2iStructures and Functions in Living Organisms
Excretion — Edexcel Linear - OL Revision Notes & Topical Questions
5 min read 7 parts Lesson 9 of 25 1 quiz
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Lesson summary
Excretion Edexcel O Level Linear Biology notes: understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf HumansDiabetes type 1no insulin; type 2: insulin resistance.Negative feedback returns values to the set poi…
- Excretion Edexcel O Level Linear Biology: what to do next
- Homeostasis
- Give / State / Name
- Evaluate / Assess
- Keywords the mark scheme looks for in this lesson
- How to get full marks (examiner guidance)
Part 1 of 6Key ideas
Key ideas
Diabetes type 1
Diabetes type 1 no insulin; type 2: insulin resistance.
Negative feedback returns values to the set point.
Part 2 of 6Syllabus points
1
understand the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf Humans
2
know the excretory products of the lungs, kidneys and skin (organs of excretion)
3
2.72B understand how the kidney carries out its roles of excretion and osmoregulation
4
2.73B describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra
5
2.74B describe the structure of a nephron, including the Bowman's capsule and glomerulus, convoluted tubules, loop of Henle and collecting duct
6
2.75B describe ultrafiltration in the Bowman's capsule and the composition of the glomerular filtrate
7
2.76B understand how water is reabsorbed into the blood from the collecting duct
8
2.77B understand why selective reabsorption of glucose occurs at the proximal convoluted tubule
9
2.78B describe the role of ADH in regulating the water content of the blood
10
2.79B understand that urine contains water, urea and ions
Part 3 of 6Process & sequence
1
Blood enters glomerulus
2
Ultrafiltration
3
Selective reabsorption (glucose)
4
Water reabsorbed (ADH)
5
Urine to bladder
Excretory organs
Kidneys – urea, water
Lungs – CO₂
Skin – sweat
Liver – bile pigments
Part 4 of 6Summary
Summary
Insulin lowers blood glucose.
The kidney unit is the nephron.
Part 5 of 6Keep going
Excretion Edexcel O Level Linear Biology: what to do next
These Excretion Edexcel O Level Linear Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Excretion Edexcel O Level Linear Biology understanding with the practice questions below, then reread any Excretion Edexcel O Level Linear Biology point you were unsure about before moving on.
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Previous lesson: 2h Transport — Notes
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Next lesson: 2j Co-ordination and response — Notes
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Course: Edexcel Linear - OL — all units
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Official syllabus: Pearson Edexcel International GCSEs
Part 6 of 6Compare: Compare
| Variable | Receptor | Control centre | Effector | Hormone / nerve | Response |
|---|---|---|---|---|---|
| Blood glucose (high) | Pancreas | Pancreas | Liver, muscles | Insulin | Glucose → glycogen |
| Blood glucose (low) | Pancreas | Pancreas | Liver | Glucagon | Glycogen → glucose |
| Body temperature (high) | Thermoreceptors | Hypothalamus | Sweat glands, vessels | Nerves | Sweating, vasodilation |
| Body temperature (low) | Thermoreceptors | Hypothalamus | Muscles, vessels | Nerves | Shivering, vasoconstriction |
| Water (low) | Osmoreceptors | Hypothalamus | Kidney collecting duct | ADH | More water reabsorbed |
Key terms
Command terms
Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.
Exam technique
Keywords the mark scheme looks for in this lesson
Keywords the mark scheme looks for in this lesson
Homeostasis · Negative feedback · Excretion · Nephron · Urea · ADH · Insulin · Glucagon
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.
How to get full marks (examiner guidance)
How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. eukaryotic/prokaryotic, enzyme–substrate complex, active site, complementary).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.
Marked practiceQuizzes for this lesson
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