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7.1Unit 1: Cells and organisms

Plant cells — Cambridge Checkpoint Biology 0893 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 4 1 quiz

📚 Cambridge Checkpoint Biology 0893 Hub / Topical Revision
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Lesson summary

7.1 Plant cells — CHECKPOINT BIOLOGY 0893 notes: Name the structures of a plant cell and state the function of each, and use a light microscope to observe plant cells.All living organisms are made of cells, the smallest units of life.Plant and animal cells both have a nucleus, cy…

  • Cell membrane
  • Mitochondria
  • Chloroplasts
  • Large permanent vacuole
  • Root hair cells
  • Palisade cells

Part 1 of 7Cells

Cells
All living organisms are made of cells, the smallest units of life.
Plant and animal cells both have a nucleus, cytoplasm, cell membrane and mitochondria.
Cells are too small to see without a microscope, which magnifies the view.

Part 2 of 7Structures found in all cells

Structures found in all cells
Nucleus
  • Nucleus contains the genetic material (DNA) and controls the activities of the cell.
Cytoplasm
  • Cytoplasm a jelly-like substance in which most of the chemical reactions of the cell take place.
Cell membrane
  • Cell membrane a thin, partially permeable layer that controls which substances enter and leave the cell.
Mitochondria
  • Mitochondria the site of aerobic respiration, which releases energy from glucose.

Part 3 of 7Structures found only in plant cells

Structures found only in plant cells
Cell wall
  • Cell wall a strong, rigid layer of cellulose outside the membrane.
  • It supports the cell and keeps its shape.
  • It is fully permeable, so it does not control what enters the cell.
Chloroplasts
  • Chloroplasts contain the green pigment chlorophyll, which absorbs light energy for photosynthesis.
  • They are found in the green parts of the plant exposed to light, such as leaf cells.
Large permanent vacuole
  • Large permanent vacuole filled with cell sap, a solution of water, sugars and salts.
  • It keeps the cell firm (turgid), which helps to support the plant.

Part 4 of 7Plant cells without chloroplasts

Plant cells without chloroplasts
Root cells have no chloroplasts because they receive no light.
Without chloroplasts they cannot photosynthesise.

Part 5 of 7Specialised plant cells

Root hair cells
  • Root hair cells have a long extension that gives a large surface area to absorb water and mineral ions.
Palisade cells
  • Palisade cells are packed with chloroplasts near the top of the leaf to absorb as much light as possible.
Xylem cells
  • Xylem cells are dead, hollow and joined end to end to form tubes that carry water up the plant.

Part 6 of 7Organisation of cells

Organisation of cells
Cell → tissue → organ → organ system → organism.
A tissue is a group of similar cells doing the same job, such as xylem.
An organ is made of several tissues, such as a leaf.

Part 7 of 7Using a light microscope

Total magnification
Total magnification eyepiece lens magnification × objective lens magnification.
Preparing an onion epidermis slide:
1
Peel a thin layer of epidermis from the inside of an onion piece using forceps.
2
Lay it flat in a drop of water on a clean microscope slide.
3
Add a drop of iodine solution to stain the cells so the nucleus can be seen.
4
Lower a cover slip at an angle to avoid trapping air bubbles.
5
Start with the lowest-power objective lens, focus with the coarse then fine focus,
  • and then change to a higher power and refocus with the fine focus only.
6
Draw some of the cells.
  • Leaf cells can be seen without a stain because chloroplasts are green.

Key terms

TermMeaning
Cell wallA rigid cellulose layer that supports a plant cell.
ChloroplastA structure containing chlorophyll where photosynthesis takes place.
NucleusThe structure that contains genetic material and controls cell activities.
Sap vacuoleA large fluid-filled space containing cell sap.
Cell membraneA thin layer that controls what enters and leaves the cell.
TissueA group of similar cells doing the same job.

Avoid these mistakes

1
Saying the cell wall controls what enters the cell — the cell membrane controls this, and the wall supports the cell.
2
Saying all plant cells have chloroplasts — root cells have none.
3
Saying chloroplasts make energy — they absorb light energy to make glucose by photosynthesis.
4
Saying the nucleus is the brain of the cell — it contains genetic material and controls the cell's activities.
5
Writing magnification as eyepiece plus objective — multiply them.

Last updated:

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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