Question 1

All of the following are considered “weak” interactions in proteins except:

Accepted Answer

peptide bonds

Question 2

The most important contribution to the stability of a protein’s conformation appears to be the:

Accepted Answer

entropy increase from the decrease in ordered water molecules forming a solvent shell around it.

Question 3

In an aqueous solution, protein conformation is determined by two major factors.  One is the formation of the maximum number of hydrogen bonds.  The other is the:

Accepted Answer

placement of hydrophobic amino acid residues within the interior of the protein.

Question 4

Which of the following is not an appropriate  description for van der Waals interactions?

Accepted Answer

They are highly specific

Question 5

Which statement about intrinsically disordered proteins is true?

Accepted Answer

They can interact with multiple protein-binding partners and are central to protein interaction networks.

Question 6

Pauling and Corey’s studies of the peptide bond showed that:

Accepted Answer

peptide bonds are essentially planar, with no rotation about the C—N axis

Question 7

Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds?

Accepted Answer

C alpha—C and N—C alpha

Question 8

Roughly how many amino acids are there in one turn of an  alpha helix?

Accepted Answer

3.6

Question 9

In the  alpha helix the hydrogen bonds:

Accepted Answer

are roughly parallel to the axis of the helix

Question 10

In an alpha helix, the R groups on the amino acid residues:

Accepted Answer

are found on the outside of the helix spiral

Question 11

Thr and/or Leu residues tend to disrupt an alpha helix when they occur next to each other in a protein because:

Accepted Answer

steric hindrance occurs between the bulky Thr side chains

Question 12

An alpha helix would be destabilized most by:

Accepted Answer

the presence of two Lys residues near the amino terminus of the alpha helix.

Question 13

The major reason that antiparallel beta-stranded protein structures are more stable than parallel beta-stranded structures is that the latter:

Accepted Answer

have weaker hydrogen bonds laterally between adjacent strands

Question 14

Amino acid residues commonly found in the middle of beta turn are:

Accepted Answer

Pro and Gly

Question 15

A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-.  The sequence is most probably part of a(n):

Accepted Answer

Beta turn

Question 16

Proteins often have regions that can fold and function as an independent entity from the whole protein.  These regions are called:

Accepted Answer

domains

Question 17

Which of the following statements concerning protein domains is true?

Accepted Answer

They may retain their correct shape even when separated from the rest of the protein.

Question 18

Experiments on denaturation and renaturation after the reduction and reoxidation of the —S—S— bonds in the enzyme ribonuclease (RNase) have shown that:

Accepted Answer

the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure

Question 19

Any given protein is characterized by a unique amino acid sequence (primary structure) and three-dimensional (tertiary) structure. How are these related?

Accepted Answer

The three-dimensional structure is determined by the amino-acid sequence.  This means that the amino-acid sequence contains all of the information that is required for the polypeptide chain to fold up into a discrete three-dimensional shape

Question 20

Name four factors (bonds or other forces) that contribute to stabilizing the native structure of a protein, and describe one condition or reagent that interferes with each type of stabilizing force

Accepted Answer

disulfide bonds by reducing conditions or mercaptoethanol or dithiothreitol, H bonds by pH extremes,  hydrophobic interactions by detergents or urea or guanidine hydrochloride, ionic interactions by changes in pH or ionic strength, and  van der Waals

Question 21

Native polypeptide:

Accepted Answer

The 3-D structure in which the polypeptide is most competent to fulfill its biological function

Question 22

Denaturated polypeptide:

Accepted Answer

Elimination of all structural features, including disulfide bridges (or called random coil) leads to no activity

Question 23

Chaotropic agents

Accepted Answer

small molecules that perturb the 3-dimensional structure by interfering with non-covalent interactions that stabilize the protein conformation

Question 24

Reducing agents

Accepted Answer

are small molecules that reduce disulfide bridges, leaving the cysteines with their original sulfhydryl groups

Question 25

Hydrophobic interactions exist mostly

Accepted Answer

when the protein folds, allowing the non-polar groups to gather inside, away from the aqueous environment

Question 26

Unlike most organic polymers, protein molecules adopt a specific three-dimensional conformation  This structure is able to fulfill a specific biological function. The structure is called

