General Biology I:lesson 1/5 Foundations of Life, Chemistry, Cell Biology, and Membrane Transport

Comprehensive vocabulary review flashcards for General Biology I covering the scientific method, atomic chemistry, chemical bonding, properties of water, biological macromolecules, cell theory, eukaryotic and prokaryotic cell structures, and membrane transport.

Scientific Method

A systematic, hypothesis-driven approach used by scientists to understand the natural world through observation, question, hypothesis formation, prediction, experimentation, and conclusion.

Deductive Reasoning

A logical process that applies general principles to make specific predictions.

Inductive Reasoning

A logical process that uses specific observations to construct general conclusions or principles.

Hypothesis

A proposed explanation for an observation that is testable, falsifiable, and provides a basis for making predictions.

Controlled Experiment

An experiment designed to compare an experimental group against a control group, keeping all variables constant except for the specific variable of interest.

Independent Variable

The variable deliberately manipulated or tested by the researcher in an experiment, whose value does not depend on another variable.

Dependent Variable

The variable measured by a researcher that changes in response to the manipulation of an independent variable.

Null Hypothesis

A statistical statement asserting that there is no difference or effect between experimental treatments.

$$p\text{-value}$$

A statistical value representing the probability that the null hypothesis is correct; a value of $0.05$ or less indicates sufficient evidence to reject the null hypothesis.

Scientific Theory

A comprehensive body of interconnected concepts supported by extensive experimental evidence and reasoning, expressing ideas of which scientists are most certain.

Emergent Properties

Novel properties that emerge at successive levels of biological organization resulting from the arrangement and interactions of individual components within a system.

Natural Selection

The process described by Charles Darwin whereby individuals with certain inherited traits tend to survive and reproduce at higher rates than others due to those advantageous traits.

Descent with Modification

Darwin's evolutionary concept stating that contemporary organisms arose through a succession of ancestral species over time.

Atomic Number

The specific number of protons contained within the nucleus of an atom, defining its elemental identity.

Mass Number

The total sum of protons and neutrons located within the nucleus of an atom.

Valence Electrons

Electrons located in the outermost electron shell of an atom that govern its chemical behavior and bonding capacity.

Cation

A positively charged ion formed when a neutral atom loses one or more valence electrons.

Anion

A negatively charged ion formed when a neutral atom gains one or more valence electrons.

Ionic Bond

A chemical attraction between oppositely charged ions resulting from the complete transfer of one or more electrons between a metal and a non-metal.

Covalent Bond

A chemical bond formed when two atoms share two or more valence electrons.

Electronegativity

The affinity or pull that an atom exerts on shared electrons within a covalent bond.

Polar Covalent Bond

A covalent bond formed between atoms of unequal electronegativity, resulting in unequal electron sharing and partial charges ($\delta^+$ and $\delta^-$).

Hydrogen Bond

A weak chemical association formed between a partially positive hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Van der Waals Interactions

Weak, transient attractions occurring between close molecules when asymmetric electron distributions create localized spots of positive and negative charge.

Cohesion

The property of water molecules sticking collectively to one another via hydrogen bonding, responsible for surface tension.

Adhesion

The property of water molecules clinging to other polar molecules or surfaces through hydrogen bonding, contributing to capillary action.

Specific Heat

The quantity of heat absorbed or lost for $1\,g$ of a substance to change its temperature by $1^\circ\text{C}$; for water, this equals $1\,\text{cal}/g/^\circ\text{C}$.

Heat of Vaporization

The amount of energy required to convert $1\,g$ of a substance from liquid into gas ($586\,\text{cal}$ for water).

Hydration Shell

A sphere of oriented water molecules that surrounds and dissolves individual ions in an aqueous solution.

Acid

Any substance that dissociates in water to increase the hydrogen ion concentration ($[H^+]$).

Base

Any substance that combines with hydrogen ions dissolved in water to reduce the hydrogen ion concentration ($[H^+]$).

pH Scale

A negative logarithmic measure of hydrogen ion concentration defined by $\text{pH} = -\log [H^+]$, where each single unit change indicates a $10$-fold difference in $[H^+]$.

Buffer

A substance that resists fluctuations in pH by absorbing excess hydrogen ions when an acid is added or releasing hydrogen ions when a base is added.

Organic Chemistry

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

Hydrocarbons

Organic molecules composed exclusively of carbon and hydrogen atoms that can release substantial energy during chemical reactions.

Functional Groups

Specific configurations of atoms commonly attached to the carbon skeleton of organic molecules that participate directly in chemical reactions and dictate molecular properties.

Hydroxyl Group

A polar functional group ($-\text{OH}$) found in alcohols that elevates the water solubility of organic molecules.

Carbonyl Group

A functional group containing a carbon atom linked by a double bond to an oxygen atom ($C=O$), categorized as an aldehyde at skeleton ends or a ketone within chains.

