Chapter 3: 3.5

Question 1

What is a lipid?

Answer 1

carbon, hydrogen and oxygen

Question 2

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

Answer 2

Fats, Oils

Question 3

What is a triglyceride made up of?

Answer 3

1 glycerol molecule + 3 fatty acids

Question 4

What are fatty acids made up of?

Answer 4

A carboxyl group

Question 5

What groups do fatty acids and glycerol molecules contain?

Answer 5

Hydroxyl groups

Question 6

What do the hydroxyl groups do?

Answer 6

Forming 3 water molecules and bonds between the fatty acids and glycerol

Question 7

What are the bonds between fatty acids and glycerol called?

Answer 7

Ester bonds

Question 8

What is the structure of saturated fatty acid chains?

Answer 8

> Double bonds between the carbon atoms
All carbon atoms form the maximum amount of bonds with hydrogen atoms
Chains are bent

Question 9

What are unsaturated fatty acid chains?

Answer 9

Contain single bonds between some carbon atoms

Question 10

What are monounsaturated fatty acid chains?

Answer 10

Contain double bonds

Question 11

What is the effect of a double bond?

Answer 11

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

Question 12

What triglycerides do plants contain? Elaborate on it

Answer 12

Unsaturated triglycerides

• Occur as oils
• Healthier than saturated fats

Question 13

What are phospholipids and what do they contain>

Answer 13

1. Modified triglycerides

2. Contain phosphorus, carbon, hydrogen and oxygen

Question 14

Where are inorganic phosphate ions found?

Answer 14

In the cytoplasm of every cell in prokaryotes and eukaryotes

Question 15

What are chemical properties of a phosphate ion?

Answer 15

Have extra electrons so are negatively charged, making them insoluble

Question 16

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

Answer 16

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

Question 17

Describe the structure of a phospholipid

Answer 17

Polar
Fatty chains
They have a phosphate group

Question 18

Describe the non-polar tails

Answer 18

• Repelled by water so are hydrophobic

- Mix easily with fat

Question 19

Describe the charged heads

Answer 19

-Attracted by water

Question 20

What happens when phospholipids mix with water?

Answer 20

1. Form a layer on the water’s surface with phosphate heads in the water and fatty acid tails sticking out of the water

Question 21

Explain what sterols are

Answer 21

• 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 22

What role does cholesterol have?

What is the result of this?

Answer 22

1. Cholesterol has an important role in the formation of membranes, where cholesterol becomes positioned between the phospholipids with hydroxyl groups on the outside of the membrane
2. cholesterol adds stability to membranes
   - regulates membrane fluidity by keeping membrane fluids at low temperatures + stopping them become too fluid at high temperatures

Question 23

What roles do lipids play?

Answer 23

1. Membrane formation + creation of hydrophilic barriers
2. Chemical production
3. Impulse transmission
4. Waterproof

Question 24

Where else are lipids stored? What does this provide?

Answer 24

1. In skin
2. In vital organs
   Provides:
3. Blocks heat loss
4. stability to protect vital organs e.g. heart and kidneys
5. Buoyancy for aquatic animals e.g. whales

Question 25

What test is used to identify lipids?

Answer 25

Emulsion test

Question 26

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

Answer 26

1. Mix sample with hydrochloric acid
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