Human Anatomy and Physiology: Orientation, Chemistry, and Cell Biology

Vocabulary flashcards generated from Human Anatomy & Physiology lecture notes covering introductory orientation, chemical foundations, cell structures, membrane transport, cell cycle, and protein synthesis.

Anatomy

The study of the structure of body parts and their relationship to one another.

Physiology

The study of the function of body parts and how they work to carry out life-sustaining activities.

Principle of Complementarity of Structure and Function

Anatomical concept stating that function always reflects structure; what a structure can do depends on its specific physical form.

Negative Feedback

The most common homeostatic control mechanism in which the output or response reduces or shuts off the original stimulus, causing the variable to change in the opposite direction of the initial change.

Positive Feedback

A homeostatic control mechanism in which the response enhances or exaggerates the original stimulus, producing a cascading or amplifying effect that drives the variable in the same direction as the initial change.

Standard Anatomical Position

The standard body reference position where the subject stands erect with feet slightly apart, palms facing forward, and thumbs pointing away from the body.

Sagittal Plane

A vertical plane that divides the body or an organ into right and left parts.

Midsagittal Plane

A specific sagittal plane that lies directly on the midline, dividing the body vertically into equal right and left halves.

Frontal Plane

A vertical plane that divides the body or an organ into anterior (front) and posterior (back) parts; also known as a coronal plane.

Transverse Plane

A horizontal plane running at a right angle to the long axis, dividing the body or an organ into superior (top) and inferior (bottom) parts.

Anion

A negatively charged ion formed when an atom gains one or more valence electrons.

Cation

A positively charged ion formed when an atom loses one or more valence electrons.

Electrolytes

Chemical substances, including salts, acids, and bases, that ionize and dissociate in water and are capable of conducting an electrical current.

pH Scale

A logarithmic measurement scale ranging from $0$ to $14$ that indicates the hydrogen ion concentration $[H^+]$ in a solution.

Buffer

A chemical substance or system that resists abrupt and large changes in pH by binding free hydrogen ions when pH rises or releasing hydrogen ions when pH falls.

Fibrous Proteins

Extended, strandlike, water-insoluble structural proteins that provide mechanical support and tensile strength, such as collagen, keratin, and elastin.

Globular Proteins

Compact, spherical, water-soluble functional proteins containing specific active sites that perform biological roles, such as antibodies, hormones, and enzymes.

Enzymes

Globular proteins that act as biological catalysts, increasing the speed of chemical reactions by lowering activation energy without being consumed.

Adenosine Triphosphate (ATP)

The primary organic energy molecule of the cell, composed of an adenine-containing RNA nucleotide with three phosphate groups, which directly powers cellular chemical reactions upon hydrolysis.

Cell Theory

The fundamental biological concept stating that the cell is the structural and functional unit of life, organismal function depends on cellular activities, and cells arise only from preexisting cells.

Plasma Membrane

A selectively permeable phospholipid bilayer containing embedded proteins that separates intracellular fluid from extracellular fluid and regulates substance movement.

Tight Junctions

Impermeable cell junctions composed of interlocking junctional proteins that form continuous seals around adjacent epithelial cells to prevent molecules from passing between them.

Desmosomes

Anchoring cell junctions composed of plaques, linker proteins (cadherins), and intermediate filaments that bind adjacent cells together like molecular Velcro to prevent tearing under mechanical stress.

Gap Junctions

Communicating cell junctions formed by transmembrane protein channels (connexons) that allow ions and small molecules to pass directly from the cytoplasm of one cell to another.

Simple Diffusion

A passive transport process in which nonpolar, lipid-soluble substances diffuse directly through the phospholipid bilayer down their concentration gradient without transport proteins or energy input.

Facilitated Diffusion

A passive transport process in which lipid-insoluble solutes or ions cross the plasma membrane down their concentration gradient via transmembrane carrier proteins or channel proteins.

Osmosis

The diffusion of a solvent (such as water) across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Aquaporins (AQPs)

Transmembrane channel proteins specifically designed to facilitate the rapid movement of water molecules across the plasma membrane.

Osmolarity

The total concentration of solute particles in a solution, expressed as the total number of solute particles per liter of solvent.

Tonicity

The ability of an extracellular solution to alter the water volume and shape of a cell by inducing osmotic water movement.

Isotonic Solution

A solution having the same solute and water concentration as the cell cytosol, resulting in no net water movement and unchanged cell volume.

Hypertonic Solution

A solution having a higher concentration of nonpenetrating solutes than the cell cytosol, causing water to flow out of the cell and leading to cell shrinkage (crenation).

Hypotonic Solution

A solution having a lower concentration of nonpenetrating solutes than the cell cytosol, causing water to flow into the cell and leading to cell swelling and potential bursting (lysis).

Primary Active Transport

A membrane transport process in which transport proteins directly hydrolyze ATP to pump solutes across a membrane against their concentration gradient.

Secondary Active Transport

A membrane transport process driven indirectly by energy stored in ionic concentration gradients created by primary active transport.

Antiporters

Carrier proteins involved in active transport that move two different substances across the plasma membrane in opposite directions.

Symporters

Carrier proteins involved in active transport that move two different substances across the plasma membrane in the same direction.

