WEEK 4 PART 2 Flashcards
(182 cards)
1
Q
What is the first learning outcome for the course?
A
To explain how enzymes are built and how they work (enzyme structure and function).
2
Q
What is the second learning outcome for the course?
A
To describe the ways enzymes speed up chemical reactions in the body (catalyze biochemical reactions).
3
Q
What is the third learning outcome for the course?
A
To describe key enzyme measurements and use the Michaelis-Menten formula to find Km, Vmax, and Kcat values.
4
Q
What does the Michaelis-Menten equation help determine?
A
It helps you calculate important enzyme measurements including binding strength (Km), maximum speed (Vmax), and turnover rate (Kcat).
5
Q
What is the fourth learning outcome for the course?
A
To describe how enzyme blockers work, their mechanisms, and how they help in creating new medicines.
6
Q
What is the fifth learning outcome for the course?
A
To measure how strong enzyme blockers are (Ki), find modified values of Km and Vmax, and understand the differences between 3 types of blocking reactions.
7
Q
What are enzyme inhibitors?
A
They are substances that slow down or stop enzyme activity by binding to the enzyme and preventing it from doing its job.
8
Q
How important is enzyme inhibition in medicine?
A
It’s one of the main strategies scientists use to develop new drugs to treat diseases.
9
Q
What are the two broad classes of enzyme inhibitors?
A
1) Reversible inhibitors (temporary binding) and 2) Irreversible inhibitors (permanent binding).
10
Q
What are the three types of reversible enzyme inhibitors?
A
1) Competitive (fights with substrate for the active site), 2) Noncompetitive (binds elsewhere), and 3) Uncompetitive (binds only to enzyme-substrate complex).
11
Q
How do reversible inhibitors interact with enzymes?
A
They form temporary connections that can easily break apart, like magnets sticking together.
12
Q
How do irreversible inhibitors interact with enzymes?
A
They form permanent chemical bonds with the enzyme, like super glue that can’t be removed.
13
Q
How are inhibitor types classified?
A
By watching how they affect enzyme speed (kinetics) and where they attach to the enzyme.
14
Q
What happens in competitive inhibition?
A
The blocker (I) only sticks to the free enzyme (E), not to the enzyme already holding substrate (ES).
15
Q
What happens in uncompetitive inhibition?
A
The blocker (I) only sticks to the enzyme when it’s already holding substrate (ES), not to the free enzyme.
16
Q
What happens in noncompetitive inhibition?
A
The blocker (I) can stick to both the free enzyme (E) and the enzyme already holding substrate (ES).
17
Q
Why is noncompetitive inhibition described as a special case of mixed inhibition?
A
Because it’s a specific situation where the inhibitor binds equally well to both E and ES, whereas mixed inhibition has different binding strengths.
18
Q
What is the most common type of reversible inhibition?
A
Competitive inhibition, where the blocker fights with the normal substrate for the same binding spot.
19
Q
Why do competitive inhibitors often look similar to the normal substrate?
A
Because they need to fit into the same pocket (active site) that the substrate normally uses.
20
Q
Does the enzyme perform any chemical reaction on a competitive inhibitor?
A
No, the enzyme doesn’t change the inhibitor - it just holds it in place, blocking the real substrate.
21
Q
What two factors determine how strong competitive inhibition is?
A
How tightly the blocker sticks (binding strength) and how much blocker is present (concentration).
22
Q
How does a competitive inhibitor block enzyme function?
A
It physically sits in the active site, preventing the substrate from entering and being processed.
23
Q
How can competitive inhibition be overcome?
A
By adding more substrate to outcompete the inhibitor, like adding more people to push someone out of line.
24
Q
What does Ki measure in enzyme inhibition?
A
Ki measures how strongly an inhibitor binds to an enzyme - like rating how sticky a glue is.
25
What does a low Ki value mean?
A low Ki means the inhibitor sticks very tightly to the enzyme, making it a strong blocker.
26
What does a high Ki value mean?
