General Biology: Foundations of Life, Chemistry of Water, Carbon, Macromolecules, and Cell Structure

Comprehensive vocabulary flashcards covering introductory themes in biology, the chemical context of life, properties of water, carbon diversity, large biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and cellular ultrastructure.

Evolution

The overarching biological theme and process of change that has transformed life on Earth, accounting for both the unity and diversity of living organisms through descent with modification from common ancestors.

Emergent Properties

Novel properties that emerge at each step upward in the biological hierarchy of life, resulting from the specific arrangement and interactions of parts within a system.

Reductionism

An approach in scientific study that reduces complex systems into simpler, more manageable components to facilitate investigation, such as isolating the molecular structure of DNA.

Systems Biology

An approach to studying biological organisms that models the dynamic behavior of whole biological systems based on the study of interactions among system parts.

Eukaryotic Cell

A type of cell containing membrane-enclosed organelles, the largest of which is typically the nucleus, characteristic of organisms in Domain Eukarya (protists, plants, fungi, and animals).

Prokaryotic Cell

A simpler and typically smaller cell lacking a membrane-enclosed nucleus and membrane-bound organelles, with DNA concentrated in an unbound region called a nucleoid; characteristic of Domain Bacteria and Domain Archaea.

Negative Feedback

A biological self-regulatory mechanism in which accumulation of an end product slows down or inhibits the initial enzymatic process that creates it.

Positive Feedback

A biological self-regulatory mechanism in which accumulation of an end product speeds up its own production process.

Natural Selection

The primary mechanism for evolutionary adaptation proposed by Charles Darwin, wherein the natural environment selects for individuals possessing beneficial heritable traits that enhance survival and reproductive success.

Hypothesis

A tentative, testable, and falsifiable proposed explanation for an observed phenomenon that leads to specific predictions in scientific inquiry.

Deductive Reasoning

A logical process in hypothesis-based science that proceeds from general premises to formulate specific predictions, typically using 'if… then' logic.

Controlled Experiment

An experimental setup designed to test the effect of an unwanted variable by comparing an experimental group with a control group, differing ideally only in the single variable of interest.

Element

A pure substance that cannot be broken down into simpler substances by ordinary chemical reactions.

Compound

A chemical substance composed of two or more distinct elements combined in a fixed ratio, exhibiting emergent properties distinct from its constituent elements.

Essential Elements

The approximately $25$ of the $92$ natural chemical elements essential for life, with carbon, hydrogen, oxygen, and nitrogen constituting approximately $96\%$ of living matter.

Trace Elements

Chemical elements essential for an organism's survival and growth but required only in minute quantities.

Isotopes

Different atomic forms of a given chemical element that have the identical number of protons but differ in their number of neutrons.

Electronegativity

An atom's relative attraction for shared electrons within a covalent bond.

Nonpolar Covalent Bond

A type of covalent chemical bond in which electrons are shared equally between atoms of similar electronegativity.

Polar Covalent Bond

A covalent chemical bond between atoms differing in electronegativity, wherein unequal electron sharing generates partial positive ($\delta+$) and partial negative ($\delta-$) charges on bonded atoms.

Ionic Bond

A chemical bond resulting from the electrostatic attraction between oppositely charged ions: a positively charged cation and a negatively charged anion.

Hydrogen Bond

A weak noncovalent attraction between a partially positive hydrogen atom covalently bonded to an electronegative atom (usually oxygen or nitrogen) and another nearby electronegative atom.

Van der Waals Interactions

Weak, transient attractions between molecules or parts of molecules that occur when electrons are distributed asymmetrically, creating momentary localized charge hotspots.

Cohesion

The collective phenomenon in which hydrogen bonds hold molecules of the same substance together, facilitating the upward transport of water against gravity in plants.

Adhesion

The attraction between different substances, such as the clinging of water molecules to plant cell walls via hydrogen bonds.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid, caused by cohesion and allowing organisms such as water striders to walk on water.

Specific Heat

The amount of heat that must be absorbed or lost for $1\,\text{g}$ of a substance to change its temperature by $1^\circ\text{C}$; for water, it is unusually high at $1\,\text{cal/g/}^\circ\text{C}$, allowing water to resist thermal changes.

Heat of Vaporization

The quantity of heat a liquid must absorb for $1\,\text{g}$ of it to be converted into a gaseous state.

Evaporative Cooling

The cooling of a liquid's remaining surface during evaporation caused by the departure of molecules having the highest kinetic energy, which stabilizes temperatures in organisms and water bodies.

Hydration Shell

The sphere of water molecules that surrounds each dissolved ion when an ionic compound dissociates in an aqueous solution.

Acid

A substance that increases the concentration of hydrogen ions ($H^+$) in an aqueous solution.

Base

A substance that reduces the concentration of hydrogen ions ($H^+$) in an aqueous solution.

Organic Chemistry

The branch of chemistry devoted to the scientific study of carbon-based compounds.

Tetravalence

The structural property of having four valence electrons, enabling carbon to form four covalent bonds with varied atoms in tetrahedral or flat planar arrangements.

