Chapter 06: A Tour of the Cell - Vocabulary Flashcards

Comprehensive set of vocabulary flashcards defining key cell biology terms, structures, organelles, and functions based on Chapter 6.

Cytology

The study of cell structure.

Light Microscope (LM)

A microscope in which visible light is passed through a specimen and then through glass lenses, magnifying the image up to about $1000\times$.

Electron Microscope (EM)

A microscope that focuses a beam of electrons through or onto a specimen, using magnets instead of glass lenses.

Magnification

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

Resolution

The measure of the clarity of an image, defined as the minimum distance between two distinguishable points.

Contrast

Visible differences in brightness between parts of a sample.

Scanning Electron Microscope (SEM)

An electron microscope that focuses a beam of electrons onto the surface of a specimen, producing images that appear 3-D.

Transmission Electron Microscope (TEM)

An electron microscope that focuses a beam of electrons through a specimen, used mainly to study the internal structure of cells.

Cell Fractionation

A technique that takes cells apart and separates major organelles using differential centrifugation.

Prokaryotic Cell

A type of cell lacking a nucleus and membrane-bound organelles, with DNA located in an unbound region called the nucleoid and containing $70S$ ribosomes.

Eukaryotic Cell

A cell containing DNA in a nucleus bounded by a double membrane, along with membrane-bound organelles and $80S$ ribosomes.

Cytosol

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

Plasma Membrane

A membrane composed of a phospholipid bilayer with proteins that controls what goes into and out of the cell.

Nucleoid

An unbound region in a prokaryotic cell where its DNA is concentrated.

Nuclear Envelope

A double membrane enclosing the nucleus, perforated by pores that regulate the entry and exit of molecules.

Nuclear Lamina

A netlike array of protein filaments lining the nuclear side of the envelope that maintains the shape of the nucleus.

Chromatin

The complex of DNA and histone proteins that forms eukaryotic chromosomes.

Nucleolus

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

Ribosomes

Complexes made of ribosomal RNA and protein that function as the sites of protein synthesis.

Endomembrane System

A dynamic cellular system comprising the nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane.

Endoplasmic Reticulum (ER)

An extensive membranous network continuous with the nuclear envelope, accounting for more than half of the total membrane in many eukaryotic cells.

Smooth ER

The region of the endoplasmic reticulum that lacks ribosomes, functioning in lipid synthesis, drug detoxification, and calcium ion storage.

Rough ER

The region of the endoplasmic reticulum studded with bound ribosomes, functioning in glycoprotein secretion and membrane production.

Glycoproteins

Secretory proteins that have carbohydrates covalently bonded to them.

Golgi Apparatus

An organelle consisting of flattened membranous sacs (cisternae) that modifies, sorts, and packages ER products into transport vesicles.

Lysosome

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

Phagocytosis

A cellular process in which a cell engulfs another cell or particle to form a food vacuole.

Autophagy

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

Contractile Vacuole

A membrane-bound organelle found in many freshwater protists that pumps excess water out of the cell.

Central Vacuole

A large vacuole in mature plant cells containing cell sap, storing inorganic ions, and playing a major role in plant cell growth.

Mitochondria

Organelles that serve as the sites of cellular respiration, using oxygen to generate $ATP$.

Cristae

Infoldings of the inner mitochondrial membrane that present a large surface area for enzymes synthesizing $ATP$.

Mitochondrial Matrix

The compartment enclosed by the inner mitochondrial membrane containing enzymes, DNA, and ribosomes.

Chloroplasts

Photosynthetic organelles found in plants and algae that convert light energy into chemical energy.

Thylakoids

Flattened, membranous sacs inside a chloroplast stacked into grana where light reactions occur.

Stroma

The dense fluid within the inner membrane of a chloroplast surrounding the thylakoids.

Endosymbiotic Theory

The theory stating that mitochondria and chloroplasts originated when an early eukaryotic ancestor engulfed oxygen-using and photosynthetic prokaryotic cells.

Peroxisomes

Single-membrane oxidative organelles containing enzymes that transfer hydrogen atoms to oxygen, forming hydrogen peroxide ($H_2O_2$).

Glyoxysomes

Specialized peroxisomes in the fat-storing tissues of plant seeds that convert fatty acids to sugar.

Cytoskeleton

A network of fibers throughout the cytoplasm that maintains cell shape, provides mechanical support, and interacts with motor proteins for cell motility.

Microtubules

Hollow tubes composed of tubulin dimers ($25\,nm$ in diameter) that maintain shape, move chromosomes in cell division, and guide organelle movement.

Microfilaments

Solid rods ($7\,nm$ in diameter) built as a twisted double chain of actin subunits, involved in cell shape changes, muscle contraction, and motility.

Intermediate Filaments

Fibrous proteins coiled into cables ($8-12\,nm$ in diameter) that maintain cell shape, anchor organelles, and form the nuclear lamina.

Centrosome

A structure in animal cells near the nucleus containing a pair of centrioles, serving as a microtubule-organizing center.

Dynein

A motor protein attached to microtubule doublets that drives the bending movements of cilia and flagella.

Pseudopodia

Cellular extensions extended by crawling cells to achieve surface movement.

Cytoplasmic Streaming

A circular flow of cytoplasm within plant cells, driven by actin-protein interactions.

Primary Cell Wall

A relatively thin and flexible extracellular wall layer secreted first by a young plant cell.

Middle Lamella

A thin layer rich in sticky polysaccharides called pectins located between primary walls of adjacent plant cells.

Secondary Cell Wall

A strong matrix layer added between the plasma membrane and primary cell wall in certain mature plant cells.

Extracellular Matrix (ECM)

An elaborate meshwork surrounding animal cells consisting of glycoproteins such as collagen, proteoglycans, and fibronectin.

Integrins

Cell-surface receptor proteins embedded in the plasma membrane that bind to ECM proteins and transmit signals into the cell.

Plasmodesmata

Membrane-lined channels through plant cell walls that connect the cytoplasm of adjacent cells.

Tight Junctions

Cell junctions in animal epithelial tissue where membranes of neighboring cells are pressed together to prevent leakage of extracellular fluid.

Desmosomes

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

Gap Junctions

Communicating junctions in animal cells that provide cytoplasmic channels between adjacent cells.