unit 1 AS BIOLOGY

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In living organisms lipids can be used for:

  • Storing energy
  • Electrical insulation
  • Waterproofing
  • Hormones (as steroids)
  • Physical protection for delicate organs
  • Buoyancy in marine animals
  • Heat insulation
  • Cell membranes (as phospholipids)
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Disaccharides are formed from a condensation reaction between two monosaccharides, resulting in the formation of a glycosidic bond. Since it is a condensation reaction, one molecule of water is removed during the process.

Glucose + glucose = maltose

Glucose + fructose = sucrose

Glucose + galactose = lactose

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A light microscope can be used to study the general strucure of living cells. However, they have a limited resolution, so the fine detail of cells and organelles cannot be studied.

An electron microscope has a high resolution so it permits the detailed images of cell and organelle structure to be studied, but they cannot be used to study living cells.

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Cell fractionation is the separation of the different components of a cell by breaking up the cells and separating the different organelles by ultracentrifugation.

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Lipids are composed of carbon,hydrogen and oxygen; triglycerides are important as an energy store; phospholipids are important components of cell membranes. A phospholipid molecule is made up of two fatty acids,glycerol and a phosphate group.

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Absorption is the process by which the soluble products of digestion pass through the wall of the ileum into the blood, except the fatty acids and glycerol, which enter the lymphatic system).

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Physical digestion involves the action of the teeth and gut muscles to break up food and mix it with digestive juices, whereas chemical digestion involves the breaking down of individual food molecules by hydrolytic enzymes.

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Digestion is the step by step process by which food is broken down into simple soluble molecules that can be absorbed and used in metabolism. Digestion takes place mainly in the duodenum, and most absorption takes place in the duodenum and ileum.

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The digestive system goes mouth, oesophagus, stomach, duodenum, ileum, colon, rectum, ****.

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