Cell Bio Exam 4

polymerization

process where monomers bind to create larger polymers

Filaments

long rope like protein based fibers that form keratin and lamin

Lamin

flexible, mesh-like structural scaffold called the nuclear lamina on the inner surface of the nuclear envelope

Microtubules

hollow cylindrical proteins made of tubulin dimers such as alpha-tubulin and beta-tubulin, that are very unstable and is essential for GTP hydrolyzation

protofilament

linear one dimensional strand of protein monomers joined from end to end

centriole

small cylindrical organelle in the cytoplasm typically near the nucleus

centrosome

a non-membrane-bound that acts as the main microtubule organizing center

MTOC

main microtubule organizing center where microtubules emerge from

Gamma tubulin ring complex

a large multiprotein complex that acts as the primary template and nucleator for cellular microtubules

basal body

barrel shaped organelle found at the base of cilia and flagella that acts as structural anchor and a template for microtubule growth

cilia

hair like eukaryotic projections

flagella

long whip-like cellular that provide motility across bacteria archaea and eukaryotic cells

vesicle transport

mechanism that moves proteins lipids and other macromolecules between membrane bound organelles or across the plasma membrane

kinesins (microtubule motors)

superfamily of ATP dependent motor proteins that walk along microtubules to transport cellular cargo

dynesins

a family of high-molecular-weight motor proteins that move retrogradely (toward the minus-end) along microtubules within eukaryotic cell

spindles/asters

specialized microtubule-based structures that form in eukaryotic cells during cell division

G. actin

the free, monomeric, globe-shaped form of the protein actin

F. actin

a thin, flexible protein polymer that forms a core part of the eukaryotic cytoskeleton

actin based structures

dynamic polymer networks formed by globular actin (G-actin) monomers that assemble into filamentous actin ~7 nm in diameter

lamellipodium

a broad, flat, sheet-like cell membrane protrusion located at the leading edge of migrating cells

filopodium

slender, finger-like membrane protrusions filled with tight, parallel bundles of actin filaments

microvillus/brush border

a specialized cell surface adaptation that dramatically increases the surface area of epithelial cells to maximize absorption and secretion

stress fiber

specialized, contractile actomyosin bundles composed of 10 to 30 actin filaments cross-linked with non-muscle myosin II and structural proteins like α-actinin

cortex

a specialized, thin network of F-actin filaments, myosin motor proteins, and actin-binding proteins located directly beneath the plasma membrane in eukaryotic cells

phalloidin

a bicyclic peptide toxin that binds tightly and specifically to filamentous actin (F-actin), preventing it from depolymerizing

profilin

a small eukaryotic actin-binding protein thatbinds to G-actin (globular actin) monomers to regulate the assembly, maintenance, and spatial organization of the actin cytoskeleton

Arp2/3 complex

a seven-subunit protein complex that nucleates actin filaments to form branched networks, driving cellular processes like cell migration and endocytosis

cofilin

a small, ubiquitous actin-binding protein (~18–19 kDa) belonging to the ADF (actin-depolymerizing factor) family

fimbrin

a major actin-bundling protein in cell biology that cross-links filamentous actin (F-actin) into tightly packed, parallel bundles

capping protein

a conserved heterodimeric protein that binds tightly to the fast-growing barbed (plus) ends of actin filaments to block the addition or loss of actin subunit

tropomyosin

a two-stranded, alpha-helical, coiled-coil protein that binds longitudinally along actin microfilaments in eukaryotic cells to regulate interactions with myosin motors and actin-binding proteins

myosin

a large superfamily of ATP-dependent motor proteins that bind to actin filaments and convert chemical energy (ATP) into mechanical force

dystrophin

a large rod-shaped cytoskeletal protein (427 kDa) that connects the internal contractile machinery of a muscle cell (specifically F-actin) to the surrounding extracellular matrix (ECM)

