Chemistry of Life and Cellular Form & Function

Vocabulary flashcards covering core concepts, chemical structures, reactions, transport mechanisms, and cellular organelles from Chapter 2 (Chemistry of Life) and Chapter 3 (Cellular Form and Function).

Acid

A proton donor that releases hydrogen ions ($H^+$) in water.

Base

A proton acceptor that accepts hydrogen ions ($H^+$) in water.

pH

The negative logarithm of hydrogen ion molarity, calculated using the formula $pH = -\log[H^+]$.

Buffer

A chemical solution that resists changes in $pH$.

Molarity (M)

A measure of solute concentration defined as the number of moles of solute per liter of solution.

Milliequivalents per Liter (mEq/L)

An expression of electrolyte concentration that accounts for both the millimolar concentration of a solute and the electrical charge of its particles.

Decomposition Reaction

A chemical reaction in which a larger molecule breaks down into two or more smaller ones, represented as $AB \rightarrow A + B$.

Synthesis Reaction

A chemical reaction in which two or more smaller molecules combine to form a larger one, represented as $A + B \rightarrow AB$.

Exchange Reaction

A chemical reaction in which two molecules exchange atoms or groups of atoms, represented as $AB + CD \rightarrow AC + BD$.

Reversible Reaction

A chemical reaction that can proceed in either direction depending on the relative abundance of substances on either side of the equation.

Catabolism

Energy-releasing (exergonic) decomposition reactions that break covalent bonds and produce smaller molecules.

Anabolism

Energy-storing (endergonic) synthesis reactions that require energy input to produce complex molecules.

Oxidation

A chemical reaction in which a molecule loses electrons and releases energy.

Reduction

A chemical reaction in which a molecule accepts electrons and gains energy.

Dehydration Synthesis

A condensation reaction linking monomers covalently by removing a hydroxyl group ($-OH$) from one monomer and a hydrogen ($-H$) from another, releasing water as a by-product.

Hydrolysis

A chemical reaction that splits a polymer into smaller monomers by adding a water molecule that ionizes into $H^+$ and $OH^-$.

Monosaccharide

The simplest carbohydrate monomer; key examples include glucose, galactose, and fructose, all sharing the molecular formula $C_6H_{12}O_6$.

Disaccharide

A sugar molecule composed of two covalently bonded monosaccharides, such as sucrose, lactose, or maltose.

Polysaccharide

A long chain of monosaccharides (ranging from about $50$ to thousands), such as glycogen, starch, or cellulose.

Proteoglycan

A macromolecule composed mostly of carbohydrate bound to a smaller protein moiety, forming supportive extracellular gels in tissues.

Fatty Acid

An organic molecule consisting of a chain of $4$ to $24$ carbon atoms with a carboxyl group ($-COOH$) at one end and a methyl group ($-CH_3$) at the other.

Saturated Fatty Acid

A fatty acid whose carbon chain contains only single covalent bonds, holding as much hydrogen as chemically possible.

Unsaturated Fatty Acid

A fatty acid containing one or more carbon-carbon double bonds ($C=C$) within its carbon chain.

Triglyceride

A neutral fat molecule consisting of three fatty acids covalently linked to a single glycerol molecule.

Phospholipid

An amphipathic lipid consisting of a glycerol backbone linked to two hydrophobic fatty acid tails and a hydrophilic phosphate head group.

Eicosanoid

A $20$-carbon lipid derived from arachidonic acid that functions as a hormone-like chemical signal between cells.

Steroid

A lipid containing $17$ carbon atoms arranged in four interconnected rings, synthesized from cholesterol.

Conformation

The unique three-dimensional shape of a protein that is essential for its biological function.

Denaturation

An extreme conformational change in a protein caused by heat or extreme $pH$ that permanently destroys its function.

Primary Structure

The specific linear sequence of amino acids within a protein chain, encoded directly by genes.

Secondary Structure

The coiled or folded shape of a protein chain, such as an alpha helix or beta sheet, held together by hydrogen bonds.

