뒤로Proteins, Carbohydrates, and Lipids: Structures and Functions in Living Systems
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Proteins, Carbohydrates, and Lipids
3.1 What Kinds of Molecules Characterize Living Things?
Living organisms are composed of a variety of large, complex molecules known as macromolecules. These macromolecules are essential for structure, function, and information storage in cells.
Proteins: Provide structure and catalyze biochemical reactions.
Carbohydrates: Serve as energy sources and provide structural support.
Lipids: Form cell membranes and store energy.
Nucleic acids: Store and transmit genetic information (DNA and RNA).
Most macromolecules are polymers, which are large molecules made up of repeating smaller units called monomers. For example, proteins are polymers of amino acids, and carbohydrates are polymers of simple sugars.
Macromolecules and Their Functions
Macromolecules: Polymers with molecular weights typically greater than 1,000.
They form the backbone of living organisms and are crucial to biological functions.
Types of Macromolecules
Proteins: Structure, catalysis (enzymes).
Nucleic Acids: Genetic information storage (DNA/RNA).
Carbohydrates: Energy, structural support.
Lipids: Membranes, energy storage.
Functional Groups in Biological Molecules
The function of a biological molecule is determined by its functional groups—specific clusters of atoms that impart characteristic chemical properties and reactivity.
Hydroxyl Group (-OH): Increases hydrophilicity (water solubility).
Carboxyl Group (-COOH): Confers acidic properties.
Amino Group (-NH2): Confers basic properties; essential in amino acids.
Phosphate Group (-PO4): Involved in energy transfer (e.g., ATP), key in nucleic acids.
Many macromolecules contain multiple functional groups, enabling complex chemical functions.
Some Functional Groups Important to Living Systems
Functional group | Class of compounds and an example | Properties |
|---|---|---|
Hydroxyl (-OH) | Alcohols (e.g., Ethanol) |
|
Carbonyl (C=O) | Aldehydes (e.g., Acetaldehyde), Ketones (e.g., Acetone) |
|
Carboxyl (-COOH) | Carboxylic acids (e.g., Acetic acid) |
|
Amino (-NH2) | Amines (e.g., Methylamine) |
|
Additional info: Other important functional groups in biology include sulfhydryl (-SH), methyl (-CH3), and phosphate (-PO4), each contributing to molecular diversity and function.
