3.5 Lipids

Question 1

What is a lipid?

Answer 1

A non-polar macromolecule containing carbon, hydrogen and oxygen

Question 2

What are the 2 types of lipids? What are they at room temperature?

Answer 2

Fats - solid at room temperature

Oils - liquid at room temperature

Question 3

What is a triglyceride made up of?

Answer 3

1 glycerol molecule + 3 fatty acids

Question 4

What group does glycerol belong to?

Answer 4

Alcohols

Question 5

What group do fatty acids belong to?

Answer 5

Carboxylic acids

Question 6

What are fatty acids made up of?

Answer 6

A carboxyl group with a hydrocarbon chain

Question 7

What groups do fatty acids and glycerol molecules contain?

Answer 7

Hydroxyl groups

Question 8

What do the hydroxyl groups do?

Answer 8

Hydroxyl groups interact, forming 3 water molecules and bonds between the fatty acids and glycerol

Question 9

What are the bonds between fatty acids and glycerol called? What is the reaction called?

Answer 9

Ester bonds

Esterification - A condensation reaction

Question 10

What’s needed when triglycerides are broken down?

Answer 10

3 water molecules are required to reverse the reaction that formed the triglyceride

Question 11

What are saturated fatty acid chains?

Answer 11

No double bonds between carbon atoms - all carbon atoms form the maximum amount of bonds with hydrogen atoms
Chains are straight

Question 12

What are unsaturated fatty acid chains?

Answer 12

Contain double bonds between some carbon atoms

Chains have a bending point

Question 13

What are monounsaturated fatty acid chains?

Answer 13

Contain only one double bond

Question 14

What are polyunsaturated fatty acid chains?

Answer 14

Contain 2 or more double bonds

Question 15

What is the effect of a double bond?

Answer 15

Causes the molecule to bend, therefore the molecule can’t be packed closely together

Question 16

What triglycerides do plants contain? Elaborate on it

Answer 16

Unsaturated triglycerides

• Occur as oils
• Healthier than saturated fats

Question 17

What are phospholipids and what do they contain?

Answer 17

1. Modified triglycerides

2. Contain phosphorus, carbon, hydrogen and oxygen

Question 18

Where are inorganic phosphate ions found?

Answer 18

In the cytoplasm of every cell

Question 19

Describe the phosphate ions

Answer 19

Have extra electrons so are negatively charged, making them soluble

Question 20

How is a triglyceride made into a phospholipid? (*Refer to Figure 3 on p.g.55)

Answer 20

One fatty acid chain in the triglyceride is replaced with a phosphate group to form a phospholipid

Question 21

Describe the structure of a phospholipid

Answer 21

Non-polar tail, the fatty acid chains

Charged head, the phosphate group

Question 22

Describe the non-polar tails

Answer 22

• Repelled by water so are hydrophobic

- Mix easily with fat

Question 23

Describe the charged heads

Answer 23

Attracted by water so are hydrophilic

Question 24

What happens when phospholipids mix with water? What are they called because of this?

Answer 24

1. Form a layer on the water’s surface with phosphate heads in the water and fatty acid tails sticking out of the water
2. Surface active agents (Surfactants)

Question 25

Explain what sterols are

Answer 25

• Also known as steroid alcohols
• Another type of lipid found in cells
• Not fats or oils
• Complex alcohol molecules
• Made of a 4 carbon ring structure with a hydroxyl (OH) group at one end
• Have hydrophilic+hydrophobic properties (OH group = hydrophilic, rest of molecule - hydrophobic)

Question 26

Give an example of a sterol

Answer 26

Cholesterol

Question 27

Where is cholesterol made?

Answer 27

Liver and intestines

Question 28

What role does cholesterol have?

What is the result of this?

Answer 28

1. Role in formation of membranes, becoming positioned between phospholipids w/ hydroxyl group on the outside of the membrane
2. Adds stability to membranes
   - regulates membrane fluidity by keeping membrane fluids at low temperatures + stopping them become too fluid at high temperatures

Question 29

Give examples of what can be made using cholesterol

Answer 29

1. Vitamin D
2. Steroid hormones
3. Bile

Question 30

What roles do lipids play?

Answer 30

1. Membrane formation + creation of hydrophobic barriers
2. Hormone production
3. Electrical insulation for impulse transmission
4. Waterproofing e.g. bird feathers + plant leaves

Question 31

Where else are lipids stored? What does this provide?

Answer 31

1. Under skin
2. Around vital organs
   Provides:
3. Thermal insulation to reduce heat loss e.g. in penguins
4. Cushioning to protect vital organs e.g. heart and kidneys
5. Buoyancy for aquatic animals e.g. whales

Question 32

What test is used to identify lipids?

Answer 32

Emulsion test

Question 33

How is the test for identifying lipids carried out? What indicates the presence of a lipid?

Answer 33

1. Mix sample with ethanol
2. Mix resulting solution with water + shake
   White emulsion forming as a layer on top of the solution means lipids are present
   If the solution remains clear, results are negative

Question 34

What is food synergy?

Answer 34

The belief that nutrients work collectively, not in isolation