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Describe the similarities and differences between plant and animal cells.

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Introduction

Essay Question Describe the similarities and differences between plant and animal cells (20 marks) There are various differences and similarities between the plant and animal cells in terms of their organelles. A main overall similarity between both cells is that they are the two mail types of the eukaryotic cell. A eukaryotic cell possesses nuclei and their DNA lies in a nucleus. Eukaryotic includes animals, plants, fungi and protoctists. In contrast, organisms that lack nuclei are called prokaryotes and are referred to as bacterium. Other similarities of a plant cell and an animal cell are as follows. The Nucleus This is the most important organelle in the cell. It is bounded by a double membrane, the nuclear envelope. It possess many large pores, 40-60nm in diameter, which permits the passage of large molecules, such as RNA, between it and the cytoplasm. Chromatin is found in the nucleoplasm and is made up of coils of DNA bound to proteins. During division the chromatin aggregates from the chromosomes but these are rarely if ever visible in a non-dividing cell. Also within the nucleus are one or two small round bodies each called a nucleus. ...read more.

Middle

Its position and size varies form cell to cell but it is well developed in secretory cells and neurones and is small in muscle cells. This suggests that the Golgi apparatus plays some role in the production of secretary material. In particular, it is thought to perform the following functions. * Produces glyco-proteins such as mucin required in secretions by adding the carbohydrate part to the protein. * Produces secretary enzymes, e.g. the digestive enzymes of the pancreas. * Secretes carbohydrates such as those involved in the production of new cell walls. * Transports and stores lipids. Also, forms lysosomes. Microtubules Microtubules occur widely throughout living cells. They are slender, unbranched tubes about 20nm in diameter and up to several micros in length. Their functions are as follows. To provide an internal skeleton (Cytoskeleton). for cells and so help determine their shape. They may aid transport within cells by providing routes along which materials move. They form a framework along which the cellulose cell wall of plants is laid down. They are the major components of cilia and flagella where they contribute to their movement. They are found in the spindle during cell division and within the centrioles from which the spindle is formed. ...read more.

Conclusion

The strength may be increased by the presence of lignin in the matrix between the cellulose fibres. * To permit the movement of water through and along it and so contribute to the movement of water in the plant as a whole, in particular in the cortex of the root. * In some cell walls the presence of cutin, suberin or lignin in the matrix makes the cell less permeable to substances. Lignin helps to keep the water within the xylem; cutin in the epidermis of leaves prevents water being lost from the plant and suberin in root endodermal cells prevents movement of water across them, thus concentrating its movement through special passage cells. * The arrangement of the cellulose fibrils in the cell wall can determine the pattern of growth and hence the overall shape of a cell. * Occasionally cell walls act as food reserves. Starch grains Starch grains occur within chloroplasts and the cytoplasm of plant cells. Starch may also be stored in specialized leucoplasts called amyloplasts. More information on starch grains can be found in the section 'glycogen granules' in this essay. The next two pages, shows diagrams of a plant cell and an animal cell. ?? ?? ?? ?? Faizah M 30/04/2007 Pg. 1 of. 6 ...read more.

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