Select the statement that best describes a buffer.

A buffer resists change in pH by accepting hydrogen ions when acids are added to the solution and donating hydrogen ions when bases are added.

Water and ammonia interact to form hydrogen bonds, as represented in the figure.

The figure presents the molecular structure of water and ammonia as well as the interactions of these two molecules. The water molecule has two H atoms bonded with an O atom, which also has 2 pairs of nonbonding electrons. The ammonia molecule has three H atoms bonded with an N atom that also has 1 pair of nonbonding electrons. A dashed line is drawn between one H atom of the water molecule and the nonbonding pair of electrons in ammonia.

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.

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

the release of heat by the formation of hydrogen bonds

How would acidification of seawater affect marine organisms?

Acidification would decrease dissolved carbonate concentrations and hinder the growth of corals and shell-building animals

Figure 1 is a diagram of water molecules at the air-water interface at the surface of a pond.

The figure presents a diagram of the alignment of water molecules at an air-water interface. Four identical water molecules are shown just below the surface of the water, near the air-water interface. Each water molecule consists of one large atom and two smaller ones. A key indicates that the smaller atoms have a partial positive charge, and the larger atom has a partial negative charge. The water molecules are identically aligned at the surface of the water. For each water molecule, one of the smaller atoms with the partial positive change is situated at the bottom of the larger atom, toward the water below. Vertical dotted lines extend downward from these smaller atoms. For each water molecule, the other small atom with the positive partial charge is positioned at the upper right of the larger atom. The upper left side of the larger atom is shown to have a partial negative charge. Horizontal dotted lines are drawn between the upper portions of neighboring water molecules.

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.

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by

polar covalent bond

The diagram shows water molecules as solid ice at 0°C and as a liquid at 25°C.

The figure shows two diagrams. Each diagram consists of water molecules. The first diagram is labeled Ice. In this diagram, each water molecule is bonded to two other water molecules. The water molecules create adjacent hexagonal shapes. The second diagram is labeled Liquid Water. In this diagram several of the water molecules are bonded to two other water molecules, some are bonded to one other water molecule, and some water molecules are unbonded.

The arrangement of the water molecules in ice causes the ice to float. Explain how ice floating on the surface of a body of water affects the water in a way that is beneficial to the organisms in it.

The response indicates that the floating ice will reduce heat loss from the water below the ice, resulting in warmer water that is not likely to freeze to the bottom of the body of water.

The four main categories of large biological molecules present in living systems are _____.

proteins, nucleic acids, polysaccharides, and lipids

What is the chemical reaction mechanism by which cells make polymers from monomers?

dehydration reactions

The label on a container of margarine lists "hydrogenated vegetable oil" as the major ingredient. What is the result of adding hydrogens to vegetable oil?

The hydrogenated vegetable oil stays solid at room temperature.

The complexity and variety of organic molecules is due to

the chemical versatility of carbon atoms.

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.

Image result for 3 hexagons and 1 hectagon
What is the structure shown in the figure?

steroid molecule

Which of the following statements is true regarding the molecule illustrated in the figure?

Molecules of this type are usually liquid at room temperature.

Humans can digest starch but not cellulose because

humans have enzymes that can hydrolyze the α glycosidic linkages of starch but not the β glycosidic linkages of cellulose.

Which of the following is true regarding saturated fatty acids?

They are the principal molecules in lard and butter

A unknown solution had Benedict's reagent added to it and heated. The solution turned a burnt orange. This is evidence for the presence of_______.

glucose

Testosterone and estradiol are male and female sex hormones, respectively, in many vertebrates. In what way(s) do these molecules differ from each other?

Testosterone and estradiol have different functional groups attached to the same carbon skeleton.

Image result for two hexagons with hydroxide
What is the name of the bond connecting the two molecules in the above figure?

gylcosidic linkage.

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are the α form. Which of the following could amylase break down?

starch

Large organic molecules are usually assembled by polymerization of a few kinds of simple subunits. Which of the following is an exception to this statement?

a steroid

Which of the following is not a polymer?

glucose

Which of the following statements regarding carbon is false?

Carbon has the capacity to form polar covalent bonds with hydrogen.

The molecular formula for glucose is C6H12O6. What would be the molecular formula for a molecule made by linking three glucose molecules together by dehydration reactions?

C18H32O16

The characteristic that all lipids have in common is that _____.

none of them dissolves in water

Image result for triglyceride formation
What is the name of the bond (highlighted in red), that forms the resulting molecule in the above figure?

ester bond

how to tell if an amino acid is nonpolar?

If it contains no oxygen or sulfur

how to tell if an amino acid is polar?

if it contains oxygen or sulfur

how to tell if the bond between two amino acids is a hydrogen bonds?

if there is an oxgyen on one side and a hydrogen on the other. or if its a polar and nonpolar with no charge present.

how to tell if the bond between two amino acids is a hydrophobic interaction?

Two nonpolar amino acids with no charge present.

how to tell if the bond between two amino acids is a ionic bond?

connecting an acidic and basic amino acid. + and -

how to tell if the bond between two amino acids is a disulfide bond?

two sulfhydryl groups (-SH) connecting

how to tell if an amino acid is acidic?

if there is a - charge

how to tell if an amino acid is basic?

if there is a + charge