CHAPTER 7 Flashcards

1
Q

A non-allosteric protein that binds oxygen independently.

A

Myoglobin

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2
Q

An allosteric protein that binds oxygen cooperatively.

A

Hemoglobin

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3
Q

An allosteric enzyme that exhibits cooperative binding similar to hemoglobin.

A

Aspartate transcarbamoylase (ATCase)

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4
Q

Proteins that change their shape in response to a signal, leading to changes in function. Examples include hemoglobin and ATCas

A

Allosteric proteins

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5
Q

Myoglobin
Hemoglobin
Aspartate transcarbamoylase (ATCase)
Allosteric proteins

A
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6
Q

Catalyzes the first step in the biosynthesis of cytidine triphosphate (CTP), a nucleotide needed for RNA and DNA synthesis.

A

ATCase function

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7
Q

An energy-intensive process involving multiple steps.

A

Pathway producing nucleotides

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8
Q

This is an excellent example of how metabolic pathways are controlled to prevent overproduction of essential compounds.

A

ATCase regulation

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9
Q

A regulatory mechanism that shuts down an entire metabolic pathway when the final product is in excess.

A regulatory mechanism where the end product of a pathway inhibits the first enzyme in the pathway, preventing overproduction.

A

Feedback inhibition

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10
Q

An allosteric enzyme that catalyzes the first step in the biosynthesis of cytidine triphosphate (CTP).

A

ATCase

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11
Q

An inhibitor of ATCase, demonstrating feedback inhibition.

A

CTP
cytidine triphosphate

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12
Q

An oligomer whose biological activity is affected by other substances binding to it changes the enzymes activity by altering its quaternary structure.

A

Allosteric enzyme

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13
Q

A substance that modifies the behavior of an allosteric enzyme.

A

Allosteric effector

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14
Q

A type of allosteric effector that increases the enzyme’s activity.

A

Allosteric activator

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15
Q

A type of allosteric effector that decreases the enzyme’s activity.

A

Allosteric inhibitor

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16
Q

Indicates allosteric behavior in enzyme kinetics.

A

Sigmoidal curve

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17
Q

Both CTP and ATP bind to the same site on ATCase, but CTP is an inhibitor while ATP is an activator

A

ATCase regulation by CTP and ATP

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18
Q

When CTP is in short supply, ATP binding ______ ATCase activity of the enzyme.

A

ATP effect on ATCase
Increases

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19
Q

Models for allosteric enzymes

A

The two main models are the Concerted Model (1965) and the Sequential Model (1966).

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20
Q

A model that assumes all subunits of an allosteric enzyme exist in either a T (tense) or R (relaxed) state, and the transition between these states is concerted.

A

Concerted Model

21
Q

A model that allows for individual subunits to change conformation independently, leading to a more gradual transition between the T and R states.

A

Sequential Model

22
Q

Comparative simplicity.

A

Concerted Model

23
Q

Provides a more realistic picture of protein structure and behavior.

A

Advantage of the Sequential Model

24
Q

The enzyme exists in two conformations: R (relaxed) and T (tight or taut). The R state binds substrate tightly, while the T state binds substrate less tightly.

A

Enzyme conformations in the Concerted Model

25
Q

A model proposed by Wyman, Monod, and Changeux in 1965 to explain allosteric behavior.

A

Concerted Model

26
Q

Conformational changes in the Concerted Model
All subunits of the enzyme change conformation simultaneously when transitioning between the T and R states.

A

Conformational changes in the Concerted Model

27
Q

In the absence of substrate, most enzyme molecules are in the __________ form. The binding of substrate shifts the equilibrium towards the _______ form.

A

Substrate binding in the Concerted Model
T(Inactive)
R (active)

28
Q

A model that explains allosteric behavior by proposing that the binding of substrate to one subunit induces a conformational change that is passed along to other subunits.

A

Sequential Model

29
Q

Substrate binding induces a conformational change from the T to the R form.
The conformational change is induced by the fit of the substrate to the enzyme (induced-fit model).
The model represents cooperativity.

A

Main features of the Sequential Model

30
Q

The binding of substrate to one subunit triggers a conformational change that is transmitted to other subunits, leading to a cooperative effect.

