Unit II Exam Review (Enzymes)

William is conducting an experiment in his chemistry class. He observes that during a chemical reaction, one or more substances, the reactants, are converted to one or more different substances, the products. Substances are either chemical elements or compounds. A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products.
Chemical reactions are an integral part of technology, of culture, and indeed of life itself. Burning fuels, making glass, pottery, and making cheese are among many examples of activities incorporating chemical reactions that have been known and used for thousands of years. Question: In chemical reactions, atoms are

• rearranged.

• created.

• neutralized.

• destroyed.

Reading Passage:  Enzymes are proteins that do the everyday work within a cell. Their basic function is to speed up the process and efficiency of a reaction without themselves being consumed in the process. Enzymes are responsible for moving large parts of a cell’s internal structure, such as pulling chromosomes apart when a cell divides. Enzymes make the energy molecules that are constantly needed for the cell to survive. And they break down molecules, recycle the old parts and make new molecules that allow the cell to grow.Question: Enzymes affect the reactions in living cells by changing the

• speed of the reaction.
• products of the reaction.
• pH of the reaction.
• temperature of the reaction.

Question: The energy needed to get a reaction started is the

• chemical energy.
• activation energy.
• adhesion energy.
• cohesion energy.

Question: What is the process that changes one set of chemicals into another set of chemicals?

• hydrogen bonding
• cohesion
• dissolving
• chemical reaction

Question: When hydrogen and oxygen combine to form water, water is

• an enzyme.
• a catalyst.
• a reactant.
• a product.

Question: A substance that speeds up the rate of a chemical reaction is called

• a molecule.
• a lipid.
• a catalyst.
• an element.

Question: Consider the energy diagram for a chemical reaction in the Figure. Overall, is energy released or absorbed?

• absorbed, because the energy level increases during the reaction
• absorbed, because the energy level of the products is greater than that of the reactants
• released, because the reaction is initiated by the addition of heat
• released because the energy level of the reactants is greater than that of the products

Question: Which is the best description of activation energy?

• Energy barrier needed to be overcome to initiate a reaction.
• Energy released as the reaction proceeds
• Energy stored within the reactant molecules.
• Energy stored within the product molecules.

Question: How does an enzyme influence a biological reaction?

• It increases the net energy difference between reactants and products.
• It lowers the activation energy necessary to initiate the chemical change.
• It increases the kinetic energy of reactants, thereby increasing their tendency to collide.
• It decreases the kinetic energy of reactants, enabling them to undergo chemical change more easily.

The following graphs shows some examples of enzyme and their corresponding function in the human body.
Question: Without enzymes, the chemical reactions in the body would

• happen too fast.
• occur at much the same rate as they do with enzymes.
• require a different pH.
• occur too slowly to support life processes.