Module 4 Respiration 1 4 9 Respiratory substrate

Module 4 Respiration 1. 4. 9. Respiratory substrate

Starter – Anaerobic recap Yeast Hydrogen acceptor ethanal Mammals Pyruvate Is carbon dioxide produced? Yes No Is ATP produced? No No Is NAD reoxidised? Yes End products Enzymes involved Ethanol and Carbon dioxide Pyruvate decarboxylase, ethanol dehydrogenase Lactate dehydrogenase

Learning Objectives Success Criteria To understand how to measure the rate of respiration Define the term respiratory substrate(Grade D-E) To explain the different energy values of respiratory substrates Calculate rates of respiration (Grade C) Explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates (Grade A-B)

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. 180 g 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 (k. J 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 CO 2 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

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 CO 2 given out volume of O 2 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 protein >1 1. 0 approx. 0. 9 lipid approx. 0. 7 9 of 39 © Boardworks Ltd 2009

Learning Objectives Success Criteria To understand how to measure the rate of respiration • Define the term respiratory substrate(Grade D-E) To explain the different energy values of respiratory substrates 13 of 39 • Calculate rates of respiration (Grade C) • Explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates (Grade A-B) © Boardworks Ltd 2009