Lectures 1-9 Biology Vocabulary Review for Midterm #1

Comprehensive vocabulary flashcards covering key biological terms, mechanisms, organelles, and signaling pathways from Lectures 1 through 9 for Midterm #1.

Evolution

The gradual change in the heritable characteristics of biological populations over successive generations, explaining how diverse species arise, adapt, and become extinct through natural selection, genetic drift, and mutation.

Adaptation

The process by which organisms develop physiological, behavioral, or structural traits that enhance their survival and reproductive success in a specific environment.

Ecosystem

A complex network of living organisms (biotic components) and their physical environment (abiotic components) interacting as a system across dynamic relationships.

Genes

Segments of DNA occupying specific locations on chromosomes that contain coded instructions for synthesizing proteins and serve as units of heredity passed from parents to offspring.

DNA (deoxyribonucleic acid)

A double-stranded helical molecule composed of nucleotides (sugar, phosphate group, nitrogenous base) that encodes genetic information essential for organism development, functioning, growth, and reproduction.

Emergent Properties

Properties that arise from the interactions of simpler elements in a complex system and cannot be predicted or understood merely by examining individual components in isolation.

Hydrogen Bond

A weak bond formed between a hydrogen atom and a more electronegative atom such as oxygen or nitrogen, crucial for maintaining the structure of water and stabilizing the DNA double helix.

Covalent Bond

A strong bond resulting from the sharing of one or more pairs of electrons between atoms, forming the backbone of organic molecules such as proteins, carbohydrates, and nucleic acids.

Ionic Bond

A bond formed through the transfer of electrons from one atom to another, yielding charged ions whose electrostatic attraction forms ionic compounds.

Atom

The basic unit of matter, composed of a nucleus containing protons and neutrons surrounded by electrons in orbitals.

Element

A pure substance consisting of only one type of atom, characterized by its atomic number (the number of protons in its nucleus).

Molecule

A structure formed when two or more atoms of the same element (e.g., $O_2$) or different elements (e.g., $H_2O$) join together through chemical bonds.

Compound

A substance formed when two or more different elements chemically combine in fixed proportions, possessing unique properties distinct from its constituent elements.

Hydration Shell

The clustering of water molecules around a solute particle dissolved in water, which stabilizes solute ions or molecules in solution and facilitates chemical reactions.

Hydrophobic

Substances that are nonpolar and cannot mix with or dissolve in water, repelling water molecules and segregating in aqueous environments.

Hydrophilic

Substances that possess a polar nature and an affinity for water, allowing them to form hydrogen bonds and dissolve readily in aqueous solutions.

Solvent

A substance, usually a liquid, in which other substances dissolve to form a homogeneous mixture.

Solute

The substance that is dissolved in a solvent, present in lesser amounts compared to the solvent.

Solution

A uniform, single-phase mixture formed when a solute completely dissolves in a solvent.

pH

A logarithmic measure of the acidity or basicity of a solution on a scale from $0$ to $14$, where $7$ is neutral, values below $7$ are acidic, and values above $7$ are basic.

Hydrogen Ion (Hydronium Ion)

A charged species ($H^+$), often associated with water as a hydronium ion ($H_3O^+$), representing a proton that has lost its electron and indicating acidic conditions.

Hydroxide Ion

A negatively charged ion ($OH^-$) formed when a water molecule loses a hydrogen ion, indicating basic (alkaline) conditions.

Buffers

Solutions that resist changes in pH upon the addition of small amounts of acids or bases by neutralizing excess $H^+$ or $OH^-$ ions.

Carbohydrates

Organic compounds composed of carbon, hydrogen, and oxygen typically in a $1:2:1$ ratio, serving as a primary energy source, structural component, and cell-signaling element.

Lipids

A broad group of hydrophobic organic molecules, primarily composed of carbon and hydrogen, that function in energy storage, cell membrane structure, and signaling.

Proteins

Large biomolecules made of one or more chains of amino acids that act as enzymes, structural components, hormones, and antibodies.

Chemical / Functional Group

A specific group of atoms within a molecule responsible for its characteristic chemical reactions, properties, solubility, and acidity.

Polymer

A large molecule composed of repeating monomer subunits linked together by covalent bonds.

Monosaccharides

The most basic form of carbohydrates, consisting of single sugar molecules with the general formula $(CH_2O)_n$, such as glucose, fructose, and galactose.

Disaccharides

Carbohydrates formed by the condensation of two monosaccharides linked by a glycosidic bond, including sucrose, lactose, and maltose.

Polysaccharides

Long chains of monosaccharides linked by glycosidic bonds that function in energy storage (starch, glycogen) and structural support (cellulose, chitin).

Saturated Fats

Fats consisting of fatty acids with no double bonds between carbon atoms, containing the maximum number of hydrogen atoms, and typically solid at room temperature.

