ap bio unit 2 study guide chapter 6

Light microscope

An optical instrument that focuses visible light through a series of lenses to magnify and resolve detailed images of small specimens, typically achieving resolutions down to approximately $200\,\text{nm}$.

Electron microscope

An advanced optical instrument that uses a beam of electrons to achieve much higher resolutions than light microscopes, typically below $1\,\text{nm}$, allowing visualization of fine cellular structures and molecular details.

SEM vs. TEM

The two major types of electron microscopes; scanning electron microscopes provide 3D images of specimen surfaces, while transmission electron microscopes allow imaging of thin specimens at high resolution, revealing internal structures.

Prokaryote

An organism characterized by the absence of a defined nucleus and membrane-bound organelles, typically unicellular, such as bacteria and archaea.

Eukaryote

An organism that possesses a defined nucleus and membrane-bound organelles, often multicellular, including animals, plants, fungi, and protists.

Cytoplasm

The gel-like substance within a cell that surrounds and supports the cell organelles, playing a crucial role in cellular processes.

Nucleus

The membrane-bound structure within a eukaryotic cell that contains the cell's genetic material, organized into chromosomes.

Chromatin

The material composed of DNA and proteins that make up chromosomes; it exists in a dispersed form within the nucleus during the interphase of the cell cycle.

Chromosome

A long, threadlike structure made of DNA and proteins that carries genetic information; becomes visible during cell division.

Nucleolus

A dense, non-membrane-bound structure within the nucleus responsible for transcribing ribosomal RNA (rRNA) and assembling ribosome subunits.

Ribosome

A complex of rRNA and protein molecules that functions as the site of protein synthesis in the cytoplasm.

Rough endoplasmic reticulum (rough ER)

A membranous network studded with protein-synthesizing complexes that actively folds, modifies, and packages newly synthesized secretory proteins into transport vesicles.

Smooth endoplasmic reticulum (smooth ER)

A tubular membrane network lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, and stores intracellular calcium ions.

Golgi apparatus

A series of flattened membranous sacs (cisternae) that modifies, sorts, packages, and routes proteins and lipids received from the endoplasmic reticulum.

Lysosome

A membrane-enclosed digestive organelle containing hydrolytic enzymes used to break down macromolecules, cellular debris, and engulfed pathogens via phagocytosis.

Vacuole and vesicle

Membrane-bound fluid-filled sacs within cells; the smaller variety mainly transports substances, while the larger variety functions primarily in bulk storage and cellular maintenance.

Central vacuole and tonoplast

A large internal storage compartment found in mature plant cells that maintains turgor pressure, surrounded by a specialized selectively permeable boundary membrane.

Chloroplast

A double-membraned photosynthetic organelle containing chlorophyll pigments, thylakoid discs, and stroma to convert solar energy into chemical energy via carbohydrate synthesis.

Mitochondria and cristae

Double-membraned power-generating organelles with folded inner membrane projections that vastly expand surface area for ATP production via cellular respiration.

Cytoskeleton

A dynamic intracellular network of protein fibers extending throughout the cytoplasm that provides structural support, anchors organelles, and facilitates cellular motility.

Microtubules

Hollow cylinders composed of tubulin protein dimers that maintain cell shape, guide organelle movements, and form the mitotic spindle during cell division.

Microfilaments

Solid structural rods composed of twisted actin chains that support cellular tension, enable amoeboid movement, and form the cleavage furrow during cytokinesis.

Intermediate filaments

Tough, fibrous protein supercoils, such as keratin, that bear tension to maintain cell shape and permanently anchor the nucleus and other organelles in place.

Centrioles

Cylindrical structures organized in pairs within the centrosome, each composed of a ring of nine microtubule triplets, which organize microtubule assembly in animal cells.

Cilia and flagella

Motile cellular appendages protruding from eukaryotic surfaces with a characteristic $9+2$ arrangement of microtubules, enabling fluid movement or cellular locomotion.

Cell wall

A rigid extracellular protective layer composed of cellulose, chitin, or peptidoglycan that maintains cell shape, prevents mechanical damage, and resists excessive water uptake.

Extracellular matrix (ECM)

A complex meshwork of glycoproteins like collagen, proteoglycans, and fibronectin surrounding animal cells that regulates adhesion, structure, and cell-cell communication.

Plasmodesmata

Open channels passing through adjacent plant cell walls that connect the cytoplasm of neighboring cells, allowing free exchange of water, ions, and small signaling molecules.

Tight junctions

Continuous belt-like seals between adjacent animal epithelial cells formed by specialized proteins that prevent the leakage of extracellular fluid across cellular layers.

Desmosomes

Anchoring junctions that fasten animal cells together into strong sheets, using intermediate filament attachments to resist strong shearing and mechanical forces.

Gap junctions

Intercellular communicating junctions in animal tissues consisting of connexon protein pores that allow direct passage of ions, sugars, and small molecules between adjacent cells.

Motor proteins (kinesin and dynein)

ATP-powered mechanical molecular transporters that move vesicles and cellular cargo along cytoskeletal tracks toward either the plus-end or minus-end of microtubules.