BIO130 Section 2 Definitions: Weeks 4-6

Fluorescence Microscope

Light microscope with same resolution but fluorescent labels are added to detect specific proteins

Transmission Electron Microscope

Uses beams of electrons, very short wavelength, resolution limit of ~1 nm, reveals detailed structures

Microtubules

Long, stiff, cylindrical structure composed of the protein tubulin. Used by eukaryotic cells to organize their cytoplasm and guide the intracellular transport of macromolecules and organelles

Immunofluorescence Microscopy

Used to determine location of proteins within cell, cells are fixed (not live imaging), primary antibody used to bind to specific protein of interest, secondary antibody binds to the primary antibody; covalently tagged to a fluorescent marker

Intermediate Filaments

Fibrous cytoskeletal element, about 10 nm in diameter, that forms ropelike networks in animal cells; helps cells resist tension applied from outside

Desmosome

A structure by which two adjacent cells are attached, formed from protein plaques in the cell membranes linked by filaments

Keratin Filaments

Class of intermediate filament abundant in epithelial cells, where it provides tensile strength; main structural component of hair, feathers, and claws; they are also the most diverse

Vimentin (and Vimentin-Related Filaments)

A type III intermediate filament protein, a key component of the cytoskeleton, found in mesenchymal cells, and plays a vital role in cell structure, migration, and adhesion

Neurofilaments

A type of cytoskeletal protein, that are highly specific to neurons and play a crucial role in maintaining axonal structure and function, with increased levels often indicating neuronal damage

Nuclear Lamins

A type V intermediate filament proteins that form the nuclear lamina, a fibrous meshwork underlying the inner nuclear membrane, providing structural support, and playing roles in chromatin organization, DNA repair, and cell-cycle regulation

Progeria

A disease caused by defects in particular nuclear lamina which causes rapid aging in children

Tubulin

Protein from which microtubules are mad

Tubulin Dimers

A subunit of a microtubule made up of a positive and negative end

Polarity

An inherent asymmetry that allows one end of an object to be distinguished from another; can refer to a molecule, a polymer, or even a cell

Centrosome

Microtubule-organizing center that sits near the nucleus in an animal cell; during the cell cycle, this structure duplicates to form the two poles of the mitotic spindle

Centriole

Cylindrical array of microtubules usually found in pairs at the center of a centrosome in animal cells; also found at the base of cilia and flagella, where they are called basal bodies

Basal Bodies

Structures that contribute to the fidelity of centrosome duplication and nucleate the growth of microtubules

Spindle Core Body

The functional equivalent of the centrosome in higher eukaryotes, serving as a microtubule organizing center (MTOC) and lacking centrioles

Cell Cortex

A specialized, actin-rich network of proteins located beneath the plasma membrane in most eukaryotic cells, playing a crucial role in cell shape, motility, and other processes

Dynamic Instability

The rapid switching between growth and shrinkage exhibited by microtubules

GTP Cap

A region at the end of a growing microtubule where GTP-bound tubulin subunits are present, which is thought to stabilize the microtubule and protect it from catastrophe (the switch from growth to shrinkage)

Augmin

A protein which increases microtubule density within the spindle by recruiting the γ-tubulin ring complex (γ-TuRC) to pre-existing microtubules and nucleating branching microtubules

Antimitotic Drugs

A class of drugs that disrupt cell division (mitosis) by targeting microtubules which prevents the proper assembling the mitotic spindle which disrupts mitosis

Saltatory Movements

The rapid transmission of nerve impulses (action potentials) along myelinated axons, where the signal appears to "jump" from one node of Ranvier to the next, increasing conduction speed

Motor Proteins

Protein such as myosin or kinesin that uses energy derived from the hydrolysis of a tightly bound ATP molecule to propel itself along a protein filament or other polymeric molecule

Kinesins

A large family of motor proteins that uses the energy of ATP hydrolysis to move toward the plus end of a microtubule

Dyneins

Motor protein that uses the energy of ATP hydrolysis to move toward the minus end of a microtubule; one form of the protein is responsible for the bending of cilia

Taxol

Binds to filaments and prevents depolymerization

Colchicine

Forms a complex with tubulin dimers that binds to the end of a microtubule, preventing further polymerization

Nocodazole

Binds tubulin dimers and prevents their polymerization

Actin Filaments

Thin, flexible protein filament made from a chain of globular actin molecules; a major constituent of all eukaryotic cells, this cytoskeletal element is essential for cell movement and for the contraction of muscle cells

Myosin

Type of motor protein that uses ATP to drive movements along actin filaments; one subtype interacts with actin to form the thick contractile bundles of skeletal muscle

