Bio 93 Lecture 8: Nucleus, Ribosomes, and the Endomembrane System

Comprehensive vocabulary flashcards covering the nucleus, ribosomes, and the endomembrane system for Bio 93 Lecture 8.

Chromatin

The complex consisting of DNA and associated packaging proteins, such as basic histones, found within the eukaryotic nucleus.

Nucleus

The membrane-bound organelle that contains the genetic library of a eukaryotic cell, measuring approximately $5\,\mu\text{m}$ in human cells and packaging roughly $2\,\text{m}$ ($6\,\text{ft}$) of compacted DNA.

Nuclear Envelope

The double membrane enclosing the nucleus, composed of two lipid bilayers separated by a perinuclear space and perforated by nuclear pores.

Perinuclear Space

The fluid-filled space between the inner and outer lipid bilayers of the nuclear envelope, which is directly continuous with the endoplasmic reticulum lumen.

Nuclear Lamina

A network of intermediate filaments lining the inner surface of the nuclear membrane (except at nuclear pores) that maintains the structural shape of the nucleus.

Nuclear Pores

Large protein-lined openings spanning both lipid bilayers of the nuclear envelope that regulate molecular traffic between the cytoplasm and the nuclear interior.

Nucleoporins

The constituent proteins that assemble into ring structures to form the functional framework of the nuclear pore complex.

Nuclear Localization Signal (NLS)

A specific targeting amino acid sequence that tags cytoplasmically synthesized proteins for transport into the nucleus through nuclear pore complexes.

Nuclear Export Signal (NES)

A peptide sequence present on proteins that marks them (and complexed RNAs) for transport out of the nucleus into the cytoplasm.

Nucleolus

A prominent non-membrane-bound subnuclear region where ribosomal RNA ($\text{rRNA}$) is transcribed and ribosomal subunits are assembled.

Ribosome

A cellular ribonucleoprotein complex composed of ribosomal RNAs ($\text{rRNAs}$) and proteins, arranged into large and small subunits to perform protein synthesis.

Free Ribosomes

Ribosomes suspended freely in the cytosol that synthesize soluble proteins functioning in the cytoplasm.

Bound Ribosomes

Ribosomes attached to the cytosolic face of the rough endoplasmic reticulum that synthesize integral membrane proteins and proteins destined for secretion or lysosomal targeting.

Endomembrane System

A coordinated network of internal eukaryotic membranes that functions collaboratively to synthesize, modify, package, sort, and transport lipids and proteins throughout and outside the cell.

Endoplasmic Reticulum (ER)

An extensive network of membranous tubules and flattened sacs continuous with the outer nuclear envelope, serving as the primary site for membrane, secretory protein, and lipid biosynthesis.

Cisternae

The individual flattened, membranous sacs and tubules that make up the structural architecture of both the endoplasmic reticulum and the Golgi apparatus.

ER Lumen

The internal aqueous compartment (cisternal space) bounded by the endoplasmic reticulum membrane, into which newly synthesized secretory proteins translocate to fold and undergo processing.

Rough Endoplasmic Reticulum (rER)

The ribosome-studded region of the ER responsible for folding and glycosylating proteins, as well as synthesizing phospholipids to expand organellar and plasma membranes.

Smooth Endoplasmic Reticulum (sER)

The ribosome-free portion of the ER that synthesizes lipids, cholesterol, and steroid hormones, metabolizes carbohydrates, detoxifies drugs and poisons, and sequesters calcium ions.

Golgi Apparatus

A polarity-exhibiting organelle composed of stacked cisternae that modifies, finishes, sorts, and packages ER-derived proteins and phospholipids before directing them to specific destinations.

Cis Face (of Golgi)

The receiving region of the Golgi apparatus situated closest to the ER, where incoming transport vesicles fuse and unload their cargo into the cisternal stack.

Trans Face (of Golgi)

The shipping side of the Golgi apparatus from which finished, sorted vesicles bud off to travel toward lysosomes, the plasma membrane, or other destinations.

Mannose-6-Phosphate (6-P-Mannose)

A specific phosphorylated carbohydrate tag attached to enzymes within the Golgi apparatus that targets them for delivery to lysosomes.

Glycosylation

The enzymatic addition and modification of carbohydrate chains on proteins and lipids within the rough ER and Golgi, producing glycoproteins and glycolipids like the ABO blood antigens.

Lysosome

A membranous organelle budding from the Golgi that contains hydrolytic digestive enzymes operating optimally in an acidic environment maintained by membrane proton pumps.

Phagocytosis

A form of endocytosis wherein a cell engulfs external particles, microorganisms, or nutrient debris to create a food vacuole that subsequently fuses with a lysosome for digestion.

Autophagy

A catabolic cellular process in which a lysosome fuses with a vesicle engulfing damaged organelles or macromolecules to digest them and recycle their fundamental components.

Central Vacuole

A large, sap-filled organelle found in mature plant cells that stores inorganic ions like potassium and chloride, supports plant structure, and drives cellular enlargement.

Lysosomal Storage Disorders (LSDs)

Inherited metabolic diseases caused by deficiencies in specific lysosomal hydrolytic enzymes, resulting in pathogenic accumulation of undigested lipids or carbohydrates within cells.

Enzyme Replacement Therapy (ERT)

A medical intervention for lysosomal storage disorders involving the administration of synthetic enzymes labeled with mannose-6-phosphate to enable receptor-mediated endocytosis into lysosomes.