Carboxyl Group

An acidic functional group ($-\text{COOH}$) consisting of a carbonyl bound to a hydroxyl group that readily dissociates to release $H^+$.

Amino Group

A functional group ($-\text{NH}_2$) consisting of nitrogen bonded to two hydrogens that acts as a base by picking up $H^+$ from solution.

Sulfhydryl Group

A functional group ($-\text{SH}$) present in thiols like cysteine that can form covalent disulfide bridges to stabilize tertiary protein structure.

Phosphate Group

A functional group consisting of a phosphorus atom bonded to four oxygen atoms that plays a major role in cellular energy transfer.

Methyl Group

A nonreactive functional group ($-\text{CH}_3$) that acts as a molecular tag regulating gene expression on DNA and influencing sex hormone shapes.

Structural Isomers

Isomeric compounds that have identical molecular formulas but differ in the covalent arrangement of their atomic skeletons.

Cis-Trans Isomers

Isomeric molecules possessing identical covalent bonds that differ in spatial orientation across an inflexible double bond.

Enantiomers

Pairs of isomeric molecules that are non-superimposable mirror images of each other due to an asymmetric carbon atom.

Dehydration Reaction

A condensation reaction that synthesizes polymers from monomer subunits through the removal of a water molecule.

Hydrolysis Reaction

A chemical reaction that breaks apart polymers into individual monomers through the addition of a water molecule.

Glycosidic Linkage

A covalent bond joining two monosaccharides together as a consequence of a dehydration reaction.

Starch

A plant storage polysaccharide consisting entirely of $\alpha\text{-glucose}$ monomers joined by $\alpha\text{-1}\rightarrow 4$ linkages.

Glycogen

A highly branched animal storage polysaccharide stored in liver and muscle cells composed of $\alpha\text{-glucose}$ with $\alpha\text{-1}\rightarrow 4$ and $\alpha\text{-1}\rightarrow 6$ linkages.

Cellulose

An unbranched structural polysaccharide found in plant cell walls composed of $\beta\text{-glucose}$ joined by $\beta\text{-1}\rightarrow 4$ linkages that cannot be digested by humans.

Nucleotide

The monomer of nucleic acids composed of three distinct units: a five-carbon pentose sugar, a phosphate group, and a nitrogenous base.

Pyrimidines

A family of nitrogenous bases characterized by a single six-membered ring, including cytosine (C), thymine (T), and uracil (U).

Purines

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

Phosphodiester Linkage

The covalent bond that polymerizes nucleotides by linking the phosphate group of one nucleotide to the sugar unit of the adjacent nucleotide.

Adenosine Triphosphate (ATP)

A specialized nucleotide composed of adenine, ribose, and a triphosphate group that acts as the primary energy currency of the cell.

Primary Structure

The precise linear sequence of amino acids linked together by peptide covalent bonds in a polypeptide chain.

Secondary Structure

Localized coil and fold configurations ($\alpha\text{-helix}$ and $\beta\text{-pleated sheet}$) formed through hydrogen bonding between backbones of amino acids.

Tertiary Structure

The unique overall three-dimensional folding of a single polypeptide chain stabilized by interactions among amino acid R groups.

Quaternary Structure

The overall macromolecular protein structure resulting from the association and interaction of two or more polypeptide subunits.

Protein Motifs

Recurring, common combinations of secondary structures (such as $\beta\text{-}\alpha\text{-}\beta$ or helix-turn-helix) present in many polypeptides that help identify protein functions.

Protein Domains

Distinct, functional modules within a larger protein structure that carry out discrete portions of the overall protein's activity.

Chaperone Proteins

Proteins that facilitate the proper folding of nascent or misfolded polypeptides in the cell.

Denaturation

The loss of native secondary, tertiary, and quaternary protein structure and biological function caused by adverse environmental shifts in pH, temperature, or ionic strength.

Triacylglycerols (Triglycerides)

Lipid molecules synthesized for energy storage composed of three fatty acid chains attached to a glycerol backbone via ester bonds.

Saturated Fatty Acid

A hydrocarbon chain that lacks double bonds and contains the maximum number of hydrogen atoms possible, packing tightly to remain solid at room temperature.

Unsaturated Fatty Acid

A hydrocarbon chain containing one or more carbon-carbon double bonds that cause bending, preventing tight packing and keeping the fat liquid at room temperature.

Micelles

Spherical lipid aggregates that form in aqueous environments where polar hydrophilic heads align facing outward toward water and hydrophobic tails cluster inward.

Steroids

Lipids characterized by a carbon framework consisting of four fused rings, such as cholesterol, estradiol, and testosterone.

Cell Theory

The biological foundation stating that all organisms consist of one or more cells, cells are the basic structural units of life, and all cells arise exclusively from preexisting cells.

