Keystone Review Molecules of Life

The opening of the stomata allows water to evaporate from inside the leaf in a process known

as transpiration. As this occurs, water molecules cling to one another and pull water in a

continuous stream up the stem of the plant from the roots to the leaves. Which property of

water makes this movement possible?

• Cohesion

• Freezing point

• Specific heat

• temperature-dependent density

Cells are largely made of organic compounds that contain carbon. Which property of the

carbon atom makes it an essential component of organic compounds?

• Carbon is a nonmetal

• Carbon oxidizes to carbon dioxide

• Carbon is solid at room temperature.

• Carbon can form four covalent bonds

Which statement best describes the event shown in the diagram?

• Glucose is being synthesized in the chloroplast using nitrogen from plants

• Amino acid monomers are joining together to form a protein macromolecule

• A polymer in the nucleus is being broken into its individual monomer subunits

• Lipid molecules are forming fatty acid chains in a dehydration synthesis reaction

Tags

NGSS.HS-LS1-6

Which characteristic allows carbon atoms to form chains and rings with other carbon atoms?

• Carbon has several forms

• Carbon can form four covalent bonds

• Carbon is the fourth most abundant element in the universe

• Carbon is a structural part of lipids, carbohydrates, proteins, and nucleic acids.

Many plants have a waxy coating on their leaves. Which statement describes the most likely

structure and function of the waxy coating?

• The waxy coating is a protein that can help attract other organisms for pollination.

• The waxy coating is a protein that can help release waste molecules during transpiration.

• The waxy coating is a lipid that can help absorb more sunlight in hot environments

• The waxy coating is a lipid that can help prevent excess water loss in dry environments

The enzyme pepsin is found in the stomach. Which medicine is most likely to directly interfere

with pepsin’s function?

• a medicine that affects pH

• a medicine that prevents clotting

• a medicine that blocks neural impulses

• a medicine that lowers cholesterol levels

Cellulose is a carbohydrate and a polymer of glucose. Which statement best describes how

cellulose is formed within living organisms?

• It is assembled by bonding individual atoms

• It is constructed by connecting smaller monomer subunits.

• It is the product of the decomposition of a much larger molecule

• It is the result of a physical change that alters the shape of a compound.

Tags

NGSS.HS-LS1-6

The diagram models how a poison bonds to the active site of an enzyme. Which

function is the enzyme most likely unable to perform because of the attachment of

the poison molecule?

• the release of stored chemical energy

• the donation of electrons to the substrate

• the supply of activation energy for a reaction

• the catalysis of the reaction with the substrate

The graph shows how the activity of an enzyme changes at different temperatures.

Which statement best describes what happens to the enzyme when the temperature

of the reaction increases to 63°C?

• The enzyme is used up and the reaction stops

• The enzyme begins to decrease the rate of the reaction

• The enzyme continues to increase the rate of the reaction

• The enzyme changes shape and can no longer speed up the reaction

Which property of water molecules explains the other properties listed below?

• adhesion

• cohesion

• hydrogen bond

• polar covalent bond