Biology Chapter 4: Enzymes and Energy

Questions and Answers

Which of these statements about enzymes is true? (Select all that apply)

Most proteins are enzymes.

Most enzymes are proteins. (correct)

Enzymes are changed by the reactions they catalyze.

The active sites of enzymes have little specificity for substrates.

Which of these statements about enzyme-catalyzed reactions is true? (Select all that apply)

The rate of reaction is independent of temperature.

The rate of all enzyme-catalyzed reactions is decreased when the pH is lowered from 7 to 2.

The rate of reaction is independent of substrate concentration.

Under given conditions of substrate concentration, pH, and temperature, the rate of product formation varies directly with enzyme concentration up to a maximum, at which point the rate cannot be increased further. (correct)

Which of these statements about lactate dehydrogenase is true? (Select all that apply)

It is a protein. (correct)

It reduces another molecule (pyruvic acid). (correct)

It oxidizes the lactic acid. (correct)

In a metabolic pathway, what happens to the product of one enzyme?

The product becomes the substrate of the next enzyme. Signup and view all the answers

What is an inborn error of metabolism?

A genetic change results in the production of a defective enzyme; intermediates produced prior to the defective step accumulate; alternate pathways are taken by intermediates at branch points that precede the defective step. Signup and view all the answers

Which of these represents an endergonic reaction? (Select all that apply)

CO2 + H2O -> glucose Signup and view all the answers

Which of these statements about ATP is true? (Select all that apply)

The conversion of ATP to ADP and Pi provides energy for biosynthesis, cell movement, and other cellular processes. Signup and view all the answers

When oxygen is combined with 2 hydrogens to make water, what happens?

Oxygen is reduced and the molecule that donated the hydrogens becomes oxidized. Signup and view all the answers

How do enzymes increase the rate of chemical reactions?

By decreasing the activation energy of the reactants. Signup and view all the answers

According to the law of mass action, which conditions will drive the reaction A + B to the right?

An increase in the concentration of A and B and a decrease in the concentration of C. Signup and view all the answers

Study Notes

Enzymes

Most enzymes are proteins, highlighting their primary composition within biological reactions.
Enzymes are not changed permanently by the reactions they catalyze, preserving their function for multiple reactions.
Active sites of enzymes are specific for their substrates, facilitating selective binding.

Enzyme-Catalyzed Reactions

Reaction rates depend on substrate concentration, pH, and temperature; they increase with enzyme concentration up to a maximum.
Lowering pH from neutral (7) to acidic (2) typically decreases the rate of enzyme-catalyzed reactions.

Lactate Dehydrogenase

Lactate dehydrogenase is a multifunctional protein that oxidizes lactic acid and reduces pyruvic acid, emphasizing its role in metabolic processes.

Metabolic Pathways

In a metabolic pathway, the product of one enzyme is the substrate for the next, creating a sequence of biochemical transformations.

Inborn Errors of Metabolism

Genetic changes can lead to defective enzymes, causing the accumulation of intermediates prior to the defective step and utilizing alternative pathways to manage these substrates.

Endergonic Reactions

Endergonic reactions require energy input; examples include the synthesis of ATP from ADP and Pi and the photosynthesis of glucose from CO2 and H2O.

ATP (Adenosine Triphosphate)

ATP is considered the "universal energy carrier" in cells, providing energy for various cellular activities.
The high-energy bond between ADP and the third phosphate facilitates energy transfer during metabolic reactions.
ATP production is coupled with energy-liberating processes, ensuring a balance between energy consumption and generation.

Redox Reactions

Combining oxygen with two hydrogen atoms to form water involves the reduction of oxygen, while the hydrogen-donating molecule undergoes oxidation.

Activation Energy

Enzymes enhance the rate of chemical reactions by lowering the activation energy required for reactants, making reactions occur more readily.

Law of Mass Action

According to the law of mass action, driving a reaction to the right can be achieved by increasing the concentrations of reactants A and B while decreasing the concentration of product C.

Description

Test your knowledge on enzymes and their role in energy transformations with these flashcards. Explore key concepts about enzyme characteristics and their catalytic function in biological reactions. Perfect for reviewing Chapter 4 material in your biology class.