science midterm

Biology

The branch of science devoted to the study of life and living organisms.

Cell

The fundamental structural and functional unit of all living organisms.

Biological organization

The orderly hierarchical arrangement shown by living systems, progressing from atoms to the biosphere.

Growth

The addition of mass and volume to an organism, typically resulting from cellular division.

Development

The natural progression of structural, physiological, and functional changes that occur across an organism's lifespan.

Reproduction

The biological mechanism through which organisms generate offspring to ensure species continuation.

Stimulus

Any internal or external environmental trigger that elicits a physiological or behavioral reaction.

Response

The specific behavioral or physiological action exhibited by an organism directly following an environmental trigger.

Homeostasis

The coordinated physiological regulation required to maintain stable, balanced internal equilibrium despite fluctuating surroundings.

Adaptation

An inherited characteristic resulting from evolutionary change over successive generations that improves survival in a specific environment.

Scientific theory

A comprehensive, highly verified explanation of natural phenomena supported by extensive observational and experimental evidence.

Scientific law

A concise statement or mathematical relationship describing what occurs in nature under specific conditions without explaining why.

Observation

The direct gathering of empirical data about events or objects through sensory perception or scientific instrumentation.

Inference

A logical deduction formulated by synthesizing prior knowledge with directly gathered empirical clues.

Hypothesis

A proposed, testable explanation for an observed phenomenon that serves as the basis for experimental investigation.

Control group

The benchmark sample in an investigation that is not exposed to the experimental manipulation, providing a baseline for comparison.

Experimental group

The sample cohort within an investigation that receives the specific treatment or factor being investigated.

Independent variable

The single operational condition deliberately altered or chosen by the investigator to test its effects.

Dependent variable

The measured outcome or resulting change recorded by the investigator in reaction to the manipulated experimental condition.

Controlled variable

Any factor kept completely uniform, unvarying, and identical across all testing setups to ensure experimental validity.

Quantitative data

Experimental information expressed as numerical measurements obtained using calibrated tools, such as mass or time.

Qualitative data

Descriptive, non-numerical observations detailing physical traits, colors, textures, or behaviors.

Accuracy

The degree of conformity between an experimentally measured quantity and its true, accepted standard value.

Precision

The closeness of agreement among repeated, independent measurements of the same quantity under identical conditions.

Significant figures

All reliably known digits determined directly from a measuring instrument plus a final estimated digit.

Graduated cylinder

A vertical glass or plastic vessel calibrated with scale markings used to determine precise liquid volumes by viewing the bottom of the curved liquid surface.

Atom

The smallest constituent unit of ordinary matter that preserves the distinctive chemical characteristics of a given chemical species.

Proton

A dense nuclear particle carrying a $+1$ elementary electrical charge with a mass of approximately $1\,\text{amu}$.

Neutron

An electrically neutral nuclear particle possessing a mass of approximately $1\,\text{amu}$.

Electron

A particle carrying a $-1$ elementary electrical charge that orbits outside the atomic nucleus within energetic clouds.

Isotope

Variants of a given chemical element that contain identical numbers of protons but different totals of neutral nuclear particles.

Chemical element

A pure substance comprised solely of atoms that possess an identical number of protons in their nuclei.

Chemical compound

A pure substance formed when two or more distinct elements unite in fixed, definite chemical proportions.

Covalent bond

An attractive linkage formed when two nonmetal atoms share one or more pairs of valence electrons.

Molecule

A discrete group of chemically bonded atoms held firmly together exclusively through shared electron pairs.

Ion

An atom or molecular group that has attained a net electrical charge through the loss or acquisition of electrons.

Ionic bond

An attractive force that binds oppositely charged cations and anions following the complete transfer of electrons.

Valence electrons

The electrons situated in the outermost energy level of an atom that govern its chemical reactivity and bonding capacity.

Van der Waals forces

Weak, non-covalent electrostatic attractions arising between temporary or permanent partial electric charges on molecules.

Chemical reaction

A molecular transformation whereby chemical bonds are broken and reformed, reorganizing constituent atoms into novel substances.

Reactants

The starting substances present prior to a chemical transformation, positioned on the left side of a chemical equation.

Products

The resulting substances generated by the completion of a chemical transformation, positioned on the right side of a chemical equation.

Law of conservation of mass

A principle establishing that matter cannot be created or destroyed, dictating that reaction equations must possess equal numbers of each atomic type on both sides.

Activation energy

The minimum kinetic energy threshold required for colliding particles to successfully initiate a chemical reaction.

Exothermic reaction

A chemical process that releases thermal energy to its surroundings, yielding substances whose chemical potential energy is lower than the starting materials.

Endothermic reaction

A chemical process that absorbs heat from its surrounding environment, resulting in substances possessing higher chemical potential energy than the starting materials.

Catalyst

A chemical agent that increases the rate of a chemical process by lowering its activation energy barrier without being permanently consumed.

Enzyme

A specialized globular protein that functions as an organic catalyst to accelerate metabolic processes within living systems.

Substrate

The specific reactant molecule upon which an organic catalyst acts during a catalyzed biochemical transformation.

Active site

The specific catalytic pocket or cleft on a protein where reactant molecules bind to undergo conversion.

Enzyme-substrate complex

The temporary molecular intermediate created when an organic catalyst binds directly to its target reactant molecule.

Protease

A specialized catalytic protein that digests large polypeptides by cleaving interior and terminal peptide linkages.

Optimal detergent protease conditions

An alkaline operating environment of $\text{pH } 10$ paired with a working temperature of $60\,^{\circ}\text{C}$.

Polar molecule

An asymmetric structure possessing an unequal distribution of shared electrons, yielding distinct regions of partial positive and partial negative charge.

Hydrogen bond

A weak intermolecular attraction established between an electropositive hydrogen atom and an electronegative atom such as oxygen or nitrogen.

Cohesion

The intermolecular attractive force that draws identical molecules together, responsible for liquid surface tension.

Adhesion

The attractive force operating between dissimilar molecules, enabling liquids to climb upward against gravity in narrow tubes.

Homogeneous mixture

A physical combination possessing an entirely uniform appearance and identical composition throughout, commonly called a solution.

Heterogeneous mixture

A physical combination whose constituent components remain visibly distinct, unevenly distributed, and physically separable.

Acid

A compound that dissociates in water to donate hydrogen ions ($H^+$), yielding a solution with a $\text{pH} < 7$.

Base

A compound that dissociates in water to donate hydroxide ions ($OH^-$), yielding a solution with a $\text{pH} > 7$.

pH scale

A numeric measure spanning $0$ to $14$ that indicates the relative acidity or alkalinity of an aqueous solution.

Monomer

A single, small chemical subunit that can link covalently with similar units to form extended molecular chains.

Polymer

A large macromolecular structure built from numerous repeating chemical subunits linked by covalent bonds.

Dehydration synthesis

A biochemical assembly reaction that joins smaller subunits together into larger chains with the simultaneous removal of a water molecule.

Hydrolysis

A biochemical cleavage reaction that breaks covalent bonds in large chains through the chemical addition of a water molecule.

Carbohydrates

Biomolecules constructed of carbon, hydrogen, and oxygen in a $1:2:1$ ratio that serve as primary rapid-energy sources and structural materials.

Lipids

Hydrophobic, nonpolar organic molecules consisting mainly of carbon and hydrogen that function in long-term energy storage, insulation, and membrane composition.

Proteins

Biomolecules composed of amino acid monomers linked by peptide bonds that perform catalytic, defensive, transport, and structural functions.

Nucleic acids

Complex biomolecules composed of nucleotide subunits that store, transmit, and express hereditary genetic instructions.