Accepted Answer

the native fold

Question 27

Protein Conformation:

Accepted Answer

The 3-dimensional shape of the protein

Question 28

Native Conformation:

Accepted Answer

Functional conformation of the protein found under normal biological conditions

Question 29

alpha helix

Accepted Answer

stabilized by hydrogen bonds between nearby residues

Question 30

beta sheets

Accepted Answer

stabilized by hydrogen bonds between adjacent segments that may not be nearby. Anti-parallele is better than parallelle

Question 31

Helical backbone is held together by

Accepted Answer

hydrogen bonds between the backbone amides of an n and n+4 amino acids

Question 32

Proline acts as a helix breaker because

Accepted Answer

the rotation around the N-Ca bond is impossible

Question 33

The interactions of ligands with proteins

Accepted Answer

are usually transient

Question 34

A prosthetic group of a protein is a non-protein structure that is

Accepted Answer

permanently associated with the protein

Question 35

When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by:

Accepted Answer

one O2 molecule and one amino acid atom

Question 36

In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:

Accepted Answer

hyperbolic

Question 37

Myoglobin and the subunits of hemoglobin have:

Accepted Answer

very similar tertiary structures, but different primary structures

Question 38

An allosteric interaction between a ligand and a protein is one in which:

Accepted Answer

binding of a molecule to a binding site affects binding properties of another site on the protein.

Question 39

In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by:

Accepted Answer

oxygen binding

Question 40

Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)?

Accepted Answer

It increases the affinity of hemoglobin for oxygen

Question 41

Which of the following is not correct concerning cooperative binding of a ligand to a protein?

Accepted Answer

It rarely occurs in enzymes

Question 42

Carbon monoxide (CO) is toxic to humans because:

Accepted Answer

it binds to the Fe in hemoglobin and prevents the binding of O2

Question 43

The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.

Accepted Answer

hydrophobic

Question 44

The fundamental cause of sickle-cell disease is a change in the structure of:

Accepted Answer

hemoglobin

Question 45

Identify the correct statements regarding the Bohr effect:
a) It shifts the fractional O2 saturation curve to the right as pH decreases.
b) shifts to the right as the pH increases.
c) favors O2 release in respiring tissues.

Accepted Answer

a and c

Question 46

Describe the concept of “induced fit” in ligand-protein binding

Accepted Answer

Induced fit refers to the structural adaptations that occur when a ligand binds to a protein.  This often involves a conformational change in the protein that alters the binding site to make it more complementary to the ligand

Question 47

Why is carbon monoxide (CO) toxic to aerobic organisms?

Accepted Answer

It binds to heme with a higher affinity than oxygen, and thus prevents oxygen from binding to hemoglobin.

Question 48

How does BPG binding to hemoglobin decrease its affinity for oxygen?

Accepted Answer

BPG binds to a cavity between the beta subunits.  It binds preferentially to molecules in the low-affinity T state, thereby stabilizing that conformation.

Question 49

What is the effect of pH on the binding of oxygen to hemoglobin (the Bohr Effect)? (b) Briefly describe the mechanism of this effect.

Accepted Answer

(a) The affinity decreases with decreasing pH.  (b)  At lower pH (i.e., higher H+ concentration), there is increasing protonation of protein residues such as histidine, which stabilizes the low affinity conformation of the protein subunits.

Question 50

Fetal hemoglobin binds BPG with lower affinity than adult hemoglobin. How does this property facilitate tranfers of O2 from mother to fetus?

Accepted Answer

Lower affinity for BPG means that fetal hemoglobin will have less BPG bound that the mother’s hemoglobin. This shifts the fetus’ fractional O2 saturation curve to the leftof the mother’s.

Question 51

What is the concept of “induced fit” as it applies to antigen-antibody binding?

Accepted Answer

The conformations of the antigen and antigen-binding site of the antibody are influenced by each other and change as binding occurs.  These conformational changes increase the chemical complementarity of the sites and result in tighter binding.

Question 52

Enzymes are potent catalysts because they

Accepted Answer

lower the activation energy for the reactions they catalyze

Question 53

The role of an enzyme in an enzyme-catalyzed reaction is to:

Accepted Answer

increase the rate at which substrate is converted into product.

