Lesson 6 – Lipids, Fatty Acids, Triglycerides, and Phospholipids

SCI260 – Introduction to Biochemistry

Lesson 6

1. Describe (in words) the overall structure of a lipid bilayer.

2. What are the properties (i.e., characteristics) of the lipid bilayer of a cell that

make it impermeable to ions and most molecules?

3. Describe the role of cholesterol in maintaining the fluidity of the lipid bilayer of a

cell?

4. The triglycerides in animals tend to be solids (i.e., fats) at room temperature

whereas the triglycerides in plants tend to be liquids (i.e., oils) at room

temperature. Based on this fact, what can you conclude about the characteristics

of the fatty acids in animal triglycerides compared to the fatty acids in plant

triglycerides?

5. Peanut oil contains a high percentage of monounsaturated triglycerides whereas

vegetable oil contains a higher percentage of polyunsaturated triacylglycerols. A

bottle of peanut oil and a bottle of vegetable oil are stored in a pantry with an

outside wall. During a cold spell, the peanut oil freezes, but the vegetable oil

remains liquid. Explain why.

6. How many molecules of ATP are generated when stearic acid (i.e., stearate), an

18-carbon saturated fatty acid, is completely oxidized via the beta-oxidation

pathway in the mitochondria?

a) 112

b) 129

c) 146

d) 163

7. Which of the following fatty acids below are essential for humans? *Select one or

more.

a) Oleic acid

b) Linoleic acid

c) Linolenic acid

d) Palmitoleic acid

e) Eicosapentaenoic acid (EPA)

8. Refer to Question 7, look up the structures of each fatty acid that is essential and

explain why they are essential for humans?

9. Are trans fatty acids saturated or unsaturated?

10. Provide four (4) examples of foods that contain trans fatty acids.

You may use your textbook and/or the internet to assist you. You will earn 10 points for

correctly answering each question (maximum points earned = 100 points).