Chap 3(Reaction Rates) Flashcards
what is a good example of metabolic reaction rates failing
Hypothermia.
List the three factors affecting the rate of reaction.
- Law mass of action: concentrations of reactants and products.
- Temperature.
- Height of reaction’s activation energy barrier.
How does concentrations affect the reaction rate?
Due to a higher concentration, there will be more collision and therefore a higher rate.
How does temperature affect reaction rate?
Higher temperature= Faster rate, Colder=Slower.
The rate of reaction________as the activation barrier_____
Increases, Decreases
What is an Enzyme
proteins that function as catalysts for reactions in biological systems
The Enzyme must first bind to ?
A reactant molecule (substrate)
How do enzymes function?
By decreasing activation energy for a specific chemical reaction
How can you identify an Enzyme
The suffix “ase”
Are enzymes changed in the reaction?
No.
Can any enzyme be used for any substrate?
No, they are used for one set of substrate or a group of similar substrates.
Equation for a general enzyme reaction.
E + S(doubleArrow) ES(Double Arrow) E + P
Explain the lock and key model of enzyme function. What is the down side?
The enzyme is free to bind to substrate, the substrate binds to the enzyme(creates the enzyme-substrate complex), Substrate may leave site at this point and become unchanged, or it may be converted to product(catalytic step) by the enzyme, product leaves the enzyme. Does not explain reverse reactions
What is substrate specificity? Are all enzymes like this?
The fact that enzymes have the ability to recognize and bind to specific particular type of substrate. No, some have the ability to bind to multiple different substrates ex:pepsin.
Explain the induced-fit model.
More like how a foot fits a sock, the enzyme is “about” that same shape as enzyme and one binded it makes that shape.
What is a co-factor? Give an example.
A co factor functions to bind tightly to the side chains of certain amino acids to hold together the enzyme. Ex: iron, copper, zinc.
Can a co enzyme be used more than once?
Yes.
What do co-enzymes do?
They carry a chemical group from one reaction to another.
Three co-enzymes that are important in energy metabolism?
- FAD
- NAD
- CoA( co-enzyme) A
What do NAD and FAD participate as?
Hydrogen carriers in certain oxidation-reduction reactions and shuttle electrons from one place to another inside cells.
What occurs to FAD?
Acquires electrons by picking up pairs of H+ atoms and then becomes FADH2. Then it releases these electrons to other acceptors and returns to oxidized form FAD.
What occurs to NAD+
Carries pairs of electrons, picks up one electron in hydrogen atom and other as a free electron. Results in NADH+H+. Also releases these electrons to acceptors and reverts back to oxidized NAD+
What does CoA do? Important for what ?
Picks up acetyl group and carries them to other reactions. Glucose oxidation.
What are the factors affecting the rates of Enzyme-catalyzed reactions?
Enzyme’s catalytic rate Enzyme concentration Substrate concentration Affinity of enzyme for substrate Temperature and pH
Enzyme can only catalyze a reaction when?
A substrate is bound to it
How does Substrate concentration affect rates?
If low concentration of substrate, most of time enzyme will be idle.
Affinity of an enzyme is a measure of what?
How tightly substrate molecules bind to its active site. (attraction between two objects.)
How does temperature and pH affect rates of enzyme-catalyzed reactions?
Enzyme activity will decline if temp or pH drop or become significantly higher.
What are the two binding sites to an enzyme?
Active and regulatory.
What binds to the regulatory site? What does this molecule do? What is this mechanism called
Modulator. Induces change in an enzymes conformation that alters the shape of the active site. Can also alter catalytic rate, affinity for substrate or both. Allosteric Regulation
A modulator that increases the activity of an enzyme is called a:
Activator
A modulator that decreases the activity of an enzyme is called a:
Inhibitor
What is covalent Regulation?
When changes in an enzymes activity are brought about by the covalent bonding of a specific chemical group to a site on the enzyme molecule.
Changing state of an enzyme requires..?
formation of a covalent bond between protein (enzyme) and chemical group
Most common chemical group used in covalent modulation?
Phosphate group.
What is needed to break these covalent bonds?
More enzymes.
What does protein Kinase do?
Phosphorylation of a target enzyme is catalyzed by Protein kinase
What is phosphorylation
Addition of a phosphate group.
What is dephosphorylation? Catalyzed by what enzyme?
Removal of a phosphate group. Phosphatase.
True or false: The rate of the entire pathway can only be as fast as the rate of the slowest reaction within the pathway.
True. This is called the rate limiting step.
What is feedback inhibition
When an intermediate products of a metabolic pathway allosterically inhibits an enzyme that catalyzes an earlier reaction in the same pathway.
Which type of enzyme is usually subjected to feedback inhibition
Rate-limiting Enzyme.
Feedback inhibition can also do what ?
Speed up or slow down metabolic reactions according to changes in the body’s needs.
What is Feed forward activation
Activation of an enzyme by an intermediate appearing upstream in a metabolic pathway.
