Research Methods Unit 1

Which of the following best describes a structural similarity between the two molecules shown in Figure 1 that is relevant to their function?

Both molecules contain nucleotides that form base pairs with other nucleotides, which allows each molecule to act as a template in the synthesis of other nucleic acid molecules. D

Which of the following is common feature of the illustrated reactions showing the linking of monomers to form macromolecules?

Monomers are joined by a covalent bond, and a water molecule is produced.

Water molecules are polar covalent molecules. There is a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms due to the uneven distribution of electrons between the atoms, which results in the formation of hydrogen bonds between water molecules. The polarity of water molecules contributes to many properties of water that are important for biological processes. Which of the following models best demonstrates the arrangement of hydrogen bonds between adjacent water molecules?

. The hydrogen bonds between these water molecules correctly show the attractive force between the hydrogen atom of one water molecule and the oxygen atom of the adjacent water molecule.

Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Which of the following best describes the process that adds a monosaccharide to an existing polysaccharide?

A specific enzyme removes the hydrogen (H) from the monosaccharide and the hydroxide (OH) from the polysaccharide, creating a bond between the two and creating a water (H2O) molecule.

The picture includes a carbon and nitrogen atom bonding to form a peptide bond

A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O. Correct. Even though the water molecule that is produced is not shown in Figure 1, it shows the formation of the peptide bond and the missing H and OH.

Amylase is an enzyme that converts carbohydrate polymers into monomers. Glycogen synthase is one of the enzymes involved in converting carbohydrate monomers into polymers. Which of the following best explains the reactions of these enzymes?

Amylase aids in the addition of a water molecule to break covalent bonds whereas glycogen synthase aids in the removal of a water molecule to form covalent bonds. Correct. Amylase breaks bonds in polymers (hydrolysis) and glycogen synthase forms bonds between monomers (dehydration synthesis). Water is added to break bonds and removed to form them.

Which statement describes how water is pulled up through the xylem to the leaves of the plant?

As water exits the leaf, hydrogen bonding between water molecules pulls more water up from below.

Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature? The picture includes a Linoleic acid (contains carbon-carbon double bonds and is bent) and a palmitic acid ( contains no carbon-carbon double bonds and is not bent)

Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature? Palmitic acid is a saturated fatty acid. The absence of carbon-carbon double bonds in palmitic acid allows the molecules to pack closely together and form a solid at room temperature.

Figure 1 represents a segment of DNA. Radiation can damage the nucleotides in a DNA molecule. To repair some types of damage, a single nucleotide can be removed from a DNA molecule and replaced with an undamaged nucleotide. Which of the four labeled bonds in Figure 1 could be broken to remove and replace the cytosine nucleotide without affecting the biological information coded in the DNA molecule?

Bonds Y and Z at the same time

Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Which of the following would most likely occur if cattle lost the ability to maintain a colony of microorganisms in their digestive tract?

Cattle would no longer be able to use cellulose as a primary source of glucose.

A student wants to modify model 1 so that it represents an RNA double helix instead of a DNA double helix. Of the following possible changes, which would be most effective in making model 1 look more like RNA than DNA?

Changing the deoxyriboses to riboses by adding −OH groups

A researcher measured the temperature at which two different samples of double-stranded DNADNA denature (separate into single strands). Sample 11 denatured at a significantly lower temperature than sample 22 did. Based on the data, the researcher claims that the DNADNA in sample 22 is composed of a higher percentage of guanine and cytosine than the DNADNA in sample 11 is. Which of the following best supports the researcher's claim?

Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between them than adenine-thymine pairs do. Three hydrogen bonds form between guanine and cytosine, while only two hydrogen bonds form between adenine and thymine.

Which of the following best explains why a cell's plasma membrane is composed of two layers of phospholipids rather than just a single layer?

Having two oppositely oriented layers of phospholipids allows only the hydrophilic heads to interact with water inside and outside of the cell. Phospholipids are oriented so the hydrophilic heads are on the membrane exterior and can interact with water inside and outside of the cell. The hydrophobic tails in the middle of the membrane create a protective barrier for the cell.

The modeled DNA triple-helix structure that can form in areas with multiple GAA triplets Which of the following types of bonds is most likely responsible for the unusual base pairing shown in Figure 3 that results in the formation of a triplex DNA structure?

Hydrogen Hydrogen bonds form between the bases on complementary strands of DNA.

Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond. Figure 1. Alignment of water molecules at air-water interface 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. Answer D Correct. Hydrogen bonds form between water molecules due to the partial charges produced as a result of the polarity of the water molecule. The strength of the attraction between the water molecules allows organisms to walk across the surface without breaking the hydrogen bonds.

Figure 1 shows a short segment of a double-stranded nucleic acid molecule. Figure 1. A short segment of a double-stranded nucleic acid molecule Which of the following statements is correct about the molecule shown in Figure 1 ?

It is DNA because of the nucleotides present.

The picture represents a peptide bond breaking

It represents a polypeptide chain that is broken down through a hydrolysis reaction. The reaction shows the polypeptide being split into two smaller units with the addition of a hydroxide ion and a hydrogen ion from water. This facilitates the breaking of the bond holding the polypeptide together.

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. A change in the primary structure of the CFTR protein will lead to changes in the secondary and tertiary structures. As a result, the protein will not fold properly and will not function normally.

The amino acid in Figure 1 is found in a region of a polypeptide that folds away from water. Which part of the amino acid most likely contributes to the hydrophobic behavior of this region of the polypeptide?

Methyl (CH3CH3) group The methyl group is one of the functional groups that differentiate the twenty amino acids found in proteins. Since the methyl group is nonpolar, it is likely to make this region of the polypeptide more hydrophobic.

Scientists examined the folded structure of a purified protein resuspended in water and found that amino acids with nonpolar R groups were primarily buried in the middle of the protein, whereas amino acids with polar R groups were primarily on the surface of the protein. Which of the following best explains the location of the amino acids in the folded protein?

Nonpolar R groups that cannot form hydrogen bonds with water are pushed into the middle of the protein.

This group of questions consists of five lettered headings followed by a list of phrases or sentences. For each phrase or sentence, select the one heading to which it is most closely related. Each heading may be used once, more than once, or not at all. 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 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. Rabbits break down the plant molecules to obtain the individual atoms or small molecules that can be built into larger, complex biological molecules.

Students conducted a controlled experiment to investigate whether sawdust provides enough nutrients to support plant growth. The students separated ten nearly identical sunflower seedlings into two groups. They grew the seedlings in the first group in potting soil and the seedlings in the second group in sawdust composed mostly of cellulose. After twenty days, the students recorded observations about the seedlings in each group. The students' observations are presented in the table.

Sawdust will not provide sufficient amounts of nitrogen and phosphorus, resulting in the seedlings having a reduced ability to produce both of the monomers shown (amino acids and nucleotides).

Which of the following describes a key difference among the 20 amino acids that are used to make proteins? A

Some amino acids are hydrophobic.

Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Based on Figure 1, which of the following best compares the atomic structures of starch and cellulose?

Starch and cellulose are composed of repeating glucose monomers; however, in cellulose every other glucose monomer is rotated 180 degrees.

Figure 1 shows three amino acids that are part of a polypeptide chain. Figure 2 shows the same section of the chain after a mutation has occurred. How might this change affect the structure and function of the protein?

The R-group of the new amino acid, valine, has different chemical properties than the R-group of cysteine. This will cause the protein to misfold and not function properly in the cell.

As shown in Figure 1, an amino acid must have which of the following properties in order to be incorporated into a polypeptide?

The ability to form a covalent bond with both its NH2 group and its COOH group

Which of the following best describes the hydrolysis of carbohydrates?

The addition of a water molecule breaks a covalent bond between sugar monomers. Correct. The hydrolysis of carbohydrates involves the addition of a water molecule, which breaks the covalent bond between monomers.

The figure shows a model of the exchange of matter between the organisms that live together in an aquarium. The model includes matter exchange between plants, fish, and bacteria. The bacteria are represented as rod-shaped organisms living in the gravel at the bottom of the aquarium. 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. Correct. As shown in the figure, the ammonia molecules released by the fish are converted by the bacteria to nitrites and nitrates. The plants absorb the nitrates, which are nitrogen-containing nutrients that the plants use to make the amino acids and nucleotides needed for building proteins and nucleic acids.

The following is a food web for a meadow habitat that occupies 25.6 km2. The primary producers' biomass is uniformly distributed throughout the habitat and totals 1,500 kg/km2. Developers have approved a project that will permanently reduce the primary producers' biomass by 50 percent and remove all rabbits and deer. Which of the following is the most likely result at the completion of the project?

The biomass of coyotes will be dramatically reduced. This option is correct. It demonstrates an understanding of the components of a food web and interactions between all of the participants. Coyotes prey on deer and rabbits, and if developers remove them, coyotes will lose their primary source of nutrition/energy. With this loss of nutrition/energy they will experience a decrease in reproductive success and therefore a significant decline in their population.

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

The carbohydrates have different properties because they have different arrangements of carbon, hydrogen, and oxygen atoms. Compounds that have the same chemical formula but different structural formulas usually have different properties.

Researchers compared similar proteins from related organisms in different habitats. They found that the proteins from organisms living in harsh environments had a greater number of cysteine amino acids than did proteins from organisms not living in harsh environments. The structure of cysteine is shown. Bonds can form between the sulfur atom of different cysteine amino acids (S-SS-S bonds). Figure 1. Chemical structure of cysteine 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-SS-S bonds in the tertiary structure of the proteins. An increased number of S-SS-S bonds are possible with the addition of more cysteine in the proteins. The S-SS-S covalent bonds should add more structural stability to the proteins.

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

The correct answer includes the image with a carbon on one end of an amino acid and a hydrogen on the end of another facing each other. When two amino acids are positioned so that the carboxyl group of one amino acid backbone is adjacent to the amine group of another amino acid backbone, they can join by a dehydration reaction.

Mammals do not produce digestive enzyme B. However, sheep and cattle are two types of mammals that contain microorganisms in their digestive tract that produce enzyme B. Which of the following statements best describes the different functions of starch and cellulose in plants?

The differences in the assembly and organization of the monomers of these two polymers result in different chemical properties.

Picture includes a biolgocial reaction in which amino acids are bonded

The formation of a covalent peptide bond in a dehydration synthesis reaction This reaction combines two smaller amino acids to form a dipeptide (a step in the formation of a protein) with the release of water. The presence of nitrogen is consistent with both amino acids and proteins. The combining of smaller molecules to form a larger molecule with the release of water is a dehydration synthesis reaction.

A small protein is composed of 110 amino acids linked together in a chain. As shown in Figure 1, the first and last five amino acids in the chain are hydrophobic (have nonpolar and uncharged RR-groups), whereas the remaining 100 amino acids are hydrophilic (have charged or polar RR-groups). The nature of the RR-group determines if the amino acid is hydrophobic or hydrophilic. A mutation results in the production of a version of the small protein that is only 105 amino acids long, as shown in Figure 2. Five of the hydrophobic amino acids are missing from one end of the chain.

The hydrophilic middle of the protein chain would be attracted to the water molecules, and the hydrophobic ends would be repelled. Hydrophobic portions of proteins in water tend to be found near the center of the tertiary structure, as far from the water as possible.

Based on the figure, which statement best describes the observed relationship between atmospheric CO2CO2 enrichment and plant growth under ideal and stressed conditions?

The increase in atmospheric CO2CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.

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

The interactions of the different RR-groups with other RR-groups and with their environment determine the tertiary structure of the protein. The tertiary structure is determined by the attractions, repulsions, and bonding between different amino acids. Changing the sequence of even two amino acids may affect the tertiary shape of the protein.

Which feature of model 1 best illustrates how biological information is coded in a DNADNA molecule?

The linear sequence of the base pairs

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 greater electronegativity of oxygen and nitrogen compared with hydrogen makes for unequal sharing of electrons, which results in partial negative charges associated with the oxygen and nitrogen atoms and partial positive charges associated with the hydrogen atoms in both molecules. The attraction between opposite charges results in the formation of the hydrogen bond represented in the figure.

Which of the following is the most likely reason for the difference in leaf growth?

The phosphorus-starved plant was unable to synthesize both the required nucleic acids and lipids, limiting growth.

A mutation in the gene coding for a single-polypeptide enzyme results in the substitution of the amino acid serine, which has a polar R group, by the amino acid phenylalanine, which has a nonpolar R group. When researchers test the catalysis of the normal enzyme and the mutated enzyme, they find that the mutated enzyme has much lower activity than the normal enzyme does.

The substitution altered the secondary and tertiary structure of the enzyme so that the mutated enzyme folds into a different shape than the normal enzyme does.

As shown in the diagram, when environmental temperatures drop below freezing, a layer of ice typically forms on the surface of bodies of freshwater such as lakes and rivers. Which of the following best describes how the structure of ice benefits the organisms that live in the water below?

The water molecules in ice are farther apart than those in liquid water, so the ice floats, maintaining the warmer, denser water at the lake bottom.

Which of the following best describes the structures of carbohydrates?

They occur as monomers, chains of monomers, and branched structures. Carbohydrates occur in many forms. Glucose is an example of a monomer, sucrose is a chain of two carbohydrate monomers, and starch is an example of a carbohydrate with a branched structure.

Ultraviolet (UVUV) radiation can damage DNA by breaking weak bonds. Which of the following best explains how this occurs?

UV radiation disrupts the double helix structure by breaking the hydrogen bonds between the nitrogenous base pairs. Hydrogen bonds, like those found between nitrogenous base pairs, are weaker than covalent bonds and are easily broken by UV radiation.

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

Water