Lipids

Question 1

What are two types of lipids?

Answer 1

Triglycerides and Phospholipids.

Question 2

What are lipids soluble in?

Answer 2

Lipids are soluble in organic solvents (alcohols for example).

Question 3

What is the structure of a triglyceride?

Answer 3

1 glycerol
3 fatty acids

Question 4

How do you form a triglyceride?

Answer 4

A condensation reactions form 3 ester bonds between the hydrogen in the glycerol and 3 hydroxides in each fatty acid releasing 3 water molecules.

Question 5

What are examples of lipids with fatty acids?

Answer 5

1. Waxes
2. Fats + Oils
3. Phospholipids

Question 6

What is an example of a lipid without a fatty acid?

Answer 6

Steroids.

Question 7

Describe saturated lipids and where they are found.

Answer 7

Saturated means the lipid contains no double carbon bonds. They are found in animal fats.

Question 8

Describe unsaturated lipids and where they are found.

Answer 8

Unsaturated means the lipid contains double carbon bond/s. They are found in plants.

Question 9

What is the difference between the saturated and unsaturated lipids?

Answer 9

Unsaturated lipids have one or more double carbon bonds which means molecule can bend.
Unsaturated fats cannot pack together as tightly and are liquids at room temp unlike saturated fats.

Question 10

How is a triglycerides structure linked to its properties?

Answer 10

1. High ratio of energy-storing C-H bonds making it good energy store.
2. High ratio of O-H bonds so when oxidised, water is released which is good for extremeophiles in dry conditions.
3. Low mass to energy ratio meaning lots of energy stored in small volume, good for animals to carry less mass.
4. Insoluble so doesn’t affect water potential of cells.

Question 11

What is the structure of a phospholipid?

Answer 11

1 glycerol with phosphate group, 2 fatty acids.

Question 12

What is are differences in structures of triglycerides and phospholipids?

Answer 12

1. P has phosphate group, T doesn’t.
2. P has 2 fatty acids, T has 3.

Question 13

How is the structure of phospholipids linked to their properties?

Answer 13

1. Polar molecule so micelles form when in contact with water (hydrophilic heads, hydrophobic tails).
2. Hydrophilic phosphaet heads make up the outer and inner layers of the cell-surface membrane.
3. Form glycolipids with carbohydrates on cell-surface membrane, act as receptors.

Question 14

How do you test for lipids?

Answer 14

Emulsion test with ethanol.

Question 15

Describe the emulsion test.

Answer 15

• Add ethanol to a test tube with the food sample.
• Shake then add distilled water and shake again.
• If lipids present, milky/cloudy-white emulsion forms.
  Control - test with water for clear solution.