Cell Biology: Cytoskeleton, Organelles, and Plastids

Comprehensive vocabulary flashcards covering the components of the cytoskeleton, motor proteins, centrosomes, cilia, flagella, mitochondria, and plastids.

Cytoskeleton

An interconnected system of protein fibers and tubes that extends throughout the cytoplasm, maintaining the cell's characteristic shape, internal organization, and functioning in movement.

Microfilaments

Thin cytoskeletal fibers ($7\,nm$ in diameter) assembled from actin monomers with defined polarity ($+$ and $-$ ends) that function in structural support and cell movement.

Intermediate filaments

Tough, ropelike assemblages ($8-12\,nm$ in diameter) assembled from a large and varied group of fibrous proteins that provide mechanical strength and stabilize cell shape in a tissue-specific manner.

Microtubules

Long, hollow cylinders ($25\,nm$ in diameter) composed of $13$ parallel protein filaments of $\alpha$-tubulin and $\beta$-tubulin dimers arranged side by side with distinct polarity ($+$ and $-$ ends).

Motor proteins

Proteins that generate eukaryotic cellular movements by hydrolyzing ATP to walk unidirectionally along cytoskeletal filaments while transporting cargo such as vesicles and organelles.

Motor domain

The region of a motor protein that binds to cytoskeletal filaments, forcefuly swiveling a short distance upon ATP hydrolysis before releasing to produce step-by-step walking motion.

Tail domain

The structural portion of a motor protein that binds and carries specific cargoes, such as vesicles or cellular organelles.

Myosin

A motor protein that walks along actin microfilaments to power movements such as muscle contraction and cytoplasmic streaming.

Kinesin

A motor protein that binds and walks along microtubules to transport intracellular cargo such as vesicles.

Dynein

A motor protein that moves along microtubules, producing sliding motions between doublet microtubules to power the movement of cilia and flagella.

Centrosome

The primary microtubule-organizing center (MTOC) of animal cells; nucleates and organizes microtubules, maintains cell polarity, and forms the mitotic spindle during cell division.

Centriole

A barrel-shaped structure found in pairs inside the centrosome, constructed of nine microtubule triplets arranged in a ring; can differentiate into basal bodies.

Pericentriolar material (PCM)

A protein-rich matrix surrounding the mother and daughter centrioles in the centrosome that nucleates and anchors microtubules.

Cilia

Short, numerous motile surface projections containing a $9 + 2$ microtubule arrangement that move fluids across the cell surface using a back-and-forth beating motion.

Flagella

Elongated, motile cell projections that propel cells through liquid media via propeller-like undulations.

9 + 2 system

The structural arrangement found in eukaryotic cilia and flagella, consisting of a ring of nine double microtubules surrounding a central pair of single microtubules.

Basal body

A centriole-derived cylindrical structure anchored at the base of a cilium or flagellum that nucleates its axoneme.

Mitochondria

Semi-autonomous double-membrane organelles derived from ancient endosymbionts that contain their own circular DNA and ribosomes and carry out cellular respiration to produce ATP.

Cristae

Infoldings of the inner mitochondrial membrane that expand surface area and contain enzymes and electron transport components for ATP generation.

Mitochondrial matrix

The fluid-filled compartment enclosed within the inner mitochondrial membrane that contains mitochondrial DNA, ribosomes, and metabolic enzymes.

Cellular respiration

The metabolic pathway in mitochondria where energy-rich food molecules are broken down in the presence of oxygen ($O_2$) to produce water ($H_2O$), carbon dioxide ($CO_2$), and ATP.

Chloroplasts

Yellow-green, semi-autonomous plastids containing chlorophyll that absorb light energy to drive photosynthesis in plant cells.

Stroma

The fluid-filled inner compartment of a chloroplast completely enclosed by the inner boundary membrane, surrounding the thylakoid network.

Thylakoids

Flattened, closed membrane sacs within the stroma of chloroplasts whose membranes contain chlorophyll and photosynthetic reaction complexes.

Grana

Stacks of interconnected thylakoid sacs located within the stroma of a chloroplast.

Photosynthesis

The metabolic process in chloroplasts that converts solar energy into chemical energy, summarized by the equation: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

Leucoplasts

Colorless plant plastids specialized for the storage of nutrients, including starch, lipids, and proteins, found in non-photosynthetic organs.

Amyloplast

A specialized type of non-pigmented leucoplast dedicated to the synthesis and storage of starch granules.

Chromoplasts

Plastids that synthesize and store red, orange, and yellow carotenoid pigments in flowers and ripening fruits.