Skip to ContentGo to accessibility page
OpenStax Logo
Biology 2e

Key Terms

Biology 2eKey Terms

Key Terms

acetyl CoA
combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B-group vitamin)
aerobic respiration
process in which organisms convert energy in the presence of oxygen
anaerobic
process that does not use oxygen
anaerobic cellular respiration
process in which organisms convert energy for their use in the absence of oxygen
ATP synthase
(also F1F0 ATP synthase) membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it
chemiosmosis
process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane
citric acid cycle
(also Krebs cycle) series of enzyme-catalyzed chemical reactions of central importance in all living cells for extraction of energy from carbohydrates
dephosphorylation
removal of a phosphate group from a molecule
fermentation
process of regenerating NAD+ with either an inorganic or organic compound serving as the final electron acceptor; occurs in the absence of oxygen
GLUT protein
integral membrane protein that transports glucose
glycolysis
process of breaking glucose into two three-carbon molecules with the production of ATP and NADH
isomerase
enzyme that converts a molecule into its isomer
Krebs cycle
(also citric acid cycle) alternate name for the citric acid cycle, named after Hans Krebs, who first identified the steps in the pathway in the 1930s in pigeon flight muscles; see citric acid cycle
oxidative phosphorylation
production of ATP using the process of chemiosmosis in the presence of oxygen
phosphorylation
addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP
prosthetic group
(also prosthetic cofactor) molecule bound to a protein that facilitates the function of the protein
pyruvate
three-carbon keto acid that can be decarboxylated and oxidized to make acetyl CoA, which enters the citric acid cycle under aerobic conditions; the end product of glycolysis
redox reaction
chemical reaction that consists of the coupling of an oxidation reaction and a reduction reaction
substrate-level phosphorylation
production of ATP from ADP using the excess energy from a chemical reaction and a phosphate group from a reactant
TCA cycle
(also citric acid cycle) alternate name for the citric acid cycle, named after the group name for citric acid, tricarboxylic acid (TCA); see citric acid cycle
ubiquinone
soluble electron transporter in the electron transport chain that connects the first or second complex to the third
PreviousNext
Order a print copy
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution-NonCommercial-ShareAlike License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute OpenStax, and must distribute any derivative works under the same license.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/biology-2e/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/biology-2e/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Jul 22, 2026 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License. The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.