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Biochemistry allosteric enzyme regulation exam review

Prepare for your biochemistry exam with these flashcards covering allosteric enzyme regulation, including key concepts, mechanisms, and examples.

MayaThomas·36 flashcards·36 questions

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What are allosteric enzymes?

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Enzymes that undergo conformational changes upon binding to an effector, impacting activity.

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Quiz(36 questions)

Question 1 of 36

1. What is the main characteristic of allosteric enzymes?

Terms in this Study Set(36)

Allosteric Basics(16)

What are allosteric enzymes?

Enzymes that undergo conformational changes upon binding to an effector, impacting activity.

True or False: Allosteric sites are the active sites of enzymes.

False. Allosteric sites are separate from active sites; they modulate enzyme function.

Describe the role of allosteric effectors.

They can be activators or inhibitors, influencing enzyme activity by binding to allosteric sites.

Fill in the blank: Allosteric regulation is ____________ than simple competitive inhibition.

more complex.

Compare allosteric regulation to competitive inhibition.

- Allosteric: non-competitive, changes shape. - Competitive: directly competes with substrate.

What is feedback inhibition?

A form of regulation where an end product inhibits an earlier step in the pathway.

Cause → Effect: Why do allosteric enzymes have multiple subunits?

Cause: multiple subunits allow for cooperative binding. Effect: enhances sensitivity to effectors.

How do allosteric enzymes show cooperativity?

Binding of substrate to one subunit increases likelihood of substrate binding to others.

What is the significance of the sigmoid curve?

Represents the cooperative binding of substrate in allosteric enzymes, unlike hyperbolic in Michaelis-Menten kinetics.

True or False: Allosteric enzymes follow Michaelis-Menten kinetics.

False. They exhibit sigmoidal kinetics due to cooperative binding.

What happens when an allosteric inhibitor binds?

It decreases enzyme activity by stabilizing the inactive conformation.

Fill in the blank: The allosteric model is also known as the __________ model.

concerted model.

What is the primary function of allosteric regulation?

To fine-tune enzyme activity in response to cellular needs.

How do allosteric activators affect enzyme activity?

They increase enzyme activity by stabilizing the active form.

Describe the term 'allosteric modulation'.

The process where an effector influences enzyme activity by binding to an allosteric site.

What is an example of an allosteric enzyme?

Aspartate transcarbamoylase (ATCase), involved in pyrimidine synthesis.

Mechanisms of Regulation(12)

What is allosteric regulation?

Allosteric regulation involves the binding of an effector molecule at a site other than the active site, causing conformational changes that affect enzyme activity.

True or False: Allosteric activators bind to the active site.

False. Allosteric activators bind to allosteric sites, enhancing enzyme activity by stabilizing the active form.

Define allosteric inhibitor.

An allosteric inhibitor binds to an allosteric site, reducing enzyme activity by stabilizing the inactive form.

What happens when an allosteric activator is present?

It increases the enzyme's affinity for substrates, promoting reactions and metabolic pathways.

Fill in the blank: Allosteric enzymes can exist in __________ states.

multiple conformational states.

Compare allosteric regulation and competitive inhibition.

- Allosteric regulation: site other than active site. - Competitive inhibition: competes for active site.

How do cooperativity and allosteric regulation relate?

Cooperativity is a form of allosteric regulation where the binding of one substrate affects the binding of additional substrates.

Provide an example of a common allosteric enzyme.

Phosphofructokinase (PFK) is a key allosteric enzyme in glycolysis, regulated by ATP and AMP levels.

What is the role of feedback inhibition?

Feedback inhibition prevents excess product formation by inhibiting an early step in the metabolic pathway through an allosteric inhibitor.

True or False: Allosteric effects are usually reversible.

True. Allosteric effects are typically reversible upon removal of the effector molecules.

What is an example of an allosteric inhibitor?

Citrate acts as an allosteric inhibitor of phosphofructokinase, reducing glycolysis when citrate levels are high.

Cause → Effect: Binding of an allosteric activator.

Increases enzyme activity and substrate affinity.

Examples of Allosteric Enzymes(8)

True or False: Allosteric enzymes only have one active site.

False. Allosteric enzymes have multiple sites, including regulatory sites that bind effectors.

