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Module 5 Respiration 5.2.2 j,k. RESPIRATORY SUBSTRATE Learning Outcomes Define the term respiratory substrate Calculate Explain rates of respiration the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates Starter – Anaerobic recap Yeast Hydrogen acceptor ethanol Mammals Pyruvate Is carbon dioxide produced? Yes No Is ATP produced? No No Is NAD reoxidised? Yes Yes End products Enzymes involved Ethanol and Carbon dioxide Pyruvate decarboxylase, ethanol dehydrogenase Lactate Lactate dehydrogenase 1. Explain how a build up of acid during glycolysis leads to muscle fatigue in mammals. 2. Suggest how diving mammals, such as seals, whales and dolphins can swim below water without suffering from muscle fatigue. Respiratory substrate Write down a definition of respiratory substrate. Any biological molecule that can be broken down in respiration to release energy is called a respiratory substrate. Cells respire glucose, but also respire other carbohydrates, lipids and proteins, but these enter respiration at different points. Energy values of different respiratory substrates Where is most ATP made during respiration? Oxidative phosphorylation, when H ions (protons) flow through channels. The H ions and electrons then combine with oxygen to produce water. The more protons, the more ATP. Which respiratory substrate would produce the most energy content? The more H atoms in a molecule of respiratory substrate, the more ATP is generated when that substrate is respired. So the more H atoms per mole of respiratory substrate, then more oxygen is needed to respire that substance. (One mole is the gram molecular mass of a substance. 180g glucose is one mole of glucose) Respiratory substrates Other substances as well as glucose can be respired. Different respiratory substrates release different amounts of energy. Respiratory substrate Mean energy value (kJ g-1) carbohydrate 15.8 lipid 39.4 protein 17.0 The difference in the relative energy values of these respiratory substrates is due to the amount of hydrogen atoms present in each one. If more hydrogen atoms are available to reduce coenzymes, more energy can subsequently be generated in the electron transport chain. 6 of 39 © Boardworks Ltd 2009 Energy values of different respiratory substrates Produce 3 flow diagrams explaining how carbohydrate, lipid and protein produce energy – Using page 96-97 Complete stretch and challenge question Respiratory rate The respiratory rate is the rate at which an organism converts glucose to CO2 and water. It can be calculated by measuring an organism’s rate of oxygen consumption. Studies on simple animals often use a respirometer. Respirometers measure the change in gas volume in a closed system. Any change is due to the respiratory activity of the study organisms. Potassium hydroxide or soda lime is used to absorb the carbon dioxide produced, meaning any changes in volume are due to oxygen consumption. 8 of 39 © Boardworks Ltd 2009 Respirometer experiments 9 of 39 © Boardworks Ltd 2009 Respiratory quotient Respiratory quotient (RQ) is the volume of carbon dioxide produced when the respiratory substrate is respired, dividing by the volume of oxygen consumed, in a set period of time. RQ = volume of CO2 given out volume of O2 taken in RQ gives an indication of the respiratory substrate being respired and whether respiration is aerobic or anaerobic. Type of respiration Substrate RQ anaerobic glucose aerobic carbohydrate >1 1.0 protein approx. 0.9 lipid approx. 0.7 10 of 39 © Boardworks Ltd 2009 Measuring Respiration • The equation for respiration using oleic acid is below. Calculate the RQ. 2C18H34O2 + 51O2 36CO2 + 34H2O + energy • What type of molecule is oleic acid? • Is it aerobic or anaerobic respiration? RQ = 36/51 = 0.71 Oleic acid is a fatty acid. Fatty acids make up triglycerides. Its aerobic respiration. • Complete workbook question page 98 OCR A2 – complete for homework 11 of 39 © Boardworks Ltd 2009 12 of 39 © Boardworks Ltd 2009 13 of 39 © Boardworks Ltd 2009