Arp2/3 side binding

dendritic branched array at an angle of 70 degrees

Rho family small G proteins

a major subfamily of the Ras superfamily that act as molecular switches to regulate the actin cytoskeleton, cell migration, polarity, and division

migration

the directed movement of single cells or cell groups in response to chemical or mechanical cues

polarization

the asymmetric organization of a cell's structure, signaling molecules, and functions

protrusion

a dynamic extension of the plasma membrane and cytoplasm driven by localized actin filament polymerization that allows cells to explore their environment, form adhesions, and migrate

cytoskeleton during mitotic division

mitotic spindle, karyokinesis, contractile ring, cytokinesis

motor proteins

myosin super family

Myosin II

head=motor domain, tail=coiled coil, bipolar filament=bare zone, non-muscle myosin II=minifilament

Myofibril

Myofibrils are the long, thread-like, rod-like contractile organelles inside skeletal muscle cells (myofibers) that create the tissue's characteristic striped, or striated, appearance

sarcomere

the basic functional and contractile unit of a striated (skeletal and cardiac) muscle fiber, spanning from one Z-disc to the next

Z-disc/Z-line

the dense, proteinaceous boundary that marks the outer limits of a sarcomere

thick filament

where the myosin motor protein attaches to in sarcomeres

thin filament

actin filament in sarcomeres

filament sliding

explains how muscle cells contract through the physical movement of protein filaments past one another without changing their individual lengths

calcium in regulation of muscle contraction

act as the primary on-off switch for skeletal and cardiac muscle contraction by controlling access to the myosin-binding sites on the thin filament

Cell cycle

Process of G1, S, G2, and M phases, including withdrawl of G0

cyclin/CDK

a family of serine/threonine protein kinases that drive cell cycle progression by phosphorylating specific target proteins

Cell Cycle Checkpoints

G1 checkpoint (which assesses cell size, nutrients, and DNA damage before entering the S phase), the G2 checkpoint (which checks for complete DNA replication and repair before mitosis), and the M (spindle) checkpoint (which ensures all sister chromatids are properly attached to spindle fibers during metaphase)

p53 DNA Damage checkpoint

protein acts as the primary "guardian of the genome" by pausing the cell cycle, triggering DNA repair, or inducing apoptosis if genomic damage is severe

spindle checkpoint

cyclin b, prevents chromosome separation in mitosis by halting the transition from metaphase to anaphase until every kinetochore is properly attached to the mitotic spindl

Apoptosis

Programmed cell death where the cells contents will be broken down by lysosomes and phagocytes

Necrosis

Cell death where contents spill out and cause a lot of inflammation

Caspase

a family of cysteine-aspartic proteases that act as central enzymes in programmed cell death (apoptosis), pyroptosis, and inflammatory signalin

Mitosis

Interphase, prophase, metaphase, anaphase, telophase, cytokinesis

DNA synthesis

replication of DNA

chromosome

a thread-like structure composed of a single DNA molecule tightly coiled around proteins called histones, located inside the nucleus of eukaryotic cells

sister chromatids

two identical copies of a single replicated chromosome that remain attached to each other at a specialized region called the centromere

mitotic spindle fibers

a microtubule-based cellular machine that ensures equal and accurate separation of replicated chromosomes on the equator into two daughter cells during mitosis

karyokinesis

the division of a cell's nucleus during eukaryotic cell division ensuring that replicated genetic material is separated equally into two daughter nuclei

kinetochore

a large, multi-protein complex that assembles on the centromere of a chromosome during cell division to physically link chromosomes to the spindle microtubules

centromere

specialized, constricted region of a chromosome that links sister chromatids together and serves as the primary site for assembling the machinery that pulls chromosomes apart during cell division

cytokinesis

division is driven by an actin-and-myosin contractile ring that pinches the plasma membrane inward to create a cleavage furrow

cytoskeleton

organizes cells, detects resists creates and directs mechanical forces, allows for regulated and directional movement