Question 54

Which one of the following statements is true of enzyme catalysts?

Accepted Answer

They can increase the reaction rate for a given reaction by a thousand-fold or more.

Question 55

Which one of the following statements is true of enzyme catalysts?

Accepted Answer

They lower the activation energy for the conversion of substrate to product

Question 56

Which of the following statements is false?

Accepted Answer

For S > P, a catalyst shifts the reaction equilibrium to the right.

Question 57

Enzymes differ from other catalysts in that only enzymes:

Accepted Answer

display specificity toward a single reactant

Question 58

Which of the following is true of the binding energy derived from enzyme-substrate interactions?

Accepted Answer

It is sometimes used to hold two substrates in the optimal orientation for reaction.

Question 59

The concept of “induced fit” refers to the fact that:

Accepted Answer

substrate binding may induce a conformational change in the enzyme, which then brings catalytic groups into proper orientation

Question 60

The benefit of measuring the initial rate of a reaction V0 is that at the beginning of a reaction:

Accepted Answer

changes in [S] are negligible, so [S] can be treated as a constant

Question 61

Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-Menten kinetics is false?

Accepted Answer

At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.

Question 62

The steady state assumption, as applied to enzyme kinetics, implies:

Accepted Answer

the ES complex is formed and broken down at equivalent rates.

Question 63

Which of these statements about enzyme-catalyzed reactions is false?

Accepted Answer

The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.

Question 64

For enzymes in which the slowest (rate-limiting) step is the reaction

	k2
	ES  > P

Accepted Answer

the dissociation constant, Kd, for the ES complex.

