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1.3.9Additional lessons

Cell Types and Structures- Skills — IB Biology SL Revision Notes & Topical Questions

5 min read 5 parts Lesson 3 of 142

📚 IB Biology SL 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 5A Systematic Approach

1
Decide whether the cell is prokaryotic or eukaryotic by looking for a nucleus enclosed by a nuclear envelope.
2
If it is eukaryotic, look for a cell wall, large vacuole or chloroplasts to decide whether it is a plant cell.
3
Identify the organelles that are present and note which are especially numerous in the cell.
4
Link each abundant organelle to its function, for example many mitochondria point to a high demand for ATP.
5
State your conclusion about what the cell does, using the evidence from the image.

Part 2 of 5Recognising Organelles

Nucleus
  • Nucleus Roughly spherical, surrounded by a nuclear envelope, and contains a darker region called the nucleolus.
Mitochondrion
  • Mitochondrion An oval structure with a double membrane, often showing folds of the inner membrane called cristae.
Chloroplast
  • Chloroplast A larger oval structure with a double membrane and stacks of thylakoids, which shows that the cell belongs to a plant.
Vacuole
  • Vacuole A large space that often looks pale in an electron micrograph and suggests a plant cell.
Cell wall
  • Cell wall A layer lying outside the plasma membrane around the edge of the cell, found in plants and prokaryotes.

Part 3 of 5Other Structures to Know

Other Structures to Know
Nucleoid
  • Nucleoid The region containing the DNA of a prokaryotic cell, which is not surrounded by a membrane.
Ribosomes
  • Ribosomes Tiny dark dots free in the cytoplasm or attached to rough endoplasmic reticulum.
Golgi apparatus
  • Golgi apparatus A stack of flattened membrane sacs that modify and package proteins into vesicles.
Microvilli
  • Microvilli Tiny finger-like projections of the plasma membrane that increase surface area for absorption.
ObservationDeduction
Many mitochondriaThe cell needs a lot of ATP, for example for active transport
Many lysosomesThe cell digests material, such as a phagocytic white blood cell
Microvilli on one surfaceThe cell absorbs substances, as in the lining of the small intestine
Chloroplasts and cell wallThe cell is from a plant and carries out photosynthesis

Part 4 of 5Worked Interpretations

Worked Interpretations
Cell with nucleus, no wall
  • Cell with nucleus, no wall It is a eukaryotic animal cell, since plant cells have a cell wall and a large vacuole.
Large irregular nucleus
  • Large irregular nucleus The shape can allow the cell to squeeze through small gaps, as in some white blood cells.
Many lysosomes
  • Many lysosomes The cell digests substances that it takes in, which fits a macrophage.
Brush border
  • Brush border Dense microvilli greatly increase surface area, which fits an absorptive cell of the small intestine.

Part 5 of 5Exam Checklist & Tips

1.3.9 – Key Points for the Exam

  • Micrograph An image of a specimen taken through a microscope.
  • Nucleolus A dense region inside the nucleus where ribosomal RNA is made.
  • Cristae Folds of the inner mitochondrial membrane.
  • Microvilli Small projections of the cell surface that increase surface area.
  • Ultrastructure The fine detail of a cell that is visible only with an electron microscope.

Common Mistakes

  • Calling a cell plant simply because it has a cell wall;
    • prokaryotes also have walls, so check for a nucleus first.
  • Naming an organelle without stating the function or why the cell needs it.
  • Confusing a chloroplast with a mitochondrion; the chloroplast is larger and has thylakoid stacks.
  • Saying a cell has no nucleus when it was simply not cut through in the section.

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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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