ANP Study Guide: Human Body Orientation, Chemistry, Cells, and Molecular Biology

The Human Body: An Orientation

Anatomical Position and Directions

The anatomical position is the standard reference for describing body parts and positions. The body stands upright, facing forward, arms at the sides with palms facing forward, and feet slightly apart.

• Directional Terms: Used to describe the location of one body part relative to another.

  • Superior (cranial): Toward the head or upper part of a structure.

  • Inferior (caudal): Away from the head or toward the lower part.

  • Anterior (ventral): Toward the front of the body.

  • Posterior (dorsal): Toward the back.

  • Medial: Toward the midline.

  • Lateral: Away from the midline.

  • Proximal: Closer to the origin of a body part.

  • Distal: Farther from the origin.

  • Superficial: Toward or at the body surface.

  • Deep: Away from the body surface.

Body Planes

• Sagittal Plane: Divides the body into right and left parts.

  • Midsagittal (median): Divides the body into equal right and left halves.

  • Parasagittal: Divides the body into unequal right and left parts.

• Frontal (coronal) Plane: Divides the body into anterior and posterior parts.

• Transverse (horizontal) Plane: Divides the body into superior and inferior parts.

Abdominopelvic Quadrants and Regions

The abdominopelvic cavity is divided for clinical and anatomical purposes:

• Quadrants: Right Upper (RUQ), Left Upper (LUQ), Right Lower (RLQ), Left Lower (LLQ).

• Nine Regions:

  • Right hypochondriac

  • Epigastric

  • Left hypochondriac

  • Right lumbar

  • Umbilical

  • Left lumbar

  • Right iliac (inguinal)

  • Hypogastric (pubic)

  • Left iliac (inguinal)

Example: The liver is primarily in the right hypochondriac and epigastric regions; the appendix is in the right iliac region.

Body Cavities and Serous Membranes

• Dorsal Cavity: Contains the cranial cavity (brain) and vertebral cavity (spinal cord).

• Ventral Cavity: Contains the thoracic cavity (heart, lungs) and abdominopelvic cavity (digestive organs, bladder, reproductive organs).

• Serous Membranes: Thin, double-layered membranes lining body cavities.

  • Parietal layer: Lines cavity walls.

  • Visceral layer: Covers organs.

  • Examples: Pleura (lungs), Pericardium (heart), Peritoneum (abdominal organs).

Chemistry Comes Alive

Atoms, Molecules, and Bonds

• Atoms: Basic units of matter, composed of protons, neutrons, and electrons.

• Molecules: Two or more atoms bonded together.

• Ions: Atoms or molecules with a net electric charge.

• Bonds:

  • Ionic bonds: Transfer of electrons between atoms.

  • Covalent bonds: Sharing of electrons.

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

Water, pH, and Functional Groups

• Water: Universal solvent, polar molecule, forms hydrogen bonds.

• pH: Measure of hydrogen ion concentration.

  • Formula: $\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

  • Acidic: pH < 7; Neutral: pH = 7; Basic: pH > 7

• Functional Groups:

  • Amino (-NH2): Found in amino acids.

  • Carboxyl (-COOH): Found in organic acids.

  • Hydroxyl (-OH): Found in alcohols.

  • Sulfhydryl (-SH): Found in some amino acids.

  • Phosphate (-PO42-): Found in nucleic acids.

  • Methyl (-CH3): Nonpolar, affects gene expression.

Macromolecules

• Lipids: Hydrophobic molecules including fatty acids, triglycerides, phospholipids, and steroids.

  • Triglycerides: Energy storage.

  • Phospholipids: Main component of cell membranes.

  • Steroids: Hormones and membrane components (e.g., cholesterol).

• Carbohydrates: Sugars and polysaccharides (starch, glycogen, cellulose) for energy and structure.

• Proteins: Polymers of amino acids; function as enzymes, structural components, and more.

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

Cells: The Living Units

Cell Structure and Organelles

• Cell: Basic unit of life.

• Organelle: Specialized structure within a cell.

• Organ: Structure composed of two or more tissue types.

• Tissue: Group of similar cells performing a common function.

• Cell Membrane: Phospholipid bilayer controlling entry and exit of substances.

• Nucleus: Contains DNA; control center of the cell.

