13 Overview of Metabolism

Metabolism

The set of life-sustaining chemical reactions in organisms, encompassing all enzyme-catalyzed reactions and pathways that occur in cells.

Catabolism

The metabolic pathways that break down complex biomolecules into simpler products, releasing energy in the process.

Anabolism

The metabolic pathways that synthesize complex biomolecules from simpler building blocks, generally requiring energy.

Enzyme Catalysis

The process where enzymes speed up biological reactions, channeling reactions to specific products while avoiding unwanted side products.

ATP (Adenosine Triphosphate)

The primary energy carrier in cells, generated during catabolism and used to power various cellular processes.

NADH

Nicotinamide adenine dinucleotide in its reduced form, a key electron carrier that stores energy during catabolic reactions.

NADPH

Nicotinamide adenine dinucleotide phosphate, used primarily as a reducing agent in anabolic pathways.

Phosphoanhydride Bonds

High-energy bonds between the phosphate groups in ATP, which release energy upon hydrolysis.

Oxidation

The process of losing electrons or increasing the oxidation state of an atom or molecule, often involving the addition of oxygen or removal of hydrogen.

Reduction

The process of gaining electrons or decreasing the oxidation state of an atom or molecule, often involving the addition of hydrogen or removal of oxygen.

Glycolysis

A metabolic pathway that converts glucose into pyruvate, generating small amounts of ATP and NADH.

TCA Cycle (Krebs Cycle)

A central metabolic pathway that oxidizes acetyl CoA to carbon dioxide, generating NADH and FADH2 for electron transport.

Hydrolysis of ATP

The reaction in which ATP is broken down into ADP and inorganic phosphate, releasing energy for cellular processes.

Coupled Reactions

Reactions in metabolism where a thermodynamically unfavorable reaction is driven by coupling it to a favorable reaction.

Hexokinase

An enzyme that catalyzes the phosphorylation of glucose to glucose-6-phosphate using ATP.

Glucose Phosphorylation

The ATP-dependent reaction where glucose is phosphorylated to glucose-6-phosphate, facilitating its metabolism.

Oxidative Phosphorylation

The metabolic pathway that produces ATP from the electron transport chain and chemiosmosis, utilizing NADH and FADH2.

Calorimeter

An instrument used to measure the amount of heat released or absorbed during a chemical reaction.

Energy Reserves in Humans

Storage of energy in the form of carbohydrates (glycogen), fats (triglycerides), and proteins, which can be mobilized when needed.

Allosteric Regulation

A regulatory mechanism whereby the binding of a molecule at one site on an enzyme affects the activity at another site.

Creatine Kinase

An enzyme that catalyzes the transfer of a phosphate group from phosphocreatine to ADP, playing a key role in ATP regeneration.