Cell as a Unit of Life
What is a cell?
- a cell is the basic unit of living things which can function on its own
- cells cannot be seen with the naked eye
- a microscope is used to study and observe cells
- Robert Hooke is the first person to study cells on a cork
Structures and Functions of Cells
- they are two types of cells: plant cells and animal cells
- most cells consist of a protoplasm (nucleus and cytoplasm) which is surrounded by a cell membrane
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Structure
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Function
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Characteristics
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Nucleus
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- controls all cell activities
- contain genes which determine
the inherited characters
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- dense, spherical structure
- contains chromosomes
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Cytoplasm
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- the site where chemical
reactions and processes take place
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- jelly-like substance
- colourless
- contains water and chemical
substances (protein, mineral, stored food)
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Cell membrane
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- controls all movement in and
out of the cells
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- semi permeable (allows certain
substances to pass through)
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*Cell wall
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- maintain the shape of the
cell
- provides mechanical support
and strengthen the cell
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- contains cellulose
- thick and rigid layer
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*Chloroplast
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- site where photosynthesis
take place
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- contain a green pigment
called chlorophyll which is used to absorb sunlight
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*Vacuoles
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- stored water and minerals,
sugars, proteins and dissolved substances
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- contains cell sap
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*only in plant cells
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| The image above is taken from BBC |
Comparisons Between Plant Cells and Animal Cells
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Animal cell
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Similarities
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Plant cells
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- have nuclei
- have cytoplasm
- have cell membranes
- are living things
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Differences
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Irregular
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Shape
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Regular
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Does not have vacuoles. If they
do, it is very small
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Vacuoles
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Have vacuoles
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Does not have chloroplast
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Chloroplast
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Have chloroplast
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Does not have cell wall
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Cell wall
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Have cell wall
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Glycogen
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Food storage
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Starch
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At the centre
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Location of nucleus
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At the edge
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Unicellular and Multicellular Organisms
Unicellular Organisms
- simple organisms that are made up of one cell
- Animal kingdom: Amoeba and Paramecium
- Plant kingdom: Pleurococcus, Euglena, Chlamydomonas and yeast
- are very tiny and also known as microorganism
Multicellular Organisms
- organisms that have more than one cell
- Animal kingdom: mammals, amphibians, reptiles, birds, fish and Hydra
- Plant kingdom: mosses, algae (Chondrus and Spirogyra), ferns and most of the flowering plants
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