1.2 Enzymes

Energy is commonly defined as "the capacity to do work." This definition is

• a. incorrect
• b. adequate in the physical sciences
• c. adequate in the biological sciences
• d. a clue to the actual properties of the concept
• e. not accepted by most scientists

According to the first law of thermodynamics

• a. the energy of a system may increase if there is a corresponding decrease in energy elsewhere in the universe
• b. the amount of energy in the universe is constant
• c. chemical reactions do not create or destroy energy
• d. energy can change from one form to another
• e. all of these are true

Which of the following statements is false?

• a. The universe has a specific amount of energy
• b. One form of energy can be converted to other forms of energy
• c. Whenever energy conversions occur, some energy is converted to less concentrated forms
• d. Once energy is utilized, it disappears
• e. There are differences in the quality of energy

Which of the following is an application of the first law of thermodynamics?

• a. The level of entropy increases as time passes
• b. Living organisms represent an exception to the laws of energy
• c. The quantity of energy does not increase or decrease in the universe
• d. Fungi and plants do not make their own energy but derive it from somewhere else
• e. The amount of energy found in the compounds on one side of an equation is equal to that on the other side

The activation energy of a reaction refers to the minimum amount of energy

• a. released by the reaction
• b. in the reactants
• c. in the products
• d. necessary to cause a reaction to proceed on its own
• e. difference between the energy of the reactants and the energy of the products

CO2 and H2O will not form glucose on their own because

• a. CO2 does not contain sufficient energy
• b. H2O does not contain sufficient energy
• c. neither CO2 nor H2O contain sufficient energy
• d. the concentration of CO2 is too low in the atmosphere
• e. the bonds of CO2 and H2O are too stable to be broken without an input of energy

Endergonic reactions

• a. result in products with less energy than the reactants
• b. require a net input of energy
• c. occur in the breakdown of glucose
• d. are used by cells to provide energy for biological reactions
• e. break down large molecules into smaller molecules

Which of the following statements about exergonic reactions is false?

• a. They release energy
• b. Glucose metabolism is an example
• c. Their products have more energy than the reactants
• d. Some energy is converted to less biologically useful forms
• e. Bonds are broken

Which of the following is NOT true of enzyme behavior?

• a. Enzyme shape may change during catalysis
• b. The active site of an enzyme orients its substrate molecules, thereby promoting interaction of their reactive parts
• c. All enzymes have an active site where substrates are temporarily bound
• d. Each enzyme can catalyze only a specific reaction
• e. Enzyme activity is not affected by pH and temperature

Enzymes do not

• a. control the speed of a reaction
• b. change shapes to facilitate certain reactions
• c. may place physical stress on the bonds of the substrate
• d. always work on their own
• e. do all of these