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1.4.6Inquiry Process

Eukaryotic Cell Structure — IB Biology HL Revision Notes & Topical Questions

5 min read 5 parts Lesson 7 of 160

📚 IB Biology HL Hub / Topical Revision
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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.
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Part 1 of 5Nucleus and Protein Production

Eukaryotic cells divide labour among membrane-bound compartments, so many reactions proceed at once without interfering.

Nucleus
  • Nucleus Surrounded by a double envelope with pores, it stores the chromosomes and is where transcription of genes takes place.
Nucleolus
  • Nucleolus A dense region inside the nucleus where ribosomal RNA is made and ribosome subunits are begun.
Rough ER
  • Rough ER Membrane sacs studded with 80S ribosomes that make proteins destined for secretion, membranes or lysosomes.
Golgi apparatus
  • Golgi apparatus A stack of flattened sacs that modifies, sorts and packages proteins into vesicles for delivery elsewhere.
Free ribosomes
  • Free ribosomes 80S ribosomes in the cytoplasm that make proteins which will work inside the cell itself.

Part 2 of 5Energy and Waste Handling

Energy and Waste Handling
Mitochondrion
  • Mitochondrion A double-membrane organelle whose folded inner membrane (cristae) is the site of aerobic respiration and ATP production.
Chloroplast
  • Chloroplast A double-membrane organelle containing thylakoids with chlorophyll that carries out photosynthesis in plant and algal cells.
Lysosome
  • Lysosome A single-membrane sac of digestive enzymes that breaks down worn organelles and material taken in by endocytosis.
Vacuole
  • Vacuole A fluid-filled sac that in plants is large, stores sap and keeps the cell firm through turgor pressure.
Smooth ER
  • Smooth ER Membrane tubes without ribosomes that make lipids and steroids and, in some cells, store calcium ions.

Part 3 of 5Support and Movement

1
The cytoskeleton of protein filaments and microtubules gives shape and anchors organelles inside the cytoplasm.
2
Microtubules form tracks along which vesicles move, driven by motor proteins using energy from ATP.
3
In animal cells a pair of centrioles organises the microtubules that make the spindle during division.
4
Plant cells add a cellulose cell wall outside the plasma membrane for strength and protection against bursting.
5
Some cells carry cilia or a flagellum, built from microtubules, to move themselves or fluid past their surface.
StructureAnimalPlant
Cell wallAbsentCellulose
ChloroplastsAbsentPresent in green cells
Large vacuoleAbsentPresent
CentriolesPresentAbsent in most

Part 4 of 5Worked Example

Question

  • A pancreatic cell secretes a digestive enzyme.
  • Describe the route of the enzyme from synthesis to release, naming each organelle used.

  1. The gene is transcribed in the nucleus and the mRNA leaves through a nuclear pore.
  2. Ribosomes on the rough ER translate the mRNA and the polypeptide enters the ER lumen.
  3. Vesicles carry the protein from the rough ER to the Golgi apparatus, where it is modified and packaged.
  4. A secretory vesicle leaves the Golgi, moves to the plasma membrane and fuses with it, releasing the enzyme by exocytosis.

Answer

  • Nucleus, then rough ER, then vesicle to Golgi apparatus, then secretory vesicle to the plasma membrane for exocytosis.
  • ATP from mitochondria powers the process.

Part 5 of 5Exam Checklist & Tips

1.4.6 – Key Points for the Exam

  • Eukaryote A cell with a nucleus and membrane-bound organelles.
  • Organelle A specialised structure within a cell with a particular function.
  • Cristae Folds of the inner mitochondrial membrane that increase surface area.
  • Cytoskeleton A network of protein fibres supporting the cell and moving contents.
  • 80S ribosome The larger ribosome of eukaryotic cytoplasm.

Common Mistakes

  • Stating that plant cells lack mitochondria; they have both mitochondria and chloroplasts.
  • Confusing the Golgi apparatus, which processes proteins, with the rough ER, which makes them.
  • Saying lysosomes are surrounded by a double membrane; they have one membrane.
  • Giving ribosomes as 70S in the eukaryotic cytoplasm; they are 80S.

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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.

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