Biology Unit 1 Exam

Which of the following statements best describes how molecules released by the fish become nutrients for the plants?

The ammonia molecules released by the fish are converted by the bacteria to nitrates, which are used by the plants to make proteins and nucleic acids.

DNA and RNA are nucleic acids that can store biological information based on the sequence of their nucleotide monomers. Figure 1 shows a short segment of each of the two types of nucleic acids. Which of the following best describes a structural difference between DNA and RNA?

The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose.

Which of the following best describes how amino acids affect the tertiary structure of a protein?

The interactions of the different R -groups with other R -groups and with their environment determine the tertiary structure of the protein.

Two groups of students attempted to re-create the primitive atmospheric conditions of early Earth using the apparatus represented below. Each group ran the experiment with different gas mixtures in the apparatus. Which of the following statements best justifies the claim that the conditions in at least one of the experiments could generate the molecular building blocks essential for life?

The nitrogen (N2 ) gas and ammonia (NH3 ) gas in experiment 1 could provide the elemental nitrogen required for the formation of amino acids.

Water and ammonia interact to form hydrogen bonds, as represented in the figure. Which statement best helps explain the formation of the hydrogen bond represented in the figure?

The nitrogen has a partial negative charge, and the hydrogen attached to the oxygen has a partial positive charge.

The synthesis of protein or carbohydrate polymers always produces which of the following as a byproduct?

Water

Which of the following statements best describes how organisms such as rabbits obtain the carbon necessary for building biological molecules?

Rabbits eat plants and break down plant molecules to obtain carbon and other atoms that they rearrange into new carbon-containing molecules.

Which of the following is an accurate description of the process shown in Figure 1 ?

The formation of a covalent peptide bond in a dehydration synthesis reaction

(Figure 1. Formation of a peptide bond) Which of the following best describes the formation of the bond shown in Figure 1 ?

A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O.

Which of the following correctly illustrates a dipeptide and an amino acid in the optimal position to form a tripeptide?

Answer A

Which of the following best depicts the tertiary structures of the two proteins in water? The diagrams in the options are not drawn to the same scale as those in Figure 1 and Figure 2.

Answer A (the protein would fold so that the hydrophobic portions would be toward the center of the tertiary structure)

(Plant and Fish Diagram) Which of the following graphs is the most appropriate representation of the experimental results documented in the table?

Answer B (Bar Graph)

Which of the following best represents the DNA of the two daughter cells produced when a bacterial cell with this particular mismatch replicates its DNA and divides?

Answer C (Mutant=A,T Normal=G,C)

Both myoglobin and hemoglobin are proteins that bind reversibly with molecular oxygen. The graph below shows the oxygen-binding saturation of each protein at different concentrations of oxygen. Which of the following statements is correct?

At 40 mm Hg partial pressure, myoglobin has a greater affinity for oxygen than hemoglobin has.

Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?

Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.

Bacteriophages are viruses that infect bacteria. In an experiment, bacteriophages were labeled with either radioactive phosphorus or radioactive sulfur. The labeled bacteriophages were incubated with bacteria for a brief amount of time and then removed. The infected bacteria cells were found to contain significant amounts of radioactive phosphorus but not radioactive sulfur. Based on the results of the experiment, which of the following types of molecules did the bacteriophages most likely inject into the bacteria cells?

DNA

Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond. Based on Figure 1, which of the following best describes how the properties of water at an air-water interface enable an insect to walk on the water's surface?

Hydrogen bonds between molecules at the surface of the water provide surface tension, which allows the water surface to deform but not break under the insect.

Which of the following is responsible for the cohesive property of water?

Hydrogen bonds between the oxygen atom of one water molecule and a hydrogen atom of another water molecule

Which of the following is most directly responsible for water's unique properties?

It forms hydrogen bonds.

Polypeptides are continuously being formed and degraded. One of these processes is shown. Which statement is the most accurate description of the reaction shown in Figure 1?

It represents a polypeptide chain that is broken down through a hydrolysis reaction.

The CFTR protein is made up of 1,480 amino acids linked together in a chain. Some humans produce a version of the CFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain. Which of the following best predicts how the amino acid deletion will affect the structure of the CFTR protein?

It will affect the primary, secondary, and tertiary structures of the CFTR protein.

This group of questions refers to the following groups of biological compounds. (A) Proteins (B) Carbohydrates (C) Nucleic acids (D) Lipids (E) Steroids Used to carry the genetic code

Nucleic Acids

Which of the following conclusions is most clearly supported by the representations of nucleic acid #1 and nucleic acid #2 ?

Nucleic acid #1 contains adenine-thymine base pairs, whereas nucleic acid #2 does not.

The carbohydrates glucose, galactose, and fructose have the same chemical formula (C6H12O6) but different structural formulas, as represented in the figure. Which of the following statements about glucose, galactose, and fructose is most likely true?

The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms.

Which of the following best describes the effect of a greater number of cysteine amino acids on the stability of the proteins?

The change leads to increased protein stability because of an increased number of S-S bonds in the tertiary structure of the proteins.

Which of the following best describes the structures of carbohydrates?

They occur as monomers, chains of monomers, and branched structures.

A feature of organic compounds NOT found in inorganic compounds is the presence of

carbon atoms covalently bonded to each other