Levels of Structural Organization

Overview

The human body is organized into hierarchical levels, each with increasing complexity. Understanding these levels is fundamental to the study of anatomy and physiology.

• Chemical Level: Atoms and molecules, the building blocks of matter.

• Cellular Level: Cells, the basic units of life.

• Tissue Level: Groups of similar cells performing a common function.

• Organ Level: Structures composed of two or more tissue types working together.

• Organ System Level: Groups of organs that perform related functions.

• Organismal Level: The complete living being.

Life Functions Necessary for Life

Key Life Processes

• Movement: Includes motion of the whole body, organs, cells, and organelles.

• Responsiveness: Ability to detect and respond to changes in the environment.

• Digestion: Breakdown of ingested food into simple molecules.

• Metabolism: All chemical reactions in the body, including catabolism and anabolism.

• Excretion: Removal of wastes from the body.

• Reproduction: Production of new cells or organisms.

• Growth: Increase in size and number of cells.

Organ Systems and Their Characteristics

Major Organ Systems

• Integumentary System: Comprises skin, hair, and nails; protects the body.

• Skeletal System: Bones and joints; supports and protects organs, facilitates movement.

• Muscular System: Skeletal muscles; allows movement, maintains posture, produces heat.

• Nervous System: Brain, spinal cord, nerves; controls body activities via electrical signals.

• Endocrine System: Glands that secrete hormones; regulates growth, metabolism, and reproduction.

• Cardiovascular System: Heart and blood vessels; circulates blood, delivers oxygen and nutrients.

• Lymphatic System: Lymph nodes and vessels; returns leaked fluids, houses immune cells.

• Respiratory System: Lungs and airways; supplies oxygen, removes carbon dioxide.

• Digestive System: Organs like stomach and intestines; breaks down food, absorbs nutrients.

• Urinary System: Kidneys, bladder; removes wastes, maintains water and electrolyte balance.

• Reproductive System: Ovaries, testes, and associated organs; produces offspring.

Homeostasis and Feedback Mechanisms

Definitions and Types

• Homeostasis: The body's ability to maintain stable internal conditions despite external changes.

• Negative Feedback: Maintains stability by reducing the effect of a stimulus (e.g., body temperature regulation).

• Positive Feedback: Amplifies the initial stimulus, leading to an increased response (e.g., blood clotting).

Basic Chemistry Terminology

Key Terms

• Matter: Anything that occupies space and has mass.

• Energy: Capacity to do work or put matter into motion (potential and kinetic energy).

• Element: Unique substance that cannot be broken down by ordinary chemical means.

• Atom: Smallest unit of an element with unique properties.

• Proton: Positively charged subatomic particle in the nucleus.

• Neutron: Neutral subatomic particle in the nucleus.

• Electron: Negatively charged subatomic particle in orbitals around the nucleus.

• Ion: Atom that has gained or lost electrons.

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

Mixtures and Solutions

Types of Mixtures

• Solutions: Homogeneous mixtures with uniform composition.

• Colloids: Intermediate mixtures; particles larger than solutions but do not settle out.

• Suspensions: Heterogeneous mixtures; large, visible solutes that settle over time.

Chemical Bonds and Reactions

Types of Chemical Bonds

• Ionic Bonds: Electrons are transferred from one atom to another, forming ions.

• Covalent Bonds: Electrons are shared between atoms (e.g., hydrogen, oxygen).

Types of Chemical Reactions

• Synthesis Reactions: Two or more atoms/molecules combine to form a larger molecule.

• Decomposition Reactions: Molecule is broken down into smaller molecules or atoms.

• Exchange Reactions: Involve both synthesis and decomposition.

• Oxidation-Reduction (Redox) Reactions: Electrons are transferred between reactants.

Energy in Reactions

• Endergonic Reactions: Consume energy.

• Exergonic Reactions: Release energy.

Properties of Inorganic Compounds

Water and Acids/Bases

• Water: High heat capacity, high heat of vaporization, polar solvent, important for chemical reactions.

• Acids: Ionize into H+ and a negative ion (anion).

• Bases: Ionize into OH- and a positive ion (cation).

• Salts: Ionize into cations and anions, but not H+ or OH-.

• pH: Measure of acid/base concentration.

Acidity and Alkalinity

• Acidic: pH below 7; hydrogen ions outnumber hydroxide ions.

• Basic (Alkaline): pH above 7; hydroxide ions outnumber hydrogen ions.

• Neutral: pH of 7; hydrogen ions equal hydroxide ions.

• Increasing pH: Decreases acidity, increases alkalinity.

• Decreasing pH: Increases acidity, decreases alkalinity.

Organic Compounds: Structure and Function

Monomers, Polymers, and Reactions

• Monomers: Simple building blocks (e.g., glucose).

• Polymers: Large molecules made of repeating monomers (e.g., starch).

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates

• Monosaccharides: Single sugar units (e.g., glucose).

• Disaccharides: Two sugar units (e.g., sucrose).

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

• Formation/Breakdown: Linked by dehydration synthesis, broken by hydrolysis.

• Storage: Plants store as starch; animals as glycogen.

Lipids

• Triglycerides: 3:1 ratio of fatty acids to glycerol; energy storage.

• Saturated Fats: Only single bonds, solid at room temperature, found in animal fats.

• Unsaturated Fats: One or more double bonds, liquid at room temperature, found in plant oils.

• Phospholipids: Modified triglycerides with a phosphate group; form cell membranes.

• Steroids: Lipids with four fused rings; include cholesterol and hormones.

• Cholesterol: Essential for cell membranes and hormone synthesis.

Proteins

• Composed of: Amino acids linked by peptide bonds.

• Primary Structure: Linear sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets stabilized by hydrogen bonds.

• Tertiary Structure: 3D folding due to R group interactions.

• Quaternary Structure: Multiple polypeptide chains forming a functional protein.

• Fibrous Proteins: Long, stable, provide support (e.g., collagen).

• Globular Proteins: Compact, water-soluble, dynamic roles (e.g., enzymes).

Enzymes

• Definition: Globular proteins that act as biological catalysts.

• Function: Speed up reactions by lowering activation energy.

• Steps in Action: Substrate binding, internal rearrangement, product release.

Nucleic Acids

• DNA: Double-stranded, deoxyribose sugar, contains thymine, stores genetic information.

• RNA: Single-stranded, ribose sugar, contains uracil, involved in protein synthesis.

• ATP: Energy transfer molecule, used in metabolism, muscle contraction, and regeneration.

Cell Structure and Function

Plasma Membrane

• Functions: Structural barrier, selective permeability, communication, flexibility.

• Protein Types: Transmembrane, peripheral, gated ion channels, connexons.

Cell Junctions

• Tight Junctions: Prevent passage through extracellular spaces.

• Desmosomes: Prevent cell separation during contraction.

• Gap Junctions: Allow ions and small molecules to pass between cells.

Transport Mechanisms

• Passive Transport: Simple diffusion, facilitated diffusion, osmosis.

• Active Transport: Uses ATP to move substances against concentration gradients.

• Vesicular Transport: Endocytosis (into cell), exocytosis (out of cell).

Table: Comparison of Major Organic Molecules

Key Equations

• pH Calculation:

• ATP Hydrolysis:

• General Reaction Types:

(Synthesis) (Decomposition) (Exchange)

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.