Question	Answer
All of the following are considered “weak” interactions in proteins except:	peptide bonds
The most important contribution to the stability of a protein’s conformation appears to be the:	entropy increase from the decrease in ordered water molecules forming a solvent shell around it.
In an aqueous solution, protein conformation is determined by two major factors. One is the formation of the maximum number of hydrogen bonds. The other is the:	placement of hydrophobic amino acid residues within the interior of the protein.
Which of the following is not an appropriate description for van der Waals interactions?	They are highly specific
Which statement about intrinsically disordered proteins is true?	They can interact with multiple protein-binding partners and are central to protein interaction networks.
Pauling and Corey’s studies of the peptide bond showed that:	peptide bonds are essentially planar, with no rotation about the C—N axis
Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds?	C alpha—C and N—C alpha
Roughly how many amino acids are there in one turn of an alpha helix?	3.6
In the alpha helix the hydrogen bonds:	are roughly parallel to the axis of the helix
In an alpha helix, the R groups on the amino acid residues:	are found on the outside of the helix spiral
Thr and/or Leu residues tend to disrupt an alpha helix when they occur next to each other in a protein because:	steric hindrance occurs between the bulky Thr side chains
An alpha helix would be destabilized most by:	the presence of two Lys residues near the amino terminus of the alpha helix.
The major reason that antiparallel beta-stranded protein structures are more stable than parallel beta-stranded structures is that the latter:	have weaker hydrogen bonds laterally between adjacent strands
Amino acid residues commonly found in the middle of beta turn are:	Pro and Gly
A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-. The sequence is most probably part of a(n):	Beta turn
Proteins often have regions that can fold and function as an independent entity from the whole protein. These regions are called:	domains
Which of the following statements concerning protein domains is true?	They may retain their correct shape even when separated from the rest of the protein.
Experiments on denaturation and renaturation after the reduction and reoxidation of the —S—S— bonds in the enzyme ribonuclease (RNase) have shown that:	the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure
Any given protein is characterized by a unique amino acid sequence (primary structure) and three-dimensional (tertiary) structure. How are these related?	The three-dimensional structure is determined by the amino-acid sequence. This means that the amino-acid sequence contains all of the information that is required for the polypeptide chain to fold up into a discrete three-dimensional shape
Name four factors (bonds or other forces) that contribute to stabilizing the native structure of a protein, and describe one condition or reagent that interferes with each type of stabilizing force	disulfide bonds by reducing conditions or mercaptoethanol or dithiothreitol, H bonds by pH extremes, hydrophobic interactions by detergents or urea or guanidine hydrochloride, ionic interactions by changes in pH or ionic strength, and van der Waals
Native polypeptide:	The 3-D structure in which the polypeptide is most competent to fulfill its biological function
Denaturated polypeptide:	Elimination of all structural features, including disulfide bridges (or called random coil) leads to no activity
Chaotropic agents	small molecules that perturb the 3-dimensional structure by interfering with non-covalent interactions that stabilize the protein conformation
Reducing agents	are small molecules that reduce disulfide bridges, leaving the cysteines with their original sulfhydryl groups
Hydrophobic interactions exist mostly	when the protein folds, allowing the non-polar groups to gather inside, away from the aqueous environment
Unlike most organic polymers, protein molecules adopt a specific three-dimensional conformation This structure is able to fulfill a specific biological function. The structure is called	the native fold
Protein Conformation:	The 3-dimensional shape of the protein
Native Conformation:	Functional conformation of the protein found under normal biological conditions
alpha helix	stabilized by hydrogen bonds between nearby residues
beta sheets	stabilized by hydrogen bonds between adjacent segments that may not be nearby. Anti-parallele is better than parallelle
Helical backbone is held together by	hydrogen bonds between the backbone amides of an n and n+4 amino acids
Proline acts as a helix breaker because	the rotation around the N-Ca bond is impossible
The interactions of ligands with proteins	are usually transient
A prosthetic group of a protein is a non-protein structure that is	permanently associated with the protein
When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are occupied by:	one O2 molecule and one amino acid atom
In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as:	hyperbolic
Myoglobin and the subunits of hemoglobin have:	very similar tertiary structures, but different primary structures
An allosteric interaction between a ligand and a protein is one in which:	binding of a molecule to a binding site affects binding properties of another site on the protein.
In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by:	oxygen binding
Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)?	It increases the affinity of hemoglobin for oxygen
Which of the following is not correct concerning cooperative binding of a ligand to a protein?	It rarely occurs in enzymes
Carbon monoxide (CO) is toxic to humans because:	it binds to the Fe in hemoglobin and prevents the binding of O2
The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.	hydrophobic
