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ENZYMES
Enzymes help with most chemical
reactions in the body
Digestion requires Enzymes
• Amylase in salivary glands
• Pepsin in stomach
• Lipase and trypsin in small intestine
Enzyme supplements
• Aid in digestion
Enzymes assist in 2 main types
of reactions in cells
1) Synthesis = Synthesize (make) compounds
A + B  AB
2) Decomposition = Decompose (break)
compounds
CD  C + D
These reactions require energy
Activation energy
• Energy required for a chemical reaction
to occur
Most chemical reactions in cells
occur too slowly for life to survive
Catalyst
• An inorganic chemical that lowers the
activation energy so a reaction can
occur
Enzymes
• Natural organic catalysts made of
protein that lower the activation energy
so a reaction can occur fast enough for
cell to survive
Enzymes are very complex
proteins
• Proteins are three dimensional
The shape of a protein determines
its function
Four levels of structure
• Primary structure – sequence of amino
acids
• Secondary structure – alpha helix, beta
pleated sheets
• Tertiary structure – Hydrogen bonds
hydrophobic interactions, ionic bonds
• Quaternary structure – 2 or more poly
peptides together
Primary structure
H bonds form secondary structure
forms with peptide bonds
Tertiary structure forms from other
bonds
Enzyme key Terms
• Enzyme – The protein that catalyzes a
reaction
• Substrate - The molecule that the enzyme
attaches to
• Active site - The spot on the enzyme that
fits into the substrate
Substrates fit into enzymes
Enzyme helps reaction occur so
substrate(s) forms the product
Enzymes and substrates have a
specific fit
• Like a lock and key
Induced fit
• When active site adjusts to fit substrate
Induced Fit and
Hexokinase
Synthesis using enzyme
• A + B + Enzyme = AB + Enzyme
Decomposition using enzyme
• CD + Enzyme = C + D + Enzyme
Enzymes are not used up!!!
• Enzymes are on both sides of equation
• Enzymes can keep working! Unless
denatured
• Heat, acid etc. can denature enzymes
Denaturing enzyme
• Heat etc. will break bonds of protein
tertiary structure. Reversible
• Primary structure can stay intact
Enzyme animation
• Claymation enzyme 30 secs
• http://www.youtube.com/watch?v=ybahzSj
UpB0&feature=related
• Pacman Animation 2 mins
• http://www.youtube.com/watch?v=CZD5xs
OKres
Enzymes in industry
• Rennin used to manufacture cheese,
Paper industry
• Enzymes remove lignin to soften paper.
Contact lenses
• Proteases clean lenses of protein
The enzyme catalase
• Peroxide kills cells
• cells have catalase to protect against peroxide
• Catalase breaks peroxide into water and
oxygen gas
• H2O2 + Enzyme  H20 + O2 + Enzyme
Enzyme Regulation
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•
•
•
Temperature
pH
Concentration of enzyme or substrate
Inhibitors
Every enzyme has an optimal
temperature
Effect of TEMPERATURE
• Increased temperature increases particle
motion and enzyme reaction rate.
BUT Enzymes are proteins and above a
certain temperature they denature
Effects of pH
• Changes in pH also denature enzyme
• Change in pH can alter the active site and
keep substrate from binding
Enzymes have an optimal pH
• Pepsin in stomach - acid
• Trypsin in intestine - base
Competitive inhibitor
• Blocks active site from substrate
Non Competitive inhibitor
• Attaches to enzyme in different place and
alters its active site
Toxic substances are often enzyme
inhibitors
• They stop important biological processes
• Ex cyanide, lead, mercury, pesticides
Allosteric enzymes
•
•
•
Enzymes that can be
altered by an noncompetitive inhibitor
A reaction product can act
as a feedback inhibitor to
slow enzyme.
These can also be
Promoters! That increase
enzyme activity
Animations of enzymes
• http://www.kscience.co.uk/animations/ani
m_2.htm