GMS 5057 MEDICAL CELL BIOLOGY EXAM 4
Collagen - Answers - structural protein found in the skin and connective tissue
Over 40 genes coding for various collagens
Characteristic of a typical collagen molecule - Answers - Long, stiff, triple-stranded
helical structure in which 3 collagen polypeptides wound around one another to form
rope-like superhelix
Collagen fibrils - Answers - Some types of collagen molecules assemble into ordered
polymers
Collagen fibrils are thin cables 10-300 NM in diameter and many micrometers long
collagen fibers - Answers - Some collagen fibrils can further assemble into thicker
collagen fibers, which are 0.5-3 micrometers in diameter
Fibroblasts - Answers - Cells that produce collagen and other ECM macromolecules in
skin, tendon, and many connective tissues
mechanical stress - Answers - Fibers - resist tension and torsion stresses
Ground substance - resists compression, torsion, and shear
Combination of fibers and ground substance - resists multiple stresses
Fibers: Collagen - Answers - - most abundant protein in the body
- create a strong and pliable tissue matrix
- secreted by many cell types
- resist pulling (tensile strength)
Fibers: Elastic fibers and sheets - Answers - - Are polymers of the proteins elastin and
fibrillin
Ground Substance - Answers - - Glycans and glycoproteins
- Glycosaminoglycans (GAGs): Highly hydrated, space-filling polysaccharides
- Hyaluronic acid: abundant long GAG that forms aggregates with PGs
- Proteogylcans (PGs): proteins to which all GAGs except HA are attached
- Multiadhesive glycoproteins (MAGs): link molecules together and to cells
Procollagen - Answers - precursor form of collagen molecules with the addition of
peptide extensions that prevent premature fibril assembly within the cell
procollagen proteinases - Answers - extracellular enzymes that cleaves procollagen
extensions
, Integrins - Answers - A transmembrane protein that interconnects the extracellular
matrix and the cytoskeleton.
Fibronectin - Answers - ECM protein that links collagens to integrins
Fibronectin binding - Answers - Fibronectin's arginylglycylaspartic acid (RGD) motif
binds to integrins
G protein-coupled receptors (GPCRs) - Answers - -Largest family of cell receptors
-Same ligand can activate many GPCR families
-7 trans-membrane spanning domains
-Receptors diverse but similar structure and common mode of action
-Transmit signal to intracellular target proteins via G proteins
-Activate heterotrimeric G-proteins that regulate effector adenylyl cyclase
Inactive G protein - Answers - -Trimeric protein with alpha, beta, & gamma subunits
-Alpha and gamma subunits covalently bond to lipids that bind them to PM
- Alpha subunit binds GDP/GTP
Mechanisms for activation of GPCRs - Answers - -Extracellular ligand binds to GPCR
receptor-binding domain, causing conformational change
-Activates GEF and induces alpha subunit to release GDP, allowing GTP to bind in its
place
-GTP binding causes conformational change to alpha subunit, releasing GP from
receptor
-Alpha subunit disassociates from other subunits
-Beta and gamma subunits interact with various targets like enzymes and ion channels
2nd messenger - Answers - -usually produced in one-step reaction
-short lived and/or are rapidly degraded
-usually have no role in biosynthetic metabolism
-signal may increase or decrease level of 2nd messenger
-multiple 2nd messengers may be produced by one signal
examples of 2nd messengers - Answers - -cAMP = activates protein kinases (PKAs)
-cGMP = activates protein kinase G (PKG)
-DAG - activates protein kinase C (PKC)
-IP3 - opens calcium channels in ER lumen
cyclic AMP (cAMP) - Answers - -synthesized from ATP by active adenylyl cyclase
-cAMP is converted to AMP (inactivated) by cAMP phosphodiesterase
-cAMP activates cAMP-dependent protein kinases (PKAs)
Intracellular cAMP concentrations alters gene expression - Answers - -cAMP activates
