BIO 130 Ch. 01-03

Anatomy & Physiology Definitions and Subdisciplines

• Anatomy is the study of structure.

  • Subdisciplines: Gross anatomy (naked-eye structures), histology/microscopic anatomy (tissues), histopathology (tissues for disease signs), and cytology (cells and ultrastructure).

• Physiology is the study of function, utilizing experimental science methods.

  • Subdisciplines: Neurophysiology (nervous system), endocrinology (hormones), pathophysiology (mechanisms of disease), and comparative physiology (studying different species to understand functions and develop drugs).

Ways to Examine Body Structure

• Inspection: Looking at appearance.

• Palpation: Feeling a structure with hands.

• Auscultation: Listening to sounds produced by the body.

• Percussion: Tapping on the body, feeling for resistance, and listening to emitted sounds for abnormalities.

• Dissection: Cutting and separating human body tissues (using a cadaver) to reveal tissue relationships.

• Comparative anatomy: Dissecting multiple species to learn about form, function, and evolution.

• Medical imaging / Exploratory surgery: Viewing inside the living body (exploratory surgery has largely been replaced by modern radiology and imaging).

Inductive vs. Hypothetico-Deductive Reasoning & Hypotheses

• Inductive method: Making numerous observations until confident in drawing generalizations and predictions; scientific truth derived this way is tentative and subject to change.

• Hypothetico-deductive method: The primary method for gaining physiological knowledge, starting with an educated speculation (hypothesis).

• Criteria for a good hypothesis: It must be consistent with what is already known, testable, and falsifiable (meaning you must be able to specify what evidence would prove it wrong).

Experimental Design & Peer Review

• Sample size: The number of subjects used in a study.

• Controls: A control group resembles the treatment group but does not receive the treatment.

• Psychosomatic effects: Effects of a subject's state of mind on their physiology; controlled by giving a placebo to the control group.

• Experimenter bias: Avoided using the double-blind method, where neither the subject nor the experimenter knows who is in the control or treatment group.

• Statistical testing: Used to provide a statement of probability that the treatment was effective.

• Peer review: Critical evaluation by other experts in the field prior to funding or publication, ensuring verification, repeatability, honesty, objectivity, and quality.

Scientific Facts, Laws, and Theories

• Scientific fact: Information that can be independently verified.

• Law of nature: A generalization about how matter and energy behave, resulting from inductive reasoning and repeated observations (stated as a verbal statement or mathematical formula).

• Theory: An explanatory statement or set of statements derived from facts, laws, and confirmed hypotheses that summarizes what is known and suggests directions for further study.

Levels of Hierarchical Structure (Most to Least Inclusive)

• Organism: A single, complete individual.

• Organ system: A group of organs with a unique collective function (e.g., circulation, respiration).

• Organ: A structure composed of two or more tissue types carrying out a specific function.

• Tissue: Similar cells and cell products forming a discrete region and performing a specific function.

• Cell: The smallest unit carrying out all basic functions of life.

• Organelle: A structure within a cell that carries out a specialized function.

• Molecule: A particle composed of two or more atoms (largest are macromolecules like proteins, fats, and DNA).

• Atom: The smallest particle with a unique chemical identity.

Reductionism vs. Holism

• Reductionism: The theory that large, complex systems can be understood by studying their simpler components; essential to scientific thinking.

• Holism: The concept that "emergent properties" occur as you ascend levels of organization that cannot be predicted from individual parts alone (humans are more than the sum of their parts).

Characteristics of Living Matter

• Organization: Exhibiting a higher level of organization than nonliving things.

• Cellular composition: Living matter compartmentalized into one or more cells.

• Metabolism: The sum of internal chemical changes.

• Responsiveness (excitability): The ability to sense and react to environmental stimuli.

• Movement: Movement of the entire organism or substances within it.

• Homeostasis: Maintaining relatively stable internal conditions.

• Development: Change in form or function over time, including differentiation (transformation of unspecialized cells into cells with committed tasks).

