Cellular Metabolism: Catabolism and Anabolism

Metabolism

• Metabolism involves two main types of processes: catabolism (breakdown of molecules, names end in 'lysis') and anabolism (synthesis of molecules, names end in 'genesis')
• Catabolism generates ATP and NADH, mostly in the mitochondria
• Anabolism uses ATP, GTP, UTP, mostly in the cytosol

Why Metabolic Pathways are Complicated

• Metabolic pathways release energy in small, usable 'packages' through stepwise breakdown
• Pathways can be regulated by regulating specific enzymes
• Different 'forward' and 'reverse' pathways allow for separate regulation

Regulation of Metabolic Pathways

• Activating enzyme 1 (and/or enzyme 2) would speed up forward and reverse pathways, creating a 'futile cycle'
• Activating enzyme 1 speeds up forward pathway
• Activating enzyme 3 speeds up reverse pathway

Activated Carrier Molecules

• Energy released at each step is stored in activated carrier molecules
• Examples of activated carrier molecules: ATP, NADH, FADH2, Coenzyme A/acetyl CoA

Importance of ATP

• ATP is the energy currency of the cell
• ATP is chemically stable at pH 6-9
• ATP has structural features recognized by specific proteins, enzymes, etc.
• Hydrolysis of ATP gives ADP + Pi, releasing energy available for cellular work and chemical synthesis

ATP Hydrolysis

• ATP hydrolysis is energetically favorable, with a ΔG of -31 to -50 kJ/mole
• ATP hydrolysis is a controlled release of energy

Introduction to Metabolism

• Learning outcomes: define metabolism, anabolism, and catabolism; give examples of anabolic and catabolic pathways; explain controlled release of energy; outline the role of activated carrier molecules; recognize the general roles of NAD/NADH, NADP/NADH, FAD/FADH2, Coenzyme A/acetyl CoA; explain the key function of ATP as the 'energy currency of living cells'

The Electron Transport Chain

• The electron transport chain generates an electrochemical gradient by pumping protons (H+) into the intermembrane space
• Protons flow back through the membrane via ATP Synthase, driving the synthesis of ATP from ADP + Pi

Amino Acid Metabolism

• Amino acid metabolism is complex and varied, but involves the removal of nitrogen (N) from amino acids
• Deamination: removal of N from amino acids, mainly occurring in the liver
• Transamination: conversion of one amino acid to another, mainly occurring in most tissues

Test your understanding of cellular metabolism, including catabolism and anabolism, and how they relate to ATP and NADH production. Covers glycolysis, lipolysis, and glycogenolysis.