BIO 150 Forensic Biology - Cellular Structure and Eukaryotic Origins

Vocabulary flashcards covering key concepts from cellular structure, organelles, plant vs animal cells, and endosymbiosis.

Cell

The smallest unit of life; all organisms are composed of one or more cells; observed with microscopes.

Animalcules

van Leeuwenhoek’s term for the protists and sperm he observed under his microscope.

Cell theory

The idea that all living things are composed of cells, the cell is the basic unit of life, and new cells arise from existing cells.

Nucleoid

The dark region in prokaryotic cells where DNA is located; not membrane-bound.

Prokaryote

A simple, unicellular organism lacking a true nucleus and membrane-bound organelles; DNA in the nucleoid.

Eukaryote

A cell with a membrane-bound nucleus and other membrane-bound organelles; literally a “true nucleus.”

Organelles

Specialized structures within a cell that perform distinct functions.

Plasma membrane

Phospholipid bilayer with embedded proteins that encloses the cell and regulates transport.

Cytoplasm

The region between the plasma membrane and the nucleus; contains cytosol and organelles in eukaryotes.

Cytosol

The water-based gel-like solution within the cytoplasm containing ions, small molecules, and macromolecules.

Ribosome

Molecular machines that synthesize proteins; composed of large and small subunits; may be free or attached to ER.

Mitochondrion

Organelle that generates ATP through cellular respiration; double-membrane; contains its own DNA and ribosomes.

Cristae

Folds of the inner mitochondrial membrane that increase surface area for respiration.

Mitochondrial matrix

The space inside the inner mitochondrial membrane where many respiration enzymes reside.

Endosymbiotic theory

Idea that eukaryotes arose from one cell engulfing another, leading to mitochondria and chloroplasts.

Alpha-proteobacteria

Bacteria group believed to be the ancestor of mitochondria.

Chloroplast

Photosynthetic plastid in plants/algae; contains chlorophyll; has its own DNA and ribosomes; two membranes.

Thylakoid

Flattened membrane-bound sacs inside chloroplasts where light reactions occur.

Granum

Stack of thylakoids within a chloroplast.

Stroma

Fluid surrounding the grana in chloroplasts; site of the Calvin cycle.

Plastid

General term for plant cell organelles involved in photosynthesis and storage; chloroplasts are a type of plastid.

Endomembrane system

Interconnected membranes that modify, package, and transport lipids and proteins; includes nuclear envelope, ER, Golgi, lysosomes, vesicles, and the plasma membrane.

Nucleus

Prominent organelle that houses DNA and directs ribosome and protein synthesis.

Nuclear envelope

Double membranes surrounding the nucleus with nuclear pores that regulate traffic.

Chromosome

Linear DNA wrapped around histone proteins; visible during cell division; otherwise chromatin.

Chromatin

DNA-protein complex; uncondensed form of genetic material in the nucleus.

Nucleolus

Dense region within the nucleus where ribosomal RNA is synthesized and ribosomal subunits begin to assemble.

Endoplasmic reticulum

Network of membranous tubules; rough ER has ribosomes and synthesizes/modifies proteins; smooth ER lacks ribosomes and makes lipids.

Rough endoplasmic reticulum

ER region studded with ribosomes; synthesizes proteins for secretion or membranes.

Smooth endoplasmic reticulum

ER region without ribosomes; synthesizes lipids, detoxifies, stores calcium.

Golgi apparatus

Modifies, sorts, tags, and packages proteins and lipids; has a receiving face near the ER and a releasing face toward the plasma membrane.

Vesicles

Membrane-bound sacs that transport materials within the cell or to the surface.

Vacuoles

Storage sacs; plant cells have a large central vacuole that maintains turgor.

Lysosome

Digestive organelle with hydrolytic enzymes; degrades macromolecules and worn-out organelles; active in acidic pH.

Peroxisome

Organelle that oxidizes fatty acids and detoxifies poisons; contains hydrogen peroxide and breaks it down.

Cytoskeleton

Network of protein fibers (microfilaments, intermediate filaments, microtubules) that maintains cell shape and enables movement.

Microfilament

Thin actin filaments; involved in movement and supporting microvilli and muscles.

Intermediate filament

Cytoskeletal filaments providing structural support and anchoring organelles (e.g., keratin).

Microtubule

Thick hollow tubes; tracks for motor proteins; segregate chromosomes during mitosis; form cilia/flagella.

Centrosome

Animal cell microtubule-organizing center near the nucleus; contains the pair of centrioles and organizes spindle during division.

Centriole

Cylinder of nine triplets of microtubules; part of the centrosome; less critical in plant cell division.

Flagellum

Long, whip-like projection used for cell movement; example: sperm.

Cilium

Short, numerous projections used to move cells or move substances along the cell surface.

Plasmodesmata

Channels through plant cell walls that connect the cytoplasm of adjacent plant cells.

Tight junction

Intercellular junction that seals gaps between animal cells to prevent leakage.

Desmosome

Intercellular junction providing strong adhesion between adjacent cells.

Gap junction

Intercellular junction allowing direct chemical communication between neighboring cells.

Cell wall

Rigid layer outside the plasma membrane; in plants and fungi; bacteria have peptidoglycan; cellulose in plants.

Cellulose

Polysaccharide that is the main structural component of the plant cell wall.

Chlorophyll

Pigment in chloroplasts that absorbs light for photosynthesis.

Primary endosymbiosis

Initial endosymbiotic event that gave rise to plastids (chloroplasts) in Archaeplastida.

Secondary endosymbiosis

Event where plastids arise in some lineages by uptake of a green or red alga; often with three or more membranes.

Archaeplastida

Major eukaryotic lineage that includes organisms with primary plastids (plants and relatives).

Paulinella

Rhizarian genus that independently acquired a cyanobacterial endosymbiont, illustrating early endosymbiotic events.

Mitosis

Nuclear division producing two genetically identical daughter nuclei; present in all eukaryotes.

Meiosis

Sexual cell division producing haploid nuclei; followed by karyogamy to form a diploid zygote.

Endosymbiosis

A relationship where one organism lives inside another, often benefiting both; explains origins of mitochondria and chloroplasts.

Autotroph

Organisms that synthesize their own organic molecules from inorganic sources (e.g., photosynthesis in plants).

Heterotroph

Organisms that obtain organic molecules by consuming other organisms or their compounds.