뒤로Chapter 3: The Chemistry of Organic Molecules – Study Notes
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Organic Molecules in Biology
Introduction to Organic Molecules
Organic molecules are the chemical compounds that form the basis of life. They are primarily composed of carbon atoms bonded with hydrogen, oxygen, nitrogen, and other elements. The diversity of organic molecules enables the complexity of biological structures and functions.
Organic chemistry studies carbon-containing compounds.
Major classes include carbohydrates, lipids, proteins, and nucleic acids.
Organic molecules are essential for cell structure, energy storage, and genetic information.
Functional Groups of Organic Molecules
Key Functional Groups and Their Properties
Functional groups are specific groups of atoms within molecules that confer particular chemical properties. They play a critical role in the structure and reactivity of organic molecules.
Group | Structure | Compound | Significance |
|---|---|---|---|
Hydroxyl | R–OH | Alcohol (e.g., ethanol) | Polar, forms hydrogen bonds |
Carbonyl | R–C=O | Aldehyde (e.g., formaldehyde), Ketone (e.g., acetone) | Polar; present in sugars, some amino acids |
Carboxyl (acidic) | R–COOH | Carboxylic acid (e.g., acetic acid) | Polar, acidic; present in fatty acids, amino acids |
Amino | R–NH2 | Amine (e.g., tryptophan) | Polar, basic, forms hydrogen bonds; present in amino acids |
Sulfhydryl | R–SH | Thiol (e.g., ethanethiol) | Forms disulfide bonds; present in some amino acids |
Phosphate | R–O–PO3H2 | Organic phosphate | Polar, acidic; present in nucleotides, phospholipids |
Biological Macromolecules
Categories, Monomers, and Polymers
Biological macromolecules are large molecules essential for life, constructed from smaller subunits called monomers. The four major categories are carbohydrates, lipids, proteins, and nucleic acids.
Category | Subunits (monomers) | Polymer |
|---|---|---|
Carbohydrates | Monosaccharide | Polysaccharide |
Lipids | Glycerol and fatty acids | Does not form polymers |
Proteins | Amino acids | Polypeptide |
Nucleic acids | Nucleotide | DNA, RNA |
Carbohydrates
Monosaccharides and Polysaccharides
Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as energy sources and structural components in cells.
Monosaccharides are simple sugars (e.g., glucose, fructose).
Polysaccharides are long chains of monosaccharides (e.g., starch, cellulose, glycogen).
General formula for monosaccharides:
Examples:
Glucose:
Glyceraldehyde (an aldose) and dihydroxyacetone (a ketose) are examples of simple sugars.
Compound | Structure |
|---|---|
Glyceraldehyde | Contains an aldehyde group |
Dihydroxyacetone | Contains a ketone group |
Dehydration synthesis joins monosaccharides to form polysaccharides, releasing water:
General reaction:
Lipids
Structure and Function of Lipids
Lipids are hydrophobic molecules that include fats, oils, phospholipids, and steroids. They are important for energy storage, membrane structure, and signaling.
Fats and oils are composed of glycerol and fatty acids.
Phospholipids are major components of cell membranes.
Steroids (e.g., cholesterol, testosterone) function as hormones and membrane components.
Lipids do not form true polymers.
Functions of lipids:
Long-term energy storage
Insulation and protection
Structural component of plasma membranes
Prevention of water loss (e.g., cuticle of plant surfaces)
Proteins
Amino Acids and Protein Structure
Proteins are polymers made of amino acids. They perform a wide range of functions, including catalysis, transport, and structural support.
Amino acid structure: Each amino acid contains an amino group (), a carboxyl group (), a hydrogen atom, and a variable R group.
General formula:
Peptide bonds link amino acids to form polypeptides.
Functions of proteins:
Enzymatic activity
Transport and signaling
Structural support
Nucleic Acids
DNA and RNA
Nucleic acids store and transmit genetic information. They are polymers of nucleotides, each consisting of a pentose sugar, a phosphate group, and a nitrogenous base.
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the two main types.
Nucleotides are joined by phosphodiester bonds.
General structure of a nucleotide: phosphate group, pentose sugar, nitrogenous base.
Summary Table: Macromolecule Categories
Category | Monomer | Polymer | Example |
|---|---|---|---|
Carbohydrates | Monosaccharide | Polysaccharide | Glucose, starch |
Lipids | Glycerol, fatty acids | Does not form polymers | Triglyceride, phospholipid |
Proteins | Amino acid | Polypeptide | Hemoglobin, enzymes |
Nucleic acids | Nucleotide | DNA, RNA | Genetic material |
Key Processes: Dehydration and Hydrolysis
Polymer Formation and Breakdown
Macromolecules are assembled and disassembled by two key reactions:
Dehydration synthesis: Joins monomers by removing water.
Hydrolysis: Breaks polymers into monomers by adding water.
General equation for dehydration synthesis:
General equation for hydrolysis:
Biological Importance of Organic Molecules
Roles in Living Organisms
Organic molecules are fundamental to the structure and function of all living things. They provide energy, build cellular structures, and carry genetic information.
Carbohydrates: Energy source and structural support
Lipids: Energy storage, membrane structure, insulation
Proteins: Enzymes, transport, structural components
Nucleic acids: Genetic information storage and transfer
Example: Glucose is a monosaccharide that serves as a primary energy source for cells. DNA is a nucleic acid that stores genetic instructions for development and functioning.
Additional info: The images of plants, animals, and cells illustrate the diversity of life forms that depend on organic molecules for their structure and metabolism.
