7. Energy and Metabolism

Enzyme Activation Energy

Function of Enzymes: Substrate, Active Site & Activation Energy

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.

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?.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/d54280c0a4dc87b0-1677714756097.jpg" style="width: 300px;">

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.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/ba07230c0b2ce511-1677714693961.jpg" style="width: 520px;">

Activation energy: Kickstarting chemical reactions - Vance Kite

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.<img class="fr-dib" src="https://lightcat-files.s3.amazonaws.com/problem_images/879e9c48a6a5099d-1677287268589.jpg" style="width: 300px;">

√ The Definition of Activation Energy of Enzymes Explained. Watch this video to find out!

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.

Enzymes and Activation Energy

Activation Energy

Enzymes and activation energy | Biomolecules | MCAT | Khan Academy

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

It is generally increased if the structure or conformation of an enzyme is altered.

It is independent of factors such as pH and temperature.

It increases the rate of chemical reactions by lowering activation energy barriers.

Which of the following statements is TRUE regarding an enzyme’s function?a) It is generally increased if the structure or conformation of an enzyme is altered.b) It is independent of factors such as pH and temperature.c) It increases the rate of chemical reactions by lowering activation energy barriers.

No. Enzymes would not alter the products in a reaction.

By harnessing heat energy to drive the breakage of bonds between atoms

No. Enzymes would not need to increase the reactivity of the molecules produced by a reaction.

The second and third choices are correct.

Think of what enzymes do to reactants to act as catalysts for a reaction.

How do enzymes lower activation energy?

Why are protists considered paraphyletic?

a. They include many extinct forms, including lineages that no longer have any living representatives.
b. They include some but not all descendants of their most recent common ancestor.
c. They represent all of the descendants of a single common ancestor.
d. Not all protists have all of the synapomorphies that define the Eukarya, such as a nucleus.

Enzymes Lower Activation Energy

the hydrogen bonds that define the structure of the enzyme's active site are unstable

the substrate becomes a competitive inhibitor at lower temperature

No. A substrate can never be a competitive inhibitor of itself.

the cofactors required by the enzyme system lack the thermal energy required to activate the enzyme

No. Cofactors do not provide activation energy for enzyme-catalyzed reactions.

there is too little activation energy available

Consider what is required for a reaction to occur, regardless of the presence of enzymes.

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

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