CHAPTER 8: AN INTRODUCTION TO METABOLISM


CONCEPT 8.1:
AN ORGANISM'S METABOLISM TRANSFORMS MATTER AND ENERGY, SUBJECT TO THE LAWS OF THERMODYNAMICS

The following information concerns how energy is used, how it moves, how it is released, and the laws that govern it.

ORGANIZATION OF THE CHEMISTRY OF LIFE INTO METABOLIC PATHWAYS

Metabolism (from the Greek metabole, change) is the collection of chemical reactions that occur in an organism. Aided by enzymes, it follows intersecting pathways, which may be catabolic (breaking down molecules, releasing energy), or anabolic (building molecules, consuming energy).

• A metabolic pathway begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product. Each step of the pathway is catalyzed by a specific enzyme.

Energy is fundamental to all metabolic processes, and a basic knowledge of energy is necessary to understand how the living cell works. Bioenergetics, is the study of how energy flows through living organisms.


FORMS OF ENERGY

Energy is defined as the capacity to do work. Things that move are said to possess kinetic energy. An object at rest can possess potential energy if it has stored energy as a result of its position or structure. Chemical energy is stored in molecules, and the amount of chemical energy a molecule possess depends on its chemical bonds.


Heat or thermal energy, is kinetic energy associated with the random movement of atoms or molecules. Light is also a type of energy that can be harnessed to perform work, such as powering photosynthesis in green plants.


Preview of vocabulary for next section:
(1) Potential Energy: energy that is not kinetic; energy that matter possess because of its location or structure.
(2) Chemical Energy: refers to the potential energy available for release in a chemical reaction. Recall that catabolic pathways release energy by breaking down complex molecules.
(3) Thermodynamics: the study of energy transformations that occur in a collection of matter.

MULTIPLE CHOICE QUESTIONS:

1. Energy can be ______ or _______ but neither created nor destroyed.
a. distorted; transferred
b. transferred; altered
c. transferred; transformed

2. Choose the phrase that best completes this sentence:
A major pathway of catabolism is _______, in which the sugar glucose and other organic fuels are broken down in the presence of oxygen to carbon dioxide and water.
a. metabolism
b. cellular respiration
c. through bio synthetic pathways

3. Chose the ending that best completes this statement:
Energy is_________
a. the ability to rearrange a collection of matter.
b. an emergent property that of life that arises from interactions between molecules within the orderly environment of the cell.
c. breaking down complex molecules to simpler compounds.


Answers: 1c, 2b, 3a