A high Ki means the inhibitor binds weakly to the enzyme, making it an ineffective blocker.
27
What are substrate and competitive inhibitor competing for?
They compete for binding to the free enzyme, like two people fighting for the same parking spot.
28
Is an ESI complex (enzyme-substrate-inhibitor) formed in competitive inhibition?
No, the enzyme cannot bind both the substrate and inhibitor at the same time in competitive inhibition.
29
When is competitive inhibition most noticeable?
When there's little substrate around (low concentration), the inhibitor has less competition.
30
Can competitive inhibition be overcome? How?
Yes, by flooding the system with lots of substrate, which increases the chance substrate will bind instead of inhibitor.
31
How does competitive inhibition affect the maximum reaction speed (Vmax)?
It doesn't change Vmax - with enough substrate, the reaction can still reach its top speed.
32
How does competitive inhibition affect the Michaelis constant (Km)?
It increases the apparent Km (also called Kmapp, Kmʹ, or aKm), meaning more substrate is needed to reach half-max speed.
33
What is the equation for calculating Ki?
Ki = [E][I]/[EI], which compares free enzyme and inhibitor concentrations to their complex concentration.
34
What formula shows enzyme reaction velocity with a competitive inhibitor?
V = (Vmax[S])/(aKm + [S]) where a = (1 + [I]/Ki), showing how substrate concentration affects reaction speed.
35
What does the factor 'a' represent in competitive inhibition equations?
The factor 'a' equals (1 + [I]/Ki) and shows how much the inhibitor increases the apparent Km.
36
Why are Ki values important in drug development?
They help scientists compare how effectively different drug candidates block target enzymes.
37
How are Ki values used in drug development?
They're used to rank potential drugs by their blocking power, like comparing different HIV protease inhibitors.
38
What makes a better enzyme inhibitor for drug development?
Lower Ki values make better inhibitors because they stick to the enzyme more tightly, requiring smaller drug doses.
39
How can you visually identify competitive inhibition on a Michaelis-Menten plot?
The curve shifts right with inhibitor present, keeping the same maximum height but requiring more substrate to reach it.
40
What's the basic Michaelis-Menten equation without any inhibitor?
V = (Vmax[S])/(Km + [S]), describing how reaction speed increases as you add more substrate.
41
What's the Michaelis-Menten equation with a competitive inhibitor added?
V = (Vmax[S])/(aKm + [S]) where a = (1 + [I]/Ki), showing how the inhibitor makes it harder for substrate to bind.
42
How is the apparent Km calculated when a competitive inhibitor is present?
Kmapp = Km(1 + [I]/Ki), showing that Km increases proportionally with inhibitor concentration.
43
In a Lineweaver-Burk plot, how can you tell if inhibition is competitive?
The lines intersect at the y-axis, showing the same Vmax but different Km values.
44
What does the Lineweaver-Burk plot transform the enzyme kinetics data into?
It transforms curved data into straight lines, making it easier to determine kinetic constants.
45
What's the basic Lineweaver-Burk equation without inhibition?
1/V = (Km/Vmax)(1/[S]) + 1/Vmax, turning the hyperbolic Michaelis-Menten curve into a straight line.
46
What's the Lineweaver-Burk equation with competitive inhibition?
1/V = (Km/Vmax)(1 + [I]/Ki)(1/[S]) + 1/Vmax, showing how the slope increases with inhibitor while y-intercept stays the same.
47
What does the slope in a Lineweaver-Burk plot represent?
The slope represents Km/Vmax, and with competitive inhibition it increases to (Km/Vmax)(1 + [I]/Ki).
48
What does the y-intercept in a Lineweaver-Burk plot represent?
The y-intercept equals 1/Vmax and stays constant with competitive inhibition because Vmax doesn't change.
49
What does the x-intercept in a Lineweaver-Burk plot represent?
The x-intercept equals -1/Km, and with competitive inhibition it shifts toward zero as Km increases.