Surface Area-to-Volume Ratio

A geometric relationship dictating that as cell size increases, volume expands much more rapidly than surface area, establishing an upper constraint on cell size for efficient diffusion.

Prokaryotic Cell

A unicellular organism lacking a membrane-bound nucleus and internal membrane-bound organelles, typically containing a nucleoid, peptidoglycan cell wall, and ribosomes.

Nucleoid

The non-membrane-enclosed region within a prokaryotic cell where the circular DNA chromosome resides.

Nucleolus

A dense subnuclear region inside the eukaryotic nucleus dedicated to ribosomal RNA (rRNA) transcription and ribosome assembly.

Rough Endoplasmic Reticulum

A region of the endomembrane system studded with ribosomes that synthesizes secretory proteins, modifies glycoproteins, and serves as a membrane factory.

Smooth Endoplasmic Reticulum

A region of the endoplasmic reticulum lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, and stores intracellular calcium ions ($\text{Ca}^{2+}$).

Golgi Apparatus

An organelle composed of stacks of flattened membranous cisternae that modifies, packages, sorts, and ships ER-derived proteins via cis and trans faces.

Lysosomes

Membrane-bound digestive organelles originating from the Golgi apparatus loaded with hydrolytic enzymes that degrade macromolecules, ingested particles, and old organelles.

Peroxisomes

Enzyme-bearing microbodies that oxidize fatty acids and produce hydrogen peroxide as a metabolic byproduct.

Endosymbiont Theory

The evolutionary model proposing that eukaryotic organelles like mitochondria and chloroplasts originated through the engulfment of free-living prokaryotes by ancestral eukaryotic host cells.

Microtubules

Hollow cytoskeletal tubes composed of $\alpha\text{-}$ and $\beta\text{-tubulin}$ dimers that facilitate chromosome movement, intracellular transport, and the internal organization of cilia and flagella.

Microfilaments (Actin Filaments)

Cytoskeletal elements consisting of two twined actin protein strands ($7\,\text{nm}$ diameter) that govern cell crawling, pinching, and muscle contraction.

Intermediate Filaments

Stable, fibrous cytoskeletal ropes ($8\text{--}12\,\text{nm}$ diameter) composed of keratin-like proteins that maintain cell morphology and construct the nuclear lamina.

Extracellular Matrix (ECM)

A complex network of glycoproteins including collagen, proteoglycans, and fibronectin situated outside animal cells that regulates cellular communication and behavior.

Integrins

Transmembrane receptor proteins that link the extracellular matrix to the internal actin cytoskeleton and alter gene expression or cell shape.

Tight Junctions

Intercellular junctions that stitch together plasma membranes of neighboring cells in an epithelial sheet to prevent fluid leakage across intercellular spaces.

Desmosomes (Adhesive Junctions)

Anchoring junctions that mechanically fasten adjacent animal cells together by linking their cytoskeletons with cadherin proteins.

Gap Junctions

Communicating junctions in animal cells formed by connexon protein complexes that provide open cytoplasmic channels for ions and small molecules to travel between cells.

Plasmodesmata

Perforations through adjacent plant cell walls that connect the cytoplasm and smooth ER of neighboring cells, functioning analogously to animal gap junctions.

Fluid Mosaic Model

The structural model describing biological membranes as a mosaic of proteins floating within or across a fluid phospholipid bilayer.

Phospholipid Bilayer

A two-layered fluid membrane matrix formed spontaneously by amphipathic phospholipids, where hydrophobic fatty acid tails pack inside and hydrophilic phosphate heads face the aqueous surroundings.

Transmembrane Proteins

Integral proteins that span across the lipid bilayer, having nonpolar hydrophobic domains of $\alpha\text{-helices}$ embedded in the interior and polar domains exposed on both surfaces.

Peripheral Proteins

Membrane proteins attached to the surface of the plasma membrane via anchoring molecules without penetrating into the hydrophobic core.

Facilitated Diffusion

The passive movement of polar or charged molecules down their concentration gradient through channel or carrier proteins without the expenditure of cellular energy.

Channel Proteins

Transmembrane proteins that form open hydrophilic pathways across the lipid bilayer, allowing specific ions or polar molecules to pass through.

Carrier Proteins

Transport proteins that bind specifically to a transported solute and undergo conformational changes to ferry the solute across the membrane.

Osmosis

The net diffusion of water across a selectively permeable membrane toward a region with a higher solute concentration.

Hypertonic Solution

An external solution with a higher solute concentration relative to the cell's cytoplasm, resulting in osmotic water efflux and cellular shriveling.

Hypotonic Solution

An external solution with a lower solute concentration compared to the cell cytoplasm, causing osmotic water influx that can swell and burst animal cells.