• Growth: Increase in size through chemical change.

• Reproduction: Producing copies of themselves and passing genes to offspring.

• Evolution: Genetic change in a population from generation to generation due to mutations.

Homeostasis & Feedback Loops

• Homeostasis: The ability to detect change, activate mechanisms that oppose it, and maintain relatively stable internal conditions around a set point (dynamic equilibrium).

• Components of a feedback loop:

  • Receptor: Structure that senses change in the body (e.g., baroreceptors monitoring blood pressure).

  • Integrating (control) center: Processes sensory information, makes a decision, and directs a response (e.g., cardiac center of the brainstem).

  • Effector: Cell or organ that carries out the final corrective action (e.g., the heart).

• Negative feedback: A self-correcting mechanism where the body senses a change and reverses/negates it (e.g., thermoregulation via vasodilation/sweating or vasoconstriction/shivering; blood pressure regulation via baroreflex).

• Positive feedback: A self-amplifying cycle that leads to greater change in the same direction to produce rapid changes (e.g., childbirth, blood clotting, protein digestion, and nerve signal generation).

Gradients

• Gradient: A difference in chemical concentration, charge, temperature, or pressure between two points.

• Flow direction: Matter and energy naturally flow down a gradient (from high to low pressure, concentration, etc.) without requiring metabolic energy. Moving up a gradient requires spending metabolic energy.

Anatomical Terminology & Precision

Standardized terminology (such as the Terminologia Anatomica) prevents confusion from regional names or eponyms (structures named after people) and is vital for maintaining patient safety.

The Anatomic Position

Upright stance, feet parallel and flat on the floor, upper limbs at the sides, palms facing anteriorly (forward), head level, and eyes looking forward.

Anatomic Planes and Sections

• Coronal (frontal) plane: Vertical plane dividing the body into anterior (front) and posterior (back) parts.

• Transverse (cross-sectional) plane: Horizontal plane dividing the body into superior (top) and inferior (bottom) parts.

• Midsagittal (median) plane: Vertical plane passing exactly down the midline, dividing the body into equal left and right halves.

• Sagittal plane: Parallel to the midsagittal plane, dividing the structure into unequal left and right portions.

• Oblique plane: Passes through a structure at an angle.

Directional Terms

Used in opposing pairs to describe relative positions while in the anatomic position (e.g., anterior/posterior, dorsal/ventral, proximal/distal, superior/inferior, medial/lateral).

Axial vs. Appendicular Regions

• Axial region: Includes the head, neck, and trunk, forming the main vertical axis of the body.

• Appendicular region: Includes the upper and lower limbs.

Major Body Cavities and Subdivisions

• Posterior aspect (completely encased in bone):

  • Cranial cavity: Formed by cranial bones; houses the brain.

  • Vertebral canal: Formed by bones of the vertebral column; houses the spinal cord.

• Ventral cavity (larger, anteriorly placed):

  • Thoracic cavity: Superior subdivision containing the mediastinum (heart, thymus, esophagus, trachea, major blood vessels), pleural cavities (lungs), and pericardial cavity (heart).

  • Abdominopelvic cavity: Inferior subdivision containing the abdominal cavity (digestive organs, kidneys, most ureters) and pelvic cavity (distal large intestine, remainder of ureters, urinary bladder, internal reproductive organs).

Serous Membranes

• Composed of a two-layered serous membrane lining subdivisions of the ventral cavity.

  • Parietal layer: Lines the internal surface of the body wall.

  • Visceral layer: Covers the external surface of organs (viscera).

  • Serous cavity & fluid: The potential space between the parietal and visceral layers containing lubricating serous fluid to reduce friction.

• Key examples: Pericardium (surrounds the heart; contains parietal/visceral layers and pericardial cavity), Pleura (surrounds the lungs; contains parietal/visceral layers and pleural cavity), and Peritoneum (surrounds abdominopelvic organs; contains parietal/visceral layers and peritoneal cavity).

