Topic 3 - Cell Biology Flashcards
(77 cards)
Treadmilling
when polymer formation reaches a steady state, subunits undergo a net assembly at the plus end and a new disassembly at the minus end at an identical rate. The polymer maintains a constant length, even though there is a net flux of subunits through the polymer
Cofilin
binds ADP-actin filaments and promotes disassembly
Profilin
binds G-actin monomers and promotes the addition of these to growing filaments. This also prevents nucleation
ion-channel-coupled receptors
also called transmitter-gated ion channels or ionotropic receptors - involved in rapid signalling between neurons and other electrically excitable target cells
G-protein-coupled receptors
activation leads to formation of an activated receptor and G-protein complex which further activates the G-protein and associated enzymes
enzyme-coupled receptors
many have intrinsic enzymatic activity, many others rely on associated enzymes. Signal molecules activate most enzyme-coupled receptors by promoting their dimerisation, which results in the interaction and activation of the cytoplasmic domains
Cotranslational translocation
if ribosomes are ER bound, proteins will be simultaneously translated and translocated
post-translational translocation
proteins on free ribosomes are first translated and then translocated
proteoglycans
form the ‘ground substance’ which resists compression and allows diffusion through the ECM
fibrous proteins
(collagen and elastin) provide strength, organisation and resilience to the ECM
glycoproteins
help with adhesion and support the cells within the ECM
Glycosaminoglycans (GAGs)
long, unbranched polysaccharides found in the extracellular matrix of connective tissues, including skin and cartilage. They are known for their ability to bind and retain water, contributing to tissue hydration and physical properties like elasticity and support
hyaluronan
acts as a space filler during tissue morphogenesis and repair
collagen
the major protein in ECM (25% of protein mass in animals). Cross-linking affects tensile strength. After secretion, covalent bonds (between lysine residues) cross-link the collagen molecules, particularly in non-helical ends. The extent of cross-linking affects tensile strength: inhibition of cross-linking reduces tensile strength, the highest level of cross-linking occurs in tendon collagen and provides the highest tensile strength
elastin
provides elasticity to tissues - It’s a crucial component of the body’s connective tissues, particularly in areas where flexibility is essential, such as the skin, lungs, and blood vessels. Elastin helps these tissues return to their original shape after being stretched or compressed
fibronectin
Fibronectin is a high-molecular-weight glycoprotein found in the extracellular matrix (ECM) of animal and human tissues. It acts as a key bridge between the ECM and cells, facilitating cell adhesion, migration, and differentiation.
basement membrane / basal lamina
specialised form of ECM. Epithelial cells produce the basement membrane upon which epithelial cells sit. A basement membrane also surrounds muscle cells, fat cells and Schwann cells
Describe how “inside-out” and “outside-in” integrin signalling regulates focal adhesion structure
Internal activation of integrin receptors. Interaction of integrins with ECM proteins. Recruitment of intracellular adaptors and kinases and interaction with cytoskeleton
The cytoskeleton
composed of intracellular structures, polymers that form an interlinked network. This network is important for cell shape, movement, division, trafficking
Actin filaments (microfilaments)
essential structural components of the cytoskeleton, playing a crucial role in cell shape, movement, and division. Helical polymers of the protein actin. G-actin (monomeric) and F-actin (filamentous). Helical, flexible, dynamic structures, 8nm diameter. Organise into linear bundles, 2D networks and 3D gels
Microtubules
long, hollow cylinders made of the protein tubulin. With an outer diameter of 25nm, they are much more rigid than actin filaments. They are long and straight and frequently have one end attached to a microtubule-organising center called a centrosome
Intermediate filaments
rope-like fibers with a diameter of about 10nm; they are made of intermediate filament proteins. One type of intermediate filament forms a meshwork called the nuclear lamina just beneath the inner nuclear membrane. Other types extend across the cytoplasm, giving cells mechanical strength. In epithelial tissue, they span the cytoplasm from one cell-cell junction to another, strengthening the entire epithelium
Arp2/3 complex
promotes filament branching
nucleation
a helical polymer is stabilised by multiple contacts between adjacent subunits. In the case of actin, two actin molecules bind relatively weakly to each other, but addition of a third actin monomer to form a trimer makes the entire group more stable. Further monomer addition can take place onto this trimer, which therefore acts as a ‘nucleus’ for polymerisation. The assembly is relatively slow, which explains the lag phase seen during polymerisation. The lag phase can be reduced or abolished by adding premade nuclei.
