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function calculateEnzymeRate() {
var c1 = parseFloat(document.getElementById('initialConc').value);
var c2 = parseFloat(document.getElementById('finalConc').value);
var t1 = parseFloat(document.getElementById('initialTime').value);
var t2 = parseFloat(document.getElementById('finalTime').value);
var cUnit = document.getElementById('concUnit').value;
var tUnit = document.getElementById('timeUnit').value;
var resultBox = document.getElementById('resultBox');
var errorDisplay = document.getElementById('errorDisplay');
var finalRateDisplay = document.getElementById('finalRate');
var interpretationDisplay = document.getElementById('interpretation');
errorDisplay.style.display = "none";
// Validation
if (isNaN(c1) || isNaN(c2) || isNaN(t1) || isNaN(t2)) {
// Do not show error immediately on typing, only if logic fails or inputs are clearly wrong upon button press
// For live calc, we usually wait for valid inputs.
return;
}
if (t2 <= t1) {
errorDisplay.innerHTML = "End Time (t₂) must be greater than Start Time (t₁).";
errorDisplay.style.display = "block";
resultBox.style.display = "none";
return;
}
// Calculation: Rate = (Change in Conc) / (Change in Time)
var deltaC = c2 – c1;
var deltaT = t2 – t1;
var rate = deltaC / deltaT;
// Formatting
var absRate = Math.abs(rate);
var formattedRate = absRate 10000 ? absRate.toExponential(4) : absRate.toFixed(4);
resultBox.style.display = "block";
finalRateDisplay.innerHTML = formattedRate + " " + cUnit + "/" + tUnit;
// Interpretation logic
if (rate > 0) {
interpretationDisplay.innerHTML = "
The concentration is increasing, indicating product appearance.";
} else if (rate < 0) {
interpretationDisplay.innerHTML = "
The concentration is decreasing, indicating substrate depletion.";
} else {
interpretationDisplay.innerHTML = "
How to Calculate the Rate of Reaction of an Enzyme
Understanding enzyme kinetics is fundamental to biochemistry and pharmacology. The rate of an enzymatic reaction tells us how fast an enzyme converts a substrate into a product. This metric is crucial for determining enzyme efficiency, studying inhibition, and analyzing metabolic pathways.
This calculator helps you determine the average rate of reaction over a specific time interval by analyzing changes in concentration or absorbance.
The Enzyme Reaction Rate Formula
The rate of reaction is defined as the change in concentration of a reactant or product per unit of time. Mathematically, it is expressed as:
Rate = Δ[C] / Δt = ([C]₂ – [C]₁) / (t₂ – t₁)
Where:
- Δ[C]: The change in concentration (Final Concentration minus Initial Concentration).
- Δt: The time interval (Final Time minus Start Time).
- [C]₁: Concentration at the start of the measurement.
- [C]₂: Concentration at the end of the measurement.
Step-by-Step Calculation Guide
To manually calculate the rate of reaction from your experimental data, follow these steps:
1. Identify Your Variables
Determine whether you are measuring the disappearance of a substrate (concentration decreases) or the appearance of a product (concentration increases). Ensure your units are consistent (e.g., millimolar (mM) for concentration and seconds or minutes for time).
2. Determine the Change in Concentration
Subtract the initial concentration from the final concentration.
Example: If a reaction starts with 0 mM product and ends with 50 mM product, the change is 50 – 0 = 50 mM.
3. Determine the Time Interval
Subtract the start time from the end time.
Example: If the measurement started at 0 seconds and ended at 60 seconds, the time interval is 60 seconds.
4. Divide Concentration Change by Time
Using the example figures above:
Rate = 50 mM / 60 s = 0.8333 mM/s
Interpreting the Results
| Result Sign |
Meaning |
Typical Context |
| Positive (+) |
Concentration Increasing |
Measuring Product Appearance (P) |
| Negative (-) |
Concentration Decreasing |
Measuring Substrate Disappearance (S) |
| Zero (0) |
No Change |
Enzyme is inactive or reaction reached equilibrium |
Note: Reaction rates are often reported as absolute values (positive numbers) even when calculating substrate loss.
Initial Rate vs. Average Rate
The calculator above determines the average rate over the entered time period. However, in enzyme kinetics (Michaelis-Menten kinetics), scientists are often interested in the initial velocity (V₀).
To find the initial rate accurately, you should measure the slope of the concentration-vs-time graph at the very beginning of the reaction (the linear phase), before substrate depletion begins to slow the reaction down.
Factors Affecting Enzyme Rate
Several variables can influence the speed of your reaction:
- Substrate Concentration: Higher concentrations generally increase rate until the enzyme becomes saturated (Vmax).
- Temperature: Rates increase with temperature up to an optimal point, after which the enzyme denatures.
- pH Level: Enzymes have an optimal pH range; deviations can reduce activity.
- Inhibitors: Presence of competitive or non-competitive inhibitors will decrease the calculated rate.