General Biology: Chemistry of Life, Water, Carbon, Macromolecules, and Biological Reactions

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Chemistry of Life & Bonds

Atomic Structure and Chemical Bonds

The chemistry of life is based on the structure of atoms and the types of chemical bonds they form. These interactions determine the properties and behaviors of biological molecules.

Atomic Number: The number of protons in an atom's nucleus, which defines the element's identity.
Covalent Bonds: Formed by the sharing of electron pairs between atoms. Can be polar (unequal sharing, leading to partial charges) or nonpolar (equal sharing).
Ionic Bonds: Created by the transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.
Hydrogen Bonds: Weak attractions between a hydrogen atom covalently bonded to an electronegative atom (like oxygen or nitrogen) and another electronegative atom. These are crucial for the structure of water and biological macromolecules.
Polarity: Molecules with uneven distribution of electrons (polar) interact differently than nonpolar molecules, affecting solubility and biological function.

Example: Water (H2O) is a polar molecule due to unequal sharing of electrons between hydrogen and oxygen.

Properties of Water

Unique Characteristics of Water

Water's molecular structure gives it several unique properties essential for life.

Cohesion: Water molecules stick to each other due to hydrogen bonding.
Adhesion: Water molecules stick to other surfaces, aiding processes like capillary action.
High Specific Heat: Water can absorb or release large amounts of heat with little temperature change, helping regulate climate and body temperature.
Evaporative Cooling: As water evaporates, it removes heat, cooling surfaces (e.g., sweating in animals).
Hydrogen Bonds: Responsible for water's cohesion, adhesion, and high specific heat.

Example: Water's high specific heat helps maintain stable temperatures in organisms and environments.

Carbon & Organic Molecules

Structure and Diversity of Organic Molecules

Carbon's ability to form four covalent bonds allows for a wide variety of molecular shapes and complex organic molecules.

Carbon Bonds: Four bonds per carbon atom enable branching, rings, and chains in organic molecules.
Functional Groups: Specific groups of atoms (e.g., hydroxyl, carboxyl, amino) attached to carbon skeletons that determine chemical properties and reactivity.
Hydrocarbons: Molecules consisting only of carbon and hydrogen; typically nonpolar, hydrophobic, and insoluble in water.

Example: Fatty acids are long hydrocarbon chains with a carboxyl group at one end.

Macromolecules & Polymers

Types and Functions of Biological Macromolecules

Macromolecules are large, complex molecules essential for life. Most are polymers, made by joining smaller units called monomers.

Carbohydrates: Made of monosaccharides (simple sugars); polymers include polysaccharides like starch and cellulose, joined by glycosidic bonds.
Proteins: Polymers of amino acids linked by peptide bonds; have four levels of structure (primary, secondary, tertiary, quaternary).
Lipids: Hydrophobic molecules used for energy storage and membrane structure; include fats (saturated and unsaturated).
Nucleic Acids: DNA and RNA are polymers of nucleotides; store and transmit genetic information.

Example: Starch is a polysaccharide composed of glucose monomers.

Macromolecule	Monomer	Bond Type	Function
Carbohydrate	Monosaccharide	Glycosidic bond	Energy, structure
Protein	Amino acid	Peptide bond	Catalysis, structure, signaling
Lipid	Fatty acid & glycerol	Ester bond	Energy storage, membranes
Nucleic Acid	Nucleotide	Phosphodiester bond	Genetic information

Reactions in Biology

Polymer Formation and Breakdown

Biological macromolecules are assembled and disassembled through specific chemical reactions.

Dehydration Synthesis: Builds polymers by joining monomers, releasing water as a byproduct.
Hydrolysis: Breaks polymers into monomers by adding water.

Example: Proteins are formed by dehydration synthesis of amino acids; digestion breaks them down by hydrolysis.

Key Equations:

Dehydration synthesis:
Hydrolysis: