BIOL 1010 Cell Biology: Large Biological Molecules, Cellular Tour, and Membrane Transport

Vocabulary practice flashcards covering large biological molecules (carbohydrates, lipids, proteins, and nucleic acids), eukaryotic and prokaryotic organelles, the endomembrane system, cytoskeleton, cell junctions, and membrane transport mechanisms.

Polymer

A long molecule consisting of many similar or identical building blocks (monomers) linked together by covalent bonds.

Dehydration Reaction

A chemical reaction in which two molecules become covalently bonded to each other with the loss of a water molecule, allowing polymers to increase in size.

Hydrolysis

The chemical breakdown of a compound due to reaction with water; the addition of a water molecule breaks covalent bonds between monomers, reversing dehydration.

Monosaccharide

The simplest carbohydrate monomer, serving as fuel and building material, typically characterized by a molecular formula that is some multiple of the unit $CH_2O$.

Glycosidic Linkage

A covalent bond formed between two monosaccharides by a dehydration reaction to create disaccharides or polysaccharides.

Starch

A storage polysaccharide found in plants, consisting entirely of glucose monomers joined by glycosidic linkages.

Glycogen

An extensively branched storage polysaccharide of glucose stored in animal liver and muscle tissues.

Cellulose

A major structural polysaccharide of plant cell walls whose distinct glycosidic linkages give it a three-dimensional shape distinct from starch.

Lipids

A diverse group of hydrophobic large biological molecules that are not true polymers and mix poorly with water; major categories include fats, phospholipids, and steroids.

Triacylglycerol

A fat molecule formed by joining a glycerol molecule to three fatty acid molecules via ester bonds.

Phospholipid

A lipid molecule composed of a glycerol backbone attached to two hydrophobic (nonpolar) fatty acid tails and a hydrophilic (polar) phosphate head, forming cellular membranes.

Steroid

A type of lipid characterized by a carbon skeleton consisting of four fused rings.

Amino Acid

An organic molecule possessing both an amino group and a carboxyl group, serving as the monomer of proteins; $20$ different kinds make up cellular proteins.

Peptide Bond

The covalent bond between the carboxyl group of one amino acid and the amino group of another, formed by a dehydration reaction in a polypeptide chain.

Primary Structure

The first level of protein structure, referring strictly to the unique, linear sequence of amino acids in a polypeptide chain.

Secondary Structure

Regions of repetitive coiling or folding in a polypeptide backbone, primarily stabilized by hydrogen bonds; predominant forms are alpha helices and beta pleated sheets.

Tertiary Structure

The overall three-dimensional shape of a protein resulting from interactions between the $R$ groups (side chains) of the various amino acids.

Quaternary Structure

The overall protein structure that results from the aggregation and association of two or more polypeptide chains (subunits).

Nucleotide

The building block of a nucleic acid, consisting of three parts: a nitrogenous base, a five-carbon sugar, and one phosphate group.

Double Helix

The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

Antiparallel

The arrangement in DNA where the two complementary sugar-phosphate backbones run in opposite $5' \rightarrow 3'$ directions.

Nucleoid

A non-membrane-enclosed region in a prokaryotic cell where its genetic material (DNA) is concentrated.

Nuclear Envelope

A double membrane perforated by nuclear pores that encloses the nucleus, separating its contents from the cytoplasm and regulating macromolecular entry and exit.

Nucleolus

A specialized structure inside the eukaryotic nucleus responsible for synthesizing ribosomal RNA ($rRNA$).

Ribosome

A complex consisting of large and small subunits made of ribosomal RNA ($rRNA$) and protein that functions as the site of protein synthesis in the cytosol or on membranes.

Endosymbiont Theory

The theory proposing that mitochondria and chloroplasts originated as prokaryotic endosymbionts that were engulfed by ancestral eukaryotic cells.

Cristae

Infoldings of the inner membrane of a mitochondrion that house electron transport chains and increase surface area for cellular respiration.

Peroxisome

A specialized metabolic organelle bounded by a single membrane that contains enzymes used to break down fatty acids.

Endomembrane System

The collection of membranes inside and around a eukaryotic cell—including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane—that regulates protein traffic and performs metabolic functions.

