Chapter One BIO 210

Cytology

The branch of microscopic anatomy that studies body cells and their internal structure.

Histology

The branch of microscopic anatomy that studies tissues.

Gross Anatomy

The branch of anatomy, also known as macroscopic anatomy, that investigates structures visible to the unaided eye through dissection.

Pathophysiology

A subdiscipline of physiology that focuses on the function of a body system during disease or injury.

Anabolism

A metabolic process in which small molecules are joined together to form larger ones.

Catabolism

A metabolic process in which large molecules are broken down into smaller ones.

Levels of Organization

The structural hierarchy of the human body, progressing from simplest to most complex: chemical level, cellular level, tissue level, organ level, organ system level, and organismal level.

Anatomic Planes

Imaginary flat surfaces passing through the body to create sections, including coronal, transverse, midsagittal, sagittal, and oblique planes.

Anatomic Directional Terms

Precise terms used in anatomical position to describe relative body locations in opposing pairs, such as anterior/posterior, superior/inferior, medial/lateral, and proximal/distal.

Cephalic Region

Anatomical term referring to the head, comprising the frontal, orbital, nasal, buccal, oral, and mental subregions.

Posterior Aspect

A body cavity completely encased in bone that is subdivided into the cranial cavity housing the brain and the vertebral canal housing the spinal cord.

Serous Membrane

A continuous two-layered membrane lining ventral cavities, consisting of a parietal layer against the body wall and a visceral layer covering external organ surfaces, separated by serous fluid.

Mediastinum

The median space in the thoracic cavity that houses the heart, thymus, esophagus, trachea, and major blood vessels.

Peritoneum

The two-layered serous membrane lining the abdominopelvic cavity, comprising an outer parietal peritoneum and an inner visceral peritoneum.

Abdominopelvic Regions

Nine compartments of the abdominopelvic cavity: umbilical, epigastric, hypogastric, right/left hypochondriac, right/left lumbar, and right/left iliac.

Homeostatic System Components

The three dynamic elements regulating internal stability: a receptor detecting a stimulus, a control center integrating input, and an effector bringing about change.

Negative Feedback Mechanism

A homeostatic control mechanism where the action resulting from the effector moves the variable in the opposite direction of the initial stimulus to maintain a set point.

Positive Feedback Loop

A homeostatic control system where the stimulus is continually reinforced in the same direction until a climactic event occurs.

Atomic Number

The unique number of protons in an atom of an element, displayed above the chemical symbol on the periodic table.

Radioisotopes

Unstable isotopes containing excess neutrons that emit radiation as alpha particles, beta particles, or gamma rays while decaying into stable forms.

Octet Rule

The principle that atoms tend to lose, gain, or share electrons to obtain a stable outer valence shell containing eight electrons.

Ionic Bond

An electrostatic attraction that binds oppositely charged cations and anions together into a lattice structure.

Isomers

Molecules that share the same molecular formula but possess different structural arrangements of atoms, such as glucose, galactose, and fructose ($C_6H_{12}O_6$).

Electronegativity

The relative attraction an atom exerts on shared electrons within a covalent bond.

Amphipathic Molecules

Large molecules that contain both polar (hydrophilic) and nonpolar (hydrophobic) regions, such as phospholipids.

Hydrogen Bond

A weak intermolecular attraction formed between a partially positive hydrogen atom of one polar molecule and a partially negative atom of another polar molecule.

Specific Heat

The amount of energy required to raise the temperature of $1\,\text{gram}$ of a substance by $1\,^\circ\text{C}$.

Hydrophobic Exclusion

The physical process in which cohesive water molecules force out and group together nonpolar, uncharged molecules.

Electrolytes

Substances that dissolve and dissociate in water into charged ions, thereby allowing the solution to conduct an electric current.

pH Scale

A logarithmic measurement scale ranging from $0$ to $14$ that expresses the relative concentration of free hydrogen ions ($[H^+]$) in a solution.

Buffer

A substance or chemical system that accepts or donates $H^+$ to prevent drastic shifts in pH when excess acid or base is added.

Colloid

A water mixture containing intermediate-sized solutes that remain suspended when motionless and scatter light without settling.

Dehydration Synthesis

A condensation reaction joining two monomers covalently where one loses an $-H$ and the other loses an $-OH$, releasing a water molecule.

Triglycerides

The primary class of lipids used for long-term energy storage, formed from a single glycerol molecule bonded to three fatty acid chains.

Glycogenesis

The metabolic pathway in which liver and skeletal muscle cells bind excess glucose monomers together to form glycogen.

