Introduction to Chemistry for Anatomy & Physiology

Overview

Chemistry is the study of matter and the changes it undergoes, which is fundamental to understanding biological processes in Anatomy & Physiology. All living organisms are composed of matter, which cycles through the environment and is transformed but not created or destroyed.

Basic Chemical Concepts

Elements, Compounds, and Molecules

• Element: A substance that cannot be broken down into simpler substances by chemical reactions. Examples include hydrogen (H), oxygen (O), carbon (C), and nitrogen (N).

• Compound: A substance formed from two or more different elements in a fixed ratio (e.g., H2O, NaCl).

• Molecule: Two or more atoms held together by chemical bonds. All compounds are molecules, but not all molecules are compounds (e.g., O2 is a molecule but not a compound).

States of Matter

• Solid: Atoms are tightly bound, fixed shape and volume (e.g., ice).

• Liquid: Atoms are close but not rigid, no fixed shape, fixed volume (e.g., water).

• Gas: Atoms are far apart, no fixed shape or volume, easily compressed (e.g., water vapor).

Elements Essential for Life

Main Elements in the Human Body

• Top 4 Elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N) – make up 96% of living matter.

• Other Important Elements: Phosphorus (P), Sulfur (S), Calcium (Ca), Potassium (K), Sodium (Na), Iron (Fe), Magnesium (Mg).

• Trace Elements: Required in minute quantities (less than 0.01% of body mass), but essential for life (e.g., zinc, copper).

Atomic Structure

Subatomic Particles

• Protons: Positively charged, located in the nucleus, define the atomic number.

• Neutrons: Neutral charge, located in the nucleus, contribute to atomic mass.

• Electrons: Negatively charged, orbit the nucleus in electron shells, involved in chemical reactions.

Atomic Number, Mass Number, and Isotopes

• Atomic Number (Z): Number of protons in the nucleus; defines the element.

• Mass Number (A): Number of protons plus neutrons.

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

Chemical Bonds and Interactions

Covalent Bonds

• Covalent Bond: Atoms share electrons to fill their valence shells (octet rule).

• Single, Double, Triple Bonds: Single (one pair shared), double (two pairs), triple (three pairs).

Non-Polar vs Polar Covalent Bonds

• Non-Polar Covalent: Electrons shared equally (e.g., O2, CH4).

• Polar Covalent: Electrons shared unequally due to differences in electronegativity (e.g., H2O).

Ionic Bonds

• Ionic Bond: One atom donates an electron to another, forming ions (cations and anions) that attract each other.

• Example: Sodium (Na) donates an electron to chlorine (Cl) to form NaCl (table salt).

Hydrogen Bonds

• Hydrogen Bond: Weak attraction between a hydrogen atom (partial positive) and an electronegative atom (O or N) in another molecule.

• Importance: Stabilizes structures of DNA and proteins, gives water its unique properties.

Molecular Shape and Function

• Molecular Shape: Determined by the positions of atoms and their bonds; crucial for biological function and molecular recognition.

Chemical Reactions

Definition and Examples

• Chemical Reaction: Making and breaking of chemical bonds, rearranging atoms into new substances.

• Reactants: Starting materials; Products: Ending materials.

• Example: Photosynthesis and cellular respiration are key reactions in living organisms.

Chemical Equilibrium

• Chemical Equilibrium: The point at which forward and reverse reactions occur at the same rate; concentrations of reactants and products remain constant.

Properties of Water

Chemistry of Water

• Polar Molecule: Oxygen is more electronegative, creating partial charges and allowing hydrogen bonding.

• Hydrogen Bonds: Allow water molecules to interact with each other and with other polar molecules.

Unique Properties of Water

• Universal Solvent: Dissolves many substances, especially ionic and polar compounds.

• High Heat Capacity: Absorbs and retains heat, moderating temperature changes.

• High Reactivity: Participates in many chemical reactions in the body.

• Lubrication: Reduces friction between body surfaces.

Solutions, Solvents, and Solutes

• Solution: Homogeneous mixture of two or more substances.

• Solvent: The dissolving agent (usually water in biological systems).

• Solute: The substance dissolved in the solvent.

Hydrophilic vs Hydrophobic Substances

• Hydrophilic: Substances that dissolve easily in water (polar or charged).

• Hydrophobic: Substances that do not dissolve in water (non-polar).

Acids, Bases, and pH

pH Scale and Biological Importance

• pH: A measure of hydrogen ion (H+) concentration in a solution.

• Acid: Increases H+ concentration (pH < 7).

• Base: Decreases H+ concentration (pH > 7).

• Neutral: pH = 7 (pure water).

• Blood pH: Normally 7.35–7.45 (slightly basic).

Buffers

• Buffer: Substance that minimizes changes in pH by accepting or donating H+ ions.

• Example: Carbonic acid–bicarbonate buffer system in blood.

Macromolecules: Carbohydrates and Lipids

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose, C6H12O6), main energy source for cells.

• Polysaccharides: Polymers of monosaccharides; storage forms include glycogen (animals) and starch (plants).

Lipids

• Fats (Triglycerides): Composed of glycerol and three fatty acids; used for long-term energy storage, insulation, and protection.

• Phospholipids: Two fatty acids and a phosphate group attached to glycerol; form cell membranes due to hydrophilic heads and hydrophobic tails.

• Steroids: Four fused carbon rings; include cholesterol and steroid hormones.

Macromolecules: Proteins and Nucleic Acids

Proteins

• Monomer: Amino acids (20 types), linked by peptide bonds to form polypeptides.

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

• Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy.

Levels of Protein Structure

• Primary: Sequence of amino acids.

• Secondary: Local folding into alpha-helices and beta-sheets.

• Tertiary: Overall 3D shape of a single polypeptide.

• Quaternary: Association of multiple polypeptide subunits (e.g., hemoglobin).

Protein Denaturation

• Denaturation: Loss of protein structure (and function) due to changes in pH, temperature, or salt concentration.

Nucleic Acids

• DNA (Deoxyribonucleic Acid): Stores genetic information; template for replication and transcription.

• RNA (Ribonucleic Acid): Involved in protein synthesis (translation); mRNA carries instructions from DNA to ribosomes.

• Central Dogma: DNA → RNA → Protein (gene expression).

Summary Table: Key Chemical Concepts for Anatomy & Physiology