Hydrocarbons

Organic molecules composed exclusively of carbon and hydrogen atoms, capable of undergoing reactions that release large amounts of energy.

Structural Isomers

Isomeric compounds that have the identical molecular formula but differ in the covalent arrangements of their atoms.

Geometric Isomers

Isomers that possess identical covalent partnerships but differ in spatial arrangements around an inflexible double bond, designated as cis (groups on same side) or trans (groups on opposite sides).

Enantiomers

Isomers that are non-superimposable mirror images of each other, occurring when four different chemical groups are attached to an asymmetric carbon atom.

Functional Groups

Specific chemical configurations of atoms that attach to carbon skeletons and participate directly in chemical reactions, giving organic molecules their unique properties.

Hydroxyl Group

A polar chemical group consisting of a hydrogen atom bonded to an oxygen atom ($\text{—OH}$), found in alcohols such as ethanol, capable of forming hydrogen bonds with water.

Carbonyl Group

A functional group consisting of a carbon atom linked by a double bond to an oxygen atom ($>\text{C=O}$), categorized as a ketone if within a carbon skeleton or an aldehyde if at the end.

Carboxyl Group

An acidic functional group consisting of a single carbon atom double-bonded to an oxygen atom and also bonded to a hydroxyl group ($\text{—COOH}$); donates $H^+$ to form a carboxylate ion ($\text{—COO}^-$).

Amino Group

A basic functional group composed of a nitrogen atom bonded to two hydrogen atoms ($\text{—NH}_2$); acts as a base by picking up $H^+$ from surrounding solution to form an ionized ion ($\text{—NH}_3^+$).

Sulfhydryl Group

A functional group consisting of a sulfur atom bonded to a hydrogen atom ($\text{—SH}$), found in thiols such as cysteine, capable of forming covalent cross-linking disulfide bridges that stabilize protein structures.

Phosphate Group

A functional group consisting of a phosphorus atom covalently bonded to four oxygen atoms ($\text{—OPO}_3^{2-}$), contributing negative charge and having the potential to release energy when reacting with water.

Methyl Group

A nonpolar functional group consisting of a carbon atom bonded to three hydrogen atoms ($\text{—CH}_3$), involved in gene expression regulation when bound to DNA.

Polymer

A long macromolecule composed of numerous similar or identical building blocks connected through covalent bonds.

Monomer

A small repeating chemical building-block molecule that serves as the subunit for synthesizing a polymer.

Dehydration Reaction

A condensation reaction in which two monomer molecules become covalently bonded to one another through the loss of a water molecule ($H_2O$).

Hydrolysis

A chemical reaction that breaks the covalent bonds between monomers in a polymer through the addition of a water molecule ($H_2O$).

Monosaccharide

The simplest carbohydrate monomer, generally having a molecular formula that is a multiple of $CH_2O$, classified by carbon skeleton length and the position of its carbonyl group.

Glycosidic Linkage

A covalent bond formed between two monosaccharides through a dehydration reaction.

Starch

A storage polysaccharide found in plants consisting entirely of glucose monomers linked by $\alpha$ 1–4 glycosidic bonds, stored as granules within chloroplasts and other plastids.

Glycogen

An extensively branched storage polysaccharide of glucose found in animal tissues, stored primarily in liver and muscle cells.

Cellulose

A structural polysaccharide that constitutes plant cell walls, composed of straight polymers of glucose joined by $\beta$ 1–4 glycosidic linkages held together in parallel bundles called microfibrils.

Chitin

A structural polysaccharide containing amino sugar monomers, found in the exoskeletons of arthropods and the cell walls of many fungi.

Fat (Triacylglycerol)

A lipid composed of three fatty acid molecules joined to a single glycerol molecule by ester linkages.

Saturated Fatty Acid

A fatty acid possessing no carbon-carbon double bonds in its hydrocarbon chain, maximizing the number of hydrogen atoms; forms saturated fats that are solid at room temperature.

Unsaturated Fatty Acid

A fatty acid containing one or more double bonds in its hydrocarbon chain (typically cis, creating kinks that prevent tight packing); liquid at room temperature.

Hydrogenation

The industrial chemical process of converting unsaturated fats into saturated fats by adding hydrogen, which can also produce trans fats containing trans double bonds.

Phospholipid

An amphipathic lipid consisting of a glycerol joined to two hydrophobic fatty acid tails and a hydrophilic head containing a phosphate group and choline; forms cellular bilayer membranes.

Steroid

A class of lipids characterized by a carbon skeleton consisting of four fused rings, functioning as hormones and structural membrane components.

Polypeptide

A linear polymer built from the same set of $20$ amino acids linked covalently by peptide bonds.

Amino Acid

An organic monomer possessing both an amino group and a carboxyl group attached to a central alpha carbon, differing from other amino acids by its side chain (R group).

Peptide Bond

The covalent bond that links adjacent amino acids together, formed between the carboxyl end of one amino acid and the amino end of another via a dehydration reaction.

Primary Structure

The unique, genetically programmed linear sequence of amino acids in a polypeptide chain.

