8 RESPIRATORY SUBSTRATES

Learning Objective  To understand about respiratory substrates Success Criteria  define the term respiratory substrate;  explain the difference in relative energy values of carbohydrate, lipid and protein respiratory substrates

Starter: Complete per Glucose Main molecule made Net Gain Red NAD Net Gain ATP Net Gain Other Where happens Glycolysis Link Reaction Krebs Cycle Oxidative Phosphory… Lactate Fermentation Alcoholic Fermentation

Answers Main molecule made Net Gain Red NAD Net Gain ATPNet Gain Other Where happens Glycolysis2x Pyruvate220Cytoplasm Link Reaction2x Acetyl CoA202 CO 2 Matrix Krebs Cycle0 (Cycle)622 red FAD 4 CO 2 Matrix Oxidative Phosphory… ATP0262 H 2 OCristae Lactate Fermentation 2x Lactate002 NADCytoplasm Alcoholic Fermentation 2 Ethanol002 NAD 2 CO 2 Cytoplasm

Respiratory substrate  Define 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 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. Other substances as well as glucose can be respired. Different respiratory substrates release different amounts of energy. Respiratory substrateMean energy value (kJ g -1 ) carbohydrate lipid protein

 Produce 3 flow diagrams explaining how carbohydrate, lipid and protein produce energy – Using page  EXT: Complete stretch and challenge question TASK: Energy values of different respiratory substrates

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.

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 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. anaerobic > 1 aerobic carbohydrate1.0 proteinapprox. 0.9 lipidapprox. 0.7 glucose SubstrateRQType of respiration

Question: Measuring Respiration  The equation for respiration using oleic acid is below. Calculate the RQ.  What type of molecule is oleic acid?  Is it aerobic or anaerobic respiration? ANSWERS: RQ = 36/51 = 0.71 Oleic acid is a fatty acid. Fatty acids make up triglycerides. Its aerobic respiration. 2C 18 H 34 O O 2  36CO H 2 O + energy

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