50
What is a Dixon Plot?
A graph showing 1/reaction rate versus inhibitor concentration at different fixed substrate levels.
51
How do you create a Dixon Plot?
Run enzyme reactions with increasing inhibitor amounts at two or more fixed substrate concentrations, then plot 1/rate vs [I].
52
Why do scientists prefer Dixon Plots for determining Ki?
They provide an easy visual way to find Ki directly from where the lines cross on the graph.
53
How does a Dixon Plot distinguish between competitive and noncompetitive inhibition?
For competitive inhibition, lines cross above the x-axis; for noncompetitive, they cross at the x-axis.
54
How do you determine Ki from a Dixon Plot?
Ki equals the negative of the inhibitor concentration at the point where the lines intersect.
55
How is ethanol used to treat antifreeze poisoning?
Ethanol acts as a competitive blocker of alcohol dehydrogenase (ADH), preventing the conversion of toxic antifreeze to harmful byproducts.
56
Why does ethanol treatment allow ethylene glycol to be excreted safely?
By blocking ADH, ethanol prevents ethylene glycol (antifreeze) from being converted to toxic compounds, so it leaves the body unchanged.
57
What is alcohol dehydrogenase (ADH)?
An enzyme that breaks down alcohols in the body - it normally processes ethanol but can also process ethylene glycol into harmful substances.
58
What are statin drugs?
Medicines that lower cholesterol by blocking an enzyme involved in making cholesterol in the liver.
59
How do statins lower cholesterol levels?
They mimic the normal substrate for HMG-CoA reductase enzyme, blocking the first step of cholesterol production.
60
What is HMG-CoA reductase?
The key enzyme that controls the first committed step in making cholesterol in the body.
61
Why are statins described as 'structural analogs'?
They have a shape similar to the normal molecule the enzyme processes, like a key that fits but doesn't work.
62
What is noncompetitive inhibition?
A type of reversible inhibition where the blocker binds to both the free enzyme and the enzyme-substrate complex.
63
Where can a noncompetitive inhibitor bind?
It can bind both when the enzyme is empty (E) and when it's already holding the substrate (ES).
64
Can substrate and noncompetitive inhibitor bind to the enzyme at the same time?
Yes, they can bind simultaneously because they don't compete for the same spot on the enzyme.
65
Why can't increasing substrate concentration overcome noncompetitive inhibition?
Because the inhibitor doesn't compete with substrate for binding - it's like blocking a different door entirely.
66
What is an allosteric site?
A binding spot away from the active site that can change how the enzyme works when something attaches there.
67
What is a ternary complex?
When three components (enzyme, substrate, and inhibitor) all bind together simultaneously.
68
How does noncompetitive inhibition affect Km?
Km stays the same because the inhibitor doesn't interfere with how substrate binds to empty enzyme.
69
How does noncompetitive inhibition affect Vmax?
Vmax decreases to a new lower value called αVmax because the inhibitor reduces the enzyme's effectiveness.
70
Why does Vmax decrease in noncompetitive inhibition?
Because either the inhibitor is processed very slowly or some enzymes are always blocked, reducing overall capacity.
71
Why doesn't Km change with noncompetitive inhibitors?
Because these inhibitors don't affect how well substrate binds to free enzyme - they reduce activity after binding.
72
What's the Michaelis-Menten equation with a noncompetitive inhibitor?
V = (Vmax[S])/(aKm + a[S]) where a = (1 + [I]/Ki), showing reduced speed at all substrate concentrations.
73
How can you identify noncompetitive inhibition on a Lineweaver-Burk plot?
The lines intersect at the x-axis, showing the same Km but different Vmax values.
74
What does a Lineweaver-Burk plot's y-intercept tell you about noncompetitive inhibition?
The y-intercept equals (1+[I]/Ki)/Vmax, increasing with inhibitor concentration as Vmax decreases.
75
What does a Lineweaver-Burk plot's x-intercept tell you about noncompetitive inhibition?
