Biology IA · C · Interaction and interdependence · topic 13 of 25

Does maltose slow amylase down? · IB Biology IA idea: guide, sample graph and step-by-step plan

a nice control puzzle in here :)

Products can fight back against the enzyme that made them. You're going to find out whether maltose slows down the amylase that produces it.

Difficulty●●○ Medium
KitWater bath, spotting tile or colorimeter, amylase, starch, maltose, iodine
TimeAbout 10 hours
FitsSL and HL (product inhibition links to HL end-product inhibition)
  • ✓ you like enzymes and rates
  • ✓ you can work carefully with timing
  • ✓ you want a control that makes you think

The big idea

← this is your RQ hook!

Amylase breaks starch into maltose and other short sugars. If a product binds the enzyme, it can compete with the substrate, so more maltose should mean slower breakdown. But dissolving a lot of any sugar also changes the solution. Your job: add maltose over a range, include a control sugar that is not a product, and measure the rate as 1/time. Clear independent variable, tricky controls, and a graph where the shape tells a story.

Make it yours: pick one twist

Copying a classic won't show your choices. Pick one of these (or invent your own) and your IA becomes yours.

Swipe for more twists →

Control sugar series

Repeat the series with a sugar that is not a product, at the same concentrations.

→ Two curves on one graph; the gap between them is the specific effect of maltose.
Colorimeter instead of eye

Measure the fading of the starch-iodine colour over time.

→ You get absorbance against time, so you can find an initial rate. Needs a calibration and a fixed wavelength.
Vary the starch concentration too

Repeat at two or three starch concentrations.

→ Tests whether maltose competes with starch. Your graph becomes a family of curves, so keep it to what you can finish.
Dixon-style graph

Plot 1/rate against maltose concentration instead of rate.

→ A different analysis of the same data; you interpret the gradient and intercept.
Different amylase source

Compare a fungal amylase with a bacterial one.

→ Adds a comparison across enzymes; both must be commercial preparations.
Change the context

Link to brewing, baking or the way digestion is regulated.

→ Gives your range a purpose; the experiment stays the same.

Your Biology IA research question: run the check

write it FIRST, then check it

Write your own question first. Then make sure it ticks every box:

  • Names the independent variable (added maltose) with its range in mol dm⁻³ and how many values.
  • Names the dependent variable (rate, from the time for starch to disappear) and what exactly counts as the end-point.
  • Says what stays fixed (amylase and starch concentration, volume, pH, temperature) and how each is checked.
  • Says how you will tell a specific maltose effect from a general effect of a sugary solution.
  • Is narrow enough for about 10 hours, with at least five concentrations and repeats.

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The set-up

One way to set it up with a spotting tile. Draw your own version, with your real volumes and temperature, for the Method section.

tube: amylase + starch +maltose (or control sugar)one iodine drop every 30 sstart the clock whenthe enzyme goes instop at orange-brownwater bath + thermometer

How your Biology IA could be laid out

The usual order for a topic like this, what each part needs to show, and roughly how much of your 3,000 words it takes. The words are all yours.

Research question and context~250
Your question, why enzyme regulation matters (brewing, digestion, food industry), and what you expect and why.
Background biology~450
How amylase works; what product inhibition and competitive inhibition mean; why rate is 1/time; what your graph should look like if your prediction holds (cite your source).
Variablestable
Independent, dependent and controlled variables, with how each is set, measured or kept constant, and why. Include the control sugar.
Method~450
How you made the maltose dilutions, the mixing order, the time and temperature, how you judged the end-point and how often, repeats; enough detail to copy.
Safety, ethics, environment~60
Specific to this method: enzyme powder you should not breathe in, iodine stains, hot water. No human saliva.
Raw datatable
One clear table: maltose concentration, each time, units and uncertainties in the headers, and notes on colour.
Processing~250
Converting time to rate, the mean and spread of repeats, uncertainty of the rate, and one worked example of each calculation.
Graphs and analysis~350
The graph you choose and why, error bars (say SD or range), a fit justified by the data; Spearman's rank for the trend or ANOVA across concentrations, and a t-test of maltose against the control sugar at the same concentration, with conditions checked.
Conclusion~400
Answer the question with numbers and uncertainties, link to the biology, compare with published findings and state limits.
Evaluation~600, the biggest part!
Weaknesses ranked by effect on your result (end-point judgement, temperature drift), and improvements linked to each.
Referencesnot counted
Every source for the biology and the method.

