Chapter 2: Chemistry of Life

States of Matter

The physical world is composed of matter, which exists in three basic states: solid, liquid, and gas. Each state has distinct properties and examples in biological systems.

• Solid: Has a definite shape and volume. Example: bones.

• Liquid: Has a definite volume but takes the shape of its container. Example: blood plasma.

• Gas: Has neither definite shape nor volume. Example: oxygen in the lungs.

Basic States of Energy

Energy exists in various forms and is essential for biological processes. The two main types are kinetic and potential energy.

• Kinetic energy: Energy of motion (e.g., muscle contraction).

• Potential energy: Stored energy (e.g., energy stored in chemical bonds).

Elements in the Human Body

Four elements make up most of the human body: carbon (C), hydrogen (H), oxygen (O), and nitrogen (N). Each has a unique atomic symbol.

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

Structure of an Atom

Atoms are the basic units of matter, composed of subatomic particles.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Atomic number: Number of protons in the nucleus.

Electrical charge: Atoms are electrically neutral when protons equal electrons.

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons. They have identical chemical properties but different atomic masses.

• Example: Carbon-12 and Carbon-14.

Electron Arrangement and Reactivity

The number and position of electrons determine an atom's chemical reactivity. Electrons are arranged in energy levels (shells) around the nucleus.

• Valence electrons: Electrons in the outermost shell, involved in chemical bonding.

Ions

Ions are atoms or molecules with a net electrical charge due to loss or gain of electrons.

• Cation: Positively charged ion (loss of electrons).

• Anion: Negatively charged ion (gain of electrons).

• Example: Na+ (sodium ion), Cl- (chloride ion).

Molecular Formulas

Molecular formulas represent the types and numbers of atoms in a molecule.

• Example: Water: H2O; Carbon dioxide: CO2

Atomic Number and Atomic Mass

Atomic number: Number of protons in the nucleus.

Atomic mass: Sum of protons and neutrons.

Chemical Bonds

Chemical bonds hold atoms together in molecules. The main types are ionic, covalent, and hydrogen bonds.

• Ionic bonds: Formed by transfer of electrons between atoms (e.g., NaCl).

• Covalent bonds: Formed by sharing electrons (e.g., H2O).

• Hydrogen bonds: Weak attractions between polar molecules (e.g., between water molecules).

Polarity and Solubility

Polarity refers to the distribution of electrical charge in a molecule. Polar molecules dissolve well in water, while non-polar molecules do not.

• Example: Water is polar; oil is non-polar.

Mixtures and Solutions

Mixtures are combinations of two or more substances. The main types are solutions, colloids, and suspensions.

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution, indicating acidity or alkalinity.

• Acidic: pH < 7

• Neutral: pH = 7

• Basic (alkaline): pH > 7

Example: Blood has a pH of about 7.4.

Chemical Reactions in the Body

Chemical reactions involve breaking and forming chemical bonds. The main types are decomposition, synthesis, and exchange reactions.

• Decomposition: Breaking down molecules (e.g., digestion).

• Synthesis: Building larger molecules (e.g., protein synthesis).

• Exchange: Rearranging parts between molecules.

Reversible reactions: Can proceed in both directions.

Activation energy: Minimum energy required to start a reaction.

Organic vs. Inorganic Compounds

Compounds are classified as organic or inorganic based on their structure and composition.

• Organic compounds: Contain carbon and hydrogen; examples include carbohydrates, proteins, lipids, and nucleic acids.

• Inorganic compounds: Do not contain both carbon and hydrogen; examples include water, salts, acids, and bases.

Carbohydrates

Carbohydrates are organic molecules that provide energy and structural support.

• General formula: (CH2O)n

• Monomers: Monosaccharides (e.g., glucose).

• Functions: Energy source, cell recognition.

Proteins

Proteins are polymers made of amino acids, essential for structure and function in cells.

• General formula: Contains amino group (-NH2), carboxyl group (-COOH), and variable R group.

• Monomers: Amino acids.

• Functions: Enzymes, structural support, transport, signaling.

Enzymes

Enzymes are proteins that catalyze biochemical reactions, increasing reaction rates without being consumed.

• Factors affecting rate: Temperature, pH, substrate concentration.

• Importance: Essential for metabolism and regulation.

Nucleic Acids

Nucleic acids store and transmit genetic information. The two main types are DNA and RNA.

• General formula: Composed of nucleotides (phosphate, sugar, nitrogenous base).

• Monomers: Nucleotides.

• Functions: Genetic information storage (DNA), protein synthesis (RNA).

• Complementary base pairing: A-T (DNA), A-U (RNA), C-G.

• Comparison: DNA is double-stranded; RNA is single-stranded.

Lipids

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

• General formula: Varies; commonly includes fatty acids and glycerol.

• Saturated vs. Unsaturated: Saturated fats have no double bonds; unsaturated fats have one or more double bonds.

• Phospholipids: Major component of cell membranes; organized into bilayers.

• Functions: Energy storage, insulation, membrane structure.

ATP (Adenosine Triphosphate)

ATP is the primary energy carrier in cells, providing energy for cellular processes.

• Structure: Adenine base, ribose sugar, three phosphate groups.

• Importance: Energy released by breaking the terminal phosphate bond.

Additional info: These notes expand on the learning objectives by providing definitions, examples, and academic context for each concept listed in the original file.