Ch. 24 Metabolism and Energy

1. Ch. 24Metabolism and Energy Chemistry II MILBANK HIGH SCHOOL

2. Introduction • Photosynthesis • 6CO2 + 6H2O + 686kcal  C6H12O6 + 6O2 • Metabolism • Entire series of chemical reactions that keep cells alive • Catabolism • Breaking down of molecules to provide energy • Anabolism • Building up of molecules of living systems

3. Introduction Con’t • Respiration • All metabolic processes in which oxygen is used to oxidize organic matter to carbon dioxide, water, and energy • Carbohydrate oxidation • C6H12O6 + 6O2 6CO2 + 6H2O + 686 kcal • Lipid oxidation • C16H32O2 + 23O2 16CO2 + 16 H2O + 2340 kcal

4. Sec. 24.1 ATP: Universal Energy Currency • ATP • Adenosine triphosphate • Figure 24.2 • Most important phosphate compound in metabolism • Energy rich compound (energy currency of the cell) • Lead to a release of energy upon hydrolysis

5. ATP Con’t • ATP hydrolyis • ATP ADP + Pi + 7.5 kcal/mol • Reaction is reversible • ATP is produced by processes that supply energy • Radiant energy in plants, breakdown of food in animals) • ATP is hydrolyzed by processes that require energy • Synthesis of carbs, lipids, and proteins; transmission of nerve impulses, muscle contractions, etc

6. Sec. 24.2Digestion and Absorption of Major Nutrients • Catabolism • Three stages (Fig. 24.5) • Digestion (stage 1) • Hydrolytic process that breaks down food molecules into simpler chemical units • Absorption occurs mainly in small intestine • Alimentary tract

7. Digestion Con’t • Mechanical Aspects • Chewed • Saliva • α-amylase • Stomach • Broken down by pepsin • Chyme • Moves into small intestine

8. Digestion of Carbohydrates (Fig. 24.7) • Mouth • α-amylase attacks α-glycosidic linkages in starch • Small Intestine • α-amylase converts remaining starch to maltose, broken down by maltase to form two glucose units • Sucrose and lactose broken down by sucrase and lactase; form glucose, fructose, and galactose

9. Digestion of Proteins (Fig. 24.9) • Stomach • Gastric juice • Hydrochloric acid opens up folds in protein molecule • Pepsin • Endopeptidase that catalyzes the hydrolysis of peptide linkages • Amino Acids • Absorbed through lining of small intestine

10. Digestion of Lipids (Fig. 24.13) • Small intestine • Bile salts from gallbladder act as emulsifiers • Break down large molecules into small globules (more surface area) • Lipases • Mono and diglycerides absorbed • Triglycerides transported by chylomicrons

11. Absorption of Digested Nutrients • Villi • Small molecules • Passive Transport • Fatty acids, monoglycerides • Active Transport • Requires energy • Monosaccharides and amino acids

12. Sec. 24.3 Overview of Stage II of Catabolism • Metabolic Pathway • Series of biochemical