Abdominopelvic Quadrants and Regions

• Four Quadrants: Divided by horizontal and vertical planes through the umbilicus into Right Upper Quadrant (RUQ), Left Upper Quadrant (LUQ), Right Lower Quadrant (RLQ), and Left Lower Quadrant (LLQ).

• Nine Regions: Divided into:

  • Middle column: Epigastric (superior), Umbilical (center), Hypogastric (inferior).

  • Lateral columns: Right and Left Hypochondriac (superior/lateral), Right and Left Lumbar (middle/lateral), and Right and Left Iliac/Inguinal (inferior/lateral).

Element, trace element, mineral

• Element: The simplest form of matter to have unique chemical properties.

• Trace element: Elements present in very small amounts (less than 0.1% of body weight), yet play vital physiological roles.

• Mineral: Inorganic elements extracted from the soil by plants and passed up the food chain (such as calcium, phosphorus, chlorine, magnesium, potassium, sodium, and sulfur).

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Basic atomic structure

Consists of subatomic particles: protons (positive charge, located in the nucleus), neutrons (no charge / neutral, located in the nucleus), and electrons (negative charge, located in the surrounding electron cloud/shells)

Ion, anion, cation, and ionic bonds

• Ion: A charged particle with an unequal number of protons and electrons.

• Anion: A particle that gains electrons, acquiring a net negative charge.

• Cation: A particle that loses electrons, acquiring a net positive charge.

• Ionization and ionic bonds: Electrons are transferred from one atom to another, creating oppositely charged ions (cations and anions) that attract each other to form an ionic bond.

Molecule, compound, isomer

• Molecule: Chemical particles composed of two or more atoms united by a chemical bond.

• Compound: Molecules composed of two or more different elements.

• Isomers: Molecules with identical molecular formulas but different arrangements of their atoms.

Covalent bond (polar vs. non-polar)

• Covalent bond: Formed by sharing one or more pairs of electrons between atoms.

• Non-polar covalent bond: A bond where electrons are shared equally between atoms.

• Polar covalent bond: A bond where electrons are shared unequally, spending more time near one nucleus than the other, creating regions of partial positive and partial negative charge.

Hydrogen Bond

• Definition: A weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another or the same molecule.

• Examples of importance: Crucial for the three-dimensional folding of proteins and nucleic acids (such as DNA), as well as the unique properties of water.

Properties of Water & Key Terms

• Five properties of water: Solvency, cohesion, adhesion, chemical reactivity, and thermal stability.

• Hydrophilic: Substances that dissolve in water because they are polarized or charged.

• Hydrophobic: Substances that do not dissolve in water because they are non-polar or neutral.

• Adhesion: The tendency of one substance to cling to another dissimilar substance.

• Cohesion: The tendency of molecules of the same substance to cling to each other.

• Calorie: The amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius.

pH

• Mathematical expression: pH = -log [H]+.

• Hydrogen ion concentration: A lower pH value indicates a higher hydrogen ion concentration (more acidic), while a higher pH value indicates a lower hydrogen ion concentration (more basic/alkaline), with each whole unit change representing a 10-fold difference.

Energy

• Energy: The capacity to do work.

• Potential energy: Energy contained in an object because of its position or internal state, but not currently doing work.

• Kinetic energy: Energy of motion, actively doing work.

• Free energy: Potential energy available in a system to do useful work.

Classes of Chemical Reactions

• Decomposition reactions: A large molecule breaks down into two or more smaller ones.

• Synthesis reactions: Two or more small molecules combine to form a larger one.

• Exchange reactions: Two molecules exchange atoms or groups of atoms with each other.

Metabolism, anabolism, and catabolism

• Metabolism: The sum of all the chemical reactions in the body.

• Anabolism: Energy-storing (endergonic) synthesis reactions that build larger molecules from smaller ones.

• Catabolism: Energy-releasing (exergonic) decomposition reactions that break down complex molecules into smaller ones.

