Compare blood initial filtrate and final urine
Use processing stage before interpreting a substance list.
Exam scope and assessment notes
Extended only (Supplement) · Biology 0970, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked; human subject-teacher review, supervised practical competence and cumulative assessment remain pending. Cambridge states that IGCSE 0970 has the same subject content as IGCSE 0610, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall cell metabolism, blood transport, amino acids and the distinction between excretion and egestion.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which stage comes before nephron reabsorption?
What you will learn
- A sequence has distinct fluids
- Avoid a stage substitution
Compare blood initial filtrate and final urine
A fluid’s processing stage matters. Shared water does not make blood, filtrate and urine identical; normal glucose return explains the stage difference. Original teaching model.
| Feature | Meaning |
|---|---|
| Blood | Supplies the glomerular vessel route |
| Initial filtrate | Water · glucose · urea · ions |
| Return step | Useful materials reabsorbed to blood |
| Urine | Urea · excess water · excess ions |
A sequence has distinct fluids
Blood, initial nephron filtrate and urine are distinct fluid categories in the kidney outline. Blood arrives through the vessel system. Filtration passes water, glucose, urea and ions into the nephron route while retaining the vessel route. Reabsorption returns specified useful materials from the nephron contents to blood before urine reaches the collection route.
The normal school-level outline includes glucose in the filtrate but returns all of that glucose to blood. Urine then contains urea and excess water and ions. A table with glucose in the initial filtrate is therefore not evidence that the same normal glucose amount must remain in urine, or that useful substances cannot be filtered.
Avoid a stage substitution
Blood normally includes cells and large proteins that are not part of the four-substance filtration list. A whole-blood sample and a nephron-fluid sample should not be identified only by a shared water or ion content: shared substances do not make two fluid categories identical. Use the stated location, stage and complete description.
A supplied table is a simplified teaching comparison, not a clinical test panel. Unexpected values in a fictional case can motivate questions about assumptions, but do not diagnose a person from one figure. The intended skill is to read the process stage accurately and distinguish filtration from selective return and the final excreted mixture.
Pause and explain
Which comparison fits the normal outline?
Worked example
Fluid X is initial filtrate and contains glucose; normal return then removes it from the tubule contents. Is X final urine?
Show the worked solution
- Its location is before reabsorption.
- The subsequent contents change.
Answer No; X is initial filtrate, before the stated normal glucose reabsorption.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →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.
Order blood, initial filtrate and final urine along the processing account.
Give me a hint
Identify supply, filtration product and processed output.
Compare my reasoning
- Blood supplies the glomerular route.
- Filtrate enters the nephron; processed contents form urine.
Blood supply → initial nephron filtrate → reabsorption and processing → final urine.
Look for these in your work
- Place the stages correctly
- Include the processing step
Why can both filtrate and blood contain water without being the same fluid category?
Give me a hint
A shared constituent does not define the full fluid.
Compare my reasoning
- The fluids occur at different locations and stages.
- Their complete contents and subsequent roles differ.
Shared water does not make them identical; blood and filtrate have different locations, contents and processing roles.
Look for these in your work
- Use stage and location
- Avoid a one-substance identity rule
A normal-outline table lists glucose in filtrate but not urine. Is that contradictory?
Give me a hint
Account for all-glucose reabsorption.
Compare my reasoning
- Glucose first enters the filtrate.
- It is returned to blood by reabsorption.
No. Glucose is filtered and then all filtered glucose is reabsorbed in the normal outline, so the two stage descriptions are consistent.
Look for these in your work
- Give both steps
- Retain the normal-outline condition
Common mistakes
- Identifying fluids from a single shared substance.
- Ignoring the processing stage.
What can you explain now?
Which comparison fits the normal outline?
Compare with the explanation
Glucose in initial filtrate; all filtered glucose returned before final urine
The processing step accounts for the difference.
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Make it stick
Compare the three fluid stages and explain the glucose difference.
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.