Chapter 04: Anatomy & Physiology - Cell Structure and Function

Vocabulary practice flashcards covering cell structure, plasma membrane transport, resting membrane potential, organelle functions, transcription, translation, and the cell cycle from McKinley's Anatomy & Physiology Chapter 4.

Cytology

The study of cells, which requires the use of microscopes to view small-scale cellular structures.

Transmission Electron Microscope (TEM)

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

Scanning Electron Microscope (SEM)

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

Cytosol

The viscous intracellular fluid of the cytoplasm that has a high water content and contains dissolved macromolecules and ions.

Inclusions

Temporary cytosolic stores of non-organelle molecules that are continuously added and removed, such as pigments, glycogen, and triglycerides.

Phospholipid Bilayer

The basic framework of the plasma membrane, composed of two parallel sheets of phospholipids arranged tail to tail, with hydrophobic tails directed inward and hydrophilic polar heads facing outward.

Integral Proteins

Membrane proteins embedded within and extending across the phospholipid bilayer, possessing hydrophobic regions that interact with the lipid interior and hydrophilic regions exposed to aqueous fluids.

Peripheral Proteins

Proteins that are not embedded in the lipid bilayer but are loosely attached to the external or internal surfaces of the plasma membrane.

Simple Diffusion

The unassisted passive movement of small, nonpolar solutes (such as $\text{O}_2$, $\text{CO}_2$, and urea) between phospholipid molecules down their concentration gradient.

Channel-Mediated Diffusion

The movement of small ions down their concentration gradient through specific, water-filled protein channels (either leak channels or gated channels).

Carrier-Mediated Diffusion

The movement of small polar molecules down their concentration gradient assisted by a carrier protein that changes shape upon substance binding.

Osmosis

The passive movement of water across a semipermeable membrane down its concentration gradient, occurring slip-wise through the bilayer or via aquaporins.

Aquaporins

Integral protein water channels through which water molecules cross the plasma membrane during osmosis.

Osmotic Pressure

The pressure exerted by the movement of water across a semipermeable membrane due to differences in solute concentration.

Tonicity

The ability of a solution to change the volume or pressure of a cell by osmosis.

Isotonic Solution

A solution that has the same relative concentration of solutes as the cytosol (such as $0.9\%\,\text{NaCl}$ normal saline), 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 induce lysis or hemolysis.

Hypertonic Solution

A solution with a higher solute concentration and lower water concentration than the cytosol, causing water to leave the cell and lead to crenation.

Crenation

The shrinking of a cell that occurs when water leaves the cell via osmosis in a hypertonic solution.

Hemolysis

The rupture of erythrocytes that occurs when excessive water enters the cell in a hypotonic solution.

Primary Active Transport

A cellular transport mechanism that moves a solute against its concentration gradient using energy derived directly from the breakdown of $\text{ATP}$, resulting in carrier phosphorylation.

Sodium-Potassium ($\text{Na}^+/\text{K}^+$) Pump

An active transport exchange pump that moves $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell against their respective concentration gradients per $\text{ATP}$ hydrolyzed.

Symport Secondary Active Transport

The simultaneous movement of two substances across the membrane in the same direction, where one substance moves down its gradient to power the movement of another substance against its gradient.

Antiport Secondary Active Transport

The simultaneous movement of two substances across the membrane in opposite directions, powered by the kinetic energy of one substance moving down its gradient.

Exocytosis

A type of vesicular bulk transport in which intracellular vesicles fuse with the plasma membrane to release large macromolecules outside the cell in an $\text{ATP}$-dependent process.

Phagocytosis

A form of endocytosis known as cellular eating, wherein a cell uses pseudopodia to engulf large external particles into a vesicle that subsequently fuses with a lysosome.

Pinocytosis

A form of endocytosis known as cellular drinking, where the plasma membrane invaginates to internalize droplets of interstitial fluid containing dissolved solutes into multiple small vesicles.

Receptor-Mediated Endocytosis

A targeted bulk-transport process where specific molecules in the interstitial fluid bind to plasma 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 ranging from $-50\,\text{mV}$ to $-100\,\text{mV}$, maintained primarily by $\text{K}^+$ leak channels and $\text{Na}^+/\text{K}^+$ pumps.

Channel-Linked Receptors

Cell surface receptors that open to permit ion passage into or out of cells in response to the binding of a specific ligand, helping initiate electrical changes.

Enzymatic Receptors

Receptors that function as protein kinase enzymes and become activated upon ligand binding to phosphorylate other intracellular enzymes.

G Protein-Coupled Receptors

Receptors that bind ligands, causing a conformational change that activates a G protein by binding $\text{GTP}$, which then stimulates an effector protein to generate a secondary messenger.

Rough Endoplasmic Reticulum

A continuous membrane network studded with ribosomes that synthesizes proteins for secretion, plasma membrane incorporation, or lysosomal enzyme storage, and packages them into transport vesicles.

Smooth Endoplasmic Reticulum

An interconnected membrane network lacking ribosomes that participates in lipid synthesis, carbohydrate metabolism, and detoxification of drugs, alcohol, and poisons.

