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2dStructures and Functions in Living Organisms

Movement of substances into and out of cells — Edexcel Linear - OL Revision Notes & Topical Questions

5 min read 7 parts Lesson 4 of 25 1 quiz

📚 Edexcel Linear - OL Hub / Topical Revision
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Lesson summary

Movement of substances into and out of cells Edexcel O Level Linear Biology notes: understand the processes of diffusion, osmosis and active transport by which substances move into and out of cells understand how factors affect the rate of movement of substances into and out of c…

  • Movement of substances into and out of cells Edexcel O Level Linear Biology: what to do next
  • Passive transport
  • Concentration gradient
  • Sodium–potassium pump
  • Endocytosis
  • Exocytosis

Section 1 of 7Process & sequence

1
Pump binds 3 Na⁺ inside.
2
ATP phosphorylates pump; shape changes.
3
Na⁺ released outside; 2 K⁺ bind.
4
Phosphate released; K⁺ released inside.
1
Na⁺ gradient
2
Cotransporter
3
Glucose moved in against gradient

Section 2 of 7Keep going

Movement of substances into and out of cells Edexcel O Level Linear Biology: what to do next

These Movement of substances into and out of cells Edexcel O Level Linear Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Movement of substances into and out of cells Edexcel O Level Linear Biology understanding with the practice questions below, then reread any Movement of substances into and out of cells Edexcel O Level Linear Biology point you were unsure about before moving on.

1
Practice: Movement of substances into and out of cells Edexcel O Level Linear Biology practice questions
2
Previous lesson: 2c Biological molecules — Notes
3
Next lesson: 2e Nutrition — Notes
4
Course: Edexcel Linear - OL — all units
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Official syllabus: Pearson Edexcel International GCSEs

Movement of substances into and out of cells Edexcel O Level Linear Biology revision notes

Section 3 of 7Compare

Membrane transport mechanisms
MechanismEnergyGradientProteinsExampleType
Simple diffusionNoneDownNoneO₂Passive
Facilitated diffusionNoneDownChannels, carriersGlucose (GLUT)Passive
OsmosisNoneDown (water)AquaporinsWaterPassive
Primary activeATPUpPumpsNa⁺/K⁺ ATPaseActive
Secondary activeGradient from pumpUp for one soluteCotransporterNa⁺–glucose symportActive
Bulk transportATP—VesiclesPhagocytosisActive

Section 4 of 7Key terms

Section 5 of 7Syllabus checklist

Syllabus points
understand the processes of diffusion, osmosis and active transport by which substances move into and out of cells understand how factors affect the rate of movement of substances into and out of cells,
  • including the effects of surface area to volume ratio, distance, temperature and concentration gradient
practical: investigate diffusion and osmosis using living and non-living systems

Section 6 of 7Command 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.

Section 7 of 7Exam technique

Keywords the mark scheme looks for in this lesson

Keywords the mark scheme looks for in this lesson
Passive transport · Active transport · Concentration gradient · Sodium–potassium pump · Endocytosis · Exocytosis
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.

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Cambridge 9700 AS Biology Core Formula

Magnification Triangle & Unit Conversion

Formula: M = I / A  ⇔  A = I / M  ⇔  I = M × A

Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.