Cell Structure, Function, and Origins

Comprehensive vocabulary flashcards covering cell structure, organelles, compartmentalization, cytoskeletal elements, and the endosymbiont theory.

Cells

The structural and functional units of an organism, characterized by having a plasma membrane, cytosol, chromosomes, and ribosomes.

Prokaryotes

Smaller organisms found in Bacteria and Archaea that have DNA located in a nucleoid and lack membrane-bound organelles.

Eukaryotes

Organisms (including plants, animals, and fungi) that contain DNA in a nucleus and possess membrane-bound organelles that compartmentalize cellular functions.

Organelles

Membrane-bound structures within eukaryotic cells that perform specialized functions.

Endomembrane System

A group of cellular membranes and organelles that work together to modify, package, and transport macromolecules.

Energy Organelles

Organelles (such as mitochondria and chloroplasts) that convert energy into forms that cells can use to perform work.

Compartmentalization

The use of internal membranes and organelles in eukaryotic cells to isolate conflicting chemical reactions, increase surface area, and maintain optimal environments for specific processes.

Nuclear Envelope

A double membrane enclosing the genetic material of the nucleus, perforated with pores that regulate entry and exit.

Nucleolus

The nuclear region where RNA is synthesized and assembled with proteins to form ribosomes that exit into the cytoplasm through pores.

Ribosomes

Cellular structures composed of RNA and protein that translate messages from mRNA into primary protein structure; their presence across all three domains reflects common ancestry.

Free Ribosomes

Ribosomes suspended in the cytosol that synthesize proteins destined to remain in the cytosol for metabolic reactions, structural roles, or signaling.

Bound Ribosomes

Ribosomes attached to the endoplasmic reticulum or nuclear envelope that synthesize proteins destined for insertion into membranes, packaging into lysosomes, or secretion outside the cell.

Endoplasmic Reticulum (ER)

A network of membranous sacs and tubules that maintains cell shape and participates in intracellular transport.

Rough ER

A compartmentalized region of the ER studded with ribosomes that synthesizes proteins and folds them within its lumen before packaging them into transport vesicles.

Smooth ER

The portion of the ER lacking ribosomes that synthesizes lipids, metabolizes carbohydrates, detoxifies compounds, and stores calcium ions needed for cellular signaling.

Golgi Complex

A system of flattened membranous sacs called cisternae that receives transport vesicles, modifies and sorts materials, adds molecular tags, and packages them for specific destinations.

Cis Face

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

Trans Face

The shipping side of the Golgi complex where modified proteins are sorted and dispatched in vesicles toward the cytosol or outside the cell via exocytosis.

Lysosomes

Membrane-bound sacs containing hydrolytic enzymes that hydrolyze macromolecules, recycle cell components, and trigger programmed cell destruction.

Autophagy

The lysosomal process of breaking down and recycling the cell's own organic materials and malfunctioning organelles to renew the cell.

Apoptosis

Programmed cell death that can be mediated by the release of lysosomal enzymes.

Peroxisomes

Metabolic compartments that break down fatty acid molecules, synthesize phospholipids, and produce $H_2O_2$ to detoxify harmful compounds.

Catalase

An enzyme in peroxisomes that breaks down toxic hydrogen peroxide ($H_2O_2$) into water and oxygen.

Vacuoles

Membrane-bound vesicles originating from the ER and Golgi that perform selective transport, storage, and assistance with endocytosis/exocytosis.

Central Vacuole

A large organelle in plant cells that stores nutrients and water, functions similarly to lysosomes, and maintains turgor pressure.

Mitochondria

Double-membrane energy organelles containing their own DNA and ribosomes that serve as the site of cellular respiration and ATP synthesis.

Cristae

The highly convoluted folds of the inner mitochondrial membrane that expand surface area for electron transport chains and ATP synthesis.

Mitochondrial Matrix

The fluid compartment enclosed by the inner mitochondrial membrane where the Krebs cycle takes place, containing enzymes, ribosomes, and circular DNA.

Chloroplast

An organelle found in plants and photosynthetic algae containing chlorophyll that serves as the site of photosynthesis.

Thylakoids

Flattened sac membranes within chloroplasts where light-dependent reactions and light capture occur.

Stroma

The dense fluid surrounding thylakoids inside the chloroplast where the Calvin cycle and carbon fixation take place; contains DNA, ribosomes, and enzymes.

Cytoskeleton

A network of fibers extending throughout the cytoplasm that provides structural and mechanical support, anchors organelles, and facilitates vesicle and organelle movement.

Microtubules

The thickest cytoskeletal fibers, which grow from centrosomes to provide structural support, assist in cell motility, and move chromosomes during division.

Microfilaments

Solid cytoskeletal rods composed of actin that bear tension, maintain cell shape, participate in cell division, and work with myosin during muscle contraction.

Intermediate Filaments

Cytoskeletal fibers made of protein subunits that bear tension, anchor the nucleus and organelles, and form the nuclear lamina.

Endosymbiont Theory

The theory that mitochondria and chloroplasts evolved when ancestral free-living prokaryotes were engulfed by a eukaryotic host cell and formed a mutually beneficial endosymbiotic relationship.