Oxidation-reduction (redox) reactions

• Definition: Chemical reactions in which electrons are transferred from one molecule to another.

• Oxidation: A reaction in which a molecule gives up electrons and releases energy.

• Reduction: A reaction in which a molecule gains electrons and energy.

Macromolecule, monomer, polymer

• Macromolecule: Very large organic molecules with high molecular weights.

• Polymer: Molecules made of a repetitive series of identical or similar subunits.

• Monomer: The identical or similar subunits that act as building blocks to form a polymer.

Dehydration synthesis and hydrolysis reactions

• Dehydration synthesis (Condensation): A hydroxyl group (-OH) is removed from one monomer and a hydrogen atom (-H) from another, joining them together with a covalent bond and producing water (H2O) as a by-product.

• Hydrolysis: The chemical splitting of a polymer into monomers by the addition of water (H2O), where the water molecule breaks down into an H+ and -OH- to attach to the resulting monomers.

Characteristics and types of carbohydrates

• Characteristics: Hydrophilic organic molecules with a 2:1 ratio of hydrogen to oxygen.

• Monosaccharides (three important ones):

  • Glucose: Blood sugar; primary energy source for most cells.

  • Galactose: Converted to glucose in the body; found combined in milk sugar.

  • Fructose: Fruit sugar; converted to glucose and used for energy.

• Disaccharides (three important ones):

  • Sucrose: Table sugar (glucose + fructose); plant transport sugar.

  • Lactose: Milk sugar (glucose + galactose); found in milk.

  • Maltose: Grain sugar (glucose + glucose); produced during starch digestion.

• Polysaccharides (three important ones & uses):

  • Glycogen: Energy storage polysaccharide made by animals (stored in the liver and skeletal muscles).

  • Starch: Energy storage polysaccharide made by plants (the only digestible plant polysaccharide for humans).

  • Cellulose: Structural polysaccharide of plant cell walls; provides dietary fiber in humans (indigestible).

Conjugated carbohydrates and proteoglycans

• Conjugated carbohydrates: Macromolecules covalently bound to lipid or protein components, including glycoproteins, glycolipids, and proteoglycans.

• Uses for proteoglycans: They form gels that hold cells and tissues together, lubricate joints, and provide structural support to connective tissues.

Characteristics of fatty acids and saturated vs. unsaturated fatty acids

• Fatty acids: Chains of 4 to 24 carbon atoms with a carboxyl group (-COOH) on one end and a methyl group (-CH3) on the other.

• Saturated fatty acid: A fatty acid with carbon atoms saturated with the maximum possible number of hydrogen atoms, containing no double bonds, allowing molecules to pack closely together (solid at room temperature).

• Unsaturated fatty acid: A fatty acid that contains one or more carbon-carbon double bonds (C=C), resulting in fewer hydrogen atoms and a bend in the molecular chain (liquid at room temperature).

Structural characteristics of a triglyceride and principal sources

• Triglyceride structure: A neutral fat consisting of a three-carbon glycerol molecule bonded to three fatty acids by dehydration synthesis.

• Principal sources: Saturated fats are primarily derived from animal sources (such as meat, butter, and dairy), while unsaturated fats are primarily derived from plant sources (such as vegetable oils, nuts, and seeds).

Structural characteristics of a phospholipid and "amphipathic"

• Phospholipid structure: Similar to a neutral fat, but one fatty acid is replaced by a phosphate group attached to a nitrogen-containing group.

• Amphipathic: Having both hydrophilic (water-soluble, polar phosphate "head") and hydrophobic (water-insoluble, non-polar fatty acid "tail") regions.

Structural characteristics of a steroid and examples/functions

• Steroid structure: A lipid with carbon atoms arranged in four interlocking rings.

• Examples and functions:

  • Cholesterol: The parent steroid from which other steroids are synthesized and a vital structural component of plasma membranes.

  • Hormones: Such as cortisol, progesterone, estrogen, testosterone, and bile acids, which regulate physiological processes like metabolism, reproduction, and digestion.

