BIOC 2580 Study Guide - Final Guide: Specific Activity, Absorbance, Catalase

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25 Apr 2016

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Enzymes decrease ea (activation energy) of a reaction. Calculation of entropy shows that each effect can speed up a reaction by 10^3 10^5 fold, max. Also applies to enzymes that have only one substrate. Proximity between substrate and reactive groups on enzyme. Ideal alignment of substrate and reactive groups of enzymes. Proximity and orientation are physical effects that speed up enzyme reactions. Enzymes can also use chemical analysis to speed up reaction by lowering the ea. Can be lowered by finding a better chemical pathway for the reaction, involving reactive groups on the enzyme. X-co-nh-y + h2o x-coo- + nh3-y: breaking peptide bonds [un-catalyzed reaction] Reaction shown hydrolysis of peptide is very slow because. H2o is very poor nucleophile and very weak acid. A chemist would use acid or base and heat the reaction to get faster hydrolysis. Cells exist close to neutral ph and at relatively low, fixed temperature.

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26. An enzymatic reaction proceeds with maximal velocity (Vmax) when A. the enzyme is in excess of the substrate. B. allosteric activators are present. the reaction is proportional to substrate concentration. D. the substrate concentration exceeds that of a noncompetitive inhibitor. E. the enzyme is saturated with substrate 27- An enzymatic reaction proceeds with maximal velocity (Vmax) when A. the substrate concentration is equal to that of a competitive inhibitor B. allosteric effectors are present. C. the enzyme substrate complex is maximal. D. the substrate concentration exceeds that of a noncompetitive inhibitor. E. all of the substrate is bound to the enzyme. 28. An enzyme affects the rate of a chemical reaction by A. decreasing the free energy change of the reaction. B. increasing the free energy change of the reaction. C. lowering the energy of activation of the reaction. D. displacing the equilibrium constant. E. raising the energy of activation of the reaction. 29. Which statement is CORRECT? A. Enzymes are small molecules that are heat stable. B. Enzymes affect rates of reactions in the forward and reverse direction. C. Enzymes will determine whether a reaction will take place. D. Enzymes are permanently altered following the conversion of substrate to product. 30. Which of the following statements is TRUE? Enzyme catalysis of a chemical reaction: A. increases the energy of the transition state. B. decreases the change in free energy of the reaction. C. increases the change in free energy of the reaction. D. decreases the change in the free energy of activation. 31. Which of the following statements about enzyme substrate complexes is TRUE? A. At high substrate concentration the rate of the reaction is first order. B. The enzyme concentration is higher than the substrate concentration under physiological conditions. C. Alteration in the conformation of the enzyme may occur when substrate binds. D. Increase in enzyme concentration does not affect the rate of the reaction. 32. All of the following statements about enzymes are correct EXCEPT A. enzymes are usually protein in nature and cause reactions to occur B. enzymes form complexes with substrates and products C. enzymes affect the rate of reactions and are not permanently altered during a reaction D enzymes can undergo structural modification during a reaction E. enzyme specificity requires specific functional groups on the enzyme and substrate

From the following statements select all that are true.

Question 6 options:

A)	All enzymes are proteins.

B)	All proteins are enzymes.

C)	Enzymes in our bodies function as biological catalysts.

D)	Biological catalysts speed up rates of chemical reactions.

E)	If an enzyme slows down a chemical reaction it is called an allosteric inhibitor.

F)	Many inorganic divalent cations like iron (Fe²⁺), zinc (Zn²⁺) and magnesium (Mg²⁺) are essential for our survival in part because they function as cofactors that activate enzymes in our bodies.

G)	Enzyme inhibitors retard an enzyme's activity and an inhibitor can be classified as a non competitive inhibitor if its effects on the enzyme's activity can be overcome simply by adding more substrate to the system.

Which of the following is FALSE with respect to coupledreactions?

	they occur in ALL cells (bacteria, plants, animals, etc.)
	enzymes are typically involved
	endergonic reactions power exergonic reactions
	the coupled reaction has a ?G value that is negative
	none of the above (i.e., all of the above are TRUE)

Which of the following reactions is LEAST likely to bespontaneous? One with a:

	very large increase in entropy and a very large decrease inenthalpy
	very large increase in entropy and a very small increase inenthalpy
	very small decrease in entropy and a very large decrease inenthalpy
	very small increase in entropy and a very small decrease inenthalpy
	very small decrease in entropy and a very small increase inenthalpy

Energy of activation refers to the:

A)	?G of a reaction
B)	difference in energy between the transition state and theproduct
C)	difference in energy between substrate and product
D)	net change in free energy
E)	energy input needed to reach the transition state

Homeostasis refers to maintaining a relatively constantenvironment, and is achieved to a large extent by how enzymes areregulated. For example, when the end product of a pathway regulatesan enzyme that acts early in the same pathway, the effect is mostoften:

	stimulation if an anabolic pathway, and inhibition if acatabolic pathway
	inhibition if an anabolic pathway, and stimulation if acatabolic pathway
	stimulation, whether an anabolic or catabolic pathway
	inhibition, whether an anabolic or catabolic pathway

Enzymes function by:

	decreasing the free energy level of the reactants
	decreasing the free energy level of the transition state
	increasing the free energy level of the reactants
	changing delta G from positive to negative
	changing delta G from negative to positive
	increasing the free energy level of the products
	decreasing the free energy level of the products

6.	When carbohydrates are oxidized, the C

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BIOC 2580 Study Guide - Final Guide: Specific Activity, Absorbance, Catalase

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