1.8 MC Answers and Review

⛔STOP!⛔ Before you look at the answers make sure you gave this practice quiz a try so you can assess your understanding of the concepts covered in unit 1. Click here for the practice questions: AP Biology Unit 1 Multiple Choice Questions.

Facts about the test: The AP Biology exam has 60 multiple choice questions and you will be given 1 hour 30 minutes to complete the section. That means it should take you around 22-23 minutes to complete 15 questions.*The following questions were not written by College Board and although they cover information outlined in the AP Biology Course and Exam Description the formatting on the exam may be different.

1.  Which statement best describes why water is a polar molecule?

A. Oxygen and hydrogen share electrons equally, creating partial positive and negative charges.

B. Oxygen and hydrogen form hydrogen bonds with each other and covalent bonds with other atoms.

C. Oxygen and hydrogen unequally share electrons which creates partial charges on oxygen and hydrogen.

D. The ionic bond between oxygen and hydrogen create partial charges on the molecule.

Answer: Oxygen is more electronegative than hydrogen so it attracts the electrons from the covalent bond more than hydrogen, giving oxygen a partially negative charge and hydrogen a partially positive charge. A polar molecule contains atoms that share electrons unequally. 

📄 Study AP Environmental Science, Unit 1.1: Structure of Water and Hydrogen Bonding

2.  Water molecules interact with one another through:

A. Covalent bonds

B. Hydrogen bonds

C. Ionic bonds

D. Intramolecular forces

Answer: Because of water's polarity, the partially negative oxygen atom of one water molecule can interact with the partially positive hydrogen of another water molecule. This interaction is a hydrogen bond. Intramolecular forces refer to the atom interactions with the atoms of one molecule. 

📄 Study AP Environmental Science, Unit 1.1: Structure of Water and Hydrogen Bonding

3.  Two students are arguing about which elements are most prevalent in living things. Which element symbols best summarize the elements commonly found in living things?

A. CHO

B. NPS

C. CON

D. CHNOPS

Answer: Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the most abundant elements in living organisms. Although CHO, NPS, and CON are true to an extent, the question asked for a summary of the elements found in living things, not a small example. 

📄 Study AP Environmental Science, Unit 1.2: Elements of Life

4.  Finish the analogy: Carbon: 4 bonds :: Hydrogen: ________

A. 1 bonds

B. 2 bond

C. 3 bonds

D. 4 bonds

Answer: Carbon atoms have four valence electrons and are most stable with 4 covalent bonds. Hydrogen has 1 electrons and can form 1 bond. 

📄 Study AP Environmental Science, Unit 1.3: Introduction to Biological Macromolecules

5.  A macromolecule has several chains containing carbon rings with one oxygen per ring. Which macromolecule must it be?

A. Lipid

B. Nucleic Acid

C. Carbohydrate

D. Protein

Answer: Carbon chains and rings are present in both carbohydrates and lipids, but lipids do not contain successive carbon rings with oxygens.  

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6. Which statement best explains why water molecules adhere to other surfaces?

A. Water can make hydrogen bonds with other water molecules.

B. The polarity of water allows it to bind covalently to other surfaces.

C. Water can only bind to surfaces that are nonpolar.

D. As a polar molecule, water is attracted to other polar substances.

Answer: Polarity refers to the unequal distribution of charge within the water molecule. Because of this, it is more easily attracted to other surfaces.

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7.  If 10 monomers join to form a polymer through the process of dehydration synthesis, how many water molecules form?

A. 9

B. 10

C. 11

D. Not enough information to answer

Answer: When 10 monomers connect, only 9 bonds are formed. Each bond required the formation of 1 water molecule.  

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

8.  Which pair of monomor: macromolecule is incorrect?

A. monosaccharide: carbohydrate

B. amino acid: nucleic acid

C. glycerol/fatty acid: lipid

D. nucleotide: nucleic acid

Answer: Monomers can combine to form polymers. Amino acids build protein, not nucleic acids. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

9.  What gives DNA its negative charge?

A. The nitrogenous base

B. The pentose sugar

C. The nucleotide

D. The phosphate group

Answer: Each phosphate group within the nucleotide of a DNA molecule has one negatively charged oxygen molecule. Because of this, the entire strand of DNA has an overall negative charge. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

10.  Protein folding is essential to proper protein function. Which level of folding is incorrectly paired with it's description?

A. primary: string of amino acids connected by peptide bonds

B. secondary: hydrogen and covalent bonds between R groups

C. tertiary: interactions between R groups

D. quaternary: interaction with more than 1 polypeptide

Answer: The secondary level of folding is limited to local folding between adjacent amino acids where hydrogen bonds mainly form between amine hydrogens and carbonyl oxygens. Interactions between R groups can be seen during tertiary folding. 

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11.  Every amino acid consists of:

A. an amine group, R-group, and a central carbon

B. a hydroxyl side chain, a central carbon with R-group, carboxyl group

C. an amine group, a central carbon with a variable R group, and carboxyl group

D. a phosphate, pentose sugar, and nitrogenous base

Answer: The name amino acid helps define the structures found within. An amine group and a carboxyl group are bound to a central carbon with a unique R group. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

12.  Students running a food analysis lab find that a food particle contains carbon, hydrogen and nitrogen. To which macromolecule group does it belong?

A. Carbohydrate

B. Protein

C. Lipid

D. Nucleic Acid

Answer: Carbohydrates and lipids do not contain nitrogen. Nucleic acids do contain nitrogen, but also contain phosphorus from their phosphate group in the nucleotide. Amino acids (the monomer of proteins) contain nitrogen in the amine group. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

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13.  The structure of biological molecules determines how they behave. In a cell's plasma membrane the saturation of carbon found in the fatty acid tails can change membrane flexibility. Which statement best explains this?

A. Unsaturated fatty acids have C-C double bonds creating bends in the fatty acid tails.

B. Saturated fatty acids have C-C double bonds creating bends in the fatty acid tails.

C. The presence of cholesterol increases the space between phospholipids, creating a more flexible membrane.

D. When carbon's a fully saturated the carbon chain does not have double bonds, creating a more flexible membrane.

Answer: The hydrocarbon chain in a fatty acid can contain carbons that are fully saturated by 4 bonds, or unsaturated meaning we see C-C double bonds. They are not fully "saturated" over covered with hydrogens. When the chain is unsaturated, the fatty acid tails are bent. These bends increase the space between the phospholipids, creating a more flexible membrane. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

14.  As a double stranded helix, each nucleotide within a DNA molecule displays base pairing between nitrogenous bases. Which statement best describes the correct base pair and number of hydrogen bonds between them?

A. Adenine and thymine pair with two hydrogen bonds

B. Adenine and thymine pair with three bonds

C. Cytosine and Guanine pair with two bonds

D. All four bases can pair and make two bonds

Answer: Due to the specific molecular structure of adenine and thymine, they are only capable of forming two hydrogen bonds, while guanine and cytosine form three bonds. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

15.  Two of the four biological macromolecules display directionality and functions that rely on specific sequences of monomers. Identify the correct pair:

A. Proteins and Carbohydrates

B. Proteins and Nucleic Acids

C. Nucleic Acids and Lipids

D. Carbohydrates and Lipids

Answer: Nucleic acids are composed of a linear sequence of nucleotides with a 5' end and 3' end. The specific sequence of nucleotides determines the specific sequence of amino acids that will be built during protein synthesis. Proteins display directionality as the linear sequence of amino acids have an amine terminus on one side and a carboxyl terminus on the other. 

📄 Study AP Environmental Science, Unit 1.1: Introduction to Ecosystems

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