Chemistry and Physiological Reactions

Introduction to Chemistry in Anatomy & Physiology

Chemistry is fundamental to understanding physiological processes such as movement, digestion, heart function, and nervous system activity. The body is composed of chemicals, and their interactions underpin all biological functions.

• Basic Chemistry: Covers the nature of matter and energy.

• Biochemistry: Focuses on the chemical processes within living organisms.

Matter and Energy

States of Matter

Matter is anything that has mass and occupies space. It exists in three states:

• Solid: Definite shape and volume.

• Liquid: Changeable shape, definite volume.

• Gas: Changeable shape and volume.

Forms of Energy

Energy is the capacity to do work or put matter into motion. It exists as:

• Kinetic Energy: Energy in action.

• Potential Energy: Stored energy.

• Chemical Energy: Stored in chemical bonds.

• Electrical Energy: Movement of charged particles.

• Mechanical Energy: Directly moves matter.

• Radiant Energy: Travels in waves (e.g., light, X-rays).

Atoms and Elements

Elements and Their Importance

Elements are substances that cannot be broken down by ordinary chemical methods. The human body is primarily composed of four elements:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

These elements make up 96% of body mass.

Common Elements Composing the Human Body

Lesser and Trace Elements

Atomic Structure

Atoms are the smallest units of elements, consisting of protons, neutrons, and electrons.

• Protons: Positive charge, found in nucleus.

• Neutrons: No charge, found in nucleus.

• Electrons: Negative charge, orbit nucleus.

Models of Atomic Structure

• Planetary Model: Electrons orbit nucleus in fixed paths (outdated).

• Orbital Model: Electrons are found in regions of probability, forming an electron cloud.

Identifying Elements

Elements are identified by their atomic number (number of protons), mass number (protons + neutrons), isotopes (same protons, different neutrons), and atomic weight (average mass of isotopes).

Atomic Structure of Smallest Atoms

• Hydrogen: 1 proton, 0 neutrons, 1 electron

• Helium: 2 protons, 2 neutrons, 2 electrons

• Lithium: 3 protons, 4 neutrons, 3 electrons

Isotopes and Radioisotopes

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

• Radioisotopes: Unstable isotopes that decay, emitting radioactivity. Used in medical diagnostics and treatments.

Combining Matter: Molecules, Compounds, and Mixtures

Molecules and Compounds

• Molecule: Two or more atoms bonded together.

• Compound: Molecule with two or more different atoms bonded together (e.g., C6H12O6).

Types of Mixtures

• Solutions: Homogeneous mixtures; solute particles are tiny and do not settle out.

• Colloids: Heterogeneous mixtures; larger particles, do not settle out, scatter light.

• Suspensions: Heterogeneous mixtures; large particles settle out.

Chemical Bonds and Reactions

Role of Electrons in Chemical Bonding

Electrons occupy energy levels called shells. The outermost shell (valence shell) determines chemical reactivity. Atoms seek stability by achieving a full valence shell (usually 8 electrons, known as the octet rule).

Types of Chemical Bonds

• Ionic Bonds: Transfer of electrons between atoms, forming charged ions (cations and anions).

• Covalent Bonds: Sharing of electrons between atoms. Can be single, double, or triple bonds.

• Hydrogen Bonds: Weak attractions between electropositive hydrogen and electronegative atoms (e.g., in water).

Polar and Nonpolar Covalent Bonds

• Nonpolar: Equal sharing of electrons (e.g., CO2).

• Polar: Unequal sharing, creating dipoles (e.g., H2O).

Hydrogen Bonds

Hydrogen bonds are essential for maintaining the structure of water and biological molecules.

Chemical Reactions

Types of Chemical Reactions

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

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

• Exchange (Displacement): Bonds are both made and broken.

Redox Reactions

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

Energy Flow in Reactions

• Exergonic: Release energy.

• Endergonic: Absorb energy.

Rate of Chemical Reactions

Influenced by temperature, concentration, particle size, and catalysts (enzymes).

Biochemistry: Inorganic and Organic Compounds

Inorganic Compounds

• Water: Most abundant; high heat capacity, solvent properties, reactivity, cushioning.

• Salts: Ionic compounds; dissociate into electrolytes.

• Acids and Bases: Acids release H+; bases accept H+. pH measures [H+] concentration.

Buffers

Buffers resist changes in pH, maintaining homeostasis.

Organic Compounds

• Carbohydrates: Sugars and starches; monosaccharides, disaccharides, polysaccharides.

• Lipids: Triglycerides, phospholipids, steroids, eicosanoids.

• Proteins: Polymers of amino acids; structural, enzymatic, transport, contractile, communication, defensive functions.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

Protein Structure and Function

Levels of Protein Structure

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets.

• Tertiary: Folding of secondary structures.

• Quaternary: Multiple polypeptides forming a functional protein.

Enzymes and Enzyme Activity

Enzyme Function

Enzymes are biological catalysts that lower activation energy and increase reaction speed.

• Specificity: Each enzyme acts on a specific substrate.

• Mechanism: Substrate binds to active site, forms enzyme-substrate complex, product is released.

Nucleic Acids: DNA and RNA

Structure and Function

• DNA: Double helix; stores genetic blueprint.

• RNA: Single-stranded; involved in protein synthesis.

ATP: Cellular Energy Currency

Structure and Function

ATP (adenosine triphosphate) stores and transfers energy for cellular work.

• Structure: Adenine, ribose, three phosphate groups.

• Function: Phosphate group transfer powers transport, mechanical, and chemical work.

Summary Table: Major Chemical Concepts in Anatomy & Physiology

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