AP Biology : Macromolecules

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #31 : Understanding Carbohydrates

The polymer chitin is made up of what carbohydrate momoner?

Possible Answers:

Fructose

N-Acetylglucosamine

Glucopyranose

N-Acetylneuraminic acid

Glucose

Correct answer:

N-Acetylglucosamine

Explanation:

Chitin is a polymer that makes up the cell wall of fungal cells as well as the exoskeleton of arthropods. It itself is made up of N-Acetylglucosamine

Example Question #31 : Understanding Carbohydrates

Which of the following is a polysaccharide stored in plants?

Possible Answers:

lipids

glucose

starch

glycogen

Correct answer:

starch

Explanation:

Starch is a polysaccharide stored in plants.  Glycogen is a polymer of glucose in animals stored in the liver and muscle cells.  Lipids are molecules made mostly of carbon and hydrogen that store energy.

Example Question #31 : Understanding Carbohydrates

Which of the following is a monosaccharide?

Possible Answers:

Lactase

Fructose

Maltose

Sucrose

Lactose

Correct answer:

Fructose

Explanation:

Sucrose is made up of a glucose molecule and a fructose molecule. Knowing this gives a hint to the correct answer. Maltose is made up of two glucose molecules. Many glucose molecules joined together make up starch. Lactose is the sugar found in milk, and is made up on a glucose and a galactose molecule. Thus, all of the other sugars listed are disaccharides. Lactase is an enzyme, as shown by the "-ase" ending. 

Example Question #32 : Understanding Carbohydrates

Monomers of sugars form disaccharides and polysaccharides via what type of bonding?

Possible Answers:

Peptide bond

Phosphodiester bond

Ester linkage

Glycosidic linkage

Hydrogen bond

Correct answer:

Glycosidic linkage

Explanation:

A phosphodiester bond occurs in DNA and RNA between nucleotides to form nucleic acids. Ester linkage occurs in fats and lipids between a carboxyl group and the carbon chain. A peptide bond occurs between two amino acids to form a peptide bond. Hydrogen bonding is the interaction of a hydrogen of one molecule with either a oxygen, nitrogen, or fluorine of another molecule.

Example Question #33 : Understanding Carbohydrates

A maltose molecule can be broken down into two molecules of glucose via what reaction?

Possible Answers:

Polymerization

Condensation

Dehydration

Hydration

Hydrolysis

Correct answer:

Hydrolysis

Explanation:

Maltose is a disaccharide and glucose is a monosaccharide so the question is asking what will break the disaccharide into its respected monosaccharide. Hydrolysis is the addition of a water molecule to break the glycosidic linkage of a sugar. Dehydration reaction is a type of condensation reaction that will ultimately join two monosaccharides together via the removal of a water molecule. Polymerization is a general term with regards of monomers forming polymers through a reaction. Hydration reactions are the addition of a water molecule but do not necessarily break any bonds but are used form an alcohol.

Example Question #1 : Identify Structure And Purpose Of Carbohydrates, Lipids, Proteins, And Nucleic Acids

Which of the following types of molecules has the most energy available per unit of carbon?

Possible Answers:

Proteins

Alcohols

Sugars

Amino acids

Fats

Correct answer:

Fats

Explanation:

Fats have an incredibly high potential to produce a lot of energy when broken down. This is because they are very saturated, which means they have a lot of bonded hydrogens. They also have a lot of carbon-carbon bonds, which have a lot of potential energy stored. When you break down a fat, especially one that has fourteen or more carbons in the chain, you release the energy from every carbon-carbon and carbon-hydrogen bond.

Comparing this to a sugar, alcohol, or protein (amino acids make up proteins), we can see that there aren't as many of these bonds to break. Proteins, in fact, require a lot of energy to break down because they have to be converted into other forms first.

Example Question #2 : Identify Structure And Purpose Of Carbohydrates, Lipids, Proteins, And Nucleic Acids

Phospholipids are amphipathic. This means that a phospholipid is __________.

Possible Answers:

found only in animal cells

only soluble in organic solvents

a trigger for the immune response

both polar and nonpolar

Correct answer:

both polar and nonpolar

Explanation:

Amphipathic molecules have both a polar and nonpolar region. This amphipathic quality allows phospholipids to create the plasma membrane in eukaryotic cells. The polar region is the phosphate head, which interacts with the aqueous cytosol and extracellular environment. The nonpolar region is the fatty acid tail, which is sequestered in the bilayer of the membrane and helps reduce the permeability to certain molecules.

Example Question #3 : Identify Structure And Purpose Of Carbohydrates, Lipids, Proteins, And Nucleic Acids

Cholesterol is soluble in organic solvents such as chloroform, but is insoluble in water. Based on this information, to which class of macromolecule does cholesterol belong?

Possible Answers:

Enzyme

Oligosaccharide 

Nucleic acid

Lipid

Correct answer:

Lipid

Explanation:

Water is a very polar substance that will not interact well with nonpolar macromolecules. Enzymes (proteins), oligosaccharides (carbohydrates), and nucleic acids all contain polar regions that make them soluble in aqueous environments. Lipids, however, are hydrocarbons and generally lack a polar region. Lipids would not be soluble in water, but would be soluble in nonpolar organic solvents, like chloroform. We can conclude that cholesterol is a lipid.

Example Question #3 : Identify Structure And Purpose Of Carbohydrates, Lipids, Proteins, And Nucleic Acids

What would happen to a group of lipids in a polar solvent?

Possible Answers:

The lipids would precipitate out of the solvent

The lipids would group together

There is no way to predict what would happen

The lipids would interact readily with the solvent

Correct answer:

The lipids would group together

Explanation:

Lipids are composed of hydrocarbon chains and are very nonpolar. Polar solvents interact well with polar solutes, but do not solvate nonpolar solutes. When lipids are placed in a polar solvent, they will group together to minimize surface contact with the solvent. These droplets of lipids, or micelles, act like containers for the lipid, keeping them grouped together instead of being distributed through the solvent.

The lipids do not precipitate as they are not necessarily in a solid form. Even lipids in the liquid state can form micelles.

Example Question #4 : Identify Structure And Purpose Of Carbohydrates, Lipids, Proteins, And Nucleic Acids

What are the main components of a triglyceride?

Possible Answers:

A glycerol backbone and three fatty acids

A polar head group, a glycerol backbone, and three fatty acids

A sugar-phosphate backbone and three fatty acids

A cholesterol molecule, a glycerol backbone, and three fatty acids

Correct answer:

A glycerol backbone and three fatty acids

Explanation:

Triglycerides are made up of a glycerol backbone and three fatty acids. They are commonly used to store energy within cells.

A polar head group, a glycerol backbone, and three fatty acids very nearly describes a phospholipid (phospholipids only have two fatty acids). The other answers are not compounds that are readily observed in cells.

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