HDL vs. LDL

• HDL (High-Density Lipoprotein): A "good" lipoprotein with a high proportion of protein to lipid; it scavenges excess cholesterol from the tissues and transports it to the liver for elimination.

• LDL (Low-Density Lipoprotein): A "bad" lipoprotein with a high proportion of lipid to protein; it transports cholesterol to cells throughout the body.

Structural characteristics of an amino acid and peptide bonding

• Amino acid structure: Consists of a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R group).

• Peptide bonding: A covalent bond formed by dehydration synthesis that joins the amino group of one amino acid to the carboxyl group of the next.

Conformation and denaturation

• Conformation: The unique, three-dimensional shape of a protein crucial to its function.

• Denaturation: A drastic conformational change in a protein caused by extreme heat or pH that destroys its function.

Four levels of protein structure

• Primary structure: A protein's sequence of amino acids, which is joined by peptide bonds.

• Secondary structure: A coiled ($\alpha$-helix) or folded ($\beta$-sheet) shape held together by hydrogen bonds between nearby peptide backbone groups.

• Tertiary structure: Further bending and folding into a globular or fibrous shape due to hydrophobic-hydrophilic interactions and disulfide bridges between $\text{R}$ groups.

Seven functions of proteins and examples

• Structure: Keratin in hair and skin, and collagen in bones and blood vessels.

• Communication: Hormones and ligand-receptor molecules.

• Membrane transport: Channel and carrier proteins in the plasma membrane.

• Catalysis: Enzymes that regulate metabolic reactions.

• Recognition and protection: Antibodies and clotting proteins.

• Movement: Motor proteins like myosin and actin for muscle contraction.

• Cell adhesion: Proteins that bind cells together.

Enzyme, substrate, activation energy, and mechanism of action

• Enzyme: Proteins that function as biological catalysts, lowering activation energy to speed up metabolic reactions.

• Substrate: The substance an enzyme acts upon and converts into products.

• Activation energy: The energy needed to get a chemical reaction started.

• Basic mechanism of action: A substrate binds to the enzyme's active site to form an enzyme-substrate complex, the enzyme catalyzes the reaction by lowering activation energy, and the resulting product is released unchanged.

Structural components of a nucleotide and why ATP is high-energy

• Nucleotide components: A nitrogenous base, a monosaccharide (sugar) ring, and one or more phosphate groups.

• Why ATP is high-energy: Its three phosphate groups are negatively charged and repel each other; the covalent bonds holding them together store a great deal of potential energy that is released quickly when broken.

Basic purposes of DNA and RNA

• DNA (Deoxyribonucleic acid): Constitutes our genes, transfers hereditary information from cell to cell, and contains the instructions for synthesizing all the body's proteins.

• RNA (Ribonucleic acid): Interprets the code in DNA and uses its instructions to assemble proteins.

Four basic components of the cell theory

• All organisms are composed of cells and cell products.

• The cell is the simplest structural and functional unit of life.

• An organism’s structure and functions are due to the activities of cells.

• Cells come only from preexisting cells.

Why cell size is limited (surface area vs. volume)

• An overly large cell cannot support itself and may rupture.

• For a given increase in diameter, volume increases much faster than surface area (volume is proportional to the cube of the diameter, whereas surface area is proportional to the square of the diameter).

Phospholipid bilayer and two other lipid types

• Phospholipids: Make up 75% of membrane lipids; amphipathic molecules arranged in a bilayer with hydrophilic phosphate heads facing the water on each side and hydrophobic tails directed toward the center.

• Cholesterol: Makes up 20% of membrane lipids; holds phospholipids still and can stiffen the membrane.

• Glycolipids: Make up 5% of membrane lipids; phospholipids with short carbohydrate chains on the extracellular face that contribute to the glycocalyx.