PKAs
Collagen - Answers - structural protein found in the skin and connective tissue
Over 40 genes coding for various collagens
Characteristic of a typical collagen molecule - Answers - Long, stiff, triple-stranded
helical structure in which 3 collagen polypeptides wound around one another to form
rope-like superhelix
Collagen fibrils - Answers - Some types of collagen molecules assemble into ordered
polymers
Collagen fibrils are thin cables 10-300 NM in diameter and many micrometers long
collagen fibers - Answers - Some collagen fibrils can further assemble into thicker
collagen fibers, which are 0.5-3 micrometers in diameter
Fibroblasts - Answers - Cells that produce collagen and other ECM macromolecules in
skin, tendon, and many connective tissues
mechanical stress - Answers - Fibers - resist tension and torsion stresses
Ground substance - resists compression, torsion, and shear
Combination of fibers and ground substance - resists multiple stresses
Fibers: Collagen - Answers - - most abundant protein in the body
- create a strong and pliable tissue matrix
- secreted by many cell types
- resist pulling (tensile strength)
Fibers: Elastic fibers and sheets - Answers - - Are polymers of the proteins elastin and
fibrillin
Ground Substance - Answers - - Glycans and glycoproteins
- Glycosaminoglycans (GAGs): Highly hydrated, space-filling polysaccharides
- Hyaluronic acid: abundant long GAG that forms aggregates with PGs
- Proteogylcans (PGs): proteins to which all GAGs except HA are attached
- Multiadhesive glycoproteins (MAGs): link molecules together and to cells
Procollagen - Answers - precursor form of collagen molecules with the addition of
peptide extensions that prevent premature fibril assembly within the cell
procollagen proteinases - Answers - extracellular enzymes that cleaves procollagen
extensions
, Integrins - Answers - A transmembrane protein that interconnects the extracellular
matrix and the cytoskeleton.
Fibronectin - Answers - ECM protein that links collagens to integrins
Fibronectin binding - Answers - Fibronectin's arginylglycylaspartic acid (RGD) motif
binds to integrins
G protein-coupled receptors (GPCRs) - Answers - -Largest family of cell receptors
-Same ligand can activate many GPCR families
-7 trans-membrane spanning domains
-Receptors diverse but similar structure and common mode of action
-Transmit signal to intracellular target proteins via G proteins
-Activate heterotrimeric G-proteins that regulate effector adenylyl cyclase
Inactive G protein - Answers - -Trimeric protein with alpha, beta, & gamma subunits
-Alpha and gamma subunits covalently bond to lipids that bind them to PM
- Alpha subunit binds GDP/GTP
Mechanisms for activation of GPCRs - Answers - -Extracellular ligand binds to GPCR
receptor-binding domain, causing conformational change
-Activates GEF and induces alpha subunit to release GDP, allowing GTP to bind in its
place
-GTP binding causes conformational change to alpha subunit, releasing GP from
receptor
-Alpha subunit disassociates from other subunits
-Beta and gamma subunits interact with various targets like enzymes and ion channels
2nd messenger - Answers - -usually produced in one-step reaction
-short lived and/or are rapidly degraded
-usually have no role in biosynthetic metabolism
-signal may increase or decrease level of 2nd messenger
-multiple 2nd messengers may be produced by one signal
examples of 2nd messengers - Answers - -cAMP = activates protein kinases (PKAs)
-cGMP = activates protein kinase G (PKG)
-DAG - activates protein kinase C (PKC)
-IP3 - opens calcium channels in ER lumen
cyclic AMP (cAMP) - Answers - -synthesized from ATP by active adenylyl cyclase
-cAMP is converted to AMP (inactivated) by cAMP phosphodiesterase
-cAMP activates cAMP-dependent protein kinases (PKAs)
Intracellular cAMP concentrations alters gene expression - Answers - -cAMP activates
PKAs
