Chapter Overview

Cells are constantly involved in an orderly activity called metabolism that encompasses all of their chemical and energy transactions.
Enzymes are essential metabolic participants that drive cell reactions.
Enzymes are protein catalysts that speed up chemical processes by lowering the required energy.
Enzymes have a specific shape tailored to perform their actions on a single type of molecule called a substrate.
Enzymes derive some of their special characteristics from cofactors such as vitamins, and they show sensitivity to environmental factors.
Enzymes are involved in activities that synthesize, digest, oxidize, and reduce compounds, and convert one substance to another.
Enzymes are regulated by several mechanisms that alter the structure or synthesis of the enzyme.
The energy of living systems resides in the atomic structure of chemicals that can be acted upon and changed.
Cell energetics involves the release of energy that powers the formation of bonds.
The energy of electrons is transferred from one molecule to another in coupled redox reactions.
Electrons are transferred from substrates such as glucose to coenzyme carriers and ultimately captured in high-energy adenosine triphosphate (ATP).
Cell pathways involved in extracting energy from fuels are glycolysis, the tricarboxylic acid cycle, and electron transport.
The molecules used in aerobic respiration are glucose and oxygen, and the products are CO₂, H₂O, and ATP.
Microbes participate in alternate pathways such as fermentation and anaerobic respiration.
Cells manage their metabolites through linked pathways that have numerous functions and can proceed in more than one direction.

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