Locations and properties of transmembrane and peripheral proteins

• Transmembrane proteins: Pass completely through the membrane, featuring hydrophilic regions that contact the watery cytoplasm and extracellular fluid, and hydrophobic regions that pass through the lipid core.

• Peripheral proteins: Adhere to only one face of the membrane (those on the inner face are usually tethered to a transmembrane protein and the cytoskeleton).

Six classes of membrane proteins and four types of channels

• Six functional classes: Receptors, enzymes, channel proteins, carriers, cell-identity markers, and cell-adhesion molecules (CAMs).

• Four types of channels:

  • Leak channels: Channel proteins that are always open.

  • Ligand-gated channels: Gates that open in response to chemical messengers.

  • Voltage-gated channels: Gates that open in response to charge changes.

  • Mechanically gated channels: Gates that open in response to physical stress on the cell.

Glycocalyx functions

• Serves as a fuzzy carbohydrate coating around the cell that acts as a surface marker.

• Protects the cell membrane, enables the immune system to recognize self from non-self cells, assists in fertilization, and aids in embryonic development and tissue binding.

Functions of microvilli, cilia, pseudopods, and flagella

• Microvilli: Extensions of the membrane that serve to increase surface area (providing 15 to 40 times more surface area) and are best developed in cells specialized for absorption.

• Cilia: Hair-like processes where single, nonmotile primary cilia serve as "sensors" or "antennas" monitoring nearby conditions, while motile cilia beat in waves to sweep material across a surface in one direction.

• Flagella: Whiplike structures that are much longer than cilia and use undulating, snake-like, corkscrew movements for cellular locomotion (the tail of a sperm is the only functional flagellum in humans).

• Pseudopods: Continually changing extensions of the cell that vary in shape and size, used for cellular locomotion and capturing foreign particles.

Selectively permeable membrane definition

A membrane that allows certain molecules or ions to pass through by means of active or passive transport while restricting others based on size, charge, or solubility.

Passive vs. active transport mechanisms

• Passive transport: Requires no cellular energy (ATP) and relies on random molecular motion and concentration gradients (includes filtration, simple diffusion, and osmosis).

• Active transport: Requires cellular energy (ATP) to move solutes against their concentration gradient or transport large quantities via vesicular transport.

Osmosis and tonicity definitions

• Osmosis: The net flow of water through a selectively permeable membrane from an area of higher water concentration (lower solute) to lower water concentration (higher solute).

• Tonicity: The ability of a surrounding solution to affect fluid volume and pressure within a cell (categorized into isotonic, hypertonic, and hypotonic solutions).

Functions of major cellular organelles

• Rough Endoplasmic Reticulum (Rough ER): Covered with ribosomes; produces phospholipids and proteins of nearly all cell membranes and synthesizes proteins packaged in other organelles or secreted.

• Smooth Endoplasmic Reticulum (Smooth ER): Tubular ER lacking ribosomes; synthesizes steroids and other lipids, detoxifies alcohol and other drugs, and stores calcium.

• Ribosomes: Small granules of protein and RNA responsible for reading genetic messages and assembling amino acids into proteins.

• Golgi complex: A system of membranous cisterns that synthesizes carbohydrates, modifies newly synthesized proteins, sorts and packages them into Golgi vesicles, lysosomes, or secretory vesicles.

• Lysosomes: Packages of enzymes bound by a membrane for intracellular hydrolytic digestion, autophagy, and autolysis.

• Peroxisomes: Resemble lysosomes; use molecular oxygen to oxidize organic molecules, producing and breaking down hydrogen peroxide to neutralize free radicals and detoxify alcohol and blood-borne toxins.

• Proteasomes: Hollow, cylindrical organelles containing enzymes that break down tagged, targeted surplus proteins into short peptides and amino acids.

• Mitochondria: Organelles surrounded by a double membrane with cristae and a matrix, specialized for extracting energy from organic molecules and transferring it to ATP.

• Centrioles: Short cylindrical assemblies of microtubules arranged in nine groups of three, playing an important role in cell division and forming basal bodies of cilia and flagella.