Tertiary Structure

The overall three-dimensional folding of a single polypeptide chain into globular or fibrous shapes resulting from R-group interactions and surrounding water.

Quaternary Structure

The complex structural level formed by the association of two or more individual polypeptide chains through non-covalent interactions or disulfide bonds.

Enzyme

A protein or ribozyme that acts as a biological catalyst to accelerate chemical reactions by lowering activation energy.

Active Site

The specific pocket or groove on an enzyme surface where substrate molecules bind to undergo a reaction.

Cofactor

A nonprotein partner, such as an inorganic metal ion or an organic coenzyme, required by an enzyme for catalytic activity.

Coenzyme

An organic cofactor, often derived from vitamins, that functions as an electron shuttle or carrier in metabolic pathways (such as $NAD^+$).

Metabolic Pathway

A series of enzyme-catalyzed chemical reactions in a cell where the product of one reaction serves as the substrate for the next.

Adenosine Triphosphate (ATP)

The primary energy-transfer molecule in body cells, composed of adenine, ribose, and three phosphate groups.

Kinase

An enzyme that transfers a phosphate group ($P_i$) from ATP to another molecule in a process called phosphorylation.

Glycolysis

The metabolic pathway that splits a glucose molecule into two pyruvate molecules, producing a net yield of $2$ ATP molecules.

Anaerobic Fermentation

A metabolic pathway that converts pyruvate into lactate in the absence of oxygen to regenerate $NAD^+$.

Aerobic Respiration

An oxygen-requiring mitochondrial pathway that breaks down pyruvate into $CO_2$ and $H_2O$, generating approximately $30$ ATP molecules per glucose.

Cyclic Adenosine Monophosphate (cAMP)

A second messenger molecule synthesized from ATP by adenylate cyclase when triggered by extracellular chemical signals.

Cell Theory

The biological concept stating that all organisms are composed of cells, the cell is the simplest functional unit of life, and cells arise only from preexisting cells.

Cytosol

The clear, gel-like intracellular fluid (ICF) surrounding organelles inside the cytoplasm.

Extracellular Fluid (ECF)

Any body fluid located outside of cells, including interstitial tissue fluid, blood plasma, lymph, and cerebrospinal fluid.

Transmembrane Protein

An amphipathic protein that spans completely through the phospholipid bilayer, contacting both extracellular and intracellular fluids.

Peripheral Protein

A membrane protein that adheres to either face of the plasma membrane without embedding in the phospholipid bilayer.

G Protein

An intracellular peripheral protein activated by membrane receptors that uses $GTP$ energy to relay signals to membrane enzymes like adenylate cyclase.

Glycocalyx

A fuzzy carbohydrate coating on the outer cell surface formed by carbohydrate moieties of membrane glycolipids and glycoproteins.

Microvilli

Short, fingerlike membrane projections ($1\text{ to }2\,\mu m$ long) that serve to increase cell surface area for absorption.

Cilia

Hairlike processes ($7\text{ to }10\,\mu m$ long) containing a $9+2$ microtubule axoneme that move materials across cell surfaces or serve sensory functions.

Axoneme

The structural core of a motile cilium or flagellum, consisting of a central pair of microtubules surrounded by nine microtubule doublets ($9+2$ structure).

Flagellum

A long, whiplike cell surface appendage containing an axoneme that propels a cell (such as sperm) with undulating motion.

Pseudopod

A temporary, continually changing extension of the cell membrane and cytoplasm used for cellular locomotion and engulfing particles.

Filtration

A passive transport process in which physical fluid pressure forces water and small solutes through a membrane or between cell clefts.

Simple Diffusion

The net movement of particles down their concentration gradient from high to low concentration due to spontaneous molecular kinetic motion.

Osmosis

The net flow of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Aquaporin

A specialized channel protein in the plasma membrane that facilitates the rapid passage of water molecules during osmosis.

Osmotic Pressure

The hydrostatic pressure required to completely stop the osmotic flow of water into a solution.

Osmolarity

The measure of total nonpermeating solute concentration expressed as the number of milliosmoles per liter ($mOsm/L$) of solution.