Examples of allosteric enzymes.

- Aspartate transcarbamoylase (ATCase) - Phosphofructokinase (PFK) - Hemoglobin (O2 binding) - Acetyl-CoA carboxylase

Aspartate transcarbamoylase (ATCase) significance?

It regulates pyrimidine nucleotide synthesis, critical for DNA and RNA production.

Fill in the blank: Phosphofructokinase is a key regulator of __________ metabolism.

glycolysis

Cause → Effect: Increased ATP concentration on phosphofructokinase.

Inhibition of PFK activity, slowing down glycolysis.

What role does hemoglobin play in allosteric regulation?

Hemoglobin exhibits cooperative binding of O2, enhancing oxygen delivery to tissues.

Compare the regulation of ATCase and PFK.

ATCase is regulated by feedback inhibition via CTP; PFK is activated by AMP and inhibited by ATP.

True or False: Allosteric regulation involves only the active site.

False. Allosteric regulation involves binding at sites distinct from the active site.

Questions in this Study Set(36)

1. What is the main characteristic of allosteric enzymes?

A.They have multiple binding sites.

B.They only catalyze one reaction.

C.They are not affected by environmental changes.

D.They cannot exist in different conformations.

2. What are allosteric enzymes primarily characterized by?

A.Undergoing conformational changes upon effector binding

B.Having a single binding site

C.Following strict Michaelis-Menten kinetics

D.Being unaffected by substrate concentration

3. Which of the following is an example of an allosteric enzyme?

A.Aspartate transcarbamoylase

B.Hexokinase

C.Lactate dehydrogenase

D.Acetylcholinesterase

4. Which of the following statements is true about allosteric inhibitors?

A.They enhance enzyme activity.

B.They bind to the active site.

C.They stabilize the inactive form of the enzyme.

D.They do not affect enzyme kinetics.

5. True or False: Allosteric sites serve as the active sites for enzymatic reactions.

A.True

B.False

C.Only in some enzymes

D.Not applicable

6. What is the primary function of phosphofructokinase in cellular metabolism?

A.Regulating the citric acid cycle

B.Catalyzing the first step of glycolysis

C.Inhibiting ATP production

D.Facilitating gluconeogenesis

7. What does cooperativity in allosteric enzymes refer to?

A.A single reaction step.

B.The binding of a substrate affecting further substrate binding.

C.The binding of inhibitors only.

D.The enzyme's activity remaining constant.

8. What is the role of an allosteric activator?

A.Inhibits enzyme activity

B.Stabilizes the inactive form

C.Enhances enzyme activity

D.Competes with substrates

9. True or False: Hemoglobin acts as an allosteric enzyme by binding oxygen cooperatively.

A.True

B.False

C.Only in the lungs

D.Only in the tissues

10. Which of the following is NOT a characteristic of competitive inhibition?

A.Inhibition can be overcome by increasing substrate concentration.

B.Inhibitors bind to sites other than the active site.

C.It directly competes with the substrate for the active site.

D.Inhibition affects the maximum reaction rate.

11. Fill in the blank: Allosteric regulation is generally __________ than simple competitive inhibition.

A.more predictable

B.more complex

C.less effective

D.more direct

12. Which of the following statements about allosteric regulation is NOT true?

A.Allosteric enzymes have multiple binding sites.

B.Allosteric regulation can enhance or inhibit enzyme activity.

C.Allosteric effectors bind exclusively to the active site.

D.Allosteric enzymes often exhibit sigmoidal kinetics.

13. What effect does an allosteric activator have on enzyme activity?

A.It decreases the enzyme's affinity for substrates.

B.It stabilizes the inactive form of the enzyme.

C.It increases the enzyme's affinity for substrates.

D.It permanently alters the enzyme structure.

14. Which statement is true about allosteric regulation compared to competitive inhibition?

A.Allosteric regulation is always reversible

B.Allosteric regulation can change enzyme shape

C.Competitive inhibition can enhance enzyme activity

D.Both have the same binding mechanism

15. How does an increase in ATP concentration affect phosphofructokinase activity?

A.It activates PFK.

B.It inhibits PFK.

C.It has no effect.

D.It destabilizes PFK.

