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BY4 – Metabolism, Microbiology and Homeostasis Learning objectives:

BY4 – Metabolism, Microbiology and Homeostasis Learning objectives:. To know the importance of chemical energy in biological processes To understand the role of ATP To draw the structure of ATP

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BY4 – Metabolism, Microbiology and Homeostasis Learning objectives:

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  1. BY4 – Metabolism, Microbiology and HomeostasisLearning objectives: To know the importance of chemical energy in biological processes To understand the role of ATP To draw the structure of ATP To understand the stages in aerobic respiration: glycolysis, link reaction, Kreb’s cycle and the electron transport chain

  2. What processes do cells need energy for? Movement e.g. movement of cilia and flagella, muscle contraction 2. Maintaining a constant body temperature to provide optimum internal environment for enzymes to function 3. Active transport – to move molecules and ions across the cell surface membrane against a concentration gradient

  3. 4. Anabolic processes e.g. synthesis of polysaccharides from sugars and proteins from amino acids 5. Bioluminescence – converting chemical energy into light e.g. ‘glow worms’ 6. Secretion – the packaging and transport of secretory products into vesicles in cells e.g. in the pancreas

  4. Respiration • Energy is released in respiration • A series of oxidation reactions taking place inside living cells which releases energy to drive the metabolic activities that take place in cells Aerobic respiration – takes place in the presence of oxygen Anaerobic respiration – takes place in absence of oxygen

  5. The role of ATP (adenosine triphosphate) • The short term energy store of the cell • Often called the ‘energy currency’ of the cell because it picks up energy from food in respiration and passes it on to power cell processes. ATP made up of: Adenine (a base) Ribose (a pentose sugar) 3 phosphate groups Draw the structure of ATP on page 286

  6. How ATP releases energy • The 3 phosphate groups are joined together by 2 high energy bonds • ATP can be hydrolysed to break a bond which releases a large amount of energy • Hydrolysis of ATP to ADP (adenosine diphosphate) is catalysed by the enzyme ATPase (ATPase) ATP ADP + Pi + 30 KJ mol-1 (H2O) Draw the hydrolysis of ATP on page 286

  7. The 2nd phosphate group can also be removed by breaking another high energy bond. • The hydrolysis of ADP to AMP (adenosine monophosphate) releases a similar amount of energy (ATPase) ADP AMP + Pi + 30 KJ mol-1 (H2O) AMP and ADP can be converted back to ATP by the addition of phosphate molecules

  8. The production of ATP – by phosphorylation • Adding phosphate molecules to ADP and AMP to produce ATP Phosphorylation is an endergonic reaction – energy is used Hydrolysis of ATP is exergonic - energy is released

  9. Advantages of ATP • Instant source of energy in the cell • Releases energy in small amounts as needed • It is mobile and transports chemical energy to where it is needed IN the cell • Universal energy carrier and can be used in many different chemical reactions Answer sample past paper question on sheet

  10. Aerobic respiration –– to release energy 4 main stages CO2 glucose Krebs cycle Glycolysis FADH2 NADH pyruvate Electron transport chain Link reaction Hydrogen atoms Acetyl coenzyme A oxygen water

  11. 1. Glucose (6C) phosphorylated to Glucose phoshate (6C) Glycolysis -the splitting of glucose The phosphate comes from ATP 3. Glucose phosphate (6C) phosphorylated to fructose biphosphate (6C) 4. Fructose biphosphate (6C) is split into two molecules of glycerate 3 phosphate 6. H+ is removed and transferred to the hydrogen acceptor NAD (nicotinamide adenine dinucleotide) 5. Each Glycerate 3 –phosphate (3C) is converted to pyruvate (3C) 7. 2 x 2 ATP produced Draw glycolysis reaction on page 287

  12. Glycolysis in detail • Takes place in cytoplasm of cells • Does not need oxygen – first stage of aerobic respiration and only stage of anaerobic respiration • Although glycolysis yields energy it does need an input of energy to get the reaction started

  13. Glycolysis – overview Glycolysis produces from 1 molecule of glucose: • 2 molecules of ATP in total (4 ATP are produced but 2 are used at the start) • 2 molecules of NADH2 (reduced NAD) • 2 molecules of pyruvate to enter the link reaction

  14. The link reaction in mitochondria in presence of oxygen Pyruvate (3C) 2. Pyruvate dehydrogenated – hydrogen removed 1. Pyruvatedecarboxylated - CO2 removed NAD+ CO2 NADH + H+ Acetate (2C) 3. Acetate (2C) combines with coenzyme A Coenzyme A Acetyl coenzyme A Don’t forget this happens TWICE as 2 molecules of pyruvate are formed from each glucose molecule

  15. Krebs cyclein matrix of mitochondria Draw Krebs cycle on page 288

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