Tonicity

The ability of a surrounding solution to affect cell volume and internal pressure by driving osmotic water movement.

Hypotonic Solution

A solution with a lower concentration of nonpermeating solutes than the intracellular fluid, causing cells to absorb water, swell, and potentially lyse.

Hypertonic Solution

A solution with a higher concentration of nonpermeating solutes than the intracellular fluid, causing cells to lose water and shrivel (crenate).

Isotonic Solution

A solution with a nonpermeating solute concentration equal to that of the intracellular fluid, causing no net change in cell volume.

Transport Maximum (T_m)

The upper limit on the rate of carrier-mediated transport reached when all membrane carrier proteins are saturated with solute.

Facilitated Diffusion

The passive, carrier-mediated transport of a solute down its concentration gradient across a membrane without consuming ATP.

Primary Active Transport

Carrier-mediated transport in which a solute is moved up its concentration gradient consuming ATP directly.

Secondary Active Transport

Carrier-mediated transport that moves a solute up its concentration gradient driven co-transportally by another solute moving down a gradient maintained by primary active transport.

Sodium-Potassium Pump (Na+-K+ ATPase)

A primary active transport antiport carrier that consumes one ATP to pump three $Na^+$ ions out of the cell and two $K^+$ ions into the cell.

Phagocytosis

A form of vesicular transport in which a cell engulfs and digests large solid particles or foreign matter using pseudopods.

Pinocytosis

A form of vesicular transport in which the plasma membrane caves inward to take in droplets of extracellular fluid containing useful solutes.

Receptor-Mediated Endocytosis

A selective form of endocytosis where target molecules bind to specific membrane receptors, cluster in clathrin-coated pits, and form internal vesicles.

Transcytosis

The transport of material across a cell by capturing it via endocytosis on one side and discharging it via exocytosis on the opposite side.

Exocytosis

A process of vesicular transport in which a secretory vesicle fuses with the plasma membrane to discharge its contents outside the cell.

Microfilaments

Thin cytoskeletal filaments ($6\,nm$ thick) made of actin protein that form the terminal web beneath the plasma membrane.

Intermediate Filaments

Tough cytoskeletal fibers ($8\text{ to }10\,nm$ thick) made of proteins like keratin that give mechanical shape and resist physical stress.

Microtubules

Hollow cylindrical cytoskeletal structures ($25\,nm$ thick) made of tubulin protofilaments that form tracks for motor proteins, spindle fibers, and axonemes.

Nucleus

The largest cellular organelle, enclosed in a double-membrane envelope and containing chromatin, nucleoli, and nucleoplasm.

Rough Endoplasmic Reticulum

A system of parallel, flattened membranous cisterns covered with ribosomes that synthesizes membrane proteins and secretory proteins.

Smooth Endoplasmic Reticulum

A network of tubular membranous channels lacking ribosomes that synthesizes steroids and lipids, stores calcium, and detoxifies drugs.

Ribosomes

Non-membranous granules composed of RNA and protein that translate messenger RNA code to assemble amino acids into proteins.

Golgi Complex

A system of stacked membranous cisterns that receives newly synthesized proteins from the rough ER, modifies and sorts them, and packages them into vesicles.

Lysosome

A membrane-bound organelle containing hydrolytic digestive enzymes involved in intracellular breakdown, autophagy, and autolysis.

Peroxisome

A membrane-bound organelle containing enzymes that oxidize organic molecules, detoxify harmful chemicals, and neutralize hydrogen peroxide ($H_2O_2$) using catalase.

Proteasome

A barrel-shaped organelle responsible for degrading targeted or damaged cellular proteins tagged for destruction into small peptides.

Mitochondrion

A double-membrane organelle containing cristae and a matrix, specialized for ATP synthesis via aerobic respiration.

Centriole

A short cylindrical assembly of nine microtubule triplets ($9 \times 3$ array) located in the centrosome, essential for cell division and basal body formation.

Inclusions

Transient, unencapsulated cellular structures consisting of stored cell products (such as glycogen or oil droplets) or phagocytized foreign matter.