Phagocytosis

A type of endocytosis in which a cell engulfs large or solid particles by forming pseudopods around them to enclose them in a membranous sac called a phagosome.

Pinocytosis

A nonspecific type of endocytosis in which the cell gulps a droplet of extracellular fluid containing dissolved solutes into tiny vesicles.

Receptor-Mediated Endocytosis

A highly selective type of endocytosis in which specific extracellular substances bind to specific transmembrane receptor proteins, enabling uptake in coated vesicles.

Exocytosis

A vesicular transport process in which intracellular secretory vesicles migrate to and fuse with the plasma membrane using v-SNARE and t-SNARE proteins to release contents outside the cell.

Mitochondria

Double-membrane enclosed cytoplasmic organelles with inner membrane folds called cristae that generate most of the cell's ATP through aerobic cellular respiration.

Rough Endoplasmic Reticulum

A membranous network continuous with the outer nuclear membrane, studded with ribosomes, that synthesizes proteins destined for secretion, plasma membranes, or lysosomes.

Smooth Endoplasmic Reticulum

A membranous network lacking ribosomes that functions in lipid metabolism, cholesterol and steroid hormone synthesis, glycogen breakdown, and calcium storage and release.

Golgi Apparatus

A stack of flattened membranous sacs that receives, modifies, concentrates, tags, and packages proteins and lipids synthesized in the rough ER.

Peroxisomes

Membranous sacs containing oxidases and catalase enzymes that detoxify harmful free radicals and convert toxic hydrogen peroxide ($H_2O_2$) into water.

Lysosomes

Spherical membranous bags containing acid hydrolases (digestive enzymes) that break down ingested particles, pathogens, and nonfunctional organelles.

Ribosomes

Nonmembranous organelles composed of protein and ribosomal RNA (rRNA) that serve as the sites of cellular protein synthesis.

Microfilaments

Cytoskeletal strands composed of spherical actin protein subunits ($7Default,nm$ diameter) that form a dense network involved in cell movement and shape changes.

Intermediate Filaments

Tough, insoluble cytoskeletal protein fibers ($10,nm$ diameter) constructed like woven ropes of tetramer fibrils that resist mechanical pulling forces on the cell.

Microtubules

Hollow cytoskeletal tubes composed of spherical tubulin protein subunits ($25,nm$ diameter) that determine cell shape and distribute organelles during cell division.

Centrosome

The microtubule organizing center located near the nucleus, containing a pair of barrel-shaped centrioles positioned at right angles to each other.

Cilia

Whiplike, motile cellular extensions containing a $9+2$ arrangement of microtubules powered by dynein motor arms that propel substances across cell surfaces.

Microvilli

Fingerlike extensions of the plasma membrane supported by an actin filament core that increase surface area for absorption.

Chromatin

Threadlike, uncoiled structures composed of $30\%$ DNA, $60\%$ histone proteins, and $10\%$ RNA, arranged into fundamental repeating units called nucleosomes.

Chromosomes

Highly condensed, packaged forms of chromatin visible during cell division that protect delicate DNA threads.

Interphase

The non-dividing period of the cell cycle during which the cell grows, conducts normal activities, and replicates its DNA in preparation for division.

S Phase

The specific subphase of interphase during which nuclear DNA replication occurs.

DNA Polymerase

The primary replication enzyme that attaches to an RNA primer and synthesizes new complementary DNA strands by adding nucleotides.

DNA Ligase

The enzyme that splices together short, discontinuous segments of the newly synthesized lagging strand during DNA replication.

Mitosis

The division of the cell nucleus during the M phase, resulting in equal distribution of duplicated DNA into two daughter nuclei.

Cytokinesis

The division of the cytoplasm following mitosis, accomplished by a contractile ring of actin microfilaments that forms a cleavage furrow.

Cyclins

A group of regulatory proteins that accumulate during interphase and bind to cyclin-dependent kinases (Cdks) to control cell cycle progression.

Gene

A segment of a DNA molecule that holds the triplet code instructions for synthesizing one single polypeptide chain.

Exons

The coding regions of a gene that contain the specific nucleotide sequences used to encode amino acids for protein synthesis.

Introns

Noncoding segments of a gene interspersed between exons that are removed during RNA processing.

Transcription

The first step of protein synthesis in which genetic information coded in a DNA template strand is rewritten into a complementary messenger RNA (mRNA) strand inside the nucleus.

RNA Polymerase

The enzyme that separates DNA strands during transcription and joins complementary RNA nucleotides together to elongate the mRNA transcript.

Translation

The second step of protein synthesis in which the nucleotide sequence of an mRNA strand is decoded at a ribosome to assemble amino acids into a polypeptide chain.

Transfer RNA (tRNA)

Small RNA molecules that transport specific amino acids to the ribosome and match their three-base anticodon with complementary mRNA codons.

Codon

A three-base sequence on an mRNA strand that specifies a particular amino acid or a signal to start or stop translation.

Anticodon

A three-base sequence on a tRNA molecule that complementary base-pairs with a specific mRNA codon at the ribosome.

Signal Recognition Particle (SRP)

A protein-RNA complex that binds to the ER signal sequence on a growing polypeptide and directs the mRNA-ribosome complex to dock at the rough ER membrane.