What your Biology IA graph could look like

error bars on EVERY point ✓

Made-up data, to show you the form of a strong graph, not the answer. The real effect may be strong, weak or absent. Let your data say. example only

0.00.10.20.30.40.50.00.10.20.30.40.50.60.7Added maltose / mol dm⁻³ (± 0.01)Rate = 1 / time / min⁻¹ (mean ± SD)falling curveno effect (flat)your data (mean of repeats), with SDflat line or falling curve?compare the gap with your error barsILLUSTRATIVE · MADE-UP DATA
  • The y-axis is a rate (1/time), so a bigger number means faster. Say that clearly in the text.
  • Error bars on every point, from your repeats. Show how many repeats there are and whether the bars are SD or range.
  • A flat line is drawn too. A strong conclusion says whether the data leave the flat line by more than the error bars, not just that they slope.
  • The control-sugar series would go on the same axes, so the reader sees whether maltose differs from a sugar that is not a product.
  • Another graph to consider: plot 1 / rate against maltose concentration. For a simple inhibitor at one substrate concentration this can give a straight line, and its gradient and intercept can be interpreted.

Which uncertainty matters most?

rank them: don't just list them

Rank by the effect on your result (the rate at 0 mol dm⁻³, assuming a time of 120 s), not on raw readings. A spotting tile every 30 s is a coarse clock. A colorimeter with a reading every 10 s would shrink the biggest bar.

End-point judged every 30 s (±15 s of 120 s)12.5%Start time on mixing (±2 s of 120 s)1.7%Dilution: 1 cm³ syringe (±0.02 cm³ in 2.0 cm³)1%biggest effect: discuss this first!% uncertainty in the rateILLUSTRATIVE · MADE-UP NUMBERS

Your game plan

don't skip the trial run! it saves you weeks

Tick steps off as you go. We'll remember on this device.

0 of 10 done

  1. Read and predictFind out what product inhibition is and whether it has been reported for amylase. Write down your prediction before you start.
  2. Choose your amylase and conditionsUse a commercial fungal or bacterial amylase. Check the supplier's data for a suitable pH and temperature, and decide your starch concentration.
  3. Trial run (1 lesson)Run starch and amylase with no maltose. Does it finish in a sensible time? Can you judge the end-point the same way twice? Does a very high maltose concentration change the time at all? Fix the problems now.
  4. Decide range, repeats and controlChoose at least five maltose concentrations, how many repeats at each, and the control sugar and its concentrations. Write down why for each choice.
  5. Prepare solutionsPlan the dilutions so every tube ends up with the same total volume and the same enzyme and starch concentration. Record each volume.
  6. Collect the dataRecord raw times straight into your table. Randomise the order of concentrations. Note colour judgements as they happen.
  7. ProcessConvert times to rates with uncertainties, and calculate means and spread for each concentration.
  8. Graph and fitPlot with error bars, then decide what fit or comparison is justified. Compare maltose with the control sugar at each concentration.
  9. EvaluateWhich weakness mattered most? Use your own error bars to rank them. Make every improvement specific to a weakness you found.
  10. Write, then checkWrite in the order of the layout. Run the checklist below before your teacher's draft.

Biology you'll need

Traps to avoid in this Biology IA

  • No control sugar: a thick, sugary solution can change the result without maltose doing anything special.
  • Making dilutions that change the total volume, so enzyme and starch are diluted differently in each tube.
  • Judging the end-point by colour at different stages each time, or testing drops at long intervals so the end-point is coarse.
  • Adding enzyme before the tubes reach temperature, so the first minutes run cooler.
  • Reading rate as 'time goes up, so the enzyme is better'. Time and rate move opposite ways.
  • Using human saliva, which is variable and not allowed here. Use a commercial amylase.
  • Averaging repeats with no spread shown, or testing whether a trend is real with no uncertainty at all.

More Biology IA ideas like this

Make sure it's yours

This guide shows how a topic like this is usually approached. It is not an IA. Your question, choices, data, analysis and words must be your own: change something, tell your teacher where the idea came from, and follow your school's rules on outside help.

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