BIOL 118 Lecture Notes - Lecture 6: Cellular Respiration, Enzyme Inhibitor, Activation Energy

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blackjackal192

18 Feb 2017

School

Binghamton University

Department

Biology

Course

BIOL 118

Professor

Dr.Mc Gee

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Document Summary

Effects of ph 2/17: affects the charge of the r-side chains/ Carboxyl and amino groups: reflects the environment in which an enzyme functions. Enzyme regulation: some enzymes are regulated by regulatory molecules, may change the enzyme"s structure. Competitive inhibition: a molecule of similar size and shape to the substrate binds to the enzyme active sire, competes with the substrate for active site binding. Allosteric regulation = activation: a regulatory molecule binds to the enzyme at a location other than the active site, causes a change in enzyme shape, can increase enzyme activity. Allosteric regulation = inhibition: a regulatory molecule binds to the enzyme at a location other than the active site, causes a change in enzyme shape, active site becomes unavailable, decreases enzyme activity. Enzyme regulation: covalent modification of the enzyme, can be reversible or irreversible, enzyme phosphorylation. Each catalyzed by a different enzyme to build a biological molecule: feedback inhibition.

Related Questions

Phosphofructokinase (PFK1) is a glycolytic enzyme that catalyzes the irreversible transfer of a phosphate from ATP to fructose -6-phosphate to form fructose-1, 6- bisphosphate.

fructose-6-phosphate + ATP --> fructose-1,6-bisphosphate + ADP

PFK1 is the key regulatory enzyme for glycolysis. When ATP levels are high in the cell, the cell no longer needs metabolic energy production to occur. In the case of these high energy levels, PFK1's activity is inhibited by allosteric regulation by ATP, which essentially closes the valve on the flow of carbohydrates through glycolysis.

Recall that allosteric regulators bind to a different site on the enzyme rather than the active (catalytic) site. ATP binds to the regulatory site and decreases PFK1 activity. ATP bound in the regulatory site acts as a modulator by lowering the affinity of PFK1 for its substrate, fructose-6-phosphate. AMP on the other hand, which is generated when the cell is in a low energy state binds to allosteric site and increases enzyme activity.

7. The enzyme PFK1 is an example of a non-regulatory enzyme or regulatory enzyme?

8. How is PFK regulated?

A. It is not regulated because it is a non-regulatory enzyme

B. allosteric enzyme regulation

C. covalent enzyme regulation

D. or proteolytic cleavage enzyme regulation?

9. What is the substrate and to which site on the enzyme does it bind? Which compounds are the positive and negative effectors?

10. In which conformational state would the enzyme be when negative inhibitors bind and in which conformational state would the enzyme be when positive inhibitors bind?

11. PFK1 is a heterotropic or homotropic regulatory enzyme?

12. Draw (or insert the picture from your course packet available on Canvas) the graph that corresponds to this reaction. Your graph should include the activity of PFK without bound effectors, with bound positive effector, and with bound negative effector. Label (or describe) each line to distinguish these along with which molecules are positive and negative effectors.

13. How does Vmax and K0.5 change with the positive and negative effectors?

Explain how the following mechanisms regulate enzyme activity.

Part A

Covalent modification

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it.

Part B

Genetic control

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it

Part C

Allosteric regulation

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it.

Part D

Feedback inhibition

a)The product of a series of reactions acts as an inhibitor for an earlier reaction.

b)Hormones control the synthesis of enzymes.

c)A regulator binds to the enzyme at a site other than the active site. This binding changes the shape of the enzyme and alters the catalytic ability of the enzyme.

d)An inhibitor binds reversibly to the enzymesubstrate complex, blocking the binding of the second substrate to the active site.

e)The activity of an enzyme is influenced by the addition or removal of a group that is covalently bonded to the enzyme.

f)An inhibitor forms covalent bonds to the active site, permanently blocking it

Enzyme Activity

1. Briefly explain the principle of spectrophotometry.

2. Which of the following statements is true about enzymes?(check all correct answers)

		__ enzymes act on (are specific for) one or just a fewsubstrates
		__ enzymes can be denatured (loose their tertiary/quaternarystructure and activity) by extreme conditions such as heat, high orlow pH,or presence of organic solvents
		__most enzymes are DNA
		__ enzymes are protein
		__enzymes perform best at specific conditions of temperature, pHand salt concentration 5. Which enzymes break the following macromolecules? Match the following with their correponding answers: ___ Nucleic acids A. proteases or proteinases such as pepsin ___ Cellulose B. none ___ Triglycerides C. lipases ___ Proteins D. amylases ___ Starch E. nucleases 6.Match the following enzymes totheir products. Answers ___ pepsin, trypsin and other digestive proteases A.Nucleotides ___ salivary and pancreatic amylases and other enzymes B. AminoAcids ___ lipases C. Monosaccharides ___ nucleases D. fatty acids and glycerol 7. Based on experiments, what is the effect of extremeconditions of pH and temperature (boiling tube) on enzymeactivity? 8. ATP stores energy in the form of___ ___ Chemical energy ___ Kinetic energy ___ Thermal energy ___ Activation energy 9. An allosteric site in anenzyme is____ __ the site where reactions occur __ the site that binds aregulator __ the site that binds thesubstrate __ the site that binds the product 10. Enzymes increase the rate of reactions by making thetransition state less stable. __ True __ False 11. Enzymes increase the rate of reactions by placing reactingparts of the molecule in favorable positions. __ True __ False 12. Which of the followingis a mechanism for regulation of enzymes? __ covalent modification __ feedback inhibition __ allosteric regulation __ all of the above 13. Which of the following represents a correct order of eventsin an enzyme catalytic cycle? 1.enzyme changes shape 2.substrate binds to active site 3.substrate is converted to products 4. products are released from activesite __ 1>2>3>4 __ 2>1>3>4 __ 3>2>1>4 __ 2>4>3>1

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BIOL 118 Lecture Notes - Lecture 6: Cellular Respiration, Enzyme Inhibitor, Activation Energy

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