Questions tagged [enzyme-kinetics]

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54 views

How to find the reaction rate in an enzyme reaction?

First time posting questions here, so let me know if I need to edit anything. I need to decide $dC/dt$ and $dP/dt$ when the reaction is like this, where I only know we must have 2 substrates $S$ to ...
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2answers
64 views

Determine vmax and enzyme concentration (Michaelis–Menten)

I am given that the enzyme concentration is $\pu{15 nM}$ and the following data: $$ \begin{array}{rl} \hline S/\pu{mM} & V/\pu{mM s^{-1}} \\ \hline 1 & 0.202 \\ 2 & 0.368 \\ 5 & 0....
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Why does allosteric binding produce a sigmoidal curve?

Allosteric binding is where the enzyme can be regulated through having ligands bind onto somewhere that is not the active site. This will then induce a conformational change on the active site, hence ...
7
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3answers
328 views

Why use Km in catalytic efficiency?

The catalytic efficiency of an enzyme is given by $k_{cat}/k_M$ where $k_{cat}$ is the turnover number, or the number of molecules that can be produced per second per active site of an enzyme. $K_{M}$ ...
5
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1answer
86 views

How do enzymes affect a reaction's equilibrium?

I am not sure to understand something I read in a educational journal (1) Introduction Lets consider the following reversible enzyme-catalysed reversible reaction; $$E + S \leftrightharpoons ES \...
3
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1answer
81 views

Why a catalyst is not consumed in a reaction when all steps are reversible?

It is said that a catalyst speeds up the rate of a reaction but is not consumed (assuming no side reactions take place). Suppose we have the following reaction: $$\ce{A + B <=> C} $$ catalysed ...
-1
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1answer
20 views

Could shear force from blending denature alpha amylase / glucoamylase enzymes?

I am trying to break down the starches in a certain variety of oats in the most efficient way possible. I have to break the whole oats down after cooking, so they are finer particles for the amylases ...
2
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0answers
42 views

Solving for Concentration Using pseudo-First Order Kinetics

The following graphs represent a pseudo-first order bi-molecular reversible reaction with the formula $\ce{A + B <=> C}$: The reaction product has an extinction coefficient of $\pu{50000 M-1 cm-...
0
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1answer
40 views

Question on notation

Here, when they write $v/(\mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-1}})$ is $0.30$ for the first row first column, do they mean that the value is $0.30\ \mathrm{mol\ s^{-1}\ (kg\ \text{protein})^{-...
7
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1answer
89 views

How can subtilisin still function without its catalytic triad?

I read chapter 9 in the book Biochemistry (5th edition), by Berg, Tymoczko, and Stryer (provided in the NCBI site here). It describes the mechanism of action of the chymotrypsin enzyme. The catalysis ...
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0answers
19 views

Given the pH optimum of Angiotensin 1, how do I determine its charge?

I'm given the following information I'm then asked to determine the charge of the substrate Angiotensin 1 at the pH-optimum. I have found the pH-optimum to be 6.9. How do I go about answering this ...
0
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1answer
195 views

How can some enzymes work faster than the diffusion rates of the reactants allow?

Quoting Wikipedia: "Some enzymes operate with kinetics which are faster than diffusion rates, which would seem to be impossible." Which are those enzymes and how can they be so fast? One example is ...
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3answers
120 views

Temperature dependence of reaction rates

Is it correct to say that "Increasing the temperature will always increase the rate of any chemical reaction"? Many articles on the internet and textbooks say yes but what about biochemical reactions ...
2
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1answer
73 views

Michaelis menten constant motivation behind 1/2?

So the michaelis constant is defined as the substrate concentration at half maximal „reaction-speed“. I was wondering why 1/2 ? I guess for higher values you need more substrate, which could be a ...
5
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1answer
518 views

Hill equation with inhibition and activation

The Hill equation for an activating enzymatic interaction with cooperative multiplicity $n$ is $$\frac{\mathrm d[\ce{P}]}{\mathrm dt} = V_\mathrm{max}\frac{[\ce{S}]^n}{K_\ce{S} + [\ce{S}]^n}\tag{1}$$ ...
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2answers
177 views

Enzyme Kinetics - Given Km find substrate concentration at a certain velocity

From what I understand about the Michaelis Menten Model Km defines the amount of substrate required to reach half-saturation. 1/2 Vmax corresponds to Km on the x axis Generic formula is v = Kcat [...
4
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2answers
91 views

Measuring a high Michaelis constant using fluorescence

We have the task of measuring kinetic parameters of an oxidase reaction that has a $K_M$ of about $2 \,\text{mM}$. For that, we want to use a fluorescence assay based on Amplex Red. The latter is a ...
0
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1answer
65 views

Inactivation of enzyme: Why inactivation constants do not follow the Arrhenius equation? [closed]

The Arrhenius equation may not account for the temperature effect on thermal inactivation rate constants. Why can the thermal inactivation kinetics not be expected to follow Arrhenius? The reason that ...
2
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1answer
187 views

High concentration of ferric ion catalyst decreases rate of decomposition of hydrogen peroxide in the Fenton reaction

I did a project on the Fenton reaction and rate of decomposition of $\ce{H2O2}$. I used colorimetry to measure the rate of decolourisation of methylene blue when I mixed $\pu{5e-6 mol}$ $\ce{FeCl3}$ ...
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1answer
227 views

Why enzyme-catalyzed reactions mostly go one way?

I listened to the lecture about enzymes. Professor downplayed the question in the subject. He said that enzymes are able to work both ways, but practically speaking reactions with overwhelming ...
1
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1answer
55 views

How to calculate the kinetic order of an enzymatic reaction?

This question is concerning the metabolism of ethanol by an alcohol dehydrogenase enzyme. Usually people metabolize alcohol equivalent to "one beer per hour". One beer is said to contain 33cL. The ...
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1answer
74 views

Are enzymes with superior catalytic properties more sensitive to temperature changes?

I am wondering whether enzymes with superior catalytic properties are more or less temperature sensitive than average enzymes. I know that enzymes lower the activation energy, Ea. So the more ...
1
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1answer
52 views

Enzyme Kinetics two enzymes in complex with one substrate

Given an enzyme reaction where two enzymes are required to form the complex, for example $\ce{2E +S-> E3S->2E +P}$, how would I calculate complex concentration assuming steady state ...
3
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1answer
102 views

Lowest Michaelis constant Km

I want to find a lower limit of the Michaelis constant for some evaluations of Michaelis-Menten enzyme kinetics. What is the lowest $K_m$ you ever encountered? Is there a theoretical limit?
3
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1answer
92 views

Michaelis-Menten rate law for enzyme which catalyzes two reactions: steady state?

Suppose an enzyme $\ce{E}$ can catalyze two reactions: \begin{align} \ce{S1 + E &<=> S1E -> P1 + E} \tag{R1} \\ \ce{S2 + E &<=> S2E -> P2 + E} \tag{R2} \end{align} I want ...
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63 views

Equations Used in Isothermal Titration Calorimetry

I have been attempting to understand and derive the formulas used for ITC which can be found here starting on page 310. I am particularly interested in the single set of identical sites. To first ...