The fundamental cause of sickle-cell disease is a change in the structure of:	hemoglobin
Identify the correct statements regarding the Bohr effect: a) It shifts the fractional O2 saturation curve to the right as pH decreases. b) shifts to the right as the pH increases. c) favors O2 release in respiring tissues.	a and c
Describe the concept of “induced fit” in ligand-protein binding	Induced fit refers to the structural adaptations that occur when a ligand binds to a protein. This often involves a conformational change in the protein that alters the binding site to make it more complementary to the ligand
Why is carbon monoxide (CO) toxic to aerobic organisms?	It binds to heme with a higher affinity than oxygen, and thus prevents oxygen from binding to hemoglobin.
How does BPG binding to hemoglobin decrease its affinity for oxygen?	BPG binds to a cavity between the beta subunits. It binds preferentially to molecules in the low-affinity T state, thereby stabilizing that conformation.
What is the effect of pH on the binding of oxygen to hemoglobin (the Bohr Effect)? (b) Briefly describe the mechanism of this effect.	(a) The affinity decreases with decreasing pH. (b) At lower pH (i.e., higher H+ concentration), there is increasing protonation of protein residues such as histidine, which stabilizes the low affinity conformation of the protein subunits.
Fetal hemoglobin binds BPG with lower affinity than adult hemoglobin. How does this property facilitate tranfers of O2 from mother to fetus?	Lower affinity for BPG means that fetal hemoglobin will have less BPG bound that the mother’s hemoglobin. This shifts the fetus’ fractional O2 saturation curve to the leftof the mother’s.
What is the concept of “induced fit” as it applies to antigen-antibody binding?	The conformations of the antigen and antigen-binding site of the antibody are influenced by each other and change as binding occurs. These conformational changes increase the chemical complementarity of the sites and result in tighter binding.
Enzymes are potent catalysts because they	lower the activation energy for the reactions they catalyze
The role of an enzyme in an enzyme-catalyzed reaction is to:	increase the rate at which substrate is converted into product.
Which one of the following statements is true of enzyme catalysts?	They can increase the reaction rate for a given reaction by a thousand-fold or more.
Which one of the following statements is true of enzyme catalysts?	They lower the activation energy for the conversion of substrate to product
Which of the following statements is false?	For S > P, a catalyst shifts the reaction equilibrium to the right.
Enzymes differ from other catalysts in that only enzymes:	display specificity toward a single reactant
Which of the following is true of the binding energy derived from enzyme-substrate interactions?	It is sometimes used to hold two substrates in the optimal orientation for reaction.
The concept of “induced fit” refers to the fact that:	substrate binding may induce a conformational change in the enzyme, which then brings catalytic groups into proper orientation
The benefit of measuring the initial rate of a reaction V0 is that at the beginning of a reaction:	changes in [S] are negligible, so [S] can be treated as a constant
Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-Menten kinetics is false?	At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.
The steady state assumption, as applied to enzyme kinetics, implies:	the ES complex is formed and broken down at equivalent rates.
Which of these statements about enzyme-catalyzed reactions is false?	The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but the equilibrium constant is more favorable in the enzyme-catalyzed reaction.
For enzymes in which the slowest (rate-limiting) step is the reaction k2 ES > P	the dissociation constant, Kd, for the ES complex.
The Lineweaver-Burk plot is used to:	solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration
In competitive inhibition, an inhibitor:	binds reversibly at the active site.
Vmax for an enzyme-catalyzed reaction:	is twice the rate observed when the concentration of substrate is equal to the Km.
A transition-state analog:	resembles the transition-state structure of the normal enzyme-substrate complex
A small molecule that decreases the activity of an enzyme by binding to a site other than the catalytic site is termed a(n):	allosteric inhibitor
Allosteric enzymes:	usually have more than one polypeptide chain.
Define the terms “cofactor” and “coenzyme.”	A cofactor is any chemical component required for enzyme activity; it includes both organic molecules, called “coenzymes,” and inorganic ions
Native fold	protein molecules that adapt to a specific three dimensional conformation that is able to fulfil a specific biological function
Weak interactions that stabilize a proteins conformation	hydrophobic effect, hydrogen bonds, van der walls forces,electrostatic interactions
phi	angle around the alpha-carbon—amide nitrogen bond
psi	angle around the alpha-carbon—carbonyl carbon bond
Some phi and psi combinations are very unfavorable because of steric crowding of	backbone atoms with other atoms in the backbone or side chains
Some phi and psi combinations are more favorable because of	chance to form favorable interactions along the backbone
Ramachandran plot	the values of phi and psi for all the amino acid residues in the enzyme pyruvate kinase are overlaid on this plot of theoretically allowed conformations
beta turns	occur frequently whenever strands in beta sheets change the direction
Proline in position 2 or Glycine in position 3 are common in	beta turns
Protein primary structure is	the sequence of the amino acids
Secondary structures	alpha helices and beta sheets
Tertiary structures	refers to the overall spatial arrangement of atoms in a protein. Folding further into globular structures
