unit test- AP BIO

The unique properties of water make life possible on Earth. Approximately three-quarters of the Earth's surface is covered by water. Cells are made up of around 70-95% water. Water comprises roughly 70% of the human body. ANSWER ONLY ONE OF THE FOLLOWING (please indicate which one you're answering; put 1 or 2). (1) Explain the properties of water that enable it to travel up through the roots and stems of plants to reach the leaves. OR (2) Explain why the temperature of the oceans can remain relatively stable and support vast quantities of both plant and animal life, when air temperature fluctuates so significantly throughout the day or over the seasons.

(1) Osmosis, cohesion, adhesion and transpiration of water allow for movement through plants. Osmosis is movement of water from the soil to the roots (from high to low water concentration). Cohesion is the attraction of water molecules to each other due to hydrogen bonding between the oxygen and hydrogen atoms of two water molecules. Adhesion is the attraction of water molecules to other hydrophilic materials, such as the glass in test tubes (forming a meniscus), or along the cellulose walls of the xylem tubes in vascular plants. Cohesion and adhesion form an attraction called capillary action. This allows for movement of water from roots to the xylem tubes of plants, and up, against the force of gravity. Transpiration, or the evaporation of water from plant leaves provides an additional pull of water up the plant from roots to leaves. As a result, water and nutrients are transported from the roots, to the leaves.

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.

How would acidification of seawater affect marine organisms?

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

Water is an excellent solvent. Select the property that justifies this statement.

As a polar molecule, it can surround and dissolve ionic and polar molecules.

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

Which of the following statements regarding carbon is false?

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

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

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

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.

how to tell if an amino acid is nonpolar?

If it contains no oxygen or sulfur

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

It forms hydrogen bonds.

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

Molecules of this type are usually liquid at room temperature.

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.

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.

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.

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. Explain why the arrangement of water molecules is different in ice and water.

The response indicates that as water cools, the water molecules slow down and, as a result, the hydrogen bonds between them become more stable. Hence, as ice forms the hydrogen bonds cause the water molecules to space out in a crystalline form. Since the liquid water molecules are at a greater temperature, the molecules are moving more rapidly and are constantly forming and breaking their hydrogen bonds.

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 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. Describe why water molecules are polar and why hydrogen bonds form between water molecules.

The response indicates that the slightly negatively charged O atom in one water molecule is attracted to one of the slightly positively charged H atoms in another water molecule, so that a weak hydrogen bond forms between the two water molecules. The response explains that the strong electronegativity of O pulls the electrons shared with each H atom within a single water molecule toward the O atom, concentrating more negative charge at the O end of the molecule and giving the H atoms a slight positive charge

Which of the following is true regarding saturated fatty acids?

They are the principal molecules in lard and butter

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

Two nonpolar amino acids with no charge present.

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

If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal?

a surface made with carbon and hydrogen atoms covalently bonded together

Why did the bear melt when it jumped into the lake?

because its a polar bear

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

connecting an acidic and basic amino acid. + and -

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

dehydration reactions

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

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

Which of the following is not a polymer?

glucose

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

gylcosidic linkage.

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.

how to tell if an amino acid is polar?

if it contains oxygen or sulfur

how to tell if an amino acid is basic?

if there is a + charge

how to tell if an amino acid is acidic?

if there is a - charge

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

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

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

none of them dissolves in water

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

polar covalent bond

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

proteins, nucleic acids, polysaccharides, and lipids

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

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

steroid molecule

One of the buffers that contributes to pH stability in human blood is carbonic acid (H2CO3). Carbonic acid is a weak acid that dissociates into a bicarbonate ion (HCO3-) and a hydrogen ion (H+). Thus, H2CO3 ↔ HCO3- + H+ If the pH of the blood drops, one would expect

the HCO3- to act as a base and remove excess H+ with the formation of H2CO3.

The complexity and variety of organic molecules is due to

the chemical versatility of carbon atoms.

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

two sulfhydryl groups (-SH) connecting