Processes of filtration, simple diffusion, and osmosis

• Filtration: A process where particles are driven through a membrane by physical pressure (such as blood pressure forcing water and small solutes through gaps or filtration pores in capillary walls).

• Simple diffusion: The net movement of particles from a place of high concentration to a place of lower concentration due to constant, spontaneous molecular motion.

• Osmosis: The net flow of water through a selectively permeable membrane from an area of higher water (lower solute) concentration to an area of lower water (higher solute) concentration.

Osmotic pressure, hydrostatic pressure, and reverse osmosis

• Osmotic pressure: The hydrostatic pressure required to stop osmosis, which rises as the amount of nonpermeating solutes increases.

• Hydrostatic pressure: Fluid pressure exerted on the membrane.

• Reverse osmosis: The process of applying mechanical pressure to override osmotic pressure, allowing the purification of water.

Effects of the three tonicities on a cell

• Hypotonic solution: Causes a cell to absorb water, swell, and possibly burst (lyse) because it has a lower concentration of nonpermeating solutes than the intracellular fluid (ICF).

• Hypertonic solution: Causes a cell to lose water and shrivel (crenate) because it has a higher concentration of nonpermeating solutes than the ICF.

• Isotonic solution: Causes no change in cell volume because the concentrations of nonpermeating solutes in the ECF and ICF are the same.

What a carrier is and basics of how it functions (uniport, symport, antiport, saturation)

• Carrier: A protein in the cell membrane that binds solutes and transfers them into or out of the cell.

• Saturation: As solute concentration rises, the rate of transport rises only to a point called the transport maximum ($T_m$), at which all carriers are occupied.

• Uniport: A carrier that moves one type of solute.

• Symport: A carrier that moves two or more solutes simultaneously in the same direction (cotransport).

• Antiport: A carrier that moves two or more solutes in opposite directions (countertransport).

Sodium-potassium pump mechanism (primary active transport)

An antiport carrier protein that uses ATP to expel 3 sodium ions (Na+) out of the cell and import 2 potassium ions (K+) into the cell against their concentration gradients.

Vesicular transport, endocytosis forms, and exocytosis

• Vesicular transport: Moves large particles, fluid droplets, or numerous molecules at once through the membrane in bubblelike enclosures called vesicles.

• Phagocytosis ("cell eating"): Engulfing and destroying large particles using pseudopods that surround the object to form a phagosome.

• Pinocytosis ("cell drinking"): Taking in droplets of ECF containing useful molecules.

• Receptor-mediated endocytosis: Particles bind to specific receptors on the plasma membrane, forming a clathrin-coated pit and vesicle to direct concentrated molecules into the cell.

• Exocytosis: Discharging material from a cell when a secretory vesicle approaches the plasma membrane, docks using linking proteins, unites to form a fusion pore, and releases its contents.

Three components of the cytoskeleton

• Microfilaments (thin filaments): 6 nm thick, made of actin protein, forming the terminal web (membrane skeleton).

• Intermediate filaments: 8 to 10 nm thick, made of protein keratin, giving the cell shape and resisting stress.

• Microtubules: 25 nm thick, consisting of protofilaments made of tubulin, radiating from the centrosome to maintain cell shape, hold organelles, form the mitotic spindle, and contribute to cilia and flagella.

Structure of the nucleus and contents of the nucleoplasm

• Nucleus structure: Usually the largest organelle (5 um in diameter), surrounded by a double-membrane nuclear envelope perforated by nuclear pores regulated by a nuclear pore complex.

• Nucleoplasm contents: Includes threadlike chromatin (DNA and proteins) and one or more nucleoli where ribosomes are produced.

Definition of inclusions and examples

Inclusions: Accumulated cell products (such as glycogen granules, pigments, and oil droplets) or foreign bodies (such as viruses, intracellular bacteria, and dust particles) in the cytoplasm that are never enclosed in a unit membrane and are not essential for cell survival.