chemical and physical features of proteins
Post on 20-Dec-2015
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Chemical and physical features of proteins
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Important terms
•ISOELECTRIC POINT (pI)
•ISOIONIC point
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Protein classification according to the size
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Classification of protein according to the size
Fewer than 50 aa called peptideMore than 50 is called protein
Insulin is 53 aa long Is it a peptide or protein hormone?
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Protein sequence and structure
The protein seq can be directly retrieved from the corresponding gene sequence ?
True False
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Protein primary structure
Amino acids are attached by .………………………These bonds are both planner and rigid
Can they rotate about their axis?
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Protein secondary structure
Stabilized by hydrogen bonding and depends on the sequence of aa in the chain
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Protein secondary structure
Some amino acids disrupt the secondary alpha helix structure :
Proline, isoleucin, tryptophan, asparagine
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Do all proteins have secondary structures?
Yes
No
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Tertiary structure
Stabilized by many types of bonds
-electrostatic bonds (-ve & +ve)
-Van der waals forces
-hydrophobic or hydrophillic attractions
Hbonds
Disulfide bridges
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Quaternary structure
All proteins do posses quaternary structure ?
True
False
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Quaternary structure
More than one polypeptide chains come together to form quaternary
structure
)we call the protein oligomeric(
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Quaternary structure
Stabilized by the same types of bonds found in the tertiary structure
Disulfide bridges can be of two types :
Intrachain
Interchains
The one polypeptide chain in oligomeric protein is called..……… :
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Oligomeric protiens
All subunits should be different
True
False
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Oligomeric protiens
4 chains Heamoglobin
2 alpha and 2 beta
chians
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Oligomeric protiens
On the otherhand, some proteins such as LDH enzyme is
composed of 4 identical subunits.
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The final folded protein shapeDetermines the final function
of this protien
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Protein folding
There are 2 main final shapes of folded proteins :
Globular proteins
fibrous proteins
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Globular proteins
Spherical in their final shapeWater solubleContains mixture of α β and other random structuresEnzymes, transport proteins, hormones and antibodies
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fibrous proteins
Are structural protiensWater insolubleBuilt of either α or β
Include cellulose fiber in the cell wall of plant cellsCollagen and elastin in humanKeratin in the hair and nailsChitin in the cuticle of some organisms
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What you need to know to investigate the protein structure
I- Molecular mass determination:
1 -SDS-PAGE
2 -Exclusion chromatography
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Size exclusion chromatography