Cell Structure and Subcellular Components

A comprehensive vocabulary review deck covering cell structure, organelles, prokaryotic vs eukaryotic differences, endomembrane system, energy organelles, endosymbiont theory, and cytoskeleton components.

Cells

The basic structural and functional units of every organism.

Prokaryotes

Organisms belonging to domains Bacteria and Archaea whose cells have DNA located in a nucleoid region, are generally smaller than eukaryotes, and lack internal membrane-bound organelles.

Eukaryotes

Organisms including protists, fungi, animals, and plants whose cells contain DNA within a nucleus and feature membrane-bound organelles that compartmentalize cellular functions.

Nucleoid Region

The non-membrane-bound area in a prokaryotic cell where its DNA is concentrated.

Organelles

Membrane-bound structures in eukaryotic cells that perform specialized subcellular functions.

Endomembrane System

A cellular network consisting of the nuclear envelope, endoplasmic reticulum, Golgi complex, lysosomes, vesicles/vacuoles, and plasma membrane that interact directly or via vesicles to modify, package, and transport polysaccharides, proteins, and lipids.

Energy Organelles

Organelles consisting of mitochondria and chloroplasts that convert energy into forms that cells can use to perform cellular work.

Compartmentalization

The separation of metabolic processes and enzymatic reactions into distinct membrane-bound locations within eukaryotic cells, which increases reaction surface area and prevents interfering reactions.

Plant Cell Unique Components

Subcellular structures unique to plant cells in contrast to animal cells, including chloroplasts, a central vacuole, a cell wall, and plasmodesmata.

Animal Cell Unique Components

Subcellular structures unique to animal cells in contrast to plant cells, including lysosomes, centrosomes, and flagella.

Nucleus

The organelle in eukaryotic cells surrounded by a nuclear envelope that contains genetic material.

Nuclear Envelope

A double membrane enclosing the nucleus that is continuous with the ER membrane and contains pores regulating the entry and exit of materials.

Nuclear Pores

Openings in the nuclear envelope that regulate the entry and exit of materials from the cell nucleus.

Nucleolus

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

Ribosomes

Subcellular complexes made of ribosomal RNA ($\text{rRNA}$) and protein that function to synthesize proteins.

Free Ribosomes

Ribosomes located suspended in the cytosol that produce proteins that generally function only within the cytosol.

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

A network of membranous sacs (cisternae) and tubules that provides mechanical support to maintain cell shape and facilitates intracellular transport.

Rough ER

A region of the endoplasmic reticulum studded with membrane-bound ribosomes that compartmentalizes protein synthesis and chemically modifies newly formed cellular products.

Smooth ER

A region of the endoplasmic reticulum that lacks ribosomes and functions to synthesize lipids and detoxify the cell.

Cisternae

Flattened membranous sacs and tubules that make up structures like the endoplasmic reticulum and Golgi complex.

Golgi Complex

An organelle consisting of flattened membranous cisternae with directionality (cis and trans faces) that receives, modifies, sorts, tags, and packages cellular products into transport vesicles for exocytosis.

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 that dispatches transport vesicles to other intracellular locations or to the plasma membrane for secretion.

Lysosomes

Membranous sacs containing hydrolytic enzymes in animal cells that digest macromolecules, recycle organic materials through autophagy, and participate in apoptosis.

Autophagy

A lysosomal process wherein a cell recycles its own organic materials and non-functioning organelles to self-renew.

Apoptosis

Programmed cell death that occurs when lysosomal membranes become permeable and release digestive enzymes into the cytoplasm.

Peroxisomes

Membrane-bound metabolic compartments that catalyze reactions producing $H_2O_2$, contain catalase to decompose $H_2O_2$ into water and oxygen, break down fatty acids, synthesize phospholipids, and detoxify compounds.

Catalase

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

Vacuoles

Membrane-bound vesicles derived from the ER and Golgi complex that participate in selective transport, storage of cellular materials, and endocytosis/exocytosis.

Central Vacuole

A large vacuole in plant cells that stores nutrients and water, plays an essential role in turgor pressure regulation, and can perform lysosome-like functions.

Mitochondria

Double-membrane-bound organelles that serve as the primary sites of cellular respiration, containing a smooth outer membrane and a folded inner membrane.

Cristae

Folds in the inner membrane of mitochondria that divide the organelle into two internal compartments and increase surface area for ATP production.

Mitochondrial Matrix

The fluid compartment enclosed by the inner mitochondrial membrane containing respiratory enzymes, mitochondrial DNA, ribosomes, and the site for the Krebs cycle.

Intermembrane Space

The fluid-filled space located between the smooth outer membrane and the folded inner membrane of a mitochondrion.

Chloroplasts

Specialized double-membrane-bound organelles in plants and photosynthetic algae containing chlorophyll, thylakoids, grana, and stroma where photosynthesis occurs.

Chlorophyll

The green photosynthetic pigment contained inside chloroplasts that absorbs light energy.

Thylakoids

Membranous sacs inside chloroplasts that stack into grana and serve as the site for light-dependent reactions of photosynthesis.

Grana

Stacks of thylakoids within chloroplasts where light-dependent reactions occur.

Stroma

The fluid portion surrounding thylakoids inside a chloroplast containing chloroplast DNA, ribosomes, and enzymes required for the Calvin cycle.

Endosymbiont Theory

The evolutionary theory stating that mitochondria and chloroplasts originated as free-living prokaryotic cells that were engulfed by an ancestral eukaryotic cell and established an endosymbiotic relationship.

Cytoskeleton

A network of protein fibers throughout the cytoplasm that provides structural and mechanical support, anchors organelles, and facilitates movement via interactions with motor proteins.

Microtubules

The thickest cytoskeletal fibers, growing from centrosomes in animal cells, that serve as tracks for organelle movement, aid chromosome division, and form cilia and flagella.

Microfilaments

Thin solid rods made of actin protein that maintain cell shape by bearing tension, assist in muscle contraction with myosin, and form the contractile ring during animal cell division.

Actin

The globular protein subunit that polymerizes to form microfilaments.

Intermediate Filaments

Permanent structural cytoskeletal fibers made of varying protein subunits that maintain cell shape, anchor organelles, and form the nuclear lamina.

Nuclear Lamina

A network of intermediate filaments lining the inner surface of the nuclear envelope that gives structural support to the nucleus.