Motifs	Specific arrangement of several secondary structure elements - All alpha-helix - All beta-sheet - Both
Motifs can be found as	reoccurring structures in numerous proteins
Domain	a part of a polypeptide chain that is independently stable or could undergo movements as a single entity with respect to the entire protein
In many cases, a domain retains	its native 3D- structure even when separated from the remainder of the polypeptide chain
Quaternary structures	Formed by the assembly of individual polypeptides (subunits) into a larger functional cluster . Held together by electrostatic subunits or salt bridges
Intrinsically Disordered Proteins	- Contain protein segments that lack definable structure - Composed of amino acids whose higher concentration forces less-defined structure
Proteostasis	Maintenance of cellular protein activity is accomplished by the coordination of many different pathways.
Proteins can be denatured by:	- heat or cold - pH extremes - organic solvents like urea - chaotropic agents
Myoglobin	has a single polypeptide that carries oxygen and CO2
Hemoglobin	is a multi-polypeptide protein that carries oxygen and CO2
Organometallic compounds such as heme are more suitable, but	Fe2+ (ferrous ion) in free heme could be oxidized to Fe3+ (ferric ion)
Protein side chains lace affinity for	O2
Hemoglobulin also differs from myo because hemo has	allosterisin
Heme : a prosthetic group	A metal ion or an organic compound that is covalently bound to a protein and is essential to its activity
O2 is a ligand,	a small compound that binds specifically to a target protein
Equilibrium constant for myoglobin	y= [Mb][O2]/Kd
Equilibrium constant when myoglobin is oxygenated	Y=pO2/pO2+kd
Hemoglobin consists of	two alpha chains and two beta chains. Each subunit has a heme prosthetic group that binds oxygen.
Allosteric protein	the activity of the binding site is affected by a different site in the protein
Binding curve for myoglobin	Y= pO2 / pO2+p50
Binding curve for hemoglobin (Hills equation)	Y= [pO2]^n / [pO2]^n + [p50]^n
How does Oxygen Affinity change?	- Must be a protein with multiple binding sites - Binding sites must be able to interact with each other. This phenomenon is called cooperativity
positive cooperativity	first binding event increases affinity at remaining sites - recognized by sigmoidal binding curves
negative cooperativity	first binding event reduces affinity at remaining sites
T : Tense state of hemoglobin	Lower affinity of O2
R: Relaxed state of hemoglobin	More flexible - Higher affinity for O2
Actively metabolizing tissues generate	protons (H+), lowering the pH of the blood near the tissues relative to the lung
Hb Affinity for oxygen depends on the pH:	H+ binds to Hb and stabilizes the T state, leading to the release of O2 (in the tissues)
The pH difference between the lung and metabolic tissue increases efficiency of the O2 transport. This is known as	the bohr effect
2,3-BPG allows for	O2 release in the tissues and adaptation to changes in altitude
Sickle Cell anemia mutation	Glu to Val substitution in the beta chain of Hb creates a “sticky” surface.Deoxyhemoglobin has a hydrophobic patch on its surface that makes molecules aggregate which sickles the cell
What determines the rates of chemical reactions?	- Concentration of Reactants - Temperature
Between the initial state and the final state of the reactants there is an	energy barrier. This is the energy required to bring the reactant(s) from its stable state into a new structural configuration
The activation energy is defined as	the energy difference between the reactants and the transition state
Enzymes increase	reaction rates by lowering the activation energy
Enzyme and substrate are	complementary. Enzymes are highly specific to their substrates
Two models proposed to describe the enzyme-substrate interaction	Lock and key method and induced fit
In terms of lock and key and induced fit, enzymes prefer	induced fit
Kinetics	the study of the rate at which compounds react
Rate of enzymatic reaction is affected by:	- enzyme - substrate - effectors - temperature
v =	velocity, the rate of product formation
v = k	reaction rate constant ( works in zero order reactions)
[A], [B] =	chemical concentrations of reactant(s)
V = k V = k[A] in	first order reactions
V = k[A][B] in	second order reactions
V0 Initial Velocity	V0=k2[ES]
A refinement of the Michaelis-Menten model was proposed by Haldane and Briggs (1925), by adding	the Steady-State Assumption : K -1[ES] + K 2[ES] = K 1[E][S]
Michaelis- Menton Equation or Ideal rate equation	V0= Vmax[S] / km + [S]
Irreversible inhibitors react with the enzyme to	: permanently shut off : powerful toxins (e.g., drugs)
Reversible inhibitors bind to/dissociate from the enzyme	: structural analogs of substrates or products : drugs to slow down a specific enzyme
There are several types of reversible (non-covalent) inhibitors:	Competitive inhibition , Uncompatitive and Mixed
Competitive inhibitors look like the substrate and binds to the active site, thereby	reducing the rate of the reaction. - Addition of excess substrate competes the inhibitor away and restores the rate. - With large excess of substrate over inhibitor it is possible to reach Vmax. Thus, the Km goes up, but the Vmax is unchanged.
There are several types of inhibitors that are not competitive. These inhibitors	bind at a site other than the active site, called “allosteric” inhibitors
Allosteric inhibitors are a common cellular mechanism to control	enzyme activity and biochemical pathways
Uncompetitive inhibitors bind only	to the enzyme-substrate complex (ES) and not to the free enzyme. : no effect on substrate binding : inhibiting catalytic function (decrease Vmax)
Mixed inhibitors bind	both to the enzyme and to the enzyme-substrate complex

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Biochem test 3