BackMacromolecules: Structure, Function, and Diversity in General Biology
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Macromolecules: Polymers Built from Monomers
Definition and Overview
Macromolecules are large, complex molecules essential for life, constructed from smaller subunits called monomers. The process of linking monomers forms polymers, which are the basis of carbohydrates, proteins, and nucleic acids. Lipids, while large, are not true polymers.
Macromolecule: A large molecule composed of thousands of atoms, typically formed by polymerization.
Polymer: A long molecule consisting of many similar or identical building blocks (monomers) linked by covalent bonds.
Monomer: The repeating unit that serves as the building block of a polymer.
Examples: Carbohydrates (monosaccharides), proteins (amino acids), nucleic acids (nucleotides).
Synthesis and Breakdown of Polymers
Polymers are assembled and disassembled by specific chemical reactions, often catalyzed by enzymes.
Dehydration Reaction (Dehydration Synthesis): Removes a water molecule to form a new bond, joining monomers into polymers.
Hydrolysis: Adds a water molecule to break a bond, splitting polymers into monomers.
Enzymes: Specialized proteins that speed up these chemical reactions.
Equation for Dehydration Synthesis:
Equation for Hydrolysis:
Diversity of Polymers
Cells contain thousands of different macromolecules, and the diversity arises from the arrangement of a limited set of monomers.
Macromolecules vary among cells, species, and even more between different species.
A huge variety of polymers can be built from a small set of monomers.
Carbohydrates: Fuel and Building Material
Types and Functions
Carbohydrates are organic molecules that serve as energy sources and structural components. They include simple sugars and polymers of sugars.
Monosaccharides: Simple sugars (e.g., glucose, C6H12O6), major fuel for cells and raw material for building molecules.
Disaccharides: Formed by joining two monosaccharides via dehydration reaction (e.g., maltose, sucrose).
Polysaccharides: Polymers of sugars, with storage (starch, glycogen) and structural (cellulose, chitin) roles.
General Formula for Monosaccharides:
Formation of Disaccharides
Disaccharides are formed when a dehydration reaction joins two monosaccharides.
Maltose: Glucose + Glucose
Sucrose: Glucose + Fructose
Equation for Disaccharide Formation:
Polysaccharides: Storage and Structure
Polysaccharides are carbohydrate macromolecules made of many sugar subunits. Their function depends on the type and arrangement of monomers.
Storage Polysaccharides:
Starch: Storage in plants, consists of glucose monomers, stored as granules in plastids. Simplest form is amylose.
Glycogen: Storage in animals, mainly in muscle and liver cells. Hydrolysis releases glucose when needed.
Structural Polysaccharides:
Cellulose: Major component of plant cell walls, polymer of glucose.
Chitin: Found in exoskeletons of arthropods and cell walls of fungi.
Summary Table: Carbohydrates
Components | Examples | Functions |
|---|---|---|
Monosaccharides (e.g., glucose, fructose) | Simple sugars | Fuel; carbon source for other molecules |
Disaccharides (e.g., lactose, sucrose) | Table sugar, milk sugar | Energy transport and storage |
Polysaccharides (e.g., starch, glycogen, cellulose, chitin) | Starch (plants), glycogen (animals), cellulose (plants), chitin (animals/fungi) | Energy storage, structural support |
Additional info: The notes above are expanded with definitions, equations, and a summary table for clarity and completeness.
