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1.1Unit 1: Cells and organisms

Plant cells — HIA International - Grade 6 Revision Notes & Topical Questions

5 min read 9 parts Lesson 2 of 5 3 quizzes

📚 HIA International - Grade 6 Hub / Topical Revision
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Lesson summary

1.1 Plant cells — HIA INTERNATIONAL notes: Name the parts of a plant cell, state the function of each, and use a microscope to look at plant cells.Living organisms — plants and animals are made of units called cells.Size — cells are so small that they cannot be seen with the eye …

  • Appearance
  • Magnification
  • Cell membrane
  • Sap vacuole
  • Chloroplast
  • Mitochondria

Section 1 of 9Cells as units of life

Living organisms
  • Living organisms plants and animals are made of units called cells.
Size
  • Size cells are so small that they cannot be seen with the eye alone.
Appearance
  • Appearance through a microscope a plant looks like a very large number of tiny boxes.
Magnification
  • Magnification a microscope magnifies the view so cells look much bigger than they are.

Section 2 of 9Parts of a plant cell

Parts of a plant cell
Cell wall
  • Cell wall strong and stiff, made of cellulose, and holds the plant cell in shape.
Cell membrane
  • Cell membrane very thin and flexible, like the skin of a soap bubble, and lies along the inner edge of the cell wall.
  • It controls what goes in and out of the cell.
Cytoplasm
  • Cytoplasm clear jelly in which chemical reactions that keep the cell alive happen.
Nucleus
  • Nucleus controls the activities of the cell and contains the genetic material (DNA).
Sap vacuole
  • Sap vacuole a large fluid-filled space containing cell sap, a solution of sugars and other substances in water.
  • It keeps the cell firm.
Chloroplast
  • Chloroplast green because it contains chlorophyll, and is where plants make their food.
  • Found in cells exposed to sunlight, such as leaf cells.
Mitochondria
  • Mitochondria found in all plant cells, and energy is released from food inside them.

Section 3 of 9Wall and membrane compared

FeatureCell wallCell membrane
StrengthStrong and stiffThin and flexible
Made ofCelluloseThin layer of cell material
Found inPlant cells onlyAll cells
JobHolds the cell in shapeControls what enters and leaves

Section 4 of 9Root cells and chloroplasts

Root cells and chloroplasts
Green parts
  • Green parts leaf cells exposed to light contain chloroplasts.
Underground
  • Underground root cells receive no light, so they have no chloroplasts.
Onion
  • Onion onion cells grow underground and do not look green for this reason.

Section 5 of 9Parts of a microscope

1Eyepiece
  • Eyepiece the lens that is looked through.
2Objective lenses
  • Objective lenses low, medium and high power lenses that magnify the specimen.
3Stage
  • Stage the platform that holds the slide, with a hole for light to pass through.
4Mirror
  • Mirror directs light up through the specimen.
5Focussing knobs
  • Focussing knobs a coarse knob and a fine knob move the lens to bring the image into focus.

Section 6 of 9Method for looking at onion cells

1
Cut a piece of onion about 1 cm square and put a drop of water in the middle of a clean slide.
2
Peel the thin layer from the inside of the onion piece with tweezers.
3
Push the layer into the water and spread it out as flat as possible.
4
Lower a cover slip gently over it so no air bubbles are trapped.
5
Turn the smallest objective lens over the stage hole and place the slide on the stage.
6
Look down the eyepiece and turn the focussing knob slowly to move the lens away from the slide until the cells are in focus.
7
Draw some of the cells, using a sharp pencil.

Section 7 of 9Magnification

Formula
  • Formula magnification = image size ÷ actual size, using the same unit for both.
Unit
  • Unit magnification is a ratio and has no unit.
Stain
  • Stain iodine or another stain makes the nucleus and walls easier to see.

Section 8 of 9Key terms

TermMeaning
CellThe basic unit of life.
Cell wallStrong cellulose layer that holds a plant cell in shape.
Cell membraneThin flexible layer that controls what enters and leaves the cell.
CytoplasmJelly in which the cell's chemical reactions happen.
NucleusControls the cell's activities and holds the genetic material.
Sap vacuoleLarge space filled with cell sap.
ChloroplastStructure with chlorophyll where photosynthesis happens.
MitochondrionStructure where energy is released from food.

Section 9 of 9Exam technique

1
Confusing the cell wall with the cell membrane — the wall is strong and only in plants, whereas the membrane is thin and in all cells.
2
Thinking all plant cells contain chloroplasts — root cells have none because they get no light.
3
Writing mm after a magnification — magnification has no unit.
4
Thinking a drawing of a cell shows all of it — a microscope shows a thin slice of three-dimensional cells.

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