Cell structure INTRODUCTION
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It’s an amazing fact that the basic structure of a ‘complex cell’ (one that contains a nucleus) is the same in all animals, plants and protoctists on Earth. Scientists say that this is because they have all evolved from a single complex cell. This cell evolved from a simple bacteria-like cell (without a nucleus) around 2 billion years ago. This is the origin of all the millions of different species of plants, animals and protoctists that live on Earth today.
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∆∆Fig. 2.4 All plant, protoctist and animal cells (apart from some very specialised cells) have a cell nucleus like this human cheek cell.
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KNOWLEDGE CHECK ✓✓Most organisms are formed from many cells. ✓✓Cells may be specialised in different ways to carry out different functions.
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LEARNING OBJECTIVES ✓✓Describe cell structures, including the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes and vacuole. ✓✓Describe the functions of the nucleus, cytoplasm, cell membrane, cell wall, mitochondria, chloroplasts, ribosomes and vacuole. ✓✓Know the similarities and differences in the structure of plant and animal cells. ✓✓Explain the importance of cell differentiation in the development of specialised cells. ✓✓Understand the advantages and disadvantages of using stem cells in medicine.
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PLANT AND ANIMAL CELLS The diagrams below show a typical animal cell and typical plant cells. These cells all have a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
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5/27/17 10:37 AM