Unsaturated Fats

Fats containing one or more double bonds in their fatty acid chains, producing kinks that prevent tight packing and keeping them usually liquid at room temperature.

Phospholipids

Amphipathic lipids consisting of two fatty acids, a glycerol molecule, and a phosphate group, forming bilayers that constitute cell membranes.

Steroids

A class of lipids characterized by a four-ring carbon structure that function as hormones (e.g., testosterone, estrogen) and membrane components.

Nucleic Acids

Biomolecules composed of nucleotides (sugar, phosphate, and nitrogenous base) that store and transmit genetic information, consisting primarily of DNA and RNA.

Amino Acid

An organic compound consisting of a central carbon bonded to an amino group (–$NH_2$), a carboxyl group (–$COOH$), a hydrogen atom, and a variable R group.

Polypeptide

A linear chain of amino acids linked together by peptide bonds formed during protein synthesis.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid composed of ribose nucleotides and the bases adenine, uracil, cytosine, and guanine, operating in protein synthesis and gene regulation.

R Group

The variable side chain of an amino acid that confers distinct chemical properties (polar, nonpolar, charged) and dictates protein folding and function.

Sugar-Phosphate Backbone

The structural framework of nucleic acids, formed by alternating sugar and phosphate groups joined together via phosphodiester bonds.

Nonpolar

Molecules that lack distinct positive and negative poles due to an even distribution of electrons, exhibiting hydrophobic properties.

Phosphodiester Linkage

The chemical bond that joins the phosphate group of one nucleotide to the sugar of another, forming the continuous backbone of DNA and RNA.

Polar

Molecules that possess partial positive and negative charges caused by an unequal distribution of electrons, resulting in an overall dipole moment and hydrophilic behavior.

Purine

A two-ring nitrogenous base found in nucleic acids, specifically adenine (A) and guanine (G).

Pyrimidine

A single-ring nitrogenous base found in nucleic acids, including cytosine (C), thymine (T), and uracil (U).

Chaperone Protein

A specialized protein that assists in proper protein folding and assembly to prevent misfolding and aggregation without becoming part of the final structure.

Ubiquitin Proteasome Degradation

A pathway wherein ubiquitin tags damaged or unneeded proteins, targeting them for destruction and peptide cleavage by the proteasome complex.

Prokaryotic Cells

Simpler, unicellular organisms (bacteria and archaea) that lack a true nucleus and membrane-bound organelles, harboring their genetic material within a nucleoid.

Eukaryotic Cells

Complex unicellular or multicellular cells containing a membrane-bound true nucleus and specialized membrane-bound organelles.

Organelle

A specialized subunit within a cell that performs distinct physiological functions, such as mitochondria, chloroplasts, and the endoplasmic reticulum.

Amphipathic

Molecules that possess both hydrophobic (water-fearing) and hydrophilic (water-loving) regions, such as membrane phospholipids.

Fluid Mosaic Model

A structural model depicting biological membranes as a dynamic, flexible phospholipid bilayer embedded with laterally moving proteins, cholesterol, and carbohydrates.

Integral Protein

A membrane protein embedded directly into the lipid bilayer, often spanning its hydrophobic core completely to serve as a channel, carrier, or receptor.

Peripheral Protein

A membrane protein loosely attached to the exterior or interior surface of the bilayer without penetrating the hydrophobic core.

Tonicity

The ability of an extracellular solution to alter cell volume and pressure by driving the osmotic movement of water across the plasma membrane.

Hypotonic Solution

A solution having a lower solute concentration than the inside of the cell, causing net water influx that leads to cellular swelling or bursting.

Isotonic Solution

A solution with an equal solute concentration relative to the cell interior, resulting in zero net water movement and stable cell volume.

Hypertonic Solution

A solution possessing a higher solute concentration than the cell interior, causing net water efflux and resulting in cellular shrinkage or crenation.

Osmosis

The passive transport of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Endocytosis

A vesicular transport process wherein the cell membrane invaginates and engulfs extracellular material to bring substances into the cell.

Exocytosis

A cellular secretion mechanism where intracellular vesicles fuse with the plasma membrane to expel their contents into the extracellular space.

Phagocytosis

A specific form of endocytosis by which specialized cells (such as macrophages) engulf large solid particles, debris, or whole microorganisms.

Pinocytosis

A non-specific type of endocytosis where the cell invaginates to take up droplets of extracellular fluid and dissolved solutes.

Hypercholesterolemia

A medical disorder marked by abnormally high levels of cholesterol in the blood, predisposing individuals to cardiovascular conditions such as atherosclerosis.

Passive Transport

The cellular movement of substances down their concentration gradient without requiring metabolic energy expenditure (e.g., simple diffusion, osmosis, facilitated diffusion).

Active Transport

The movement of substances across a biological membrane against their concentration gradient, requiring energy input typically derived from ATP.

Microfilaments

Thin, threadlike cytoskeletal elements composed of actin protein that maintain cell shape, drive cell motility, and assist in muscle contraction and cell division.