• Rough Endoplasmic Reticulum (RER): Studded with ribosomes; protein synthesis.

• Smooth Endoplasmic Reticulum (SER): Lipid synthesis and detoxification.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Mitochondria: Site of ATP (energy) production.

• Lysosomes: Contain digestive enzymes; break down waste.

• Centrioles: Involved in cell division.

Cellular Components and Cytoskeleton

• Three Parts of a Cell: Plasma membrane, cytoplasm, nucleus.

• Cytoskeleton: Network of protein filaments.

  • Microtubules: Hollow tubes; shape, transport, cell division.

  • Microfilaments: Thin filaments; cell movement, shape.

  • Intermediate Filaments: Strength and support.

Membrane Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between cells.

Cell Cycle and Mitosis

• Mitosis: Division of the nucleus into two identical daughter cells.

  • Prophase: Chromosomes condense, spindle forms.

  • Metaphase: Chromosomes align at the cell equator.

  • Anaphase: Sister chromatids separate to opposite poles.

  • Telophase: Nuclear envelopes reform, chromosomes decondense.

Homeostasis and Feedback Mechanisms

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes.

• Negative Feedback: Reduces the effect of the original stimulus (e.g., body temperature regulation).

• Positive Feedback: Enhances the original stimulus (e.g., blood clotting, labor contractions).

DNA, RNA, and Gene Expression

DNA Structure and Replication

• DNA: Double-stranded helix; deoxyribose sugar; bases: adenine (A), thymine (T), cytosine (C), guanine (G).

• RNA: Single-stranded; ribose sugar; bases: adenine (A), uracil (U), cytosine (C), guanine (G).

• Base Pairing: A-T (DNA), A-U (RNA), C-G; held by hydrogen bonds.

• Antiparallel Strands: DNA strands run in opposite 5' to 3' directions.

• Replication Bubble and Fork: Sites where DNA is unwound for replication.

• Enzymes in Replication:

  • Helicase: Unwinds DNA.

  • Primase: Synthesizes RNA primer.

  • DNA Polymerase III: Synthesizes new DNA strand.

  • DNA Ligase: Joins DNA fragments.

• Leading vs Lagging Strand: Leading strand synthesized continuously; lagging strand in Okazaki fragments.

Gene Expression: Transcription and Translation

• Transcription: Synthesis of RNA from DNA template.

  • Promoter: DNA sequence where RNA polymerase binds.

  • RNA Polymerase: Enzyme that synthesizes RNA.

  • Coding vs Template Strand: Template strand is used to make RNA; coding strand matches RNA sequence (except T/U).

  • Direction: RNA synthesized 5' to 3', antiparallel to template.

  • Types of RNA: mRNA (messenger), rRNA (ribosomal), tRNA (transfer).

• Genetic Code: Triplet codons specify amino acids.

• Translation: mRNA is decoded to build a polypeptide.

  • Initiation: Ribosome assembles at start codon.

  • Elongation: Amino acids added one by one.

  • Termination: Stop codon reached; polypeptide released.

DNA vs RNA Comparison Table

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Strands	Double	Single
Location	Nucleus	Nucleus & Cytoplasm

Molecular Transport

Types of Transport

• Passive Transport: No energy required; moves substances down concentration gradient.

  • Simple Diffusion: Movement of small, nonpolar molecules.

  • Facilitated Diffusion: Movement via protein channels or carriers.

  • Osmosis: Diffusion of water across a membrane.

• Active Transport: Requires energy (ATP); moves substances against gradient.

  • Primary Active Transport: Direct use of ATP (e.g., sodium-potassium pump).

  • Secondary Active Transport: Uses energy from another gradient.

  • Vesicular Transport: Endocytosis and exocytosis.

Summary Table: Types of Membrane Transport

Type	Energy Required?	Direction	Example
Simple Diffusion	No	High to Low	O2 across membrane
Facilitated Diffusion	No	High to Low	Glucose via carrier protein
Osmosis	No	High to Low (water)	Water movement
Active Transport	Yes	Low to High	Na+/K+ pump
Vesicular Transport	Yes	Varies	Endocytosis, exocytosis

Additional info: These notes cover foundational concepts from Chapters 1-3 and parts of Chapter 2 (chemistry), as well as molecular biology topics relevant to gene expression and cell structure.