Biol131 Lecture 3: Cells - Vocabulary Flashcards

Vocabulary practice flashcards covering cell theory, cellular structures, organelles, membrane transport mechanisms, and cell division from Biol131 Lecture 3.

Cell Theory

The foundational principle stating that the cell is the structural and functional unit of life, organismal activity depends on individual and combined cellular functions, biochemical functions are dictated by cell shape and subcellular structures, and cells arise only from preexisting cells.

Plasma Membrane

A flexible outer boundary that acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF) and regulates dynamic cellular transport.

Interstitial Fluid

The extracellular body fluid in which cells are submersed and bathed.

Fluid Mosaic Model

A structural model of the plasma membrane consisting of a flexible lipid bilayer with specialized floating membrane proteins creating a constantly changing pattern.

Phospholipids

Membrane lipids composing $75\%$ of the lipid bilayer, consisting of polar hydrophilic phosphate heads and nonpolar hydrophobic fatty acid tails.

Glycolipids

Lipids with attached sugar groups located on the outer membrane surface, comprising $5\%$ of membrane lipids.

Cholesterol

A $4$-ring steroid lipid structure making up $20\%$ of membrane lipids that stiffens the membrane and decreases its water solubility.

Glycocalyx

A sugar coating on the outer surface of the plasma membrane formed by carbohydrates attached to lipids and proteins that acts as biological markers for cell-to-cell recognition.

Integral Proteins

Transmembrane proteins firmly inserted into the lipid bilayer that possess hydrophobic and hydrophilic regions to function as transport channels, carriers, enzymes, or receptors.

Peripheral Proteins

Proteins loosely attached to integral proteins on the membrane surface that function as enzymes, motor proteins for shape changes, or cell-to-cell connections.

Cytosol

The gel-like solution of cytoplasm made up of water and soluble molecules such as proteins, salts, and sugars.

Inclusions

Insoluble molecules suspended in the cytoplasm that vary with cell type, including glycogen granules, pigments, lipid droplets, vacuoles, and crystals.

Mitochondria

Membranous, double-membraned organelles referred to as the "power plant" of cells because they produce most ATP via aerobic cellular respiration.

Cristae

Infoldings of the inner mitochondrial membrane that increase the surface area for enzymes involved in ATP production.

Rough Endoplasmic Reticulum

A network of interconnected membranous cisterns studded with ribosomes that synthesizes secreted proteins, plasma membrane proteins, and phospholipids.

Smooth Endoplasmic Reticulum

A network of continuous membranous tubules involved in lipid metabolism, steroid synthesis, fat transport, chemical detoxification, and calcium storage.

Golgi Apparatus

A stack of flattened membranous cistern sacs that acts as the "traffic director" by modifying, concentrating, and packaging proteins and lipids received from the rough ER.

Peroxisomes

Membranous sacs containing oxidase (which converts toxins to $\text{H}_2\text{O}_2$) and catalase (which converts $\text{H}_2\text{O}_2$ to water) to neutralize toxic free radicals.

Free Radicals

Toxic, highly reactive molecules generated as natural byproducts of cellular metabolism.

Lysosomes

Spherical membranous bags containing digestive enzymes (acid hydrolases) that degrade pathogens and nonfunctional organelles, and mediate autolysis in injured cells.

Autolysis

The self-digestion of a cell caused by the intracellular release of lysosomal digestive enzymes when the cell is injured.

Ribosomes

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

Microfilaments

The thinnest cytoskeletal elements ($7\,\text{nm}$ diameter) made of semiflexible actin protein strands involved in cell motility, shape changes, and endocytosis/exocytosis.

Intermediate Filaments

Tough, ropelike protein fibers ($10\,\text{nm}$ diameter) composed of tetramer fibrils twisted together that help cells resist pulling forces.

Microtubules

The largest cytoskeletal elements ($25\,\text{nm}$ diameter) consisting of hollow tubes of tubulin subunits radiating from the centrosome to determine cell shape and serve as tracks for motor proteins.

Centrosome

The microtubule organizing center located near the nucleus consisting of a granular matrix and a pair of centrioles positioned at right angles.

Cilia

Whiplike, motile cellular extensions made of microtubules synthesized by centrioles that move substances such as mucus across cell surfaces.

Flagella

Long microtubular extensions synthesized by centrioles that propel an entire cell, such as the tail of a sperm cell.

Microvilli

Fingerlike projections of the plasma membrane stiffened by an actin microfilament core that extend from select cells to increase surface area for absorption.

Nuclear Envelope

A double-membrane barrier enclosing the nucleoplasm whose outer layer is continuous with rough ER and inner layer is lined by the nuclear lamina.

Nuclear Lamina

A netlike protein meshwork composed of lamins (intermediate filaments) lining the inner nuclear membrane that maintains nuclear shape.

Nucleoli

Dark-staining spherical bodies within the nucleus responsible for ribosomal RNA (rRNA) synthesis and ribosome subunit assembly.

Nucleosome

The fundamental unit of chromatin ($10\,\text{nm}$ diameter) consisting of DNA wrapped around an octamer of histone proteins.

Interphase

The subphase period of the cell cycle ($G_1$, $S$, $G_2$) during which the cell carries out routine metabolic activities, grows, and replicates its DNA.

$G_0$ Phase

The permanent non-dividing state entered by cells that cease division after failing to pass the $G_1$ checkpoint.

Mitosis

The division of the cell nucleus during the mitotic phase ($M$ phase), divided into prophase, metaphase, anaphase, and telophase.

Cytokinesis

The division of the cytoplasm during late anaphase and telophase mediated by a contractile ring of actin microfilaments forming a cleavage furrow.

Contact Inhibition

A stop signal for cell division where normal cells stop dividing upon coming into physical contact with adjacent cells.

Simple Diffusion

Passive transport of nonpolar, lipid-soluble hydrophobic substances directly through the phospholipid bilayer down their concentration gradient.

Facilitated Diffusion

Passive movement of polar or charged molecules down their concentration gradient aided by transmembrane protein carriers or water-filled channel proteins.

Aquaporins

Transmembrane channel proteins that facilitate the passage of water across plasma membranes during osmosis.

Osmosis

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

Osmolarity

The measure of the total concentration of solute particles in a solution, expressed in osmoles per liter ($\text{osmol/L}$).

Tonicity

The ability of a surrounding solution to alter a cell's shape or tone by changing its internal water volume via osmosis.

Isotonic Solution

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

Hypertonic Solution

A solution containing a higher concentration of nonpenetrating solutes than inside the cell, causing net water loss from the cell and resulting in crenation.

Crenation

The shrinking and shriveling of cells when exposed to a hypertonic solution.

Hypotonic Solution

A solution containing a lower concentration of nonpenetrating solutes than inside the cell, causing net water entry into the cell, cell swelling, and potential lysing.

Hemolysis

The bursting or lysing of red blood cells due to excessive swelling in a hypotonic solution.