Chapter 4 Evolutionary Origin of Cells - VOCABULARY Flashcards

Vocabulary flashcards covering core terms from the lecture notes on cell structure, organelles, and protein sorting.

Cell theory

A foundational idea that all organisms are composed of cells; cells are the basic units of life; new cells arise from preexisting cells; modern additions include identical chemical composition, energy use, and DNA duplication during cell division.

Prokaryote

A simple cell lacking a membrane-bound nucleus; includes Bacteria and Archaea; typically small (1–10 μm) with no true nucleus.

Eukaryote

A more complex cell with a membrane-bound nucleus and internal membranes forming organelles; generally larger than prokaryotic cells.

Plasma membrane

Phospholipid bilayer with embedded proteins that encloses the cell; regulates transport, signaling, and cell–cell adhesion.

Cytosol

The fluid portion of the cytoplasm outside organelles where many metabolic processes occur.

Nucleus

Membrane-bound organelle containing DNA and the nucleolus; site of transcription and genetic information storage.

Nuclear envelope

Double membrane surrounding the nucleus with nuclear pores controlling traffic between nucleus and cytoplasm.

Nuclear pore

Protein channels in the nuclear envelope that regulate transport of molecules between the nucleus and cytoplasm.

Chromatin

DNA wrapped around histone proteins; condenses into chromosomes during cell division.

Nucleolus

Substructure within the nucleus where rRNA synthesis and ribosome assembly occur.

Endomembrane system

Network of membranes including the nuclear envelope, ER, Golgi, lysosomes, vacuoles, vesicles, and plasma membrane involved in protein and lipid processing and transport.

Rough endoplasmic reticulum (RER)

ER studded with ribosomes; synthesizes secreted and membrane proteins and distributes transport vesicles.

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; synthesizes lipids, metabolizes carbohydrates, detoxifies poisons, and stores calcium.

Golgi apparatus

Stacked membrane sacs (cisternae) that process, modify, sort, and package proteins for secretion or delivery to other organelles.

Lysosome

Organelle with acid hydrolases that digest macromolecules; functions best at low pH (about 5).

Central vacuole

Large plant cell organelle that stores water and maintains turgor pressure.

Vacuole

Membrane-bound sacs involved in storage and transport; includes contractile vacuoles in some organisms.

Vesicle

Membranous sacs that transport molecules between organelles and to the plasma membrane; involved in exocytosis and endocytosis.

Exocytosis

Process by which substances are released from the cell when vesicles fuse with the plasma membrane.

Endocytosis

Process by which substances are taken into the cell via vesicle formation from the plasma membrane.

Mitochondrion

Semiautonomous organelle that produces ATP through cellular respiration; double membrane, contains own DNA and ribosomes.

Chloroplast

Semiautonomous organelle in plants/algae that conducts photosynthesis; has a double membrane, stroma, grana with thylakoids, and its own DNA.

Endosymbiosis

Theory that mitochondria and chloroplasts originated from intracellular bacteria; explains their own DNA and double membranes.

Semiautonomous organelle

Organelle that grows and divides but relies on the cell for some components; mitochondria and chloroplasts are examples.

Cytoskeleton

Network of protein filaments (microtubules, intermediate filaments, microfilaments) that provides structural support, aids in division and movement, and facilitates organelle transport.

Microtubules

Long hollow tubules made of tubulin with plus and minus ends; exhibit dynamic instability and serve as tracks for motor proteins; originate from MTOC.

Microtubule Organizing Center (MTOC)

Site where microtubules originate; in animals, typically the centrosome; plants lack centrosomes and centrioles.

Centrosome

Animal cell organizing center for microtubules, containing a pair of centrioles.

Centriole

Cylindrical structure within the centrosome involved in organizing microtubules in many animal cells.

Intermediate filaments

Filaments providing tensile strength and structural support; include keratins and lamins.

Actin filaments (microfilaments)

Thin filaments involved in cell shape, membrane support, and movement; dynamic plus and minus ends.

Motor proteins

Proteins that move along cytoskeletal filaments using ATP to transport cargo; include kinesin, dynein, and myosin.

Kinesin

Motor protein that moves cargo toward the plus end of microtubules.

Dynein

Motor protein that moves toward the minus end of microtubules; involved in bending cilia and flagella.

Myosin

Motor protein that moves along actin filaments, driving muscle contraction and intracellular transport.

Cilia and flagella

Microtubule-based projections enabling cell movement; movement driven by dynein-driven sliding of microtubules.

Plasmodesmata

Channels through plant cell walls that connect adjacent plant cells for transport and communication.

Plasma membrane proteins

Proteins embedded in the lipid bilayer performing transport, enzymatic, recognition, adhesion, and receptor functions.

Receptor protein

Membrane protein that binds extracellular signals and initiates a cellular response via signal transduction.

Transport protein

Membrane protein that moves ions and molecules across the plasma membrane.

Signal transduction pathway

Series of molecular events triggered by receptor activation that lead to a cellular response.

Protein sorting

Directed targeting of proteins to their proper destinations within or outside the cell; involves sorting signals and sometimes cotranslational or post-translational mechanisms.

Signal recognition particle (SRP)

Cytosolic complex that binds ER signal sequences and directs ribosome–nascent chain complexes to the ER.

Cotranslational sorting

Protein sorting that occurs as the protein is being synthesized on the ER, directing it to the ER, Golgi, lysosomes, vacuoles, plasma membrane, or secretion.

Post-translational sorting

Sorting that occurs after translation; targets nucleus, mitochondria, chloroplasts, peroxisomes; often requires chaperones to keep proteins unfolded.

Ribosome

RNA–protein particle that synthesizes proteins; free ribosomes synthesize cytosolic proteins; bound ribosomes on the rough ER synthesize secreted or membrane proteins.