Golgi Apparatus

A polar organelle composed of elongated saclike cisternae (with cis- and trans-faces) that modifies, packages, and sorts proteins received from the rough ER into secretory vesicles or lysosomes.

Lysosomes

Small membrane-enclosed sacs containing digestive enzymes formed by the Golgi apparatus that participate in digesting endocytosed material, autophagy of damaged organelles, and autolysis.

Autophagy

The lysosomal process of removing and digesting damaged cellular organelles and components.

Autolysis

The rapid digestion and breakdown of cellular components by lysosomal enzymes following cell death.

Peroxisomes

Membrane-enclosed sacs pinched off from the rough ER that digest molecules such as fatty acids and amino acids (producing hydrogen peroxide) and synthesize lipids like bile salts and plasmalogens.

Mitochondria

Oblong double-membraned organelles, known as the powerhouses of the cell, that harvest energy through aerobic cellular respiration to generate $\text{ATP}$.

Proteasomes

Large, barrel-shaped, non-membrane-bound protein complexes located in the cytosol and nucleus that degrade ubiquitin-tagged damaged, misfolded, or unneeded proteins in an $\text{ATP}$-dependent pathway.

Cytoskeleton

A non-membrane-bound network extending throughout the cytoplasm composed of microfilaments, intermediate filaments, and microtubules that provides structural support, facilitates movement, and assists in cell division.

Microfilaments

The smallest cytoskeleton components, composed of actin monomers twisted into two filaments, that maintain cell shape, provide internal support, and execute cytokinesis.

Microtubules

The largest components of the cytoskeleton, composed of tubulin protein, that form tracks for organelle movement, separate chromosomes during mitosis, and form the core of cilia and flagella.

Centrosome

A non-membrane-bound organelle consisting of a pair of perpendicularly oriented cylindrical centrioles surrounded by amorphous protein that organizes microtubules and forms spindle fibers during cell division.

Tight Junctions

Membrane junctions formed by continuous strands of proteins that seal neighboring cells together, preventing substances from passing between them and maintaining epithelial polarity.

Desmosomes

Mechanical cell junctions consisting of protein plaques, protein filaments, and intermediate filaments that bind adjacent cells together to provide resistance to mechanical stress.

Gap Junctions

Membrane junctions composed of connexons with fluid-filled pores that provide direct passageways for ions and small molecules to travel between adjacent cells.

Nucleolus

A dark-staining, spherical, non-membrane-bound structure in the nucleus composed of protein and RNA that produces the large and small subunits of ribosomes.

Nucleosome

A structural unit of chromatin formed when double-stranded DNA wraps around a cluster of nuclear proteins called histones.

Gene

A functional stretch of nucleotides along DNA that contains the instructions for the synthesis of a specific protein, delineated by a promoter start region and a terminator stop region.

Transcription

The process occurring in the nucleus where RNA polymerase synthesizes a complementary pre-mRNA molecule from free ribonucleotides using the template strand of a DNA gene.

Translation

The process occurring at ribosomes in the cytosol where the mRNA sequence is converted into an amino acid sequence to assemble a functional protein.

Introns

Noncoding transcribed sequences in pre-mRNA that are excised and removed during splicing before the mRNA exits the nucleus.

Exons

Coding nucleotide sequences in pre-mRNA that are spliced together by spliceosomes to form mature mRNA.

Codon

A three-base nucleotide sequence on mRNA that codes for a specific amino acid, a start signal ($\text{AUG}$), or a stop signal ($\text{UAA}$, $\text{UAG}$, or $\text{UGA}$).

Anticodon

A specific sequence of three bases on a tRNA molecule that base-pairs with a complementary codon on mRNA during translation.

Interphase

The roughly $23\text{-hour}$ phase of the cell cycle during which a cell grows and prepares for division through $\text{G}_1$, $\text{S}$ (DNA replication), and $\text{G}_2$ stages.

S Phase

The period of interphase during which all $46$ double-stranded DNA molecules are replicated by DNA polymerase to form pairs of identical sister chromatids.

Prophase

The first stage of mitosis, characterized by chromatin supercoiling into visible chromosomes, nucleolus breakdown, spindle fiber elongation from centrioles, and eventual breakdown of the nuclear envelope.

Metaphase

The second stage of mitosis in which chromosomes are aligned along the cell's equatorial plate by spindle fibers attached to their centromeres.

Anaphase

The third stage of mitosis where spindle fibers pull sister chromatids apart toward opposing cell poles, converting each separated chromatid into an independent single chromosome.

Telophase

The final stage of mitosis during which chromosomes uncoil back into chromatin, nucleoli and nuclear envelopes re-form, and spindle fibers disappear.

Cytokinesis

The division of cytoplasm between two newly formed daughter cells, initiated by a contracting ring of microfilaments that forms a deepening cleavage furrow.

Apoptosis

Programmed, orderly cellular suicide initiated by ligand-receptor signaling that involves DNA destruction, organelle condensation, and bleb formation without provoking uncontrolled lysis.