Patterns in Nature
Topic 4: Cell Structure and Functioning
Part of the Patterns in Nature Module
Biology in Focus, Preliminary Course
Glenda Childrawi and Stephanie Hollis
Introduction: Levels of Organisation
 Most living organisms that are seen every day consist of many
cells and are termed multicellular.
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Introduction: Levels of Organisation
Some living things however consist of only 1 cell that carries
out all of its life functions. These are called unicellular
organisms.
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Introduction: Levels of Organisation
The term ‘cell’ is used to describe the basic unit of any
organism, whether its only one unit or consisting of many units.
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DOT Point
 Identify cell organelles seen with current light and electron
microscopes
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The structure of cells (as seen with a
light microscope)
The general contents of cells can be studied using the light
microscope. Electron microscopes can provide us with greater
details.
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The structure of cells (as seen with a
light microscope)
Cells vary greatly in shape, size, structure and function. There
is no ‘typical’ cell. To allow a general understanding of the
structure and functioning of cells, a hypothetical cell of plants
and animals is often studied.
The structure of cells (as seen with a
light microscope)
Cells that are found in plants and animals have the same basic
features with some variations. Over the next few slides we are
going to explore the parts that are visible with a light
microscope.
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The structure of cells (as seen with a
light microscope)
Protoplasm
 The part of the cell which functions essential to life are
carried out. This includes the inside of the nucleus and all of
the cytoplasm
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The structure of cells (as seen with a
light microscope)
Cytoplasm:
 This is the part of the protoplasm that is outside the nucleus. It
consists of a liquid based background (cytosol) in which there
are dissolved chemical substances, suspended organelles and
insoluble granules.
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90% of the cytoplasm is water which is the medium in which all cell
chemicals are dissolved or suspended.
The structure of cells (as seen with a
light microscope)
Nucleus
 The large, spherical, oval or sometimes elongate structure in
the cytoplasm. It is colourless, transparent and slightly more
jelly like than the rest of the cell.
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It is the control centre of the cell
The structure of cells (as seen with a
light microscope)
Cell Membrane
 Surrounds the cell contents in all cells and separates the cell
contents from its surroundings.
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It controls the passage of water and other chemical substances into and
out of the cell
Plant Cells
Plant cells have some additional structures which can be viewed
under a light microscope.
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These structures are exclusive to plant cells and therefore not usually
found in animal cells.
Plant Cells
Chloroplasts
 Organelles that are green in colour due to the presence of a
pigment called chlorophyll. Under a light microscope they
appear as green, disc shaped structures, smaller than the
nucleus.
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Chloroplasts are responsible for photosynthesis (the manufacture of
sugar in plants, using the energy from the sun)
Plant Cells
Vacuole
 In plant cells are large, permanent, fluid-filled sacs in the
cytoplasm of mature cells. Each vacuole consists of a watery
solution called cell sap, surrounded by a single membrane,
the tonoplast.
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Vacuoles are used for storage but also play an important role in
providing the plant with support.
Comparing Plant and Animal Cells
To compare two things, both similarities and differences must
be examined. A good way to compare plant and animal cells is
using a diagram.
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Homework
Answer the following questions in your notebook. Be prepared
to discuss next lesson.
 Identify organelles only seen with a light microscope
Hand out Observing Plant and Animal Cells PRAC and discuss for next
lesson.