosphate group, a glycerol head and two fatty acid tails

Question 23

Is a phospholipid hydrophilic or hydrophobic?

Answer 23

It is amphipathic, both hydrophilic and hydrophobic

Question 24

What part of a phospholipid is hydrophilic?

Answer 24

The phosphate group

Question 25

What does hydrophilic mean?

Answer 25

It loves water

Question 26

What part of a phospholipid is hydrophobic?

Answer 26

The fatty acids

Question 27

What does hydrophobic mean?

Answer 27

It doesn’t like water

Question 28

What does the phospholipid do in water and why?

Answer 28

It forms a double bilayer spontaneously in water otherwise the fatty acids would have to be in contact with water

Question 29

What do phospholipids play a key role in?

Answer 29

Forming cell membranes as they are able to separate the aqueous environment

Question 30

What are sterols?

Answer 30

Lipids that are neither fats nor oils

Question 31

What are sterols otherwise known as?

Answer 31

Steroid alcohols

Question 32

Give an example of a sterol:

Answer 32

Cholesterol

Question 33

What happens when sterols react with water?

Answer 33

They are amphipathic; the hydroxyl group in sterols are polar as it is attracted to water

Question 34

Where is cholesterol made and what role does it play?

Answer 34

It is made in the liver and intestines, it plays an important role in the formation of the cell membrane, it becomes positioned between the phospholipids adding stability to the cell

Question 35

What does cholesterol do?

Answer 35

It regulates cell membrane fluidity:
• it keeps them fluid at low temperatures (stops them freezing)
• it stops them becoming too fluid at high temperatures

Question 36

What are made using cholesterol?

Answer 36

Vitamin D, steroid hormones and bile

Question 37

What are the roles of lipids?

Answer 37

• membrane formation
• hormone production
• electrical insulation (fatty sheath)
• waterproofing (birds feathers)
• energy storage
• thermal insulation