Test Your Knowledge On Lipids!

1. The primary function of fats is...

To provide structure within specialized cells

To secrete fatty acids into the body at a moderate rate

To store energy

To act as risk factors for diseases, such as cardiovascular diease

Act as a hydrophobic element in the body to ward off excess water

Fats primarily function to store energy in the body. They are a concentrated source of energy, providing more than double the amount of calories per gram compared to carbohydrates and proteins. When the body has excess energy from food, it converts it into fat and stores it for later use. This stored fat can then be broken down and used as fuel when the body needs energy between meals or during periods of physical activity.

Explanation

Fats primarily function to store energy in the body. They are a concentrated source of energy, providing more than double the amount of calories per gram compared to carbohydrates and proteins. When the body has excess energy from food, it converts it into fat and stores it for later use. This stored fat can then be broken down and used as fuel when the body needs energy between meals or during periods of physical activity.

2. A phospholipid is a type of lipid which makes up cell membranes. Which of the following does not characterize a phospholipid?

A phosphate functional group

A hydrophilic head and hydrophobic tails

The ability to form a bilayer

A hydrophobic head and hydrophilic tails

An ester bond between glycerol and fatty acids

A phospholipid is composed of a hydrophilic (water-loving) head and hydrophobic (water-hating) tails. This arrangement allows phospholipids to form a bilayer, which is a characteristic feature of cell membranes. Additionally, a phospholipid contains a phosphate functional group and an ester bond between glycerol and fatty acids. However, a phospholipid does not have a hydrophobic head and hydrophilic tails, as it is the opposite - hydrophilic head and hydrophobic tails.

Explanation

A phospholipid is composed of a hydrophilic (water-loving) head and hydrophobic (water-hating) tails. This arrangement allows phospholipids to form a bilayer, which is a characteristic feature of cell membranes. Additionally, a phospholipid contains a phosphate functional group and an ester bond between glycerol and fatty acids. However, a phospholipid does not have a hydrophobic head and hydrophilic tails, as it is the opposite - hydrophilic head and hydrophobic tails.

3. The label on a container of margarine lists 'hydrogenated vegetable oil' as the major ingredient. What is the result of adding hydrogens to vegetable oil?

The hydrogenated vegetable oil has a lower melting point.

The hydrogenated vegetable oil stays solid at room temperature.

The hydrogenated vegetable oil has more "kinks" in the fatty acid chains.

The hydrogenated vegetable oil has fewer trans fatty acids.

The hydrogenated vegetable oil is less likely to clog arteries.

By adding hydrogen to the unsaturated vegetable oil, the result is a saturated fatty acid. The vegetable oil is now 'saturated' with hydrogen. This causes the oil to solidify at room temperature and therefore, produce margarine.

Explanation

By adding hydrogen to the unsaturated vegetable oil, the result is a saturated fatty acid. The vegetable oil is now 'saturated' with hydrogen. This causes the oil to solidify at room temperature and therefore, produce margarine.

4. Large organic molecules are usually assembled by polymerization of a few kinds of simple subunits. Which of the following is an exception to this statement?

A steroid

Cellulose

DNA

An enzyme

A contractile protein

Steroids are an exception to the statement because they are not assembled by polymerization of simple subunits. Steroids are a class of organic compounds that have a specific structure and are derived from cholesterol. They are composed of four interconnected carbon rings and have various functional groups attached to them. Unlike polymers, which are made up of repeating subunits, steroids have a unique and complex structure that is not formed through polymerization. Therefore, a steroid is an exception to the statement that large organic molecules are usually assembled by polymerization of simple subunits.

Explanation

Steroids are an exception to the statement because they are not assembled by polymerization of simple subunits. Steroids are a class of organic compounds that have a specific structure and are derived from cholesterol. They are composed of four interconnected carbon rings and have various functional groups attached to them. Unlike polymers, which are made up of repeating subunits, steroids have a unique and complex structure that is not formed through polymerization. Therefore, a steroid is an exception to the statement that large organic molecules are usually assembled by polymerization of simple subunits.

5. Steroids are specialized lipids composed of four fused carbon rings. Based on this knowledge, what would you expect to be the chemical formula of a steroid?

CO2

C96H150O9

C4H12

C27H46O

NH3

The formula C27 H46 O is the formula for cholesterol, a specialized steroid in animals.

Explanation

The formula C27 H46 O is the formula for cholesterol, a specialized steroid in animals.