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globular proteins
- most enzymes
- maintained tertiary structure due to hydrophobic effect, "salt bridges" and "disulfide bridges"
- ability to bind specific substrates at the active site
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what are the types of cofactors
- organic: contains co-enzyme (vitamin derived, soluble, easily removed) and prosthetic group (covalently attached)
- inorganic: Fe,Cu, Mg
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what is the significance of a glycoprotein
- able to form 6 bonds due to 6 different glycosylated groups
- a globular protein that has a sugar unit attached through glycosylation
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what is high information content?
where there is sugar modification and different linkages that allow for cell-cell recognition and communication
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what is a membrane protein
- has a globular domain and is anchored to a membrane.
- Types: transporters, receptors, and cell-cell recognition proteins
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what is a structural (fibrous) protein
- insoluble proteins that have one repeating secondary structural pattern. Usually forms framework of connective tissue, muscle or other structural components of the body
- ex: collagen, elastin, keratin
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describe clinical significance of AGE (advanced glycosylation endproducts)
When glucose levels remain uncontrolled for long term, the attached glucose will form a non reversible crosslink with a second amino group forming AGEs that are then used as an indicator of diabetic patients
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how is hemoglobin glycosylated?
in an "non enzymatic fashion" by shiff base formation where aldehyde groups react with free amines on circulating proteins
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describe collagen structure
- primary: amino acid sequence with glycine at every third position
- secondary: collagen helix, with 3.0 residues per turn
- triple helix: three collagen helices wound tightly together
- Quaternary: triple helices with covalent crosslinks forming collagen fibrils
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discribe the five modication of amino acid residues in collagen
- proline --> hydroxyproline. Co-factor: ascorbic acid (vitamin C)
- lysine --> hydroxylysine. Co-factor: ascorbic acid
- hydroxylysine is glycosylated
- cyteine residues form disulfide bridges
- oxidation of lysine-NH3+ --> allysine-C=O, Cofactor: copper, vit B6
- lysine-NH3 + allysine-C=O --> shiff base
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what are the features that elastin and collagen share?
- some prolines are hydroxylated
- some lysines are oxidized to active aldehydes (allysine)
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what features are unique to elastin
- lacks genetic complexity, diversity and helical structure of collagen
- four crosslinked in a unique fashion called desmosine
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describe the structure of keratins and its ability to disrupt and reform
- keratins are insoluble structural proteins found in skin, nails, and hair.
- a-helices are crosslinked by disulfide bridges. In nails there are numerous disulfide bridges making them resitant to chemical changes. In hair, the few disulfide bonds can be easily disrupted by reducing agents or heat
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what is menkes disease
- when lack of copper causes inactive lysyl oxidase. therefore unable to modify lysine-NH3 to allysine-C=O.
- results to lack of fibril formation.
- caused by genetic mutation
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What is ehlers-danos syndrome
genetic defect resulting in defective collagen protein production. Results to hypermobile joints, super elastic skin and improper fibril formation
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what is osteogenesis imperfecta
too little or poor quality type I collagen
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