Cell Biology and Signal Transduction Vocabulary

Flashcards covering key vocabulary terms and definitions from Chapters 5 and 7 including cellular organelles, cytoskeleton components, extracellular structures, and cell signaling mechanisms.

Cell Theory

The unifying biological principle stating that functions of all cells are similar, life is continuous, and the origin of life starts with the origin of cells.

Magnification

The increase in the apparent size of an object under a microscope.

Resolution

The clarity of a magnified object.

Prokaryotic Cells

Primitive, typically small cells that lack membrane-bound organelles and possess a nucleoid region instead of a nucleus.

Eukaryotic Cells

Larger cells that contain membrane-bound organelles such as mitochondria, endoplasmic reticulum, and a true nucleus.

Plasma Membrane

A flexible, moving outer boundary of the cell made of a fluid phospholipid bilayer that regulates transport, cell communication, signal reception, and cell recognition.

Ribosomes

Structures composed of ribosomal RNA and more than 50 protein molecules that perform protein synthesis by decoding mRNA codons and using tRNA to join amino acids.

Nuclear Envelope

The double membrane surrounding the nucleus that allows free passage of small molecules and selective transport of large molecules.

Nucleolus

A specialized, non-membrane bound structure located inside the nucleus responsible for producing and assembling ribosomes.

Chromosomes

The highly condensed, tightly packed form of chromatin that appears when a cell prepares to divide.

Chromatin

The loose, uncondensed form of cellular DNA inside the nucleus.

Nucleoplasm

The gel-like fluid contained inside the nucleus.

Nuclear Matrix

A fibrous, protein-based internal skeleton that supports and organizes the nucleus.

Endomembrane System

An interconnected system of membrane-bound structures comprising the nuclear envelope, rough ER, smooth ER, Golgi apparatus, transport vesicles, lysosomes, vacuoles, and plasma membrane.

Rough Endoplasmic Reticulum (RER)

A system of flattened membranous sacs studded with ribosomes, involved in protein synthesis, protein folding, quality control, initial protein modification, and vesicle transport to the Golgi.

Smooth Endoplasmic Reticulum (SER)

A network of tubular membranes lacking ribosomes, responsible for lipid synthesis, detoxification, calcium storage, and carbohydrate metabolism.

Golgi Apparatus

An organelle that modifies proteins and lipids, sorts and packages molecules, ships materials in vesicles, generates lysosomes, and processes secreted substances.

Cis Face (Golgi)

The receiving face of the Golgi apparatus facing the endoplasmic reticulum where transport vesicles fuse to enter proteins and lipids.

Trans Face (Golgi)

The exit face of the Golgi apparatus facing the plasma membrane where vesicles depart.

Lysosomes

Membrane-bound organelles filled with hydrolytic enzymes produced by the Golgi apparatus.

Phagocytosis

A cellular process in which certain cells engulf large external particles.

Phagosome

The vesicle formed inside a cell following the engulfment of a particle via phagocytosis.

Autophagy

The cellular process where a cell breaks down and recycles its own damaged or unnecessary components.

Mitochondria

Double-membrane organelles featuring folded cristae and an inner matrix that perform cellular respiration, including the Krebs cycle, electron transport chain, and ATP synthesis.

Mitochondrial Matrix

The fluid space inside the inner mitochondrial membrane holding mitochondrial DNA and ribosomes, where parts of cellular respiration take place.

Chloroplasts

Double-membrane plant organelles containing stroma, thylakoids, and grana where photosynthesis occurs.

Thylakoids

Individual membrane-bound sacs located inside chloroplasts.

Grana

Stacks of thylakoid membranes located within chloroplasts.

Vacuole

A fluid-filled cellular sac responsible for storage, maintaining turgor pressure, waste disposal, digestion, defense, and pigment storage.

Microfilaments

Cytoskeletal elements composed of actin monomers that commonly associate with myosin motor proteins to enable cellular functions.

Pseudopodia

Soft, flexible cellular projections used for movement, engulfing particles, and environmental sensing.

Intermediate Filaments

Cytoskeletal elements that provide tensile strength, maintain cell shape, anchor organelles, and support the nuclear envelope.

Microtubules

Dynamic cytoskeletal polymers made of alpha-tubulin and beta-tubulin subunits that associate with kinesin and dynein motor proteins.

Cilia and Flagella

Cellular movement structures containing microtubules arranged in a $9+2$ layout and powered by dynein motor proteins.

Centrioles

Short, hollow cylindrical structures composed of microtubule triplets arranged in a $9 \times 3$ layout.

Plasmodesmata

Tiny membrane-lined channels connecting adjacent plant cells to enable direct intercellular communication.

Extracellular Matrix

An extracellular network in animal cells made of structural proteins, specialized glycoproteins, and proteoglycans that provides support, adhesion, signaling, tissue organization, and cushioning.

Endosymbiosis Theory

The theory that mitochondria evolved from aerobic bacteria and chloroplasts evolved from photosynthetic cyanobacteria through internal symbiotic relationships.

Signal Transduction Pathway

A series of molecular events that converts an external cellular signal into a specific internal response.

Paracrine Signals

Signaling molecules that act on cells located in close physical proximity to the emitting cell.

Autocrine Signals

Signaling molecules that act directly on the same cell that released them.

Hormone Signals

Long-distance signaling molecules that travel through the bloodstream to reach target cells.

Receptor

A protein that detects a stimulus, undergoes a conformational change, and initiates an intracellular signaling cascade.

Ligand

A specific signaling molecule that binds to a receptor to initiate a signal transduction pathway.

Protein Kinase

An enzyme that transfers phosphate groups to target proteins, thereby altering their activity, shape, or cellular interactions.

Antagonist

A molecule or drug that binds to a receptor without activating it, blocking the natural ligand from binding and inhibiting downstream signaling.

Ion Channel Receptors

Plasma membrane receptors that open or close an ion channel upon ligand binding, altering the cell's electrical state.

Protein Kinase Receptors

Receptors that undergo dimerization and autophosphorylation upon ligand binding, activating intrinsic kinase activity and triggering downstream cascades.

Phosphorylation Cascade

A sequential chain of kinase activation events that amplifies an intracellular signal and permits tight regulation.

First Messenger

The extracellular ligand that binds to a specific receptor to initiate cellular signaling.

Second Messenger

Small non-protein intracellular molecules, such as cAMP, IP3, DAG, or $\text{Ca}^{2+}$, that relay signals inside the cell.

Cyclic AMP (cAMP)

A common second messenger synthesized from ATP by the action of the enzyme adenylate cyclase.

DAG and IP3

Intracellular second messengers synthesized from PIP2 through cleavage by the enzyme phospholipase C.

Gap Junctions

Specialized intercellular junctions in animal cells that permit direct cytosolic communication between neighboring cells.