Chapter 6b Flashcards
Enzymes
Small amount of energy input required in order for chemical reactions to occur
Activation energy
Substance that helps a chemical reaction to occur
Catalyst
special molecules that catalyze biochemical reactions
enzyme
Chemical reactants to which an enzyme binds
Substrate
Alteration of the natural properties on an enzyme and render it weak or ineffective
Denaturation
Inorganic helper ions such as iron or magnesium
Cofactor
Organic helper molecules such as Vitamin C
Coenzyme
What factors determine the rate of an enzymatic reaction?
Activation energy typically through heat energy
Does a higher activation energy result in a faster or slower reaction rate?
Higher the activation energy, the slower the reaction will be
What is the source of activation energy for most chemical reactions?
Heat energy
Why does increased temperature increase the rates of reaction?
Heat speeds up the motion of molecules, causing them to collide with more force, and more often
Cellular reactions cannot use heat energy from their surroundings as activation energy. Why not?
The activation energies for most cellular reactions are too high for heat energy from the surroundings to overcome
How does an enzyme catalyze a reaction? How does it lower the activation energy?
They lower the activation energy by binding to the reactant molecules and holding them in such a way as to make the chemical bond-breaking and bond-forming process easier
What is the “active site” and what properties give it it’s specificity?
The place on the enzyme where the substrate binds; there is a unique combination of R-groups present at an enzyme’s active site
What are some benefits and some drawbacks of having a high level of specificity?
It is vulnerable to environmental influences that alter it’s structure but it is for a specific chemical reaction
Name some environmental changes that might denature an enzyme.
Temperature, pH
What is the “lock and key” model?
The idea that the enzyme active site and substrate fit together perfectly in one step
How does the lock and key model differ from the “induced fit” model?
In the induced fit, the enzyme and substrate are specific to each other, but also undergo changes in their conformation upon binding
What happens to enzymes once they have catalyzed a reaction?
It will always return to its original state at the completion of the reaction
What is competitive inhibition? How does it help regulate enzyme activity and therefore chemical reaction rate?
An inhibitor molecule is similar enough to the substrate that it can bind to the active site and block the substrate from binding; the inhibitor molecule competes with the substrate for active site binding
What is non-competitive inhibition? How does it differ from competitive inhibition?
An inhibitor molecule binds to the enzyme in a location other than the active site; activity of the enzyme is greatly reduced
What is allosteric inhibition? How does it help regulate enzyme activity?
An inhibitor molecule binds to the enzyme in a location other than the active site, resulting in reduced affinity of the enzyme for its substrate; cause slight conformational changes at the active site so substrate bind less efficiently
How does allosteric inhibition differ from allosteric activation?
Inhibition makes the substrate bind less efficiently and activation makes the substrate bind more efficiently
What is the purpose of cofactors and coenzymes? How are they similar? How are they different?
Several enzymes don’t work well, or at all, unless they are also bound by specific non-protein helper molecules; cofactors are inorganic and coenzymes are organic
How do cofactors and coenzymes assist in the regulation of enzymatic reactions?
Several enzymes don’t work well, or at all, unless they are also bound by specific non-protein helper molecules
Give an example of “compartmentalization” of enzymes. How is this used by eukaryotic cells to regulate chemical reactions?
Metabolic enzymes in the mitochondria; or digestive enzymes in lysosomes; enzymes required only for certain cellular processes can be housed separately inside structures along with their substrates
Give an example of compartmentalization of enzymes.
Metabolic enzymes in the mitochondria; or digestive enzymes in lysosomes
What is “feedback inhibition?” Give examples of feedback inhibition in cellular respiration.
The use of a reaction product to regulate its own further production; the cellular production of amino acids and nucleotides
