7. Energy and Metabolism

How do enzymes lower activation energy?

A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________.

What is a transition state? a. the shape adopted by an enzyme that has an inhibitory molecule bound at its active site b. the amount of kinetic energy required for a reaction to proceed c. the intermediate complex formed as covalent bonds in the reactants are being broken and re-formed during a reaction d. the enzyme shape after binding an allosteric regulatory molecule

What would happen if activation energy barriers didn't exist? a. Substrates would not bind properly to enzymes; b. Chemical reactions in the body would never occur; c. Enzyme function would not be affected; d, Metabolic reactions would proceed even if their products were not needed.

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur? a. Additional substrate will be formed. b. The reaction will change from endergonic to exergonic. c. The free energy of the system will change. d. Nothing; the reaction will stay at equilibrium.

If you were to expose glucose to oxygen on your lab bench, why would you not expect to see it burn as described by the reaction in Figure 8.6? a. The reaction is endergonic and requires an input of energy. b.The reaction is not spontaneous unless an enzyme is added. c. The sugar must first be phosphorylated to increase its potential energy. d. Activation energy is required for the sugar and oxygen to reach their transition state.

Why is the barrier of the activation energy beneficial for cells? Explain how enzymes lower activation energy.

A biologist performed two series of experiments on lactase, the enzyme that hydrolyzes lactose to glucose and galactose. First, she made up 10% lactose solutions containing different concentrations of enzyme and measured the rate at which galactose was produced (grams of galactose per minute). Results of these experiments are shown in Table A below. In the second series of experiments (Table B), she prepared 2% enzyme solutions containing different concentrations of lactose and again measured the rate of galactose production. (b) Graph and explain the relationship between the reaction rate and the substrate concentration. How and why did the results of the two experiments differ?.

A biologist performed two series of experiments on lactase, the enzyme that hydrolyzes lactose to glucose and galactose. First, she made up 10% lactose solutions containing different concentrations of enzyme and measured the rate at which galactose was produced (grams of galactose per minute). Results of these experiments are shown in Table A below. In the second series of experiments (Table B), she prepared 2% enzyme solutions containing different concentrations of lactose and again measured the rate of galactose production. (a)Graph and explain the relationship between the reaction rate and the enzyme concentration.