C3: Enzymes Flashcards
What are intracellular and extracellular enzymes?
Intracellular -> works inside cells
Extracellular -> works outside cells
How do enzymes speed up reactions?
by lowering activation energy
What is activation energy?
the energy needed to start a chemical reaction
What are the 3 ways in which enzymes lower activation energy?
- binding and orienting substrates
- rearranging electrons in a substrate
- straining substrate and forcing it to a transition state
What are endergonic and exergonic reactions?
Endergonic -> products contain more free energy than reactants
Exergonic -> products contain less free energy than reactants (releases energy in the form of heat)
What are anabolic and catabolic reactions?
Anabolic -> enzymes bring the substrate molecules together
Catabolic -> enzymes break substrates
What are the two hypotheses of enzymes’ mode of action?
Lock-and-key hypothesis: the substrate has to perfectly fit the active site
Induced-fit hypothesis: the enzyme/substrate can change shape to ensure a perfect fit (more efficient)
What type of proteins are enzymes?
globular proteins
What is a turnover number?
the number of substrate molecules transformed per second by one enzyme
Why are enzymes present in small amounts?
They have high molecular activity.
What factors affect reaction rates?
temperature, pH, enzyme concentration, and substrate concentration
How does temperature affect reaction rates?
At low temperatures, enzymes have low kinetic energy and do not react with substrates a lot. At high temperatures, enzymes denature. Enzymes have an optimum temperature where their reaction rate is the greatest.
What is the optimum temperature for most human enzymes?
40º C
How does pH affect reaction rates?
Each enzyme has its own optimum pH, and extremes of pH can denature them.
How do you measure the effect of an enzyme?
compare the non-catalyzed rate with the catalyzed rate
Why do we measure the initial rate of reaction?
to measure before factors like substrate concentration had time to change; reflects the graph
What is affinity?
The attraction of enzyme to substrate
What are the two types of reversible inhibitors, and how do they affect the rate of reaction?
Competitive inhibitors compete with substrates for the active site. Non-competitive inhibitors bind to an enzyme’s allosteric site, which alters the shape of the active site.
What are free and immobilized enzymes?
Free enzymes are not bound and are free to add to solutions. Immobilized enzymes are bound to a stationary and insoluble material.
What are the three advantages of using immobilized enzymes?
- There are no enzymes in the product
- They can be reused multiple times
- They have a greater tolerance of temperature and pH changes.
