BIOL213 Lecture Notes - Lecture 15: Enzyme Catalysis, Enzyme, Nucleophile
Lecture 15 – Enzymes and how they work
Enzymes:
• Enzymes are catalysts —> they increase reaction rates without being used up
• Most enzymes are globular proteins, however some RNA also catalyse reactions.
• Why are biocatalysts used over inorganic catalysts?
-Greater reaction specificity
-Milder reaction conditions
-Higher reaction rates
-Capacity for regulation
• Catalysis increases the rates of reactions. An organisms must be able to
catalyse chemical reactions efficiently and selectively. Life is not sustainable
without catalysis.
• Enzymes have amazing catalytic power —> can increase reaction rates 10^12
times.
• Enzymes have various regulatory roles; are useful for diagnosing diseases; and
are exploited in treating diseases.
• Enzymes normally have an active site where data;ysis takes places.
• Enzymes often function in a narrow pH range
• They are very specific in the substrates they bind and the reactions they catalyse.
Active site:
• Left or crevices in the protein that hose the catalytically active groups.
• Substrates are bound to enzymes by multiple weak attractions.
• How is specificity controlled? The specificity of binding depends on the
precisely defined arrangement of atoms in an active site. In the presence of the
substrate, the conformation of the enzyme is changed. This helps binds the
substrate, and positions the active site components into the correct position to
perform the catalysis —>induced fit
pH and enzyme activity:
• Interactions between enzyme and substrates crucial for catalysis are due to the
arrangement of the R groups within the active site. Changes in pH affect changes
in ionisable groups.
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Lecture 15 – Enzymes and how they work
Cofactors and coenzymes:
• some enzymes require and additional chemical component called a cofactor for
activity. Eg. Inorganic ions such as iron, magnesium or zinc.
• Other enzymes require a complementary organic or metalloorganic molecule
called a coenzyme to act as transient carriers of specific functional groups. Most of
these coenzymes are derived from vitamins in the diet.
• A coenzyme or metal ion very tightly covalently bound to an enzyme is called a
prosthetic group.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Capacity for regulation: catalysis increases the rates of reactions. An organisms must be able to catalyse chemical reactions efficiently and selectively. The specificity of binding depends on the precisely defined arrangement of atoms in an active site. In the presence of the substrate, the conformation of the enzyme is changed. This helps binds the substrate, and positions the active site components into the correct position to perform the catalysis >induced fit ph and enzyme activity: Interactions between enzyme and substrates crucial for catalysis are due to the arrangement of the r groups within the active site. Changes in ph affect changes in ionisable groups. Cofactors and coenzymes: some enzymes require and additional chemical component called a cofactor for activity. Inorganic ions such as iron, magnesium or zinc: other enzymes require a complementary organic or metalloorganic molecule called a coenzyme to act as transient carriers of specific functional groups.
