Enzyme

Are most chemical reactions in living cells at equilibrium?

• Yes

• No

• only the exergonic reactions

• all reactions except those powered by ATP hydrolysis

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as is to .

• exergonic; spontaneous

• exergonic; endergonic

• free energy; entropy

• work; energy

A reaction has a ∆G of –5.6 kcal/mol. Which of the following would most likely be true?

• The reaction could be coupled to power an endergonic reaction with a ∆G of +8.8 kcal/mol

• The reaction is nonspontaneous.

• To take place, the reaction would need to couple to ATP hydrolysis.

• The reaction would result in products with a greater free-energy content than in the initial reactants

• The reaction would proceed by itself but might be very slow

The oxidation of glucose to CO2 and H2O is highly exergonic: ∆G = –636 kcal/mole. This is spontaneous, but why is it very slow?

• Few glucose and oxygen molecules have the activation energy at room temperature.

• There is too much CO2 in the air.

• CO2 has higher energy than glucose.

• The formation of six CO2 molecules from one glucose molecule decreases entropy.

A friend is designing an industrial process around an endergonic biological reaction. You recommend finding a way to provide

• ATP

• minerals

• a lower pH

• a plasma membrane

• mitochondria

Which of the following statements about enzymes is incorrect?

• Enzymes can be used to accelerate both anabolic and catabolic reactions

• An enzyme lowers the activation energy of a chemical reaction

• An enzyme is very specific in terms of the substrate to which it binds

• An enzyme is consumed during the reaction it catalyzes

• Most enzymes are proteins

When a substrate molecule binds to an enzyme, it binds to a particular location known as the …………

• active site

• regulatory site

• allosteric site

• binding site

In the energy diagram, what is the difference between the red and black curves?

• A. The red curve is for a

  reaction powered by

  ATP hydrolysis.

• B. The black curve occurs

  at higher temperature

• C. The red curve is

  catalyzed by an

  enzyme

• D. The black curve has a

  higher activation energy

• Both C and D

Enzymes increase the rate of an enzyme catalyzed reaction by

• Increasing the activation energy barrier

• Decreasing the activation energy barrier.

• Increasing the free energy of the reactant.

• Increasing the free energy of the product

• Decreasing the free energy of the reactant

Which of the following statements about enzymes is/are true?

• Enzymes increase the rate of a reaction by raising the activation energy for reactions

• Enzymes speed up the rate of the reaction without changing the DG for the reaction

• The more heat that is added to a reaction, the faster the enzymes will function

• Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme

• All of the listed responses are correct