Smooth Endoplasmic Reticulum

The portion of the endoplasmic reticulum that lacks bound ribosomes; functions include lipid synthesis, carbohydrate metabolism, drug detoxification, and calcium ion storage.

Rough Endoplasmic Reticulum

The portion of the endoplasmic reticulum studded with ribosomes; synthesizes secretory proteins and membrane proteins, and acts as a membrane factory.

Golgi Apparatus

An organelle consisting of stacks of flat membranous sacs (cisternae) not physically connected, featuring cis (receiving) and trans (shipping) faces to stage, refine, and dispatch cellular products.

Lysosome

A membrane-enclosed sac of hydrolytic enzymes working optimally in acidic pH environments, responsible for digesting macromolecules.

Phagocytosis

A type of endocytosis where a cell engulfs large particles or food, creating a food vacuole that fuses with a lysosome for digestion.

Autophagy

A recycling process in which damaged organelles or cytoplasmic components become surrounded by a double membrane and fuse with a lysosome to release small organic compounds back into the cytosol.

Contractile Vacuole

A membranous sac found in many freshwater protists that maintains ion and molecule concentration homeostasis by pumping excess water out of the cell.

Cytoskeleton

A dynamic network of protein fibers organizing cellular structures and activities, providing mechanical support to maintain animal cell shape, and enabling cell motility.

Microtubule

A hollow rod constructed from tubulin dimers (composed of alpha-tubulin and beta-tubulin) that originates from centrosomes to provide tracks for organelle movement and form the core of cilia and flagella.

Microfilament

A thin solid rod made of actin subunits that functions in cell motility and interacts with the motor protein myosin to power muscle contraction.

Intermediate Filament

A component of the cytoskeleton composed of specialized fibrous proteins such as keratin, providing tensile strength and mechanical support to cells.

Extracellular Matrix (ECM)

The meshwork surrounding animal cells, primarily consisting of glycoproteins and other carbohydrate-containing molecules secreted by the cells.

Tight Junction

A type of intercellular junction between animal cells that forms a continuous, leakproof seal to prevent fluid movement across a layer of cells.

Desmosome

A type of anchoring intercellular junction in animal cells that functions like a rivet, fastening cells together into strong structural sheets.

Gap Junction

A communicating intercellular junction in animal cells consisting of membrane proteins surrounding a pore, providing cytoplasmic communicating channels for ions and small molecules.

Fluid Mosaic Model

The structural model of the cell membrane depicting protein molecules embedded in or attached to a fluid bilayer of phospholipids.

Amphipathic Molecule

A molecule that possesses both a hydrophilic (water-loving) region and a hydrophobic (water-fearing) region, such as a membrane phospholipid or integral protein.

Integral Membrane Protein

A transmembrane protein embedded within the hydrophobic interior of the lipid bilayer, requiring at least one hydrophobic region composed of nonpolar amino acids.

Peripheral Protein

A membrane protein not embedded in the hydrophobic portion of the lipid bilayer at all, being loosely bound to the surface of the membrane.

Membrane Potential

The voltage or difference in electrical charge across a cell's plasma membrane.

Electrochemical Gradient

The combined diffusion gradient of an ion, determined by both its concentration (chemical) gradient across a membrane and the electrical charge gradient (membrane potential).

Proton Pump

An active transport protein that utilizes ATP hydrolysis to translocate hydrogen ions ($H^+$) across a membrane, generating a voltage and electrochemical gradient.

Sucrose-$H^+$ Cotransporter

A secondary active transport carrier protein that couples the downhill diffusion of $H^+$ along its electrochemical gradient to the uphill transport of sucrose against its concentration gradient; its transport rate increases when extracellular pH is decreased.

Sodium-Potassium Pump

An electrogenic transport protein in animal plasma membranes that actively pumps three sodium ions ($\text{Na}^+$) out of the cell and two potassium ions ($\text{K}^+$) into the cell while consuming one ATP per cycle.

Pinocytosis

A type of endocytosis commonly described as cellular drinking, in which the cell continuously gulps droplets of extracellular fluid into tiny vesicles.