Keystone Biology Biochemistry

Lipase is an enzyme that breaks down lipids in the digestive system of humans. It functions best at a pH range of 4.0 to 5.0. When a person takes an antacid tablet to relieve heartburn, the antacid increases the pH to around 7 in certain areas of the digestive system. Which initial effect would most likely be caused by a change in pH?

• More lipids would be digested

• Fewer lipids would be digested.

• The production of lipase molecules would increase.

• The production of lipase molecules would decrease.

Which action must occur for an enzyme to catalyze a chemical reaction?

• A competitive inhibitor must first bind to an active site

• A substrate must bind to an active site of the enzyme.

• A substrate must bind to an allosteric site of the enzyme.

• A noncompetitive inhibitor must first bind to an active site

Molecule 1 made mostly of carbon with two nonpolar chains and a polar head, and it is a component of plasma membranes

Molecule 2 is a polar molecule made of repeating units of sugar bonded to a phosphate and a nitrogenous base and it stores genetic information

• molecule 1: lipid molecule 2: nucleic acid

• molecule 1: lipid molecule 2: protein

• molecule 1: carbohydrate molecule 2: nucleic acid

• molecule 1: carbohydrate molecule 2: protein

Which statement correctly describes how a protein is formed?

• A monosaccharide bonded to a side chain is broken apart.

• Amino acids are bonded together in a long chain to form a new molecule

• A molecule containing glycerol bonded to three fatty acids is broken apart.

• A nitrogenous base, a sugar, and a phosphate group combine to form a new molecule.

Tags

NGSS.HS-LS1-1

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

Tags

NGSS.MS-LS2-1

NGSS.MS-LS2-4

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.

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

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

A scientist formed Chemical X in a laboratory. The material was then analyzed by other scientists. Analysis showed that the chemical was composed of long chains of repeated copies of CH₂ molecules. A researcher noticed that a similar CH₂ molecular structure was also located in the plasma membrane of an animal cell. This CH₂ molecular structure contained a negatively charged phosphate group. Which type of organic molecule was most likely formed by the scientist in the laboratory?

• lipid

• protein

• nucleic acid

• carbohydrate

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.