Microtubules

Hollow cytoskeletal cylinders made of tubulin dimers that guide intracellular transport, provide structural support, and form the mitotic spindle.

Intermediate Filaments

Rope-like cytoskeletal fibers made of diverse fibrous proteins that provide mechanical strength and maintain cell architecture under mechanical stress.

Centriole

A cylindrical barrel composed of organized microtubules, typically paired inside the centrosome, that helps organize the mitotic spindle and form cilia and flagella.

Centrosome

The principal microtubule-organizing center (MTOC) of animal cells containing a pair of centrioles, essential for directing mitotic spindle formation during division.

Myosin

A motor protein that binds and hydrolyzes ATP to move along actin filaments, generating muscle contractions and intracellular movements.

Kinesin

A motor protein that transports cellular cargo along microtubules toward the plus end, usually directed outward toward the cell periphery.

Dynein

A motor protein that moves cargo along microtubules toward the minus end, toward the cell center, and powers the beating of cilia and flagella.

Pseudopodia

Temporary, actin-driven cytoplasmic projections used by cells such as amoebas and macrophages for amoeboid locomotion and phagocytic engulfment.

Cilia

Short, numerous, hair-like cellular appendages that beat coordinately to move fluids or mucus across tissue surfaces.

Flagella

Long, whip-like undulating structures, typically fewer in number, that propel single cells (such as sperm) through liquid environments.

Extracellular Matrix (ECM)

A complex network of extracellular proteins, glycoproteins, and carbohydrates that provides structural anchoring, coordinates tissue signaling, and aids cell adhesion.

Cell Wall

A rigid external layer surrounding the plasma membrane in plants, fungi, and some prokaryotes, providing structural support, shape, and resistance to turgor pressure.

Tight Junctions

Intercellular junctions that stitch adjacent animal cell membranes together, preventing fluid leakage across epithelial cell sheets.

Gap Junctions

Intercellular protein channels in animal tissues that allow the direct cytoplasmic passage of ions, small metabolites, and signaling molecules between adjacent cells.

Desmosomes

Anchoring junctions that mechanically fasten adjacent cells into strong sheets, providing tensile resistance against mechanical stress.

Plasmodesmata

Microscopic cytoplasmic channels traversing plant cell walls that allow direct transport and signaling between adjacent plant cells.

Chromatin

The structural complex of DNA and histone proteins inside the eukaryotic nucleus, existing as either transcriptionally active euchromatin or transcriptionally inactive heterochromatin.

Nucleus

The membrane-bound organelle housing the eukaryotic genome, enclosed by a pore-perforated nuclear envelope that directs gene expression and ribosome synthesis.

Rough Endoplasmic Reticulum (Rough ER)

A network of ribosome-studded membranous flattened sacs dedicated to folding, modifying, and sorting proteins destined for membranes, lysosomes, or export.

Smooth Endoplasmic Reticulum (Smooth ER)

A ribosome-free membranous network that carries out lipid and phospholipid synthesis, carbohydrate metabolism, calcium storage, and poison/drug detoxification.

Golgi Apparatus

A series of flattened membranous cisternae that receives, modifies, sorts, and packages ER-derived lipids and proteins for targeted delivery.

Lysosome

A membrane-enclosed acidic organelle filled with hydrolytic digestive enzymes that degrades macromolecules, foreign debris, and worn-out cell parts via autophagy.

Lumen

The distinct interior fluid-filled space within a tubular organelle or sac, such as that inside the endoplasmic reticulum, Golgi apparatus, or vacuole.

Vacuole

A large membrane-bound vesicle found predominantly in plant cells that maintains hydrostatic turgor, stores metabolic reserves and waste, and sequesters defensive compounds.

Endomembrane System

The interconnected group of eukaryotic internal membranes (nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane) working together to synthesize, modify, and transport lipids and proteins.

Autophagy

A catabolic recycling mechanism by which a cell delivers damaged internal organelles and aggregated proteins to the lysosome for degradation and nutrient salvage.

Hormone

A long-range biochemical messenger secreted by endocrine glands into the circulatory system that targets distant organs to regulate physiology and maintain homeostasis.

Reception

The initial stage of cell signaling wherein an extracellular signaling molecule (ligand) binds specifically to a receptor protein, inducing a structural conformational change.

Transduction

The intermediate cascade step of cell signaling where the receptor conformation change triggers a relay pathway of intracellular secondary molecules and enzymatic activations.

Response

The final downstream biological endpoint of a signal transduction pathway, manifesting as transcriptional changes, enzymatic modulation, or cellular behavior adjustments.

Ligand

Any specific molecule that binds reversibly to a complementary receptor site to trigger an intracellular biochemical cascade.

Paracrine Signaling

A mode of short-distance cell communication where secreted ligand molecules diffuse locally through extracellular fluid to target nearby neighboring cells.