A

Substrate binding in the Sequential Model

31
Q

An enzyme whose activity is ________ by molecules binding at sites other than the active site.

A

modulated
Allosteric enzyme

32
Q

____, the pathway’s end product involving ATCase, inhibits ______ activity through feedback inhibition.

A

CTP, ATCase

33
Q

The regulation of an enzyme’s activity by the binding of molecules at sites other than the active site.

A

Allosteric regulation

34
Q

A molecule that binds to allosteric sites on ATCase and inhibits its catalytic activity.

A

CTP

34
Q

A non-allosteric enzyme that does not exhibit allosteric regulation.

A

Chymotrypsin

35
Q

An inactive precursor of an enzyme that requires proteolytic activation to become the active enzyme.

A

Zymogen

36
Q

A single-chain of polypeptide composed of ____ amino acid residues cross-linked by __ disulfide bonds.

A

245, 5
Chymotrypsinogen structure

36
Q

A zymogen ______ and _____ in the pancreas, destined for secretion into the small intestine.

A

synthesized, stored
Chymotrypsinogen

37
Q

Non-protein chemical compounds or metallic ions that help enzymes perform their catalytic functions.

A

Cofactors

37
Q

___________ molecules that assist enzymes in their catalytic activities.

A

Non Protein
Cofactors and Coenzymes

37
Q

Cleavage of a __-amino acid peptide of trypsin from the N-terminus gives Pi - chymotrypsin that removes ___ dipeptide fragments leading to the formation of fully _________-chymotrypsin.

A

15, 2
active α
Activation of chymotrypsinogen

38
Q

Organic molecules that are a _____ of cofactors.

A

subset
Coenzymes

39
Q

Cofactors can ______ enzyme structure, _______ in the actual catalytic reaction, or____ in substrate binding

A

stabilize, participate, assist
Role of cofactors

39
Q

Examples of cofactors:

A

Mg2+ for DNA polymerase, Zn2+ for alcohol dehydrogenase. and Fe2+ they are also inorganic ions

39
Q

Organic cofactors that assist enzymes in catalyzing reactions by acting as carriers for _________ or electrons.
Often derived from vitamins.

A

chemical groups
Coenzymes
Nature of coenzymes: Organic Molecules

40
Q

Participate in reactions by _______ accepting or donating atoms, ions, or functional groups.

A

temporarily
Role of coenzymes

41
Q

often regenerated after the reaction, allowing for their repeated use.

A

Coenzymes

42
Q

Biotin
Back: A coenzyme involved in carboxylation reactions. Vitamin precursor: _____

Coenzyme A
A coenzyme involved in acyl transfer reactions. Vitamin precursor: ________

Flavin coenzymes
Coenzymes involved in oxidation-reduction reactions. Vitamin precursor: _________.

Lipoic acid
A coenzyme involved in acyl transfer reactions. Vitamin precursor: None.

Nicotinamide adenine coenzymes
Coenzymes involved in oxidation-reduction reactions. Vitamin precursor: _______

Pyridoxal phosphate
A coenzyme involved in transamination reactions. Vitamin precursor:_________

Front: Tetrahydrofolic acid
Back: A coenzyme involved in the transfer of one-carbon units. Vitamin precursor: _______

Front: Thiamine pyrophosphate
Back: A coenzyme involved in aldehyde transfer reactions. Vitamin precursor: _______

A

Biotin
Pantothenic acid.
Riboflavin (B2)

Niacin
Pyridoxine (B6).
Folic acid.
Thiamin (B1).

42
Q

Cofactors
Non-protein chemical compounds or metallic ions that assist enzymes in their catalytic functions.

Coenzymes
Organic molecules that are a subset of cofactors.

Difference between cofactors and coenzymes
Cofactors can be inorganic (metal ions) or organic, while coenzymes are always organic.

Relationship between cofactors and coenzymes
All coenzymes are cofactors, but not all cofactors are coenzymes.

Role of coenzymes in enzymatic reactions
Coenzymes often participate directly in the enzymatic reaction.

Role of cofactors in enzymes
Some cofactors may play more structural or stabilizing roles.

A

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