The x-intercept stays constant at -1/Km.
76
What does a Lineweaver-Burk plot's x-intercept tell you about noncompetitive inhibition?
The x-intercept stays constant at -1/Km because Km doesn't change with noncompetitive inhibitors.
77
What's the Lineweaver-Burk equation with noncompetitive inhibition?
1/V = (1/Vmax)(1 + [I]/Ki) + (Km/Vmax)(1/[S]), showing both increased y-intercept and slope.
78
How is the factor (1 + [I]/Ki) reflected in a noncompetitive inhibition Lineweaver-Burk plot?
It multiplies both the slope and y-intercept, creating a family of lines that all cross at the x-axis.
79
How can you distinguish noncompetitive inhibition on a Dixon Plot?
The lines from different substrate concentrations intersect right at the x-axis.
80
How do you estimate Ki from a Dixon Plot for noncompetitive inhibition?
Ki equals the inhibitor concentration where the lines intersect at the x-axis.
81
What common substances act as noncompetitive enzyme inhibitors?
Heavy metals (lead, mercury), certain medicines like tranylcypromine, nifedipine, and proton pump inhibitors.
82
How do heavy metals inhibit enzymes noncompetitively?
They bind to sulfur-containing groups (-SH) in cysteine amino acids, breaking important bonds that hold the enzyme's shape.
83
What is tranylcypromine?
A drug that noncompetitively blocks CYP2C9 enzyme and is used as a monoamine oxidase (MAO) inhibitor.
84
How does nifedipine affect cytochrome P450?
It noncompetitively blocks the CYP2C9 enzyme, preventing it from processing other substances.
85
What are proton pump inhibitors and how do they work?
Drugs like omeprazole that noncompetitively block CYP3A4 enzyme while also reducing stomach acid production.
86
What is cytochrome P450?
A family of enzymes that break down drugs and other foreign substances in the body.
87
What is uncompetitive inhibition?
A rare type where the inhibitor only binds to the enzyme after the substrate has already attached.
88
How is the inhibitor binding site created in uncompetitive inhibition?
The substrate binding changes the enzyme shape, creating a new site where the inhibitor can attach.
89
What happens when substrate concentration increases in uncompetitive inhibition?
More substrate means more enzyme-substrate complexes, which leads to more inhibition.
90
Why is uncompetitive inhibition considered rare?
Because it requires a specific mechanism where the inhibitor can only recognize and bind to the enzyme-substrate complex.
91
What is the reaction sequence in uncompetitive inhibition?
First substrate binds (E+S→ES), then inhibitor binds to that complex (ES+I→ESI), preventing product formation.
92
How does uncompetitive inhibition affect Km and Vmax?
Both decrease by the same factor, so their ratio stays constant (maintaining the same reaction curve slope).
93
What do Lineweaver-Burk plots look like with uncompetitive inhibition?
They show parallel lines with different y-intercepts and x-intercepts - never intersecting.
94
What's the Michaelis-Menten equation with uncompetitive inhibitor?
V = (Vmax[S])/(Km + a[S]) where a = (1 + [I]/Ki), showing how both binding and maximum speed are affected.
95
What does Ki represent in uncompetitive inhibition?
Ki = [ES][I]/[ESI], measuring how strongly inhibitor binds to the enzyme-substrate complex.
96
What's the Lineweaver-Burk equation for uncompetitive inhibition?
1/V = (a/Vmax) + (Km/Vmax)(1/[S]), creating parallel lines with increasing y-intercepts as [I] increases.
97
How does competitive inhibition affect Km and Vmax?
Km increases (more substrate needed) while Vmax stays the same (can still reach full speed with enough substrate).
98
How does noncompetitive inhibition affect Km and Vmax?
Vmax decreases (lower maximum speed) while Km stays the same (binding affinity unchanged).
99
How does uncompetitive inhibition affect Km and Vmax?
Both Km and Vmax decrease proportionally, like turning down the overall enzyme system.
100
What are the two main classes of enzyme inhibitors?
Reversible inhibitors (temporary binding) and irreversible inhibitors (permanent binding).
101
What are the three types of reversible enzyme inhibition?
Competitive (fights for active site), noncompetitive (binds anywhere), and uncompetitive (binds only to ES complex).
102
How do reversible inhibitors attach to enzymes?
Through weak, temporary bonds like hydrogen bonds that can form and break easily.
103
How do irreversible inhibitors attach to enzymes?
Through strong, permanent chemical bonds or extremely tight associations that don't release.
104
What causes irreversible enzyme inhibition?
Destruction or permanent change of a crucial amino acid that the enzyme needs to work.
105
Why is irreversible inhibition permanent?
Because it forms unbreakable chemical bonds between the enzyme and inhibitor, like welding parts together.
106
What specific parts of enzymes do irreversible inhibitors target?
They target specific amino acids in the active site that are essential for the enzyme's function.
107
Why do irreversible inhibitors often look similar to the normal substrate?
So they can be recognized by the enzyme and fit into the active site before forming permanent bonds.
108
What types of chemical bonds form during irreversible inhibition?
Strong, permanent covalent bonds (shared electrons) or extremely tight non-covalent bonds form between enzyme and inhibitor.
109
What happens to the enzyme's active site in irreversible inhibition?
The substrate can no longer enter the active site because the inhibitor has permanently blocked or altered it.
110
Can an enzyme with irreversible inhibition still make products?
No, the enzyme is permanently disabled and can no longer convert substrate into products.
111
Can adding more substrate overcome irreversible inhibition?
No, because the inhibitor is permanently bound and won't come off even if substrate concentration increases.
112
Can techniques like dialysis or dilution reverse irreversible inhibition?
No, these techniques only remove loosely bound molecules - irreversible inhibitors remain permanently attached.
113
How does irreversible inhibition develop over time?
It happens gradually as more and more covalent bonds form between enzymes and inhibitors.
114
What kinetics pattern do irreversible inhibitors follow?
They follow the pattern of noncompetitive inhibitors, but the effect gets stronger over time.
115
Why does the inhibition strength (Ki) change with time for irreversible inhibitors?
Because more enzyme molecules become permanently inactivated as time passes.
116
What is a suicide inhibitor?
A special irreversible inhibitor that tricks the enzyme into chemically attaching it permanently to itself.
117
How does a suicide inhibitor work?
It starts like a normal substrate, but when the enzyme tries to process it, it forms a permanent bond instead.
118
What gives suicide inhibitors their targeting ability?
They specifically fit the active site of just one enzyme, like a key made for only one lock.
119
What makes a suicide inhibitor 'good' for drug development?
It only targets one specific enzyme and stays inactive until it reaches that target.
120
Why might drugs based on suicide inhibition cause fewer side effects?
Because they only affect their specific target enzyme rather than binding to many different proteins.
121
What common antibiotic is an example of a suicide inhibitor?
Penicillin, which permanently blocks the enzyme bacteria need to build their cell walls.
122
What specific enzyme does penicillin target?
Glycopeptide transpeptidase, the enzyme that creates cross-links in bacterial cell walls.
123
How does penicillin form a permanent bond with its target enzyme?
The serine amino acid in the enzyme's active site attacks penicillin's unstable ring structure, forming a permanent bond.
124
Why is penicillin described as causing enzyme 'suicide'?
Because the enzyme's normal mechanism for processing molecules is hijacked to create its own permanent inactivation.
125
What is glycopeptide transpeptidase?
The enzyme that connects fragments of bacterial cell wall together, creating a strong mesh-like structure.
126
What is a transition state in enzyme reactions?
The unstable, high-energy moment when bonds are being broken and formed during the reaction.
127
What does ΔG‡ represent in enzyme reactions?
The energy barrier (activation energy) that must be overcome for the reaction to proceed.
128
Why is the transition state important in enzyme reactions?