16. How does feedback inhibition function in metabolic pathways?

A.By increasing substrate concentration.

B.By activating the first enzyme in the pathway.

C.By inhibiting an early step through a product.

D.By promoting allosteric activators.

17. What defines feedback inhibition?

A.Activation of the first enzyme in a pathway

B.Inhibition by the end product of a pathway

C.Effect of a substrate on enzyme activity

D.Inhibition of all enzymes in a pathway

18. What is the regulatory role of CTP in aspartate transcarbamoylase?

A.It inhibits ATCase.

B.It activates ATCase.

C.It has no effect on ATCase.

D.It enhances ATP binding.

19. What is a common example of an allosteric enzyme?

A.Hexokinase

B.Phosphofructokinase

C.Lactate dehydrogenase

D.Aldolase

20. Why do allosteric enzymes typically have multiple subunits?

A.To increase the number of active sites

B.To allow for cooperative binding

C.To enhance substrate specificity

D.To reduce energy costs

21. Which enzyme is primarily responsible for regulating glycolysis?

A.Glycogen phosphorylase

B.Phosphofructokinase

C.Pyruvate kinase

D.Lactate dehydrogenase

22. True or False: Allosteric effects are often irreversible.

A.True

B.False

C.Only in certain conditions.

D.They depend on the enzyme type.

23. How do allosteric enzymes exhibit cooperativity?

A.By binding more than one substrate at a time

B.By changing shape upon substrate binding

C.By being inhibited by their own products

D.By having competitive inhibitors only

24. In terms of enzymatic kinetics, how do allosteric enzymes typically behave compared to Michaelis-Menten enzymes?

A.They exhibit hyperbolic kinetics.

B.They exhibit linear kinetics.

C.They exhibit sigmoidal kinetics.

D.They are always inactive.

25. Which effect occurs when an allosteric activator binds to the enzyme?

A.Decreases substrate binding.

B.Increases reaction rate.

C.Stabilizes the inactive form.

D.Prevents substrate binding.

26. What does a sigmoid curve in enzyme kinetics indicate?

A.Constant enzyme activity

B.Non-cooperative binding

C.Cooperative binding of substrates

D.Exclusively competitive inhibition

27. Fill in the blank: Allosteric enzymes can exist in __________ conformational states.

A.one

B.two

C.four

D.multiple

28. True or False: Allosteric enzymes can display Michaelis-Menten kinetics.

A.True

B.False

C.Only under certain conditions

D.They are identical

29. What is the relationship between allosteric regulation and enzyme kinetics?

A.Allosteric regulation does not affect kinetics.

B.It often results in sigmoidal kinetics.

C.It always increases Vmax.

D.It prevents any reaction from occurring.

30. What occurs when an allosteric inhibitor binds to an enzyme?

A.It increases enzyme activity

B.It stabilizes the active form

C.It decreases enzyme activity

D.It converts the enzyme to a competitive inhibitor

31. Which of the following statements correctly describes an allosteric site?

A.It is identical to the active site.

B.It is where substrates bind.

C.It regulates enzyme activity.

D.It is always occupied.

32. Fill in the blank: The model of allosteric regulation is also called the __________ model.

A.random

B.induced fit

C.concerted

D.linear

33. What is the primary function of allosteric regulation?

A.To stop enzyme activity completely

B.To fine-tune enzyme activity

C.To permanently modify enzyme structure

D.To enhance substrate binding only

34. How do allosteric activators influence enzyme function?

A.They cause irreversible changes

B.They stabilize the inactive form

C.They increase activity by stabilizing the active form

D.They decrease substrate affinity

35. Which of the following is an example of an allosteric enzyme?

A.Aspartate transcarbamoylase (ATCase)

B.Hexokinase

C.Ribonuclease

D.Chymotrypsin

36. Which of the following statements about allosteric enzymes is NOT true?

A.They can exist in multiple conformations.

B.They only bind substrates at the active site.

C.They can be regulated by allosteric effectors.

D.They often show cooperative binding.

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Biochemistry allosteric enzyme regulation exam review

Quiz(36 questions)

Terms in this Study Set(36)

Allosteric Basics(16)

Mechanisms of Regulation(12)

Examples of Allosteric Enzymes(8)

Questions in this Study Set(36)

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