Secondary Structure

The localized coils and folds within a polypeptide chain formed by hydrogen bonds between repeating constituents of the polypeptide backbone, including the $\alpha$ helix and $\beta$ pleated sheet.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain, determined by interactions between amino acid side chains (R groups), such as hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.

Disulfide Bridge

A strong covalent bond formed between the sulfhydryl groups of two cysteine monomers that reinforces a protein's tertiary or quaternary structure.

Quaternary Structure

The structural level of a protein formed when two or more distinct polypeptide subunits aggregate to yield one functional macromolecule, as in collagen (three polypeptides) or hemoglobin (four polypeptides).

Sickle-Cell Disease

A genetic blood disorder caused by the substitution of a valine for glutamic acid at the sixth amino acid position of the $\beta$ subunit of hemoglobin, leading to fiber crystallization and sickle-shaped red blood cells.

Denaturation

The unraveling of a protein resulting in the loss of its native three-dimensional conformation and biological function, induced by changes in pH, salt concentration, or temperature.

Chaperonin

A protein complex consisting of a hollow cylinder and a cap that assists in the proper folding of other polypeptides by providing an isolated, hydrophilic environment.

Gene

A discrete unit of hereditary inheritance composed of DNA that programs the primary amino acid sequence of a polypeptide.

Nucleotide

The monomer of a nucleic acid, consisting of a nitrogenous base, a five-carbon pentose sugar, and one or more phosphate groups.

Nucleoside

The component of a nucleotide consisting solely of a nitrogenous base attached to a pentose sugar, lacking the phosphate group.

Pyrimidine

A class of nitrogenous bases characterized by a single six-membered ring, comprising cytosine (C), thymine (T, in DNA), and uracil (U, in RNA).

Purine

A class of nitrogenous bases characterized by a six-membered ring fused to a five-membered ring, comprising adenine (A) and guanine (G).

Antiparallel

The structural arrangement of the DNA double helix in which the two sugar-phosphate backbones run in opposite $5' \rightarrow 3'$ directions relative to one another.

Magnification

The ratio of an object's image size produced by a microscope to its actual real size.

Resolution

The measure of image clarity in microscopy, defined as the minimum distance two points can be separated and still be distinguished as separate points.

Scanning Electron Microscope (SEM)

A microscope that directs an electron beam across the surface of a specimen, creating detailed three-dimensional topographical images.

Transmission Electron Microscope (TEM)

A microscope that transmits an electron beam through an ultra-thin specimen section to reveal internal cellular ultrastructure.

Cell Fractionation

A laboratory technique that breaks cells open and employs differential centrifugation to separate major cellular organelles and components based on size and density.

Plasma Membrane

A selective phospholipid bilayer barrier studded with proteins that encloses the cell and regulates the influx and efflux of oxygen, nutrients, and wastes.

Nuclear Envelope

A perforated double membrane enclosing the nucleus of a eukaryotic cell, separating nuclear contents from the cytoplasm.

Nuclear Lamina

A netlike array of protein filaments lining the inner surface of the nuclear envelope that mechanically supports nuclear shape.

Chromatin

The complex of DNA and protein molecules that condenses to form discrete chromosomes during eukaryotic cell division.

Nucleolus

A prominent structure situated within the eukaryotic nucleus where ribosomal RNA (rRNA) is synthesized and assembled with proteins to form ribosomal subunits.

Ribosome

A cellular complex composed of rRNA and proteins that carries out protein synthesis, functioning either suspended freely in the cytosol or bound to the rough ER and nuclear envelope.

Smooth Endoplasmic Reticulum

The portion of the endoplasmic reticulum devoid of ribosomes, active in lipid synthesis, carbohydrate metabolism, drug detoxification, and calcium ion storage.

Rough Endoplasmic Reticulum

The portion of the endoplasmic reticulum studded with ribosomes, responsible for synthesizing secretory glycoproteins, generating transport vesicles, and expanding cell membranes.

Golgi Apparatus

An organelle composed of stacks of flattened membranous sacs (cisternae) possessing cis (receiving) and trans (shipping) faces, functioning in modifying, sorting, and packaging products of the ER.

Lysosome

A membranous sac of hydrolytic enzymes found in eukaryotic animal cells that digests macromolecules, engulfed food particles, and damaged cellular organelles.

Phagocytosis

A form of endocytosis in which a cell engulfs large particulate matter or other cells to form an intracellular food vacuole, which subsequently fuses with a lysosome.

Autophagy

A cellular recycling process wherein a lysosome fuses with a vesicle surrounding damaged organelles to digest and recycle intracellular components.

Central Vacuole

A large membranous sac occupying much of a mature plant cell's volume, responsible for storing inorganic ions, holding water, and maintaining cell turgor.

Mitochondrion

A semi-autonomous eukaryotic organelle bounded by a double membrane with folded cristae and a fluid matrix, serving as the site of cellular respiration and ATP generation.

Chloroplast

A semi-autonomous photosynthetic organelle in plants and algae containing thylakoids arranged into grana and surrounded by stroma, which captures light energy to produce sugars.

Peroxisome

A specialized metabolic compartment bounded by a single membrane that produces hydrogen peroxide ($H_2O_2$) while breaking down organic substrates, then converts $H_2O_2$ to water.