5 – Regulating Cellular Respiration and Other Metabolic Pathways - MHR Grade 12 Biology

5 – Regulating Cellular Respiration and Other Metabolic Pathways MHR Grade 12 Biology Textbook: Page 130 - 132 Guiding Questions: 1.How does the cell control the rate at which to produce ATP? 2.Explain how proteins & lipids can be used for energy Regulation of Aerobic Respiration Rate of...

5 – Regulating Cellular Respiration and Other Metabolic Pathways MHR Grade 12 Biology Textbook: Page 130 - 132 Guiding Questions: 1.How does the cell control the rate at which to produce ATP? 2.Explain how proteins & lipids can be used for energy Regulation of Aerobic Respiration Rate of cellular respiration depends on: Supply and demand High demand when exercising Low demand when resting Basal metabolic rate Amount of energy expended per unit time at rest Measured in oxygen consumption  Regulation of Aerobic Catabolic Pathways Feedback Inhibition = a process that allows the cell to ensure that when biochemical reactions occur in pathways, the product of the last reaction of the pathway is a non-competitive inhibitor of the enzyme that catalyzes a reaction at the beginning of the pathway Ensures enough product is available for each reaction and all reactions are turned off or reduced, as appropriate  1) Feedback Inhibition of Enzymes in Aerobic Respiration Many enzymes in glycolysis and Krebs cycle are controlled by feedback inhibition of ATP and NADH Phosphofructokinase (PFK)is the main control point for glycolysis ATP inhibits PFK; When there is sufficient ATP, it binds to an allosteric site on the enzyme Citrate inhibits PFK; if citrate accumulates, pyruvate is not converted to acetyl-CoA until  Feedback Inhibition of Enzymes in Aerobic Respiration Pyruvate dehydrogenase Inhibited by NADH; slows conversion of pyruvate to Acetyl- CoA and CO2. 2) Other Factors Affecting Rate of Reaction Temperature Higher temp = faster reactions move Concentration of Nutrients Higher concentration = faster reactions Availability of Oxygen  Interconnections of Metabolic Pathways Okay, so now we know how our mitochondria are able to harvest energy from one molecule of glucose. Carbohydrates that can be broken down into glucose enter glycolysis What happens when we eat a meal that contains macromolecules other than carbohydrates? https://food- guide.canada.ca/en/  Protein Catabolism Proteins are first broken down into individual amino acids (hydrolysis) Before amino acids can feed into glycolysis or Krebs cycle, amino groups must be removed Deamination = removal of amino group (-NH2) from amino acid Can feed into different points of glycolysis or Krebs cycle Process occurs in the liver  Protein Catabolism Amine group converted into ammonia (NH3), then to urea (excreted by kidneys in urine) Amine group can also be transferred to other amino acids (called transamination) Remaining carbon skeleton can feed into different points of glycolysis or Krebs cycle  This is FYI only! This diagram is to simply give you an appreciation for where different amino acids can “feed” into glycolysis or Krebs Cycle at different points  Lipid Catabolism Fat molecules are broken down into glycerol and fatty acids 2 glycerol molecules can combine to form a glucose molecule (called gluconeogenesis) OR Glycerol is converted into Glyceraldehyde 3-Phosphate, which makes pyruvate  Lipid Catabolism Fatty acids are transported to mitochondrial matrix Undergo a process called β- oxidation to become Acetyl- CoA Carbon atoms are removed 2 at a time Each 2-carbon unit becomes an acetyl Co-A to enter Krebs Cycle Ex: 12 carbon fatty acid chain = 6 Acetyl-CoA molecules  Each cleavage of the fatty acid: Uses 1 ATP Produces 1 NADH, 1 FADH2 How many ATP does each cleavage produce? Why are fats a good source of energy?  How many ATP could you produce with a fatty acid that is 18 carbons long? ATP  Discussion Question: How many ATP could you produce with a fatty acid that is 14 carbons long? What assumptions do you have to make in order to answer this question? In Summary…  FYI… If learning about metabolic pathways in the human body interests you, check out this website: https://interactivepathways.stanford.edu/ This is FYI only! This diagram is to simply give you an understanding of how complex the biochemical reactions are in metabolism! If learning about metabolic pathways in the human body interests you, here’s another, more detailed website (click to zoom and scroll): http://biochemical-pathways.com/#/map/1