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Sources of Energy

Sources of Energy. Unit 5. Carbohydrates. All contain Carbon, Hydrogen & Oxygen Monosaccharide (‘single’ sugar): E.g. glucose, fructose Water soluble Many are reducing sugars - donate electrons to other substances Disaccharides (‘double’ sugars) E.g maltose, sucrose Water soluble

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Sources of Energy

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  1. Sources of Energy Unit 5

  2. Carbohydrates • All contain Carbon, Hydrogen & Oxygen • Monosaccharide (‘single’ sugar): • E.g. glucose, fructose • Water soluble • Many are reducing sugars • - donate electrons to other substances • Disaccharides (‘double’ sugars) • E.g maltose, sucrose • Water soluble • Maltose is reducing, sucrose is non-reducing • Acid hydrolysis can make sucrose reducing

  3. Carbohydrates • Polysaccharides: • Long chains of monosaccharides • Water insoluble • E.g. starch – long chain of glucose (stored in plants) • E.g. glycogen – branched chain of glucose (stored in animals) • All carbohydrates are energy rich • Many need to be broken down into monosaccharides to release energy

  4. Carbohydrate tests • Water solubility: Polysaccharides wont dissolve • Benedicts: brick-red colour indicates presence of reducing sugar • - (glucose, lactose, fructose, maltose) • Acid Hydrolysis: If soluble, but –ve for Benedicts • – after acid hydrolysis should be +ve for Benedicts • Clinistix: specifically for glucose • Barfoed’s: rapid change = monosaccharide, slow change = disaccharide • Iodine: black = starch, purple-red = glycogen

  5. Lipids • Contain Carbon, Hydrogen & Oxygen, but much less oxygen overall • All are water insoluble • Simple Lipids • e.g. fats (solid) and oils (liquid at room temp) • Known as triglycerides • Made of glycerol and 3 fatty acids

  6. Lipids • Phospholipid: • Glycerol, 2 fatty acids, 1 phosphate • Phosphate ‘head’ is hydrophilic (water soluble) • Fatty acids ‘tail’ is hydrophobic (water insoluble) • Steroids: • 3 6-carbon rings attached to a 5-carbon ring • E.g cholesterol – basic molecular structure

  7. Role of lipids • 1) Energy Store: • Fat is stored in fatty (adipose) tissue • Triglyceride is broken down by enzymes into glycerol and fatty acids • Glycerol 3 C sugar Pyruvic Acid • Fatty Acids Acetyl CoA • Fat produce x2 more energy than carbohydrate • All above reactions are reversible • Therefore excess glucose can be stored as fat

  8. Role of lipids • 2) Insulation: • Adipose tissue under the skin insulates heat • Nerve fibres are sheathed in myelin (insulates nerve impulses) • 3) Vitamins: • Vitamins A,D,E & K are fat-soluble • – can be transported from digestive to lymphatic system • Hormones & Fat Pads: • Sex Hormones – e.g. testosterone, oestrogen • Pads – cushion palms of hands, soles of feet, kidneys

  9. Proteins • Broken down into amino acids • Excess dietary amino acids cannot be stored • Dietary proteins undergo deamination • Urea & organic acids (e.g pyruvic) produced • Organic acids & intermediates go into aerobic respiration - ATP production • Tissue protein is an energy source only after prolonged starvation

  10. Marathon Running • First few mins – glucose from muscle glycogen used • As race continues – blood-borne fuels used up (blood glucose & slow-acting fatty acids) • Latter stages – fatty acids are the main source • If athlete loads up on carbs, fat reserves may not be affected as much

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