Part 1: Basic Chemistry

2.1 Matter and Energy

Understanding matter and energy is fundamental to the study of anatomy and physiology, as all body processes depend on chemical interactions.

• Matter: Anything that occupies space and has mass.

• Energy: The capacity to do work or put matter into motion. Exists as potential energy (stored) and kinetic energy (active).

• Forms of Energy in the Body: Chemical, electrical, radiant, and mechanical. Chemical energy (in bonds) is most important for physiology.

• Energy Conversion: Energy can change forms, but some is always lost as heat.

2.2 Elements and Atomic Structure

Elements and their atomic structure determine the chemical properties essential for life.

• Elements: Unique substances that cannot be broken down by ordinary chemical means. Four elements (carbon, hydrogen, oxygen, nitrogen) make up 96% of body weight.

• Atoms: Building blocks of elements, composed of protons (+), neutrons (0), and electrons (−).

• Atomic Structure: Protons and neutrons are in the nucleus; electrons orbit in shells. Number of protons = number of electrons in a neutral atom.

• Atomic Number: Number of protons.

• Mass Number: Number of protons + neutrons.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Radioisotopes: Unstable isotopes that emit radiation; used in medical diagnosis and research.

2.3 Molecules, Compounds, and Mixtures

Atoms combine to form molecules and compounds, which can also mix physically to form mixtures.

• Molecule: Smallest unit formed by chemical bonding of two or more atoms.

• Compound: Molecule formed from different elements.

• Mixtures: Physical combinations of solutes in a solvent; components retain individual properties.

• Types of Mixtures: Solutions (smallest solutes), colloids, suspensions (largest solutes).

• Concentration: Expressed as percent or molarity (moles/liter).

• Compounds vs. Mixtures: Compounds are chemically bonded and homogeneous; mixtures can be homogeneous or heterogeneous and are physically separable.

2.4 Chemical Bonds

Chemical bonds are energy relationships between electrons of reacting atoms, crucial for molecular structure and function.

• Valence Shell: Outermost electron shell; electrons here are most reactive.

• Inert Atoms: Atoms with full valence shells are chemically unreactive.

• Ionic Bonds: Formed by transfer of electrons from one atom to another, creating ions.

• Covalent Bonds: Formed by sharing electron pairs. Nonpolar if shared equally, polar if unequally (dipole).

• Hydrogen Bonds: Weak bonds between hydrogen (already covalently bonded) and another electronegative atom (e.g., O or N). Important in water and protein structure.

2.5 Chemical Reactions

Chemical reactions involve making or breaking bonds, essential for metabolism and physiology.

• Chemical Equation: Symbolic representation of a chemical reaction.

• Types of Reactions:

  • Synthesis (Anabolic): Building larger molecules from smaller ones.

  • Decomposition (Catabolic): Breaking down molecules into smaller units.

  • Exchange: Both synthesis and decomposition occur.

  • Oxidation-Reduction: Special exchange reactions involving electron transfer.

• Energy Flow: Exergonic reactions release energy; endergonic reactions absorb energy.

• Chemical Equilibrium: State where forward and reverse reactions occur at the same rate.

• Reversibility: Most reactions are theoretically reversible, but many biological reactions proceed in one direction due to energy or product removal.

• Factors Affecting Rate: Particle size, temperature, concentration, and catalysts (enzymes) increase reaction rates.

Part 2: Biochemistry

2.6 Inorganic Compounds

Inorganic compounds, though lacking carbon, are vital for physiological processes.

• Water: Most abundant compound in the body; absorbs/releases heat, universal solvent, participates in reactions, cushions organs.

• Salts: Ionic compounds that dissociate in water to form electrolytes. Calcium and phosphorus salts harden bones and teeth; ions are essential for physiological functions.

• Acids: Proton donors; release H+ in solution.

• Bases: Proton acceptors; common bases include hydroxides, bicarbonate, and ammonia.

• pH: Measures hydrogen ion concentration.

• Blood pH: Normal range is 7.35–7.45.

• Buffers: Prevent excessive pH changes in body fluids.

2.7 Organic Compounds: Synthesis and Breakdown

Organic compounds contain carbon and are synthesized and broken down by specific reactions.

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

• Major Classes: Carbohydrates, lipids, proteins, nucleic acids (all contain C, H, O; proteins and nucleic acids also contain N).

2.8 Carbohydrates

Carbohydrates are the body's primary source of energy.

• Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose, ribose, deoxyribose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose, maltose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen).

• Function: Glucose is the main fuel for ATP production; excess stored as glycogen or fat.

2.9 Lipids

Lipids are important for energy storage, insulation, and cell membrane structure.

• Solubility: Insoluble in water, soluble in fats/organic solvents.

• Triglycerides: Three fatty acids + glycerol; main energy storage form. Unsaturated fatty acids (oils), saturated fatty acids (solid fats).

• Phospholipids: Modified triglycerides with phosphorus; have polar and nonpolar regions; major component of cell membranes.

• Steroids: Cholesterol forms basis for steroid hormones, bile salts, vitamin D; found in cell membranes.

2.10 Proteins

Proteins are essential for structure and function in the body.

• Amino Acids: Building blocks of proteins; 20 types in the body.

• Peptide Bonds: Link amino acids to form polypeptides.

• Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha-helix or beta-pleated sheet.

  • Tertiary: 3D folding.

  • Quaternary: Multiple polypeptide chains.

• Fibrous Proteins: Structural (e.g., keratin, collagen).

• Globular Proteins: Functional (e.g., enzymes, hormones, antibodies, hemoglobin).

• Denaturation: Loss of structure (and function) due to extreme temperature or pH.

• Enzymes: Biological catalysts; lower activation energy, often require cofactors.

2.11 Nucleic Acids (DNA and RNA)

Nucleic acids store and transmit genetic information and direct protein synthesis.

• Nucleotides: Building blocks; each has a nitrogenous base (A, G, C, T/U), a sugar (ribose or deoxyribose), and a phosphate group.

• DNA: Double-stranded helix; deoxyribose sugar; bases A, G, C, T. Stores genetic information and replicates before cell division.

• RNA: Single-stranded; ribose sugar; bases A, G, C, U. Types include messenger, ribosomal, and transfer RNA; involved in protein synthesis.

2.12 ATP (Adenosine Triphosphate)

ATP is the universal energy carrier in cells, transferring energy from food breakdown to cellular processes.

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

• Function: Stores energy released from glucose and other fuels; transfers energy to energy-consuming reactions.

• ATP Hydrolysis Equation:

Additional info: This summary expands on the provided outline with definitions, examples, and equations for clarity and completeness, suitable for Anatomy & Physiology students.