Nucleotide

The monomer of nucleic acids, consisting of a five-carbon pentose sugar, a phosphate group at carbon 5, and a nitrogenous base at carbon 1.

Deoxyribonucleic Acid (DNA)

A double-stranded nucleic acid composed of deoxyribonucleotides containing adenine, guanine, cytosine, and thymine linked by phosphodiester and hydrogen bonds.

Peptide Bond

The covalent bond joining amino acid monomers, formed via dehydration synthesis between the amine group of one amino acid and the carboxyl group of another.

Quaternary Structure

The highest level of protein structure, characterized by a complex composed of two or more separate polypeptide chains.

Denaturation

A structural change in protein conformation that disrupts its three-dimensional shape and biological activity, typically caused by elevated temperature or pH changes.

Monosaccharide

A simple sugar monomer, such as glucose, galactose, or fructose, typically having an $\text{-H}$ and an $\text{-OH}$ attached to every carbon atom.

Disaccharide

A carbohydrate formed from two monosaccharides bonded together, such as sucrose, lactose, or maltose.

Polysaccharide

A complex carbohydrate composed of three or more monosaccharides linked together, such as glycogen, starch, or cellulose.

Glycogenesis

The metabolic process in which liver and skeletal muscle cells bind excess glucose monomers together to form glycogen.

Glycogenolysis

The enzymatic breakdown of glycogen into glucose monomers by the liver when energy is required by the body.

Gluconeogenesis

The metabolic process by which the liver forms glucose from non-carbohydrate sources.

Glycosaminoglycan (GAG)

A large carbohydrate molecule with attached amine groups found in connective tissue, which can bind to proteins to form proteoglycans.

Pyrimidine

A category of single-ring nitrogenous bases that includes cytosine (C), uracil (U), and thymine (T).

Purine

A category of double-ring nitrogenous bases that includes adenine (A) and guanine (G).

Adenosine Triphosphate (ATP)

A nucleotide composed of the nitrogenous base adenine, a ribose sugar, and three phosphate groups, serving as the central energy transfer molecule in cells.

Peptide Bond

The covalent bond linking two amino acids, formed during dehydration synthesis between the amine group of one amino acid and the carboxylic acid group of another.

Primary Structure

The linear sequence of amino acids joined together by covalent peptide bonds in a protein strand.

Alpha Helix

A spiral coil secondary structure pattern in proteins formed by hydrogen bonds, providing elasticity to fibrous proteins like skin and hair.

Beta Sheet

A planar pleat secondary structure pattern in proteins formed by hydrogen bonds, conferring flexibility to globular proteins like enzymes.

Quaternary Structure

The level of protein organization present in proteins composed of two or more separate polypeptide chains, such as hemoglobin.

Denaturation

A usually irreversible conformational change in a protein's three-dimensional structure caused by factors like elevated temperature or pH changes, which disrupts its biological activity.

Cytology

The scientific study of cells using microscopic and staining techniques.

Transmission Electron Microscope (TEM)

A microscope that directs an electron beam through thin-cut sections of a specimen to produce two-dimensional images with high magnification and resolution.

Scanning Electron Microscope (SEM)

A microscope that directs an electron beam across the surface of a specimen to capture three-dimensional images.

Amphipathic Molecule

A molecule possessing both polar (hydrophilic) and nonpolar (hydrophobic) regions, such as a phospholipid.

Glycocalyx

A sugar coat on the outer surface of the plasma membrane formed by carbohydrate molecules attached to glycolipids and glycoproteins.

Integral Protein

A membrane protein embedded within and spanning across the hydrophobic interior of the phospholipid bilayer.

Peripheral Protein

A membrane protein that is not embedded within the lipid bilayer but is loosely attached to either the external or internal surface of the plasma membrane.

Simple Diffusion

The unassisted passive movement of small, nonpolar solutes across the plasma membrane down their concentration gradient.

Channel-Mediated Diffusion

The movement of small ions across the plasma membrane down their concentration gradient through specific water-filled protein channels.

Carrier-Mediated Diffusion

The passive transport of small polar molecules across the plasma membrane down their concentration gradient facilitated by shape changes in a specific carrier protein.

Osmosis

The passive movement of water across a semipermeable membrane down its concentration gradient toward a higher solute concentration.

Aquaporin

An integral membrane protein that functions as a specialized water channel, allowing rapid passage of water molecules across the plasma membrane.

