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PROTEINS(Polymers of Amino Acids)
20 Amino Acids
• Grouped by properties of their side chains– Non-polar (hydrophobic)– Polar (hydrophilic)– Acidic (-COOH grp)– Basic (-NH2)
• Polypeptide– Many amino acids linked together
Types of Proteins
• Structural – ligaments, hair, horns, webs• Storage (energy) – seeds, egg whites• Transportation – blood & Facillitated Diffusion• Regulation – hormones: insulin & testosterone• Movement/Reaction – reflex, contraction• Immunology – antigens & antibodies• Enzymes – speed up rxns (digestion)
DENATURATION
• Protein loses its shape & no longer function– More shape changes, greater impact on its ability
to function
• Causes:– Temperature– pH (toxic chemicals)– Radiation
• Example: Sickle Cell Anemia
MOLECULAR STRUCTURE
• PRIMARY– Sequence of amino acids
MOLECULAR STRUCTURESingle (point) mutations can cause problems
Normal hemoglobin: VAL – HIS – LEU – THR – PRO – GLU –
GLU
Sickle Cell Hemo.: VAL – HIS – LEU – THR – PRO – VAL
– GLU
MOLECULAR STRUCTURE
• SECONDARY– A.A. chain coil or fold due H-bonds– Alpha Helix: -- Pleated Sheets
MOLECULAR STRUCTURE• TERTIARY– 3-D shape– Globular – (round clusters – hemoglobin)– Fibrous – (long threads – collegen)
– Hydrophobic interaction – nonpolar sections of molecule clump to middle of protein away from any possible sources of water
MOLECULAR STRUCTURE
• QUATERNARY– Interaction of multiple polypeptide chains
ENZYMES
• Substrate – substance being broken down• Active site – area where substrate/enzyme
connect
• Induced Fit – slight change of shape as enzyme & substrate join
Affects on Reaction Rates
• Cofactors / coenzymes – an additional enzyme working on same substrate
• Competitive Inhibitors – block active site
Affects on Reaction Rates• Noncompetitive
Inhibitors – changes shape of the enzyme without attaching to the active site
• Allosteric regulation – attachment of another molecule which changes the shape of the enzyme
Metabolic Controls
• Feedback Inhibition – the
product of the reaction binds to the enzyme & prevents it
from doing its job. Avoid excess production
Metabolic Controls• Cooperativity – (form allosteric regulation)
when another molecule helps maintain shape of enzyme