Extracellular Structure and Cell Junctions Flashcards
What is the difference between gram positive and gram negative bacteria
Gram positive have a thicker cell wall
Gram positive have a single membrane system
Gram negative have a dual membrane system with the cell wall in between membranes
what are bacterial cell walls composed of
Peptidogylcan
what is the mode of action for penicillin
inhibits the enzyme DD-transpeptidase that forms the cross-links, preventing cell wall synthesis and bacterial growth.
Know how collagen is made
Procollagen triple helix formed in the ER
Hydroxyproline and hydroxylysine formed
Procollagen secreted from cell
In the intercellular space, procolloagen peptidase converts procollagen to collagen in the intercellular space.
The enzyme remove amino acids from both the N- and C- terminal ends
The resulting collagen molecules spontaneously associate and polymerize to form mature collagen fibrils
which then assemble laterally into fibers
What is Osteogenesis Imperfecta
Brittle Bone disease
both can present with BLUE SCLERA
Type I - make the correct form of collagen but not enough
prone to hearing loss in early 20s or 30s
Type II - make a improper form of collagen
frequently lethal in kids
what is Ehlers-Danlos Syndrome
an array of disorders that involve collagen and connective tissue
HYPERMOBILE joints
HYPERELASTIC skin
what is Scurvy
vitamin C deficiency Petechial Hemorrhages Perifollicular hemorrhages bleeding gums loss of teeth poor wound healing
what is Menkes syndrome
X-linked Recessive
mutation in COPPER TRANSPORT ATPase gene (ATP7A)
The enzyme primarily affect is Lysyl Oxidase
The disorder causes severe cerebral degeneration and arterial changes, resulting in death in infancy.
The disease can often be diagnosed by looking at a victim’s hair, which appears to be both whitish and kinked when viewed under a microscope
what is the structure and function of elastin
Connective tissue with elastic fibers is common in organs that stretch and return to shape, such as the lungs
Elastin impart elasticity and flexibility to the extracellular matrix
Elastin molecules are cross-linked to one another by covalent bonds between lysine residues
what is Marfan Syndrome
Caused by a mutation in FIBRILLIN-1 (FBN1)
Autosomal Dominant
S - skeletal anomalies (long arms, and chest deformities
H- heart (aortic dissection and tetralogy of Fallot)
E - eye (myopia and detached lenses)
arachnodactly (spider fingers)
Walker Murdoch Sign
being able to wrap your hand around your wrist
Steinburg sign
extension of your thumb beyond the ulnar border of the hand
what are the structure and function of proteoglycans
glycoproteins in which a large number of glycosaminoglycans are attached to a single protein molecule
Key function: trap water (act like sponges can hold up to 50 X their weight)
Proteoglycan networks are resistant to compression and regain their shape if distorted
what are Glycosaminoglycans (GAGs)
long polysaccharide chains, usually consisting of two monosaccharides or monosaccharide derivatives in strictly altering order
what are fibronectin and laminins, and their primary functions
they are both adhesive glycoproteins that bind to proteoglycans and collagen in the ECM and also with membrane receptors
fibronectins bind cells to the matrix and guide cellular movement
bind the RGD sequence recognized by integrins
also promotes blood clotting
Laminins Laminins bind cells to the basal lamina Three large polypeptides –a, b, g Multiple binding domains Collagen IV, Heparin, Integrins Held together by disulfide bonds
what is the structure and function of the basal lamina
Basal lamina: a thin sheet of specialized extracellular material (50 nm) that underlies epithelial cells thereby separating them from connective tissue
function
Structural support of tissue
Permeability barrier
Organize proteins on cell membranes and helps regulates differentiation
All forms of basal laminae contain type IV collagen, proteoglycans, laminins and sometimes entactin or nidogen
what are integrins and their role in mediating interactions between cells and ECM
structure
Two large transmembrane polypeptides a & b that associate noncovalently
Specificity determined by alpha subunit
Cytoplasmic side forms complex that interacts with cytoskeleton
Function
Mediate interactions between the ECM and cytoskeleton
The ECM can influence the organization of the cytoskeleton and the cytoskeleton can affect the orientation of the ECM components
Regulating cell movement and attachment
signaling
Anchorage-dependent growth involves pathways induced by integrin clustering.
Kinases recruited to clusters by adaptor proteins include focal adhesion kinase (FAK) and integrin-linked kinase (ILK)
what are focal adhesion
Focal adhesions develop from small clusters of integrins
Focal complexes recruit formin, which initiates actin bundle formation; and myosin II which develops tension
Integrins can reversibly bind matrix components due to the ability to change conformation between active and inactive states
what are hemidesmosomes
Integrins (a6b4) are attached to intermediate filaments (keratin)
anchor the epithelial cells to basement membrane
associated with
Bullous pemphigoid: skin blistering autoimmune disease (antigen: BPAG proteins)
Junctional epidermolysis bullosa: severe blistering disease of the skin caused by mutation in the b4subunit.
what is a matrix metalloprotease
The matrix metalloprotease family digest a variety of matrix proteins, including collagens, laminin, and perlecan, and cell surface receptors and adhesion molecules
what are CAMs
they are cell adhesion molecules
Members of the IgSF
Interact in a calcium-independent manner
N-CAM (neuronal) and L1-CAM involved in the outgrowth and bundling of neurons
what are cadherins
Interact in a calcium-dependent manner
Characterized by a series of structurally similar extracellular subunits
Tissue specificity (E-cadherin: epithelial, N-cadherin: nervous tissue, P-cadherin: placenta)
Play important roles during embryonic development
Metastasizing cells often lose expression of cell surface cadherins
linked together by Beta Catenin
What are the steps of leukocyte migration from blood vessels into infected tissue
rolling
activation
arrest/firm binding
diapedesis
•Selectins binding to carbohydrates involved with loose attachment
Interactions of leukocytes with endothelial cells lining blood vessels are mediated by selectins near sites of inflammation
Selectins recognize carbohydrates on the cell surface
what is the interaction with ICAM and integrins
More stable adhesion established by interaction between integrins on leukocyte with ICAM on the endothelial cells
•Know the basic structure & function of adhesive junctions:
Adherens Junction
Cadherin-mediated adhesive junctions connected to the cytoskeleton by actin filaments
In epithelial cells, adherens junctions typically form a continuous adhesion belt, an extensive zone that completely encompasses entire cells in a sheet of tissue
Desmosomes
Gives structural integrity
Desmosome core: Extracellular space between two membranes
Desmosome plaque: cytoplasmic
•what is the structure and function of Tight Junctions
Tight Junctions
prevent the movement of molecules across cell layers
Structure
Claudins and occludin and Junctional adhesion molecules (JAMs) in the plasma membrane of adjoining cells make contact across the intercellular space and bind tightly to each other, thereby connecting the cells together
what is the structure and function of Gap junctions
allow direct electrical and chemical communication between cells
Allow passage of molecules up to 1200
Regulated by calcium
Open at low calcium concentrations
Closed at high concentrations
Found in most cell types, especially the heart and cerebellum
what is Charcot-Marie-Tooth disease
a connexon disorder
CMTX1 is caused by a mutation in the Cx32 gene (a connexin) on the X chromosome
is a collection of neuropathies caused by mutations in numerous genes.
CMT is an inherited disease leading to progressive degeneration of peripheral nerves, with slow loss of muscle control and eventual muscle degeneration
Awareness of the Junctional complex
It is the whole assembly which includes tight junctions, adherens junctions and desmosomes
