Download Enzyme

Fig. 6.5a
Fig. 6.5b
Fig. 6.5
Enzymes bring substrates close enough, and hold them so that
they are able to react at a much lower temperature
Fig. 6.6a
Hydrolysis:
Fig. 6.6b
Synthesis
Fig. 6.7a
Fig. 6.7b
Enzyme-Substrate
complex
Fig. 6.7
Fig. 6.7a
Enzyme is recycled-ready to bind to
another substrate
Fig. 6.8b
What Effect will Temperature have on Enzyme Rate?
Fig. 6.8a
Fig. 6.8
Fig. 6.9
• Enzymes work best at a CERTAIN pH
• Stomach enzymes work best in an acidic environment
(pH 2-3)
• Small intestine enzymes work best in a basic or
alkaline environment (pH 7-9)
• It is incorrect to say low pH denatures enzymes—as
this is not true in the stomach
• Each enzyme has its own optimum pH
• Below or above the optimum, the enzyme will alter
its’ shape, and therefore its’ ability to function
• The further away from optimum, the lower the ability
to function
Fig. 6.10
Fig. 6.10a
Fig. 6.10b
• COMPETITIVE INHIBITION: Lowers the
reaction rate as the active site gets “filled-up” by
something other than the substrate. Often, this
something is the product.
• NON-COMPETITIVE INHIBITION:
Also
lowers the reaction rate, but by something that binds
to the enzyme—at some other (allosteric) site that
alters the enzyme—now, it is no longer able to fit with
the substrate. Often these NCI’s are the products,
from a metabolic pathway much further on, or are
unwanted POISONS such as Cyanide.
• FEEDBACK INHIBITION
When the active site is prevented from combining with the
substrate, INHIBITION occurs
This can be a very effective way of controlling reaction rates. In
some reactions, the PRODUCT competes with the substrate.
High Product means lower reaction rate!
In a Metabolic Pathway, The end product may be substantially
different—It binds to the enzyme in ANOTHER LOCATION,
called an allosteric site. This alters the shape of the enzyme—
the active site also changes, and the reaction rate lowers.
Fig. 6.p109
• VITAMINS AND MINERALS—What do these
things have to do with enzymes?
• Cofactors—enzyme “helpers”
Many cofactors are minerals such as Cu, Zn, or Fe
required in small amounts by our bodies
• Coenzymes are also helpers, but are larger, organic,
non-protien molecules commonly called VITAMINS.
These too, are obtained from our diet.
Fig. 6.p113
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Fig. 6.p113a
Fig. 6.p113b
Fig. 6.p113c
Fig. 6.p113d