Overview of Metabolism and Energy

Overview of Metabolism

• Metabolism is the set of enzyme-catalyzed transformations of organic molecules in living cells
• Living cells and organisms perform work to stay alive, grow, and reproduce
• Organisms carry out diverse energy transductions (conversions of one form of energy to another)
• Organisms utilize chemical energy from fuels (food) to synthesize complex molecules and maintain gradients
• ATP is a crucial energy-rich compound

Anabolism and Catabolism

• Anabolism is the energy-requiring biosynthesis of cell components from smaller precursors, typically a reductive process
• Catabolism is the energy-yielding degradation of nutrient molecules, typically an oxidative process

Basic Principles Governing Energy Manipulations in All Cells

• Molecules are degraded or synthesized in metabolic pathways
• Some pathways release energy, others require it
• ATP is the energy currency of life, supplying and storing energy for pathways that need it, or being produced by pathways that release energy
• ATP is formed through the oxidation of carbon compounds, including glucose and fatty acids
• Metabolic pathways are highly regulated by regulatory enzymes

ATP - Adenosine Triphosphate

• ATP is the energy currency of cells
• Links catabolism and anabolism
• Structure: Adenine (nitrogenous base) + Ribose (carbohydrate) + 3 phosphate groups
• Phosphate groups carry negative charges, leading to instability and spontaneous hydrolysis, releasing energy
• ATP cycle involves phosphorylation (adding phosphate to ADP) and hydrolysis (removing phosphate from ATP)
• ATP is replenished through the metabolism of nutrients in catabolism

How ATP is Synthesized

• Substrate-level phosphorylation is a quicker, less efficient method of ATP synthesis that happens in the absence of mitochondria or anaerobic conditions occurring when energy from another high energy bond phosphorylates ADP to ATP
• Oxidative phosphorylation, via the ATP synthase, is the most frequent source of ATP, that occurs in mitochondria through aerobic respiration

Catabolism Overview

• Catabolism is the oxidative process where substrates lose electrons
• Oxidize coenzymes (NAD+ and FAD+) collect and reduce electrons (NADH and FADH2), that are transferred to the electron transport chain to form ATP
• Different nutrient molecules (lipids, carbohydrates, and proteins) enter catabolic pathways and are broken down to release energy.

Oxidation-Reduction (Redox) Reactions and Coenzymes

• Redox reactions involve the transfer of electrons from a donor to an acceptor
• Oxidation is the loss of electrons, reduction is the gain
• Coenzymes (NAD+, FAD+) participate in redox reactions by accepting and donating electrons in catabolism and anabolism

Energy- Rich Compounds

• ATP is not the only energy-rich compound.
• Other compounds like Phosphoenolpyruvate (PEP), 1,3-Bisphosphoglycerate (1,3-BPG), Creatine phosphate and others can be hydrolyzed to release energy which can, in turn, be used to resynthesize ATP.

This quiz covers the fundamental concepts of metabolism, including anabolism and catabolism, as well as the principles governing energy transformations in living cells. Explore the roles of ATP and the processes involved in synthesizing and degrading molecules. Test your knowledge on how organisms manage energy for life processes.