It's when the enzyme binds most tightly to the reacting molecules, stabilizing them as they transform.
129
What is a transition-state analogue?
A molecule designed to mimic the structure of the transition state, binding extremely tightly to the enzyme.
130
Can scientists directly observe or measure the transition state?
No, it exists for just a tiny fraction of a second and can't be directly observed or isolated.
131
How do scientists design transition-state analogues without seeing the transition state?
They predict the chemical structure based on knowledge of how the reaction works.
132
What types of bonds form between transition-state analogues and enzymes?
Many non-covalent bonds (like hydrogen bonds) form - more than with the normal substrate.
133
How strongly do transition-state analogues bind compared to normal substrates?
They bind much more strongly than normal substrates or products, often essentially irreversibly.
134
Can adding more substrate overcome transition-state analogue inhibition?
No, the transition-state analogue binds so tightly that substrate cannot displace it.
135
Why is the transition-state analogue concept useful in drug design?
It helps create extremely tight-binding inhibitors like HIV protease inhibitors that are hard to displace.
136
What is allosteric regulation of enzymes?
Control of enzyme activity by molecules that bind to sites away from where the substrate binds.
137
Where does an allosteric inhibitor attach?
To a special site away from the active site, like pushing a distant button to shut down a machine.
138
What types of chemical connections form during allosteric binding?
Temporary connections between molecules (non-covalent bonds) that can influence the enzyme's shape.
139
How does allosteric binding change the enzyme?
It changes the overall shape of the enzyme through a domino effect called induced fit.
140
How does this shape change affect how the enzyme works with substrates?
It changes how substrates can bind and be processed, like bending a key so it no longer fits the lock.
141
Can adding more substrate overcome allosteric inhibition?
No, because allosteric inhibitors don't compete with substrate - they affect the enzyme in a different way.
142
Do allosteric inhibitors look like the enzyme's normal substrates?
No, they usually have completely different structures because they bind to different parts of the enzyme.
143
What is an example of an allosteric inhibitor used as medicine?
6-mercaptopurine, which blocks purine synthesis and is used to treat leukemia.
144
Where in metabolic pathways are enzymes with allosteric sites often found?
At the beginning of multi-step pathways, where they can control the entire process.
145
Why do these regulatory enzymes need a separate binding site for the final product?
Because the final product has been transformed and no longer fits in the active site.
146
What is feedback control in enzyme systems?
When the final product of a pathway shuts down the first enzyme, like a thermostat turning off a heater.
147
How does feedback control regulate enzyme activity?
As final product builds up, more binds to the allosteric site, increasingly shutting down production.
148
How can scientists use feedback mechanisms to design enzyme inhibitors?
By creating drugs that mimic the final product's structure to bind to the regulatory site.
149
What is the most common way enzymes are modified to control their activity?
Through phosphorylation (adding phosphate) and dephosphorylation (removing phosphate).
150
What is phosphorylation in simple terms?
Adding a phosphate group (PO₄³⁻) to an enzyme, like turning on a switch.
151
How does phosphorylation affect enzyme behavior?
It acts like an on/off switch, changing how the enzyme works by altering its shape and function.
152
Where does the phosphate group come from during phosphorylation?
From ATP (adenosine triphosphate), the cell's energy molecule that donates a phosphate group.
153
What enzymes control phosphorylation?
Protein kinases - specialized enzymes that attach phosphate groups to other proteins.
154
What enzymes control dephosphorylation?
Protein phosphatases - specialized enzymes that remove phosphate groups from proteins.
155
Does a slower reaction have a higher or lower energy barrier?
A slower reaction has a higher energy barrier - it needs more energy to get started.
156
Is the Michaelis-Menten equation designed for one substrate or multiple substrates?
It's designed for reactions with just one substrate; more complex equations are needed for multiple substrates.
157
Does competitive inhibition create a three-way complex with enzyme and substrate?
No, a ternary complex doesn't form because inhibitor and substrate can't bind simultaneously.