Tonicity

The ability of a solution to alter a cell's volume or pressure by osmotic movement of water.

Isotonic Solution

A solution that has the same relative concentration of solutes as the cell cytosol, resulting in no net movement of water.

Hypotonic Solution

A solution with a lower solute concentration and higher water concentration than the cytosol, causing water to enter the cell and potentially trigger lysis.

Hypertonic Solution

A solution with a higher solute concentration and lower water concentration than the cytosol, causing water to exit the cell and result in crenation.

Hemolysis

The rupturing of red blood cells (erythrocytes) caused by excessive water entry when placed in a hypotonic environment.

Crenation

The shrinking or shriveling of a cell due to water loss when immersed in a hypertonic solution.

Primary Active Transport

The movement of a solute against its concentration gradient across a membrane powered directly by energy from ATP breakdown.

Sodium-Potassium (Na+/K+) Pump

An active exchange pump that maintains ionic gradients by continuously moving $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell against their concentration gradients using ATP.

Symport

A secondary active transport process where two different substances are moved across the plasma membrane in the same direction.

Antiport

A secondary active transport process where two different substances are moved across the plasma membrane in opposite directions.

Exocytosis

A vesicular transport process requiring ATP in which large substances packed in intracellular vesicles are released from the cell upon vesicle fusion with the plasma membrane.

Phagocytosis

A form of endocytosis ('cellular eating') in which a cell extends pseudopodia to surround and engulf large particulate matter or microorganisms.

Pinocytosis

A form of endocytosis ('cellular drinking') where a cell non-specifically internalizes droplets of interstitial fluid containing dissolved solutes within small vesicles.

Receptor-Mediated Endocytosis

A selective endocytotic process where molecules in the interstitial fluid bind to specific membrane receptors and are internalized within clathrin-coated vesicles.

Resting Membrane Potential (RMP)

The electrical charge difference across the plasma membrane when a cell is at rest, typically measuring between $-50\,\text{mV}$ and $-100\,\text{mV}$.

Ligand

A signalling molecule, such as a neurotransmitter or hormone, that specifically binds to a macromolecular cell surface receptor.

Enzyme-Linked Receptor

A cell surface receptor that, upon ligand binding, activates an intracellular protein kinase enzyme to phosphorylate other proteins.

Rough Endoplasmic Reticulum (Rough ER)

An extensive organelle composed of interconnected sacs studded with bound ribosomes that functions in protein synthesis, modification, and transport vesicle formation.

Smooth Endoplasmic Reticulum (Smooth ER)

An interconnected membranous network lacking ribosomes that carries out lipid synthesis, carbohydrate metabolism, and detoxification of drugs and poisons.

Golgi Apparatus

An organelle composed of elongated membranous cisternae displaying cis- and trans-faces that modifies, packages, and sorts proteins received from the rough ER.

Autophagy

The lysosomal degradation process of removing damaged or unwanted organelles and cellular components.

Peroxisome

A membrane-bound organelle pinched off from the ER that uses enzymes for beta-oxidation of fatty acids, lipid synthesis, and detoxification of hydrogen peroxide.

Mitochondrion

An oblong, double-membrane organelle containing cristae and a matrix that harvests energy via aerobic cellular respiration to generate ATP.

Centrosome

A non-membrane-bound structure containing a pair of perpendicular centrioles that organizes microtubules and forms spindle fibers for cell division.

Proteasome

A large, barrel-shaped protein complex in the cytosol and nucleus that degrades damaged, misfolded, or unneeded proteins tagged with ubiquitin.

Microfilaments

The smallest cytoskeleton filaments, composed of twisted actin monomers, which maintain cell shape, support microvilli, and facilitate cytokinesis.

Microtubules

The largest cytoskeleton components, composed of tubulin protein, which provide tracks for organelle movement, form cilia and flagella, and separate chromosomes during cell division.

Tight Junction

A membrane junction composed of linking protein strands that seals adjacent epithelial cells together to prevent substances from passing between them.

Desmosome

A cell junction consisting of protein plaques and intermediate filaments that mechanical anchors neighboring cells together to withstand mechanical stress.

Gap Junction

A junction composed of transmembrane protein connexons that form fluid-filled pores, allowing direct passageway for ions and small solutes between adjacent cells.

Nucleolus

A dark-staining, spherical, non-membrane-bound structure within the nucleus composed of RNA and protein that synthesizes ribosome subunits.

Nucleosome

A repeating structural unit of chromatin consisting of a length of double-stranded DNA wrapped around nuclear histone proteins.