Campbell Biology Chapter 06: A Tour of the Cell

Comprehensive vocabulary flashcards covering microscopy, prokaryotic versus eukaryotic structures, cellular organelles, the endomembrane system, cytoskeleton, and intercellular junctions from Campbell Biology Chapter 06: A Tour of the Cell.

Magnification

The ratio of an object's image size to its real size in microscopy.

Resolution

The measure of the clarity of an image, or the minimum distance two distinguishable points can be separated and still be distinguished.

Contrast

Visible differences in brightness between different parts of a sample.

Light Microscope (LM)

A microscope in which visible light passes through a specimen and through glass lenses, which refract the light to magnify the image up to approximately $1,000$ times.

Scanning Electron Microscope (SEM)

A microscope that focuses a beam of electrons onto the surface of a specimen, producing three-dimensional images of its topography.

Transmission Electron Microscope (TEM)

A microscope that passes a beam of electrons through a specimen; used primarily to study the internal structure and ultrastructure of cells.

Cell Fractionation

A technique that takes cells apart and separates major organelles and subcellular structures from one another using differential centrifugation.

Cytosol

The semifluid substance in the cytoplasm in which subcellular components are suspended.

Prokaryotic Cell

A type of cell lacking a nucleus, containing DNA in an unbound region called the nucleoid, with no membrane-bound organelles, and cytoplasm bound by the plasma membrane (characteristic of Bacteria and Archaea).

Eukaryotic Cell

A type of cell characterized by having DNA in a nucleus bounded by a double membrane, membrane-bound organelles, and cytoplasm between the plasma membrane and nucleus.

Nucleoid

The non-membrane-enclosed region in a prokaryotic cell where DNA is concentrated.

Plasma Membrane

A selective barrier consisting of a double layer of phospholipids and other lipids that regulates what enters and exits the cell.

Nucleus

The eukaryotic organelle that houses most of the cell's genetic instructions and contains most of its genes.

Nuclear Envelope

A double membrane enclosing the nucleus and separating it from the cytoplasm; each membrane consists of a lipid bilayer perforated by pores.

Chromatin

The complex of DNA and proteins that condenses to form discrete chromosomes as a eukaryotic cell prepares to divide.

Nucleolus

A specialized region located within the nucleus that serves as the site of ribosomal RNA ($\text{rRNA}$) synthesis.

Ribosomes

Cellular complexes composed of ribosomal RNA and protein that carry out protein synthesis in the cytosol (free ribosomes) or bound to the endoplasmic reticulum/nuclear envelope (bound ribosomes).

Endomembrane System

A system of internal membranes that regulates protein traffic and performs metabolic functions, consisting of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

Endoplasmic Reticulum (ER)

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

Smooth ER

The region of the endoplasmic reticulum lacking ribosomes; functions in lipid synthesis, detoxification of drugs and poisons, and calcium ion storage.

Rough ER

The region of the endoplasmic reticulum studded with ribosomes; secretes glycoproteins, distributes transport vesicles, and manufactures membranes for the cell.

Glycoproteins

Secretory proteins synthesized by bound ribosomes on the rough ER that are covalently bonded to carbohydrates.

Transport Vesicles

Secretory proteins or other cargo surrounded by membrane spheres that transit from one part of the cell to another.

Golgi Apparatus

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

Cis Face of Golgi

The "receiving" side of the Golgi apparatus, oriented toward the endoplasmic reticulum.

Trans Face of Golgi

The "shipping" side of the Golgi apparatus from which sorted vesicles pinch off.

Lysosome

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

Phagocytosis

A cellular process in which a cell engulfs another cell or large particles, forming a food vacuole that subsequently fuses with a lysosome.

Autophagy

A recycling process in which lysosomes use hydrolytic enzymes to break down and recycle the cell's own damaged organelles and macromolecules.

Mitochondria

Eukaryotic organelles that serve as the sites of cellular respiration, using oxygen to generate ATP.

Cristae

Infoldings of the inner mitochondrial membrane that provide a large surface area for enzymes that synthesize ATP.

Mitochondrial Matrix

The compartment enclosed by the inner mitochondrial membrane containing mitochondrial DNA, ribosomes, and enzymes that catalyze metabolic steps of cellular respiration.

Chloroplasts

Organelles found in plants and algae that are the sites of photosynthesis, converting light energy into chemical energy.

Peroxisomes

Metabolic compartments specialized as oxidative organelles.

Endosymbiont Theory

The theory stating that an early ancestor of eukaryotic cells engulfed an oxygen-using nonphotosynthetic prokaryote (which evolved into a mitochondrion) and later engulfed a photosynthetic prokaryote (which evolved into a chloroplast).

Cytoskeleton

A network of fibers extending through the cytoplasm that supports cell shape, anchors organelles, and interacts with motor proteins to facilitate cell motility.

Microtubules

Hollow tubes about $25\text{ nm}$ in diameter with a $15\text{-nm}$ lumen, composed of tubulin dimers ($\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$); responsible for cell shape, chromosome separation, and organelle movement.

Centrosome

A region near the nucleus in animal cells from which microtubules grow, functioning as a microtubule-organizing center.

Centrioles

A pair of cylindrical structures within an animal centrosome, each composed of nine triplets of microtubules arranged in a ring.

Cilia and Flagella

Microtubule-containing extensions projecting from cell surfaces that beat to propel unicellular protists or sweep fluids over tissues; composed of nine outer doublets and two central single microtubules.

Basal Body

A cellular structure composed of microtubule triplets that anchors a motile cilium or flagellum.

Dynein

A motor protein with two "feet" that walk along microtubules, driving the bending movements of cilia and flagella.

Microfilaments (Actin Filaments)

Solid rods about $7\text{ nm}$ in diameter built from a twisted double chain of actin subunits; responsible for cell shape maintenance, muscle contraction (with myosin), and amoeboid movement via pseudopodia.

Intermediate Filaments

Fibrous protein cables with diameters ranging from $8\text{ nm}$ to $12\text{ nm}$ (including keratins) that maintain cell shape, anchor the nucleus and organelles, and form the nuclear lamina.

Extracellular Matrix (ECM)

An elaborate meshwork outside animal cells composed of glycoproteins such as collagen, proteoglycans, and fibronectin; regulates cell behavior and communicates with the nucleus.

Integrins

Transmembrane cell-surface receptor proteins that bind to ECM fibronectin and bridge the extracellular environment with the internal cytoskeleton.

Tight Junctions

Intercellular junctions in animal epithelial tissues where adjacent plasma membranes are tightly pressed together to form a barrier preventing fluid leakage across cell layers.

Desmosomes

Anchoring junctions that fasten animal cells together into strong sheets, mechanically anchored by intermediate filaments.

Gap Junctions

Communicating junctions that provide open cytoplasmic channels between adjacent animal cells for the direct passage of ions and small molecules.