AP Biology : Understanding Lipids

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #31 : Understanding Lipids

Which of the following is an example of a lipid?

Possible Answers:

Cholesterol

Amino acid

Disaccharide

Cellulose

Correct answer:

Cholesterol

Explanation:

Cholesterol is a type of steroid, which is a lipid. Amino acids are part of proteins. Cellulose and disaccharides are examples of carbohydrates.

Example Question #101 : Macromolecules

Which of the following includes all the other answer choices?

Possible Answers:

Fats

Waxes

Phospholipids

Lipids

Correct answer:

Lipids

Explanation:

Lipids are a large class of hydrocarbon-based molecules that includes waxes, steroids, phospholipids and fats. Lipids are hydrophobic and have functions in energy storage, providing support to the cell/organism, cell signaling, and make up the majority of the cell membrane. 

Example Question #32 : Understanding Lipids

A lipid that consists of a long chain of hydrocarbons with the maximum number of hydrogens possible is referred to as __________.

Possible Answers:

a saturated fatty acid

a vitamin

a steroid

a triglyceride

Correct answer:

a saturated fatty acid

Explanation:

Saturated fatty acids contain the maximum number of hydrogens on their hydrocarbon tails. These molecules form long, straight chains that can be very densely packed. By contrast, unsaturated fatty acids, do not contain the maximum number of hydrogens on their hydrocarbon tails, and thus have "kinks" in their tails. This does not allow for dense packing and storage of unsaturated fatty acids, and thus make them easier to burn.

Example Question #31 : Understanding Lipids

Hemoglobin is an example of a __________.

Possible Answers:

nucleic acid

steroid

protein

phospholipid

Correct answer:

protein

Explanation:

Hemoglobin is the protein in red blood cells that binds and transports oxygen to the body tissues. It contains an iron core, and each hemoglobin molecule can bind up to four oxygen molecules.

Example Question #31 : Understanding Lipids

If a phospholipid's phosphate group is replaced with another fatty acid chain, the result is a __________.

Possible Answers:

fat (triglyceride)

steroid

wax

saturated fatty acid

Correct answer:

fat (triglyceride)

Explanation:

A phospholipid has two fatty acid chains and a phosphate group attached to glycerol. By replacing the phosphate group of a phospholipid with another fatty acid, the result is a glycerol with three fatty acid chains which makes it a fat (triglyceride). Saturated fatty acids are single chains of fatty acids, the resulting molecule has three fatty acids, which each could be saturated or unsaturated. Steroids have structures that consist of four fused carbon rings. 

Example Question #31 : Understanding Lipids

Fat is composed of which of the following smaller molecules?

Possible Answers:

Glycerol

None of these

Glycerol and fatty acids

Fatty acids

Correct answer:

Glycerol and fatty acids

Explanation:

Fat is made up of glycerol and fatty acids. Specifically, a fat is composed of three fatty acids chains—composed of 16 or 18 carbon atoms in length—connected to a glycerol by way of an ester linkage.

Example Question #34 : Understanding Lipids

Which of the following best describes the composition of glycerol molecules?

Possible Answers:

An alcohol with three carbons each bearing a hydroxyl group

An alcohol with three carbons without any hydroxyl group

An alcohol with two carbons each bearing a hydroxyl group

An alcohol with one carbon bearing a hydroxyl group

Correct answer:

An alcohol with three carbons each bearing a hydroxyl group

Explanation:

Glycerol is composed of an alcohol attached to three carbons each bearing a hydroxyl group.

Example Question #35 : Understanding Lipids

Fatty acids vary in length and in the number and locations of double bonds between the carbon atoms. If there are no double bonds between the carbon atoms in the tail then the fatty acid is said to be __________.

Possible Answers:

low density

saturated

unsaturated

monounsaturated

Correct answer:

saturated

Explanation:

A saturated fatty acid has no double bonds between the carbon atoms making up the tail of the fatty acid. This lack of double bonding allows for as many hydrogen atoms as possible to be bonded to the carbon skeleton, thus the fatty acid is said to be saturated with hydrogen atoms.

Example Question #111 : Macromolecules

A fatty acid that has two double bonds between its carbon atoms is called __________.

Possible Answers:

a saturated fatty acid

good cholesterol

a hydrogenated fatty acid

an unsaturated fatty acid

Correct answer:

an unsaturated fatty acid

Explanation:

An unsaturated fatty acid has one or more double bonds in its hydrocarbon tail. These double bonds are formed by the removal of hydrogen atoms from the carbon tail, resulting in a kink in the tail. As such, they are not fully saturated with hydrogen atoms. Cholesterol is a type of lipid that contains four hydrocarbon rings in its structure. Hydrogenated fatty acids are unnatural saturated fatty acids that are modified for their physical properties.   

Example Question #32 : Understanding Lipids

Three fatty acids each joined to glycerol by an ester linkage is a __________.

Possible Answers:

phospholipid

steroid

triacylglycerol

cholesterol

Correct answer:

triacylglycerol

Explanation:

A triacylglycerol (also called commonly referred to as a fat or a triglyceride) is composed of three fatty acid chains linked to glycerol via an ester linkage. The fatty acids can be the same or two or three different types. Steroids are derived from cholesterol, a molecule that contains four hydrocarbon rings attached together. Phospholipids only have two fatty acid tails linked to a glycerol head and a phosphate group.  

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