4.1.1Unit 4: Energy, Environment, Microbiology and Immunity
Plant Cell Structure — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 3 parts Lesson 8 of 28 Unit 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.
Part 1 of 4Wall and Connections
The wall and the links between neighbouring plant cells give plants their support and communication routes.
Cell wall
- Cell wall Built of cellulose outside the cell membrane, it is rigid, freely permeable, and gives the cell its regular shape and support.
Middle lamella
- Middle lamella The outermost layer, made mainly of pectin, which acts like glue to stick adjacent plant cells together.
Plasmodesmata
- Plasmodesmata Narrow cytoplasmic threads lined by membrane that pass through walls and link neighbouring cells into one connected system, the symplast.
Pits
- Pits Thin regions of wall lacking secondary thickening, found in matching pairs,
- which allow substances to pass sideways between cells such as xylem vessels.
Part 2 of 4Plant Organelles
Several organelles are characteristic of plant cells.
Plant Organelles
Chloroplast
- Chloroplast A double-membrane organelle larger than a mitochondrion, with stacks of thylakoids called grana, and the site of photosynthesis.
Chloroplast contents
- Chloroplast contents The stroma contains small circular DNA and ribosomes,
- which are used to make proteins for chloroplast replication and photosynthesis.
Amyloplast
- Amyloplast A small membrane-bound organelle packed with starch granules, abundant in storage organs such as potato tubers.
Vacuole and tonoplast
- Vacuole and tonoplast A large permanent sac of cell sap bounded by the selectively permeable tonoplast, which keeps the cell turgid.
Part 3 of 4Function Summary
Link each structure to the job it does.
1
Cellulose in the wall resists the pressure of water entering the cell, preventing bursting and keeping the plant upright.
2
Plasmodesmata allow transport of substances and cell-to-cell communication without the materials crossing a membrane twice.
3
Chlorophyll in thylakoid membranes captures light, while the stroma carries out the later stages of photosynthesis.
4
Amyloplasts store starch and release glucose when the plant needs it for respiration.
5
The vacuole keeps cells turgid and also stores pigments and waste, and can break down unwanted chemicals.
Part 4 of 4Exam Checklist & Tips
4.1.1 – Key Points for the Exam
- Cell wall A rigid layer of cellulose outside the plasma membrane that supports a plant cell.
- Middle lamella A pectin-rich layer cementing adjacent plant cells together.
- Plasmodesmata Cytoplasmic channels linking the cytoplasm of neighbouring plant cells.
- Tonoplast The membrane surrounding the permanent vacuole.
- Amyloplast An organelle that stores starch in plant cells.
Common Mistakes
- Saying the cell wall is the same as the cell membrane;
- the wall is outside the membrane and is freely permeable.
- Stating that plasmodesmata are gaps in the membrane without cytoplasm, when they are cytoplasmic threads lined by membrane.
- Writing that only plant cells contain mitochondria; plant cells have both mitochondria and chloroplasts.
- Forgetting that chloroplasts have a double membrane and an internal system of thylakoid membranes.
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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.