Cell Organelles and Their Functions

A comprehensive collection of vocabulary flashcards defining cell organelles, structural components, and differences between prokaryotic and eukaryotic cells based on lecture notes.

Prokaryotic Cell

A cell type (e.g., eubacteria, archaebacteria) generally $0.2\text{ to }5\text{ }\frac{1}{1000}\text{ mm}$ or 0.2\text{ to }5\text{ }\text{̧}\text{m} (0.2\text{ to }5\text{ }̧\text{m}) in diameter, mainly unicellular, lacking a cytoskeleton and internal membrane-bound organelles, with circular DNA free in the cytoplasm or nuclear region.

Eukaryotic Cell

A cell type (e.g., protists, fungi, plants, animals) generally 10\text{ to }50\text{ }̧\text{m} in diameter, mainly multicellular with cellular differentiation, containing a cytoskeleton and internal membrane-bound organelles.

Cell Envelope

The membrane system of prokaryotes consisting of an outer glycocalyx layer, a cell wall, and an inner cell membrane layer.

Mesosomes

Inward membrane structures connected to the cell envelope in prokaryotes, composed of a phospholipid bilayer.

Nucleus

The largest subcellular organelle enclosed by a double-membrane nuclear envelope, where genetic information is stored as DNA (90\text{%} in nucleus), transmitted, and replicated.

Inner Nuclear Membrane

The inner phospholipid layer of the nuclear envelope that defines the boundary of the nucleus itself.

Outer Nuclear Membrane

The outer phospholipid layer of the nuclear envelope that is continuous with the rough endoplasmic reticulum (ER).

Nuclear Pores

Interruptions of the double-membrane nuclear system that function as channels regulating movement of materials (e.g., RNA) between the nucleus and cytosol.

Nucleolus

A very electron-dense suborganelle within the nucleus where ribosomal RNA (rRNA) biosynthesis occurs.

Nuclear Organizer

A region of one or more chromosomes located in the nucleolus containing multiple copies of DNA that direct the synthesis of ribosomal RNA.

Nucleoplasm

The non-nucleolar region of the nucleus.

Chromatin

Nuclear material with regions of less electron density containing the major portion (95\text{%} or more) of total cellular DNA associated with histone proteins.

Mitochondria

Rod-shaped organelles with a length of 1.5\text{--}2.0\text{ }̧\text{m} (approximately $\frac{1}{20}$ the size of the nucleus) that function as the powerhouse of the cell by producing nearly all required cellular energy.

Outer Mitochondrial Membrane

The smooth, continuous outer membrane of the mitochondria composed of 50\text{%} lipid and 50\text{%} protein.

Cristae

Inward folds of the inner mitochondrial membrane that serve as the site for the citric acid cycle (Krebs Cycle) and oxidative phosphorylation.

Mitochondrial Matrix

The fluid-filled interior space of the mitochondrion containing ribosomes and mitochondrial DNA (2\text{--}4\text{%} of total cellular DNA).

Endoplasmic Reticulum (ER)

A netlike system of flattened, membrane-bound regions localized within the cytoplasm forming an interconnected array of membranous vesicles.

Rough Endoplasmic Reticulum (RER)

The portion of the ER characterized by attached ribosomes that function in the biosynthesis of membrane, organelle, and secreted proteins.

Smooth Endoplasmic Reticulum (SER)

The portion of the ER lacking attached ribosomes that functions in protein storage and transport, fatty acid and phospholipid synthesis, and chemical detoxification.

Microsomes

Smaller fragmented vesicles of the reticulum network produced when whole cells are disrupted and randomly cleaved during laboratory isolation.

Golgi Body

A network of flattened, membrane-bound vesicles stacked in small clusters near the nucleus that acts as the traffic police of the cell by packaging, modifying, and sorting proteins.

Microbodies

Small, single-membrane-bound compartments containing high concentrations of proteins ($10\text{ to }1000$ per cell), including lysosomes, peroxisomes, and glyoxysomes.

Lysosomes

Single-membrane-bound organelles containing acid hydrolases maintained at about $\text{pH }4.8$ that degrade polymers into monomeric subunits via hydrolysis.

Primary Lysosomes

Roughly spherical lysosomes that do not contain obvious particulate or membrane debris.

Secondary Lysosomes

Larger, irregularly shaped lysosomes containing active digesting particles and membranes formed by the fusion of primary lysosomes with other membrane-bound organelles.

Peroxisomes

Small membrane-limited organelles in animal and plant cells that degrade fatty acids and amino acids, generating heat and utilizing catalase to convert toxic hydrogen peroxide to water and oxygen.

Catalase

An enzyme found in copious amounts within peroxisomes that catalyzes the conversion of toxic hydrogen peroxide into water and oxygen.

Glyoxysomes

Microbodies found exclusively in plant cells that contain enzymes for converting lipids into carbohydrates through intermediate production of glyoxylic acid.

Cell Membrane

A thin lipid and protein membrane ($75\text{--}95\text{ Å}$ or 0.0075\text{--}0.0095\text{ }̧\text{m} thick) that acts as a semi-permeable barrier defining the outer perimeter of eukaryotic cells.

Receptor Proteins

Highly specific membrane proteins that bind to specific substances on one side of the plasma membrane to mediate cell signaling and transport.

Glycocalyx

A viscous layer covering the cell membrane or cell wall made of complex polysaccharides bound to proteins and lipids, responsible for cell recognition, filtering, and contact inhibition.

Contact Inhibition

A cell-to-cell communication mechanism mediated by the cell coat (glycocalyx) that regulates growth upon interaction with neighboring cells.

Cytoskeleton

An intricate cytoplasmic protein network composed of microtubules, intermediate filaments, microfilaments, and microtrabecular strands that directs cell movement, division, and structural organization.

Microtrabecular Strand

A thin, thread-like protein structure in the cytoplasm connected to microtubule structures to form a lattice network.