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IGCSE · Cambridge (CIE) · 0973

Interpret high and low glucose feedback records

Measure departure from a supplied model reference without inventing a clinical dose.

Homeostasis · Cambridge IGCSE 0973 · B13.3
Exam scope and assessment notes

Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.

Before you begin

  • Recall hormone production and blood transport, respiration, liver storage and electrical impulses along neurones.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

What are the departure magnitudes at 10 minutes?

What you will learn

  • Compare departures at matched times
  • Calculate changes using separate baselines

Interpret high and low glucose feedback records

Invented reference 5 model units: high 7→6→5; low 3→4→5 at 0, 10 and 20 minutes. Both departures shrink 2→1→0. Original teaching model.

Invented glucose records — reference 5 model units
Time / minHigh start / model unitsLow start / model units
0 min73
10 min64
20 min55
Homeostasis model reference
FeatureMeaning
High change2-unit decrease; 28.6%
Low change2-unit increase; 66.7%
Matched departure2, 1, 0 model units
LimitsNot a clinical threshold, dosing rule or sole-cause proof

Compare departures at matched times

The invented teaching record uses reference 5 model units. At 0, 10 and 20 minutes the high-start concentration is 7, 6 and 5, while the low-start concentration is 3, 4 and 5. Both start two units away from the reference, move to one unit away and finish at the reference in this simplified model. One concentration decreases and the other increases, yet both patterns show correction.

The high-start absolute decrease is 7 − 5 = 2 model units. Its percentage decrease is 2/7 × 100, approximately 28.6% to one decimal place. The low-start absolute increase is 5 − 3 = 2 model units, but its percentage increase is 2/3 × 100, approximately 66.7%. Equal absolute changes do not establish equal percentages because the baselines differ.

Calculate changes using separate baselines

The high branch is consistent with insulin promoting liver glucose storage, and the low branch with glucagon promoting liver glycogen breakdown and glucose release. The record illustrates those taught directions. Without direct hormone measurements and controls, a concentration table alone would not prove a unique hormonal cause for each change in an actual organism.

Use model units exactly as supplied. The reference is not a diagnosis boundary and the table contains no dose-response relationship, so it cannot prescribe an insulin dose. At a later reading still one unit from the reference, describe partial correction rather than claiming full return. A data answer should combine accurate calculation with a properly limited biological interpretation.

Sources for this lesson

Pause and explain

Which percentage pair is correct?

Put the idea to work

Worked example

Compare the two complete changes.

Show the worked solution
  1. High: decrease 2 units; 2/7 × 100 ≈ 28.6%.
  2. Low: increase 2 units; 2/3 × 100 ≈ 66.7%.

Answer Equal 2-unit changes towards reference 5; high decreases 28.6% and low increases 66.7% because the baselines differ.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

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From guided practice to a new situation

Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.

1 · Guided

Find departure magnitudes at 0, 10 and 20 minutes for both displayed records.

Give me a hint

Measure distance from reference 5.

Compare my reasoning
  1. At 0: both are two units away.
  2. At 10: one unit; at 20: zero units.

Both records have departure magnitudes 2, 1 and 0 model units at 0, 10 and 20 minutes.

Look for these in your work

  • Use distance from reference
  • Compare matched times
2 · Independent

Calculate percentage changes from 7→5 and 3→5, to one decimal place.

Give me a hint

Use each starting value as denominator.

Compare my reasoning
  1. High decrease: 2/7 × 100 ≈ 28.6%.
  2. Low increase: 2/3 × 100 ≈ 66.7%.

High: 28.6% decrease. Low: 66.7% increase.

Look for these in your work

  • Use separate baselines
  • Retain directions and rounding
3 · Transfer

What additional claims are not justified by this concentration-only model?

Give me a hint

Consider direct causal evidence and personal treatment.

Compare my reasoning
  1. No measured hormone concentration or sole-cause control is supplied.
  2. No clinical dosing relationship or personal care plan is supplied.

The model does not prove a sole hormonal cause and does not supply a personal insulin dose. It illustrates corrective concentration directions.

Look for these in your work

  • Limit causal inference
  • Keep educational data separate from treatment

Common mistakes

  • Using the reference instead of the baseline for percentage change.
  • Claiming the table proves sole hormonal causation.
Recall without your notes

What can you explain now?

Which percentage pair is correct?

Compare with the explanation

High decrease 28.6%; low increase 66.7%

Each uses its own starting value.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Calculate both changes and evaluate what the invented feedback record supports.

If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.

Keep learning Sciences — Co-ordinated (9-1)

Course scope and assessment

This 9–1 pathway maps all 152 detailed subject-content sections in the published 0973 syllabus for exams in 2028 and 2029. The course map follows the same 2028–2029 section codes as Cambridge's A*–G 0654 syllabus, while keeping 0973's grading and entry rules separate. It adapts lessons from the related single-science courses and excludes clear single-science-only topics. A 0973-specific objective-by-objective review, Core/Supplement audit, human subject-teacher review, supervised laboratory experience and cumulative assessment remain in progress. Written practice is self-checked and does not predict an official grade. The separate 2025–2027 syllabus has not been reconciled here. Cambridge lists 0973 only in a limited number of administrative zones: June in zone 3 and centres in Oman and the UAE; November in zone 3 only. Confirm entry with your centre.

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