In all cells, energy from the catabolism of fuel molecules is transferred to ATP. The hydrolysis of ATP to ADP and Pj then transfers this energy to cell functions.


metabolism anabolism catabolism calorie kilocalorie activation energy catalyst reversible reaction chemical equilibrium irreversible reaction law of mass action enzyme substrate active site cofactor coenzyme

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

PART ONE Basic Cell Functions vitamin


enzyme activity metabolic pathway rate-limiting reaction end-product inhibition adenosine triphosphate (ATP)


1. How do molecules acquire the activation energy required for a chemical reaction? List the four factors that influence the rate of a chemical reaction and state whether increasing the factor will increase or decrease the rate of the reaction.

What characteristics of a chemical reaction make it reversible or irreversible?

List five characteristics of enzymes.

What is the difference between a cofactor and a coenzyme?

From what class of nutrients are coenzymes derived? Why are small concentrations of coenzymes sufficient to maintain enzyme activity? List three ways in which the rate of an enzymemediated reaction can be altered. How can an irreversible step in a metabolic pathway be reversed?

What is the function of ATP in metabolism? Approximately how much of the energy released from the catabolism of fuel molecules is transferred to ATP? What happens to the rest?


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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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