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The plant cell and its components Free essay! Download now

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The plant cell and its components

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The plant cell and its components essay previewThe plant cell and its components essay previewThe plant cell and its components essay preview

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THE ULTRASTRUCTURE OF THE PLANT AND ANIMAL CELLS COMPARED. THE LABELS IN GREEN IDENTIFY STRUCTURES THAT OCCUR IN PLANT CELLS ONLY, WHILE RED LABELS SHOW STRUCTURES THAT ARE UNIQUE TO ANIMAL CELLS


For Comparison purposes, the diagram above shows a cell which is part animal and part plant. Plant cells do not have centrioles and plant cells may have chloroplasts which are never found in animal cells. Plant cells contain large, permanent vacuoles. The tonoplast is the membrane of the permanent vacuole. Plant cells have cell walls which are not found in animal cells.
Write the similarities and differences between plant and animal cells.
Similarities ........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Differences
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Chloroplasts: Belong to the group of organelles called plastids
Amyloplasts: Colourless plastids which store amylopectin, a form of starch. Found in large numbers in areas that store starch, i.e. potato tubers.

Chloroplasts: Large plastids which are green, about 7 ?m long. In leaves, each cell may have up to 50 chloroplasts. They contain their own DNA and are surrounded by double membrane. It is thought that, like mitochondria, they were once free living organisms. They are the site of photosynthesis.

Cell sap: The sap is the liquid that fills the permanent vacuole and it has many functions, including storage of useful materials, and provides mechanical support for non-woody plants.
Cell wall: Made mostly of cellulose (a polysaccharide). Cellulose is a straight chain polymer of glucose. Glucose monomers are linked together by ?-1,4-glycocydic linkages. This construction results in a long, straight-chain molecule that naturally packs closely together in bundles of about 200 chains, held together by hydrogen bonds. Each bundle is known as a microfibril. Microfibrils are laid down in layers held together by a matrix of hemicellulose and other short-chain carbohydrates (mannose, xylose and arabinose) which behave like glue. Cellulose has high tensile strength, is insoluble, tough, durable and slightly elastic. It can be broken down to glucose in the presence of cellulase enzyme. Cellulose is the most abundant carbohydrate. Cells are mostly turgid and thus strong to support the plant in a vertical position. When water is in short supply, the cells become flaccid and the plant wilts.

Vacuoles: A vacuole is a fluid filled space inside the cytoplasm. In plant cells the vacuole is large and permanent surrounded by a membrane called tonoplast. It is filled with cell sap which causes water to move in by osmosis and make the cell turgid. Some vacuoles are used to store substances (such as the red pigment in beetroot). They can store proteins or even lytic enzymes. They can also store waste products such as digitalis.
Mitosis in plant cells
During cytokinesis, a cell wall is laid across the old cell. First, a gel-like layer called middle lamella is formed made mainly ...

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