Cell Structure and Function: Subcellular Components and Compartmentalization

Comprehensive vocabulary flashcards covering prokaryotic versus eukaryotic cells, endomembrane and energy organelles, cellular compartmentalization, the endosymbiont theory, and the three main components of the cytoskeleton.

Cells

The basic structural and functional units of every organism.

Shared Components of All Cells

Four basic features present in all cells: a plasma membrane, cytosol, chromosomes, and ribosomes.

Prokaryotes

Cells belonging to the domains Bacteria and Archaea characterized by having DNA located in a nucleoid region, generally smaller size, and lacking membrane-bound organelles.

Eukaryotes

Cells found in protists, fungi, animals, and plants that store DNA inside a nucleus and contain membrane-bound organelles.

Organelles

Membrane-bound structures located within eukaryotic cells, categorized into endomembrane organelles and energy organelles.

Compartmentalization

The organization of cellular processes into distinct organelles to increase surface area for reactions and prevent interfering reactions from occurring in the same location.

Nuclear Envelope

A double membrane enclosing the nucleus that features pores regulating the entry and exit of materials.

Nucleolus

A dense region of the nucleus where ribosomal RNA ($\text{rRNA}$) is synthesized and combined with proteins to assemble large and small ribosomal subunits.

Ribosomes

Subcellular structures composed of ribosomal RNA and protein that synthesize proteins by translating mRNA instructions into polypeptide primary structures.

Free Ribosomes

Ribosomes suspended in the cytosol that typically produce proteins functioning within the cytosol, such as metabolic enzymes.

Bound Ribosomes

Ribosomes attached to the endoplasmic reticulum or nuclear envelope that synthesize proteins destined to be inserted into membranes or secreted from the cell via transport vesicles.

Endoplasmic Reticulum (ER)

A membranous network of sacs and tubes that synthesizes membranes and compartmentalizes the cell to segregate proteins produced in the rough ER from free cytosolic proteins.

Rough ER

A region of the endoplasmic reticulum studded with bound ribosomes that ensures newly formed proteins are folded or modified correctly.

Smooth ER

A region of the endoplasmic reticulum that lacks ribosomes and functions in synthesizing lipids, metabolizing carbohydrates, and detoxifying the cell.

Golgi Complex

An endomembrane organelle made of cisternae that receives, modifies, sorts, tags, and packages materials into transport vesicles for delivery or exocytosis.

Cisternae

Flattened, disconnected membranous sacs within the Golgi complex that separate its internal contents from the cytosol.

Cis Face

The receiving side of the Golgi complex that takes in transport vesicles arriving from the endoplasmic reticulum.

Trans Face

The shipping side of the Golgi complex that releases vesicles out into the cytosol for delivery to other locations or to the plasma membrane for secretion.

Lysosomes

Membranous sacs containing hydrolytic enzymes found in animal cells that break down macromolecules.

Autophagy

A lysosomal recycling process in which the cell digests and recycles its own organic materials to renew itself.

Peroxisomes

Metabolic compartments that catalyze reactions producing hydrogen peroxide ($H_2O_2$), which is subsequently broken down into water by enzymes within the organelle.

Food Vacuoles

Vesicles formed by phagocytosis (cell eating) that merge with lysosomes for enzymatic digestion.

Contractile Vacuoles

Organelles found in certain cells that function to pump out excess water and maintain balance in cellular water levels.

Central Vacuole

A large plant organelle containing water and inorganic ions that is essential for maintaining cellular turgor pressure.

Endosymbiont Theory

The evolutionary theory stating that an early eukaryotic cell engulfed a prokaryote, which then lived inside the host as an endosymbiont and evolved into mitochondria or chloroplasts.

Mitochondria

Double-membrane energy organelles that serve as the site of cellular respiration and ATP generation.

Cristae

Folds within the inner mitochondrial membrane that divide the interior into two compartments and significantly increase the surface area available for cellular respiration.

Mitochondrial Matrix

The compartment enclosed by the inner mitochondrial membrane that houses the Krebs cycle, mitochondrial DNA, ribosomes, and respiratory enzymes.

Chloroplasts

Specialized double-membrane organelles in photosynthetic organisms that contain chlorophyll and serve as the site of photosynthesis.

Thylakoids

Membranous sacs inside chloroplasts organized into stacks called grana, where the light-dependent reactions of photosynthesis take place.

Stroma

The fluid-filled space surrounding the thylakoids inside the chloroplast double membrane where the Calvin cycle occurs, containing chloroplast DNA, ribosomes, and enzymes.

Cytoskeleton

A network of protein fibers extending throughout the cytoplasm that provides structural and mechanical support, anchors organelles, and enables cell and vesicle motility through interactions with motor proteins.

Microtubules

Hollow rod-like fibers constructed from the protein tubulin that grow from centrosomes, act as tracks for motor proteins, separate chromosomes during cell division, and enable cell motility via cilia and flagella.

Microfilaments

Thin solid rods composed of the protein actin that bear tension, maintain cell shape, interact with myosin to produce muscle contraction, and form the contractile ring in the cleavage furrow during animal cell division.

Intermediate Filaments

Permanent structural fibers made of diverse fibrous protein subunits that maintain cell shape, anchor the nucleus and other organelles, and form the nuclear lamina lining the nuclear envelope.