Cell Biology
C.S. Sureka, C. Armpilia in Radiation Biology for Medical Physicists, 2017
Metabolism is generally divided into two basic processes. They are (1) catabolism and (2) anabolism (Figure 1.6). Catabolism (destructive metabolism) is the process of breaking up large molecules (mostly carbohydrates and fats) into more simple molecules and produces energy by the way of cellular respiration (respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water) and heat. This energy is used as fuel for anabolism, heats the body, and enables the muscles to contract and the body to move. It also produces waste products, such as CO2 etc., which is removed from the body through the skin, kidneys, lungs, and intestines. Anabolism (constructive metabolism) is the process of building and storing large biomolecules (proteins and nucleic acids) from small molecules (amino acids and nucleotides) using the energy generated from catabolism. Hence, it supports the growth of new cells, the maintenance of body tissues, and the storage of energy for future use. Anabolic and catabolic reactions take place simultaneously in cells throughout the body so that at any given moment, some biomolecules are being synthesized while others are being broken down. The energy released from or stored in the chemical bonds of biomolecules during metabolism is commonly measured in kilocalories (kcal).
Nutritional Requirements in Extreme Sports
Datta Sourya, Debasis Bagchi in Extreme and Rare Sports, 2019
Metabolism is the summation of competing pathways of anabolism—the synthesis of energy-storing complex molecules—and catabolism—the breakdown of complex molecules yielding energy. Though different tissues have preferred fuel sources to meet their specific functions, the metabolic state of any tissue is determined by the predominant pathway at any given time. For a much more detailed explanation of metabolism of various tissues, the reader is referred to Chapter 30 of Berg, Tymoczko, and Stryer (2002). It is also important to mention that all tissues do not need to be in the same metabolic state. In fact, the metabolic state of a tissue will vary based on function and state of the whole body. In this way, the body can compartmentalize systems and distribute energy based on demand in order to adapt and overcome a variety of stressors.
Regulation of Mammalian Hexokinase Activity
Rivka Beitner in Regulation of Carbohydrate Metabolism, 1985
as a parameter having wide significance for regulation of metabolic activity. Briefly, it was proposed that energy (ATP) utilizing pathways would contain enzymes responsive to the EC, with increasing activity at higher EC, i.e., when there was relatively abundant energy available in the form of high energy phosphoryl groups in the adenine nucleotide pool. Conversely, metabolic sequences generating ATP would contain enzymes responding with increased activity at lower EC, resulting in increased flux through pathways serving to replenish the high energy phosphates of the adenylates. The net result of these opposing responses was to be a stabilization of the EC at a value of ~0.8 to 0.9, presumably characteristic of the stable metabolic state. Despite criticism212,236,238 directed at both theoretical and practical aspects of the adenylate EC proposal, it has been defended239 and has continued to receive attention from many investigators.240
Simple techniques to study multifaceted diabesity in the fly model
Published in Toxicology Mechanisms and Methods, 2019
Nibedita Nayak, Monalisa Mishra
Various biochemical processes occur within our body is known as metabolism. When metabolism is disrupted, cell losses the ability to utilize or store the energy (Huynh et al. 2016) resulting in an abnormal physiological conditions (Patel 2014). Various metabolic disorders occur due to faulty metabolism (Buettner et al. 2007; Froy 2010; Patel 2014; da Silva et al. 2014). Molecules like lipids, carbohydrates, nucleosides, and peptides (also known as metabolites) play a significant role in regulating the process of metabolism (Fiehn 2002). Thus, the analysis of metabolites reflects the physiological status of the cell (Tweeddale et al. 1998; Griffin 2003; Fernie et al. 2004). Abnormality in metabolites was reported in various diseases, like obesity (faulty lipid metabolism) (Després 1991), glutaric acid urea (fault in amino acid metabolism) (Goodman et al. 1975), or diabetes (error in glucose metabolism) (Giugliano et al. 2008). Thus, molecular profiling of metabolites helps us to understand the onset of the disease (Saghatelian and Cravatt 2005).
Hypothesis of using albumin to improve drug efficacy in cancers accompanied by hypoalbuminemia
Published in Xenobiotica, 2021
Soghra Bagheri, Ali A. Saboury
Drug resistance is the main cause of more than 90% of cancer patients' deaths, which its mechanism includes increasing drug metabolism, altering drug transport (increasing drug efflux/decreasing drug influx), enhancing DNA repair capacity, growth factors, and genetic factors (Bukowski et al. 2020; Zahreddine and Borden 2013). Drug metabolism does not refer to the usual metabolic pathways that include anabolism and catabolism, but rather changes that facilitate the excretion of the drug from the body (Benet and Zia-Amirhosseini 1995). There are two main phases in drug metabolism. The first phase involves processes such as oxidation, reduction, and hydrolysis that alter the pharmacological activity of the drug, usually resulting in loss of activity, and the second phase increases its solubility in water by adding endogenous molecules to the drug (Caira and Ionescu 2005). Most drugs lose their medicinal properties in this way and produce highly soluble metabolites that are easily excreted (Li et al. 2019). The main organ that metabolizes drugs is the liver. However, other organs, such as the kidneys, lungs, intestine, and skin, also have metabolizing enzymes (Alfarouk et al. 2015). Understanding drug resistance mechanisms is critical to overcoming them in order to develop new effective treatment strategies.
Subcutaneous catabolism of peptide therapeutics: bioanalytical approaches and ADME considerations
Published in Xenobiotica, 2022
Simone Esposito, Laura Orsatti, Vincenzo Pucci
The most relevant biotransformation occurring at the SC injection site is the cleavage of peptide bonds by means of proteases or peptidases, which generates smaller peptides or amino acids. This type of biotransformation is referred to as catabolism, in contrast to the term metabolism used for biotransformation mainly observed in small molecules. Proteolytic enzymes are broadly divided into two categories: exopeptidases, which catalyse the cleavage at the N-terminal or C-terminal removing a single amino acid, and endopeptidases, which cleave peptide bonds within the sequence (López-Otín and Bond 2008). Exopeptidases are intuitively divided into aminopeptidases and carboxypeptidases, while endopeptidases are traditionally classified on the basis of their catalytic site as cysteine peptidases (e.g. dipeptidyl peptidase IV), aspartic peptidases (e.g. pepsin), serine peptidases (e.g. cathepsin B), and metallopeptidases (e.g. matrix metalloprotease 2 and 9) (de Veer et al. 2014a).