Download - The basic structure of a cell
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The basic structure of a cell
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Introduction
• Cells are the basic units of organisms– Cells were first observed by scientist
under microscope
• Two basic types of cells– Plant cells– Animal cells
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Plant cell
– Made of cellulose which forms very thin fibres
– Strong and rigid
• Cell wall
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Plant cell
• Cell wall– Protect and
support the enclosed substances (protoplasm)
– Resist entry of excess water into the cell
– Give shape to the cell
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Plant cell
• Cell wall– Large spaces
present between cellulose fibres
freely permeable
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Plant cell
• Cell membrane– Lies
immediately against the cell wall
– Made of protein and lipid
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Plant cell
• Cell membrane– Can control the
movement of materials into and out of the cell
Selectively permeable
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Plant cell
• Cytoplasm– Jelly-like
substance enclosed by cell membrane
– Provide a medium for chemical reactions to take place
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Plant cell
• Chloroplasts– Contain the
green pigment chlorophyll• To trap light
energy to make food by photosynthesis
– Contain starch grains (products of photosynthesis)
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Plant cell
• Mitochondrion– Rod-shape– For respiration
to take place• Active cells
(sperms, liver cells) have more mitochondria
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Plant cell
• Non-living granules– Starch granules– Oil droplets– Crystals of
insoluble wastes
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Plant cell
• Nucleus– Control the
normal activities of the cell
– Bound by a nuclear membrane
– Contains thread-like chromosomes• Chromosomes
carry genes
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Plant cell
• Vacuole– Surrounded by
tonoplast– Contains cell
sap• a solution of
chemicals (sugars, proteins, mineral salts, wastes, pigments)
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Different kinds of plant cells
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Animal cell
• No cell wall and chloroplast
• Stores glycogen granules and oil droplets in the cytoplasm
mitochondrion
nucleus
oil droplet
glycogen granule
cell membrane
cytoplasm
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Different kinds of animal cells
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Similarities between plant cells and animal cells• Both have a cell membrane
surrounding the cytoplasm
• Both have a nucleus
• Both contain mitochondria
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Differences between plant cells and animal cells
Animal cells Plant cells
Relatively smaller
Irregular in size
No cell wall
Vacuole small or absent
Glycogen granules as food store
Nucleus at the centre
Relatively larger
Regular in size
Cell wall present
Large central vacuole
Starch granules as food store
Nucleus near cell wall
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Microscope
• Instrument for observing small objects
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Different parts of a microscope
EyepieceBody tube
Coarse adjustment
Fine adjustment
Objective
Nose piece
Stage
Clip Condenser
Condenser adjustment Diaphragm
Mirror
Arm
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The cell as the basic unit of life• Cell is the smallest unit of living
organisms• Unicellular organisms are made of one
cell only• The cells of multicellular organisms
are specialized to perform different functions– e.g. mesophyll cells and root epidermal
cells in plants
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Levels of organisation
• Cells are group together and work as a whole to perform special functions
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Tissue
• A group of similar cells to perform a particular job– Animals: epithelial tissue, muscular
tissue– Plants: vascular tissue, mesophyll
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Organ
• Different tissues group together to carry out specialized functions– Heart: consists of muscles, nervous
tissue and blood vessels– Leaf: consists of epidermis, mesophyll
and vascular tissue
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System
• Several organs and tissues work together to carry out a particular set of functions in a co-ordinated way– Human: digestive, respiratory,
excretory, circulatory and reproductive systems
– Plant: root and shoot systems