158
What information does the y-intercept of a Lineweaver-Burk plot provide?
It tells you 1/Vmax - so the maximum reaction speed can be calculated from its inverse.
159
Which inhibition mechanism does a suicide inhibitor resemble kinetically?
Noncompetitive inhibition, with decreasing Vmax but unchanged Km.
160
What substrate concentration gives half the maximum reaction speed?
Km (the Michaelis constant) - it's the concentration where reaction runs at exactly half speed.
161
What type of molecular interactions define reversible enzyme inhibition?
Non-covalent interactions - temporary bonds like hydrogen bonds that can form and break easily.
162
Which type of inhibition can be defeated by adding more substrate?
Competitive inhibition - like winning a game of musical chairs by adding more of your team members.
163
What does Km measure about enzyme-substrate interaction?
It measures how strongly substrate binds to the enzyme - a lower Km means tighter binding.
164
Does a reaction with a higher activation energy run faster or slower?
Slower - higher activation energy creates a bigger energy barrier that's harder to overcome.
165
For how many substrates does the basic Michaelis-Menten equation work?
Just one substrate - the basic equation only describes single-substrate reactions.
166
Does competitive inhibition allow both inhibitor and substrate to bind simultaneously?
No - they compete for the same binding site, so only one can bind at a time.
167
What enzyme parameter does the y-intercept of a Lineweaver-Burk plot reveal?
Vmax - the maximum speed the enzyme can achieve (calculated from 1/Vmax).
168
Which inhibition type resembles suicide inhibition in its effects?
Noncompetitive inhibition - both reduce the amount of functional enzyme.
169
What substrate concentration equals the Km value?
The concentration where the enzyme works at exactly half its maximum speed.
170
What type of chemical bonds characterize reversible inhibition?
Weak, temporary bonds that can easily form and break without permanent changes.
171
Which inhibition type can be overcome by flooding the system with substrate?
Competitive inhibition - adding more substrate improves its chances of binding versus the inhibitor.
172
What does a low Km value tell you about an enzyme-substrate pair?
The enzyme has high affinity for the substrate - they bind together strongly even at low concentrations.
173
What is the Lineweaver-Burk equation without inhibitor?
1/V = (Km/Vmax) × (1/[S]) + (1/Vmax) - transforms curved enzyme kinetics into a straight line.
174
What is the Lineweaver-Burk equation with competitive inhibitor?
1/V = (Km/Vmax) × (1 + [I]/Ki) × (1/[S]) + (1/Vmax) - shows increased slope but unchanged y-intercept.
175
How do you calculate Ki for competitive inhibitor from slope changes?
Ki = [I]/((slope/slope₀) - 1) - compares the inhibited slope to the uninhibited slope.
176
What is the Lineweaver-Burk equation with non-competitive inhibitor?
1/V = (Km/Vmax) × (1 + [I]/Ki) × (1/[S]) + (1/Vmax)(1 + [I]/Ki) - shows both slope and y-intercept increase.
177
How do you calculate Ki for non-competitive inhibitor?
Ki = [I]/((1/(1/Vmax)) - 1) - uses the change in y-intercept to determine inhibitor strength.
178
What is the Lineweaver-Burk equation with un-competitive inhibitor?
1/V = (Km/Vmax) × (1/[S]) + (1/Vmax)(1 + [I]/Ki) - shows unchanged slope but increased y-intercept.
179
How do you calculate Ki for un-competitive inhibitor?
Ki = [I]/(([I]×Vmax) - 1) - uses the change in y-intercept to determine inhibitor strength.
180
What is neostigmine used for in medicine?
It treats muscle weakness in myasthenia gravis and reverses muscle-paralyzing drugs used during surgery.
181
What enzyme does neostigmine block?
Acetylcholinesterase - the enzyme that breaks down the neurotransmitter acetylcholine.
182
What happens when acetylcholinesterase is inhibited?
Acetylcholine builds up in nerve junctions, increasing nerve-to-muscle communication.