Treadmilling

Process by which a protein filament simultaneously adds subunits at one end while losing them at the other; in the process, an individual subunit will move along the length of the filament, which itself may remain stationary (like a passenger riding an escalator); occurs in both microtubules and actin filaments

Phalloidin

Binds to filaments and prevents depolymerization

Cytochalasin

Caps filament plus ends, preventing polymerization and leading to filament depolymerization at minus ends

Latrunculin

Binds actin monomers and prevents their polymerization

Actin-Binding Proteins

Protein that interacts with actin monomers or filaments to control the assembly, structure, and behavior of actin filaments and networks

Formins

A group of proteins crucial for actin polymerization, acting as actin end-binding proteins that catalyze the nucleation and elongation of actin filaments

Actin-Related Proteins

A family of proteins structurally similar to actin, involved in diverse cellular processes like cytoskeleton regulation, chromatin remodeling, and gene expression

Myosin I

A two-headed myosin motor that interacts with actin filaments to form contractile bundles, driving dynamic changes in cell shape that contribute to cell movement and division

Cell Cortex

Specialized layer of cytoplasm on the inner face of the plasma membrane; in animal cells, it is rich in actin filaments that govern cell shape and drive cell movement

Myosin II

Type of myosin that exists as a dimer with two actin-binding heads and a coiled-coil tail; can associate to form long myosin filaments

Myosin Filament

Polymer composed of interacting molecules of myosin II; interaction with actin promotes contraction in muscle and nonmuscle cells

Myofibril

Long, cylindrical structure that constitutes the contractile element of a muscle cell; constructed of arrays of highly organized bundles of actin, myosin, and accessory

Cytoplasmic IFs

In animal cells subjected to mechanical stress; provide mechanical strength

Nuclear IFs

Nuclear lamina (2D meshwork) formed by lamins which are in all animal cells (plants have different lamin-like proteins)

Epithelium

Sheet of cells covering an external surface or lining an internal body cavity

Growing

Free αβ-tubulin dimers bound to GTP and are added to growing microtubule at plus end (minus end stabilized at MTOC), shortly after dimer added to microtubule, β-tubulin hydrolyzes GTP to GDP, rapid addition of αβ-tubulin dimers is faster than GTP hydrolysis in newly added αβ-tubulin dimers

Shrinking

Free αβ-tubulin dimers bound to GTP and are added to growing microtubule at plus end (minus end stabilized at MTOC), shortly after dimer added to microtubule, β-tubulin hydrolyzes GTP to GDP, slower addition of αβ-tubulin dimers is slower than GTP hydrolysis in newly added αβ-tubulin dimers

αβ-tubulin dimers

Addition or loss at plus end (minus end stabilized at MTOC)

MTOCs (Microtubule Organizing Centres)

Dynamic structures that have nucleating sites for microtubule growth to start assembling new microtubules

Microtubule Associated Proteins

These proteins nucleate growth of new microtubules, promote microtubule polymerization, promote microtubule disassembly, and stabilize microtubules

Actin Monomers

Free monomers are bound to ATP which are bound in the center of the protein

Cell Crawling

Dynamic changes in actin filaments

Lateral

Facing the neighbouring cells

Basal

Facing the basal-luminal cells

Tight Junction

The apical-most junction, seals the neighbouring cells together in an epithelial sheet to prevent leakage of extracellular molecules between them; helps polarize cells

Adherens Junction

Joins an actin bundle in one cell to a similar bundle in a neighbouring cell

Gap Junction

Also known as an intercellular channel, it is formed from two hemichannels; it forms channels that allow small, intracellular water-soluble molecules, including inorganic ions and metabolites to pass from cell to cell

Hemidesmosome

Anchors intermediate filaments in the cell to the basal lamina (extracellular matrix)

Homophilic Interactions

The binding of a cell adhesion molecule (CAM) on one cell to an identical CAM on an adjacent cell

Heterophilic Interactions

Where different cell adhesion molecules (CAMs) bind to each other

Intracellular Linker Proteins

Cytosolic proteins which links transmembrane adhesion proteins to cytoskeleton filaments

Connexin

Formed from one protein subunit (gap junction)

Hemichannel

Formed from six connexins and by itself is closed

Plasmodesmata

Intercellular junctions in plants which allow for communication between cells; are cytoplasmic channels which are continuous plasma membrane and ER

Gating

The blocking movement of larger soluble molecules

Epithelial Tissue

Cells are closely associated and are attached to each other, have a limited ECM (a thin basal lamina), cytoskeletal filaments provide resistance to mechanical stress

Connective Tissue

Tissues such as bone, tendons, and the dermis of the skin, in which extracellular matrix makes up the bulk of the tissue and carries the mechanical load

GAGs (Glycosaminoglycans)

Long, linear, chains of a repeating disaccharide; highly negatively charged (attract Na+ and water), form hydrated gels, resist compression; are space-filling; most are synthesized inside cell and released by exocytosis

Hyaluronan

Is a simple GAG made of a long chain of repeating disaccharide subunits (up to 25,000); is spun directly from cell surface by a plasma membrane enzyme complex

Proteoglycans

This is a subclass of glycoproteins, it is a protein with at least one sugar side chain which must be a glycosaminoglycan (GAG); typically, more extensive addition of sugars (up to 95% of total weight)

Collagen

Triple-stranded, fibrous protein that is a major component of the extracellular matrix and connective tissues; it is an abundant main protein in animal tissues, and different forms can be found in skin, tendon, bone, cartilage, and blood vessels

Fibronectin

Extracellular matrix protein that helps cells attach to the matrix by acting as a “linker” that binds to a cell-surface integrin molecule on one end and to a matrix component, such as collagen, on the other

Integrin

One of a family of transmembrane proteins present on cell surfaces that enable cells to make and break attachments to the extracellular matrix, helping them to crawl through a tissue

Elastin

A fibrous protein and networks of elastin gives tissues elasticity, stretch and relax like a rubber band, and gives the ECM provide strength, preventing tissue from excessive stretching

Basal Lamina

A specialized type of ECM which underlies all epithelia; is thin (40-120 nm thick), secreted by the epithelial cells, and influences cell polarity (apical–basal), and separates epithelium from underlying tissue and prevents fibroblasts in underlying connective tissue from interacting with epithelial cells

Laminin

A family of glycoproteins of the extracellular matrix of all animals; they play important roles in cell differentiation, adhesion, and migration

Perlecan

A large, multidomain heparan sulfate proteoglycan found in the extracellular matrix, particularly in basement membranes and cartilage, playing crucial roles in cell adhesion, growth factor binding, and tissue development

Plant Cell Wall

A supportive matrix of plant cell that is more rigid than ECM of animal tissue and mainly made up of cellulose and pectin

Cellulose Microfibrils

These provide tensile strength and pectin is space-filling and provides resistance to compression

Cellulose Synthase Complex

Makes many cellulose molecules and assembles them into a microfibril

Tissue

Cooperative assembly of cells and matrix woven together to form a distinctive multicellular unit with a specific function

Extracellular Matrix

Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells; a structural component of tissues that also influences their development and physiology

Cellulose

An insoluble substance which is the main constituent of plant cell walls; a polysaccharide consisting of chains of glucose monomers

Pectin

A complex plant polysaccharide, a major component of plant cell walls, particularly in the primary cell wall and middle lamella, contributing to cell adhesion, wall hydration, and overall plant structure and function

Primary Cell Walls

Thin, flexible, and extensible layers surrounding plant cells, composed mainly of cellulose, pectin, and hemicellulose, allowing for cell growth and expansion

Turgor Pressure

The hydrostatic pressure exerted by the fluid within a cell against its cell wall, crucial for cell rigidity, growth, and overall plant structure

Secondary Cell Walls

A thicker, stronger layer deposited inside the primary cell wall of some plant cells after they stop expanding, providing structural support and protection, and often containing lignin for added rigidity

Lignins

A complex, natural polymer that provides rigidity and structural support to plant cell walls, particularly in woody tissues, and is the second most abundant biopolymer on Earth after cellulose

Middle Lamella

A layer of pectin-rich material that acts as a "glue" between the primary cell walls of adjacent plant cells, cementing them together and providing structural support

Type I Collagen

This type of collagen makes up 90% of your body's collagen and is densely packed and used to provide structure to your skin, bones, tendons and ligament

Type II Collagen

A type of collagen found in elastic cartilage, which provides joint support

Type III Collagen

This collagen is found in muscles, arteries, and organs

Collagen Fibrils

The fundamental structural units of fibrous collagenous tissues, forming a scaffold for cells in animal tissues and providing mechanical support; composed of collagen molecules arranged in a specific, repeating pattern

Collagen Fibers

Multiple collagen fibrils packed together

Osteoblasts

Bone-forming cells that synthesize and deposit the organic bone matrix

Fibroblasts

Cell type that produces the collagen-rich extracellular matrix in connective tissues such as skin and tendon; proliferates readily in wounded tissue and in tissue culture

Procollagen

A precursor molecule of collagen, containing globular extensions (propeptides) at both ends that are cleaved off to allow collagen assembly into fibrils

Procollagen Proteinases

An enzyme involved in the processing of procollagens by removing the carboxyl propeptides