AP Biology

Which of the following best describes water's ability to dissolve certain substances such as glucose, but remain separate from other substances such as oils?

• Water molecules are polar, consisting of two partially positive hydrogen atoms, and one partially negative oxygen atom.

• Water molecules can only form ionic bonds with polar molecules, such as glucose.

• Due to hydrogen bonding, water is more dense as a liquid than a solid.

• Water has an overall negative charge, which allows it to easily dissolve nonpolar substances like glucose.

Which of the following examples explains how biological activity relies on water's adhesive properties?

• Water travels through vascular tissue (xylem) from the roots to the leaves of a plant.

• Stomata (openings) in leaves control transpiration of water out of the leaf as water vapor.

• Vacuoles in plant cells swell as water dilutes the contents of the vacuole.

• Feathers retain an oily coating that repels water droplets.

Given the structure of water (H₂O), which of the following must be true?

• Each water molecule can form four hydrogen bonds.

• Each water molecule will form covalent bonds with its neighbors.

• Water has an overall negative charge.

• Water is able to easily dissolve nonpolar substances.

Which of the following describes a covalent bond?

• It involves an atom that gains an electron.

• Two or more atoms share electron pairs.

• Molecules linked by covalent bonds are less dense when in solid form than when in liquid form.

• A hydrogen atom with a partial positive charge is attracted to another atom with a partial negative charge.

Which of the following statements regarding carbon is FALSE?

• Carbon has the capacity to form single and double bonds.

• Carbon has the ability to bond together to form extensive branched or unbranched "carbon skeletons."

• Carbon has the ability to bond with up to six other atoms.

• Carbon has a tendency to form covalent bonds.

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NGSS.HS-LS1-6

NGSS.HS-PS1-1

Which of the following best describes the role that water plays in the reaction depicted here?

• Water catalyzes the formation of a covalent bond in the dimer through hydrolysis.

• When water condenses out of the reaction, a dimer is created as a covalent bond forms between two monomers.

• When water combines with the two monomers, a dimer forms.

• Water is an input of the reaction, leading to the formation of a covalent bond in the dimer product.

Which of the following questions would a researcher most likely ask if they wanted to know whether a hydrolysis reaction or a dehydration synthesis reaction is occurring?

• Are the monomers identical to one another?

• Is an enzyme involved in the reaction?

• Which polymer is involved in the reaction?

• Is water a reactant or product of the reaction?

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NGSS.HS-LS1-6

Lactose is a dimer sugar composed of two monomeric subunits (galactose and glucose). In an investigation, researchers placed intestinal cells in a nutrient medium containing lactose. The researchers determined that the lactose had broken down to galactose and glucose in the manner depicted in the reaction shown here.

The cells were then modified and re-exposed to the lactose medium. The researchers were no longer able to detect the presence of galactose and glucose. Which of the following conclusions best explains an outcome of this modification?

• The cells were unable to hydrolyze lactose, resulting in the formation of a covalent bond between galactose and glucose.

• The cells were unable to hydrolyze the lactose dimer into its monomeric subunits.

• The cells were able to perform dehydration synthesis reactions in order to break down lactose into its monomeric subunits.

• The cells were able to undergo a reverse reaction and build lactose.

A researcher wants to identify a newly isolated DNA strand. The first step in identifying the DNA strand is to measure its length. To do this, the researcher wants to develop a fluorescent tag that emits light once it binds to both ends of the strand.

Which of the following best describes how the researcher should develop a fluorescent tag with an ability to bind to both ends of the strand?

• The tag should have an affinity to bind only guanine (G) and cytosine (C) nitrogenous bases.

• The tag should have an affinity to bind only free amino (-NH₂) and carboxyl (-COOH) functional groups.

• The tag should have an affinity to bind only adenine (A) and thymine (T) nitrogenous bases.

• The tag should have an affinity to bind only free 3' hydroxyl (-OH) and 5' phosphate (-PO₄) functional groups.

The image depicts how the bacterial protein barnase undergoes modifications that involve changing its conformation, or shape. In order to function in the cell, barnase has to be folded from a nonfunctional conformation into a functional conformation.

• The functional conformation of barnase has a tertiary structure because it consists of a polypeptide chain folded into a three-dimensional shape.

• The functional composition of barnase has a quaternary structure because it consists of interactions between multiple polypeptide units.

• The functional composition of barnase has a secondary structure because it consists of a single alpha-helix.

• The functional composition of barnase has a primary structure because it consists of a linear chain of amino acids.

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NGSS.HS-LS1-1