Transcript PROTEINS (Polymers of Amino Acids)

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
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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 STRUCTURE
Single (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