The Chemistry of Life: Foundations for General Biology

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Chapter 2: The Chemistry of Life

Overview of Molecules and Atoms

Understanding the chemistry of life is fundamental to biology. All living and nonliving things are composed of matter, which is made up of elements and atoms. Biological processes depend on chemical interactions at the molecular level.

Matter: Anything that occupies space and has mass. Exists in three physical states: gas, liquid, and solid.
Chemistry: The scientific study of matter, essential for understanding biological processes.
Atoms: The smallest units of matter that retain the properties of an element. Atoms bond to form molecules.
Molecules: Combinations of two or more atoms held together by chemical bonds.
Elements: Pure substances that cannot be broken down by chemical means. Each element consists of one type of atom.

Atom Composition

Atoms are composed of subatomic particles: protons, neutrons, and electrons. The arrangement and number of these particles determine the atom's properties and identity.

Protons: Positively charged, located in the nucleus. The number of protons defines the element (atomic number).
Neutrons: No charge, located in the nucleus. The number of neutrons determines the isotope of an element.
Electrons: Negatively charged, orbit the nucleus at high speeds. The number of electrons determines the atom's ion state and chemical reactivity.

Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are unstable and radioactive.

Ions are atoms that have gained or lost electrons, resulting in a net electrical charge.

Chemical Bonds

Atoms are held together by chemical bonds, which are essential for forming molecules and compounds. There are several types of chemical bonds:

Ionic Bonds: Involve the transfer of electrons from one atom to another, resulting in oppositely charged ions that attract each other.
Covalent Bonds: Involve the sharing of one or more pairs of electrons between atoms. Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.
Polar Covalent Bonds: Electrons are shared unequally, resulting in partial charges on the atoms (e.g., in water molecules).
Hydrogen Bonds: Weak attractions between a hydrogen atom in one molecule and an electronegative atom (like oxygen) in another. Important in the structure of water and biological macromolecules.

The Properties of Water

Water's unique properties are critical for life. These properties arise from its polar covalent bonds and ability to form hydrogen bonds.

Polarity: Water is a polar molecule, with a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms.
Hydrogen Bonding: Water molecules form networks of hydrogen bonds, giving rise to its unique properties.
Ice Floats: Solid water (ice) is less dense than liquid water due to stable hydrogen bonds, allowing ice to float and insulate aquatic environments.
Solvent Properties: Water is an excellent solvent, dissolving many substances essential for life.
Temperature Regulation: Water can absorb and release large amounts of heat with little temperature change, stabilizing environments and organisms.
Cohesion and Adhesion: Water molecules stick together (cohesion) and to other surfaces (adhesion), contributing to processes like water transport in plants and surface tension.

pH and Acidity

The pH scale measures the concentration of hydrogen ions (H+) in a solution, indicating its acidity or basicity.

pH Scale: Ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.
Each unit change in pH represents a tenfold change in H+ concentration.
Acids: Substances that release H+ ions in solution (pH < 7).
Bases: Substances that remove H+ ions from solution (pH > 7).
Buffers: Chemicals that minimize changes in pH by accepting or donating H+ ions, helping maintain homeostasis in organisms.

Environmental Impact: Increased CO2 in the atmosphere leads to ocean acidification, which can harm marine life by reducing the ability to form shells and skeletons.

Life is Based on Carbon

Carbon is the backbone of organic molecules due to its ability to form four covalent bonds, resulting in a diversity of molecular structures.

Organic Compounds: Molecules containing carbon bonded to other elements, especially hydrogen, oxygen, and nitrogen.
Carbon Skeletons: Can be straight, branched, or ring-shaped, forming the framework for complex molecules.
Functional Groups: Specific groups of atoms attached to carbon skeletons that confer unique chemical properties and reactivity.

Polymers and Macromolecules

Most biological macromolecules are polymers, large molecules made by joining smaller units called monomers.

Polymerization: Monomers are linked by dehydration synthesis (removal of water), forming polymers.
Hydrolysis: Polymers are broken down into monomers by adding water, a process important in digestion.

Carbohydrates

Carbohydrates are a major source of energy and structural material in living organisms.

Monosaccharides: Simple sugars (e.g., glucose, fructose) that serve as monomers.
Disaccharides: Formed by joining two monosaccharides (e.g., sucrose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose, chitin) with storage or structural roles.

Lipids

Lipids are hydrophobic molecules important for energy storage, membrane structure, and signaling.

Fats (Triglycerides): Composed of glycerol and three fatty acids. Store energy and provide insulation.
Phospholipids: Major components of cell membranes, with hydrophilic heads and hydrophobic tails forming bilayers.
Steroids: Lipids with four fused rings (e.g., cholesterol, sex hormones).
Cholesterol: Maintains membrane fluidity and is a precursor for steroid hormones.

Types of Dietary Fats

Type	Structure	Physical State	Source	Health Impact
Saturated Fats	No double bonds, straight chains	Solid at room temperature	Animal products	Less healthy
Unsaturated Fats	One or more double bonds, bent chains	Liquid at room temperature	Plant products	Healthier
Trans Fats	Artificially hydrogenated, unusual bonds	Solid	Processed foods	Unhealthy
Omega-3 Fats	Polyunsaturated, essential	Liquid	Fish, nuts, seeds	Beneficial

Proteins

Proteins are polymers of amino acids and perform a vast array of functions in living organisms.

Amino Acids: 20 different types, each with a unique side chain. Linked by peptide bonds to form polypeptides.
Polypeptides: Chains of amino acids that fold into specific three-dimensional shapes, determining protein function.
Protein Function: Includes structural support, transport, enzymes, signaling, and immune defense. Function depends on precise amino acid sequence and shape.
Mutations: Changes in amino acid sequence can alter protein shape and function (e.g., sickle cell anemia).

Enzymes

Enzymes are proteins that catalyze (speed up) chemical reactions by lowering the activation energy required.

Metabolism: The sum of all chemical reactions in an organism, most of which require enzymes.
Substrate: The specific molecule an enzyme acts upon.
Active Site: The region of the enzyme where the substrate binds and the reaction occurs.
Enzyme Specificity: Each enzyme recognizes only its specific substrate.
Inhibitors: Molecules that prevent enzyme function. Competitive inhibitors bind the active site; noncompetitive inhibitors bind elsewhere, changing enzyme shape.
Denaturation: Changes in temperature, pH, or mutations can alter enzyme shape, reducing or eliminating activity (e.g., lactose intolerance).

Key Equations and Concepts

Dehydration Synthesis: Monomer + Monomer → Polymer + Water
Hydrolysis: Polymer + Water → Monomer + Monomer
pH Calculation:

Additional info: The notes above synthesize and expand upon the provided lecture slides, filling in standard academic context for a General Biology course.