Ch. 6

Vocabulary flashcards covering cell biology notes on cell structure, organelles, endomembrane system, cytoskeleton, and intercellular junctions.

A microscope that focuses electrons onto the surface of a specimen, providing 3-D looking images.

Scanning Electron Microscope (SEM)

A microscope that focuses a beam of electrons through a specimen to study internal structure.

Transmission Electron Microscope (TEM)

A technique that takes cells apart and separates the major organelles from one another using centrifuges.

Cell Fractionation

The semifluid substance within the cell in which subcellular components are suspended.

Cytosol

An unbound region in prokaryotic cells where the DNA is located.

Nucleoid

A lipid bilayer structure that encloses the nucleus, separating its contents from the cytoplasm.

Nuclear Envelope

Structures in the nuclear envelope that regulate the entry and exit of molecules from the nucleus.

Nuclear Pores

A protein structure that maintains the shape of the nucleus.

Nuclear Lamina

DNA associated with proteins inside the nucleus, which condenses into chromosomes as a cell prepares to divide.

Chromatin

A structure located within the nucleus that is the site of ribosomal RNA ($rRNA$) synthesis.

Nucleolus

Particles made of ribosomal RNA and protein that carry out protein synthesis.

Ribosomes

An extensive membranous network that accounts for more than half of the total membrane in the eukaryotic cell and is continuous with the nuclear envelope.

Endoplasmic Reticulum (ER)

The region of the endoplasmic reticulum lacking ribosomes; synthesizes lipids, metabolizes carbohydrates, detoxifies drugs and poisons, and stores calcium ions.

Smooth ER

The region of the endoplasmic reticulum studded with ribosomes; secretes glycoproteins, distributes transport vesicles, and acts as a membrane factory for the cell.

Rough ER

An organelle consisting of flattened membrane sacs called cisternae; modifies products of the ER, manufactures certain macromolecules, and sorts and packages materials into transport vesicles.

Golgi Apparatus

Flattened membrane sacs that make up the Golgi apparatus.

Cisternae

A membranous sac of enzymes that digests macromolecules and functions best in an acidic environment.

Lysosome

A process by which a cell or lysosome engulfs food particles or other cells.

Phagocytosis

A process where lysosomes use digestive enzymes to recycle the cell's own old or damaged organelles.

Autophagy

Structures found in many freshwater protists that pump excess water out of the cell.

Contractile Vacuoles

A large vacuole found in many mature plant cells that holds organic compounds and water.

Central Vacuole

The infoldings of the inner mitochondrial membrane that house machinery for ATP generation.

Cristae

The compartment of the mitochondrion enclosed by the inner membrane, containing enzymes and metabolic reaction pathways.

Mitochondrial Matrix

Membranous sacs inside chloroplasts that are stacked to form a granum.

Thylakoids

A stack of membranous thylakoids inside a chloroplast.

Granum

The internal fluid surrounding the thylakoid membranes within a chloroplast.

Stroma

The theory stating that mitochondria and chloroplasts originated as prokaryotic bacteria engulfed by eukaryotic host cells.

Endosymbiont Theory

Single-membrane oxidative organelles involved in metabolism that produce hydrogen peroxide ($H_2O_2$) and convert it to water ($H_2O$).

Peroxisomes

A network of fibers extending throughout the cytoplasm that provides shape, support, and transport guides.

Cytoskeleton

The thickest fibers of the cytoskeleton, composed of dimers of $\alpha$ and $\beta$ tubulin.

Microtubules

The thinnest fibers of the cytoskeleton, composed of actin proteins; also called actin filaments.

Microfilaments

Cytoskeletal fibers of intermediate size made of a variety of proteins.

Intermediate Filaments

A structure located near the nucleus that serves as the microtubule-organizing center.

Centrosome

A pair of structures within the centrosome of animal cells, each consisting of nine triplets of microtubules arranged in a ring.

Centrioles

A motor protein that drives the bending movements of cilia and flagella.

Dynein

Cellular extensions driven by actin and myosin interactions that mediate amoeboid movement.

Pseudopodia

A circular flow of cytoplasm within cells driven by actin-myosin interactions.

Cytoplasmic Streaming

An extracellular structure present in plants, prokaryotes, fungi, and some protists that protects the cell, maintains shape, and prevents excessive water uptake.

Cell Wall

An elaborate external network surrounding animal cells composed of glycoproteins such as collagen, proteoglycans, and fibronectin.

Extracellular Matrix (ECM)

Receptor proteins embedded in the plasma membrane that bind ECM proteins to mediate cell signaling and adhesion.

Integrins

Intercellular junctions present only in plant cells that facilitate transport of water, ions, small molecules, and rarely macromolecules between neighboring cells.

Plasmodesmata

Intercellular junctions in animal cells that hold cells together tightly to prevent fluid leakage.

Tight Junctions

Anchoring intercellular junctions in animal cells that fasten cells together into strong sheets.

Desmosomes

Communicating intercellular junctions in animal cells that allow transport of water, ions, and small molecules directly between adjacent cells.

Gap Junctions