Cells: The Basic Units of Life

Comprehensive vocabulary flashcards detailing historical cell theory developments, cell organelles, plasma membrane components, transport mechanisms, and cellular structures based on lecture notes.

Metabolism

The total of all chemical reactions occurring within a cell.

Anabolic Reactions

Metabolic processes that build complex molecules from simpler ones in cells, such as protein synthesis.

Catabolic Reactions

Metabolic processes that break down complex molecules into simpler ones, such as cellular respiration.

Plasma Membrane

A selectively permeable outer barrier of a cell that separates intracellular contents from the extracellular environment and regulates passage of materials.

Cytoplasm

Everything located between the plasma membrane and the nuclear membrane, consisting of cytosol, organelles, and inclusions.

Cytosol

The gel-like fluid portion of the cytoplasm in which cellular organelles and other cytoplasmic elements are suspended.

Nucleus

The largest cellular organelle that functions as the control center, containing hereditary units (genes) in DNA formatted as chromosomes.

Fluid Mosaic Model

Structural concept describing the plasma membrane as a dynamic layer composed of fluid lipids studded with movable proteins.

Phospholipid Bilayer

A double layer of phospholipids with polar hydrophilic phosphate heads facing liquid environments and nonpolar hydrophobic lipid tails facing each other in the interior.

Glycolipids

Membrane lipids with attached carbohydrate groups extending into the extracellular fluid as part of the glycocalyx.

Cholesterol (Plasma Membrane)

A lipid molecule embedded in the plasma membrane that stabilizes structure and maintains membrane fluidity.

Integral Proteins

Membrane proteins, largely glycoproteins, embedded directly within the phospholipid bilayer, functioning as channels, carriers, receptors, enzymes, or identity markers.

Chemically Gated Channels

Integral channel proteins triggered to open or close when specific chemical ligands bind to them.

Voltage Gated Channels

Integral channel proteins triggered to open or close by changes in membrane voltage.

Mechanically Gated Channels

Integral channel proteins triggered to open or close by physical forces, such as changes in temperature or pressure.

Transporters (Carriers)

Integral proteins that undergo conformational shape changes to move specific small molecules or ions across the plasma membrane.

Identity Markers

Major histocompatibility complex (MHC) glycoproteins and glycolipids that allow cells to distinguish 'self' cells from 'nonself' entities.

Peripheral Proteins

Proteins loosely attached to the inner or outer surface of the plasma membrane, serving as enzymes, second messengers, motor proteins, cytoskeletal supports, or cell-adhesion molecules.

Microvilli

Microscopic cell surface extensions that increase the membrane's surface area for absorption.

Cilia

Short, hair-like protein extensions arranged in a $9 + 2$ microtubule structure that move substances across the cell surface.

Flagellum

A long, whiplike extension arranged in a $9 + 2$ microtubule cylinder that propels an entire cell, such as a sperm cell.

Tight Junctions

Cellular junctions where adjacent plasma membranes fuse to form fluid-tight seals, preventing passage of materials between cells.

Desmosomes

Rivet-like anchoring cell junctions that fasten adjacent cells to one another or to extracellular material in tissues subject to friction and stretching.

Gap Junctions

Cellular connections formed by transmembrane proteins (connexons) that create direct fluid channels allowing ions and small molecules to pass between cells.

Nucleolus

A dense non-membranous region inside the nucleus composed of proteins, DNA, and RNA, responsible for ribosome assembly.

Ribosomes

Organelles composed of rRNA and proteins, located either free in the cytosol or attached to the endoplasmic reticulum, that synthesize proteins.

Rough Endoplasmic Reticulum

A membrane network continuous with the nuclear envelope studded with ribosomes, involved in protein synthesis, glycoprotein formation, storage, and vesicle formation.

Smooth Endoplasmic Reticulum

A membrane network lacking ribosomes that synthesizes lipids and steroids, detoxifies toxins, and regulates release of $\text{Ca}^{2+}$.

Golgi Apparatus

A stack of flattened membranous sacs (cisternae) that processes, sorts, and delivers ER-derived proteins and lipids for export or membrane integration, and forms lysosomes.

Lysosomes

Membrane-bound vesicles containing acidic hydrolase enzymes designed to digest foreign material, worn-out organelles (autophagy), or entire cells (autolysis).

Peroxisomes

Small membranous organelles containing oxidase enzymes that neutralize and detoxify harmful chemicals such as alcohol.

Mitochondrion

An organelle with a smooth outer membrane and a folded inner membrane (cristae) surrounding a matrix, hosting enzymes for aerobic cellular respiration to synthesize ATP.

Microfilaments

Thin cytoskeletal strands composed of actin that support plasma membrane structure and interact with myosin for endocytosis, exocytosis, and muscle contraction.

Intermediate Filaments

Medium-sized protein filaments, such as keratin and collagen, that strengthen cells and maintain structural stability.

Microtubules

Thick, hollow cytoskeletal elements composed of tubulin that coordinate cell movement and form centrioles, cilia, and flagella.

Centrioles

A pair of cylindrical microtubular structures within a centrosome, composed of nine tubulin triplets in a $9 + 0$ arrangement, responsible for organizing spindle fibers during cell division.

Cell Inclusions

Non-membrane bound cell products stored in cytosol, including glycogen granules (glycosomes) and triglyceride lipid droplets.