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Definition
| The solution within the cell membrane. It contains enzymes for glycolysis (part of respiration) and other metabolic reactions together with sugars, salts, amino acids, nucleotides and everything else needed for the cell to function. |
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Definition
| This is the largest organelle. Surrounded by a nuclear envelope, which is a double membrane with nuclear pores - large holes containing proteins that control the exit of substances such as RNA and ribosomes from the nucleus. The interior is full of chromatin- a DNA/protein complex containing the genes. |
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Term
| Mitochondrion (pl. Mitochondria). |
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Definition
This is a sausage-shaped organelle where aerobic respiration takes place. Surrounded by a double membrane: the outer membrane is simple and quite permeable, while the inner membrane is highly folded into cristae, which give it a large surface area. The space enclosed by the inner membrane is called the matrix, and contains small circular strands of DNA. The inner membrane is studded with stalked particles, which are the site of ATP synthesis. |
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Definition
| Where photosynthesis takes place, so only found in plants and algae. They are enclosed by a double membrane, but have a third membrane called the thylakoid membrane. This is folded into thylakoid disks, which are then stacked into piles called grana. The space between the inner membrane and the thylakoid is called the stroma. The thylakoid membrane contains chlorophyll and other photosynthetic pigments arranged in photosystems, together with stalked particles, and is the site of photosynthesis and ATP synthesis. Also contain starch grains, ribosomes and circular DNA. |
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Definition
| The smallest and most numerous of the cell organelles, and are the sites of protein synthesis. Composed of protein and RNA, and are manufactured in the nucleolus of the nucleus. Either found free in the cytoplasm, where they make proteins for the cell's own use, or they are found attached to the RER, where they make proteins for export from the cell. |
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Term
| Smooth Endoplasmic Reticulum (SER). |
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Definition
| Series of membrane channels involved in synthesising and transporting materials, mainly lipids, needed by the cell |
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Term
| Rough Endoplasmic Reticulum (RER). |
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Definition
| Similar to the SER, but studded with numerous ribosomes, which give it its rough appearance. The ribosomes synthesise proteins, which are processed in the RER (e.g. adding carbohydrates), before being exported from the cell via the Golgi Body |
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Term
| Golgi Body (or Golgi Apparatus). |
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Definition
| Series of flattened membrane vesicles, formed from the endoplasmic reticulum. Its job is to transport proteins from the RER to the cell membrane for export. Parts of the RER containing proteins fuse with one side of the Golgi body membranes, while at the other side small vesicles bud off and move towards the cell membrane, where they fuse, releasing their contents by exocytosis. |
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Definition
These are small membrane-bound vesicles formed from the RER containing a cocktail of digestive enzymes. They are used to break down unwanted chemicals, toxins, organelles or even whole cells, so that the materials may be recycled. They can also fuse with a feeding vacuole to digest its contents. |
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Definition
| This is a pair of short microtubules involved in cell division. Before each division the centriole replicates itself and the two centrioles move to opposite ends of the cell, where they initiate the spindle that organises and separates the chromosomes. |
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Definition
| These are small finger-like extensions of the cell membrane found in certain cells such as in the epithelial cells of the intestine and kidney, where they increase the surface area for absorption of materials. They are just visible under the light microscope as a brush border. |
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Term
| Cell Membrane (or Plasma Membrane). |
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Definition
| This is a thin, flexible layer round the outside of all cells made of phospholipids and proteins. It separates the contents of the cell from the outside environment, and controls the entry and exit of materials. |
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Definition
| A thick layer outside the cell membrane used to give a cell strength and rigidity. Cell walls consist of a network of fibres, which give strength but are freely permeable to solutes. Plant cell walls are made mainly of cellulose, but can also contain hemicellulose, pectin, lignin and other polysaccharides. They are built up in three layers called the primary cell wall, the secondary cell wall and the middle lamella. Fungal cell walls are made of chitin. |
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