AP Bio Unit 1 MCQ Review

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

As water exits the leaf, hydrogen bonding pulls more water molecules up through the leaf and xylem by cohesion.

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. -This is a description of dehydration synthesis, which joins multiple monosaccharides to create a polysaccharide and produces water (H2O) molecules.

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 -By breaking bonds Y and Z at the same time, the cytosine nucleotide could be removed from the DNA molecule and replaced with an undamaged cytosine without changing the biological information stored in the DNA.

Figure 1. Molecule 1 represents RNA, and molecule 2 represents DNA. 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.

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. -Without the enzyme B produced by microorganisms in their digestive tract, cellulose would pass through the digestive tract without being digested.

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 -RNA contains ribose, whereas DNA contains deoxyribose. A ribose sugar has an −OH group linked to the 2′ carbon that a deoxyribose sugar does not have

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

Due to having nonpolar R-groups, 10 of the 20 amino acids are hydrophobic. Interactions between hydrophobic amino acids play an important role in determining protein structure and function.

Figure 1 shows 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 figure indicates that one of the nucleotides is thymine. Thymine is found in DNA and not in RNA.

Phosphorous (P) is an important nutrient for plant growth. Figure 1 shows Arabidopsis thaliana plants grown under phosphorus‐sufficient (left) (much taller) and phosphorus‐starved (right) (much smaller) conditions for six weeks. most likely reason for the difference in leaf growth?

Phosphorus is used to make nucleic acids and certain lipids. Without phosphorus atoms, nucleic acids and lipids cannot be made for the plant to use for growth.

Different polysaccharides are used by plants for energy storage and structural support. The molecular structures for two common polysaccharides are shown in Figure 1. Starch is used by plants for energy storage, and cellulose provides structural support for cell walls. The monomer used to construct both molecules is glucose. photo A study determined the effect of two different digestive enzymes, A and B, on these two polysaccharides. Table 1 presents the data from the study. Table 1. Effect of Enzymes A and B on Cellulose and Starch Test Tube Polysaccharide Added Enzyme Added Glucose Detected after 5 Minutes at 37°C 1 Cellulose A No 2 Cellulose B Yes 3 Starch A Yes 4 Starch B no 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.

Based the information provided, which of the following statements best describes why starch and cellulose provide different functions in plants?

The differences in the assembly and organization of the monomers of these two polymers result in different chemical properties. -The identical orientations of the glucose monomers in starch create a polysaccharide with alpha bonds that is easy to break down into glucose for energy use. The alternating orientations of the glucose monomers in cellulose create beta bonds that produce a rigid polymer that is difficult to digest for energy use.

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.

layer of ice 0 degree C, air -5 degree C, water 4 degree C 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 statement best describes the observed relationship between atmospheric CO2 enrichment and plant growth under ideal and stressed conditions? -In ideal conditions: standard CO2 environment (400 ppm CO2) or in an enriched CO2 environment (700 ppm) plants grew more while in stressed conditions plants did not -measured by total dry weight of plant per g

the increase in atmospheric CO2 resulted in a greater increase in plant growth under stressed conditions than under ideal conditions.

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

The linear sequence of the base pairs

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

The monomers of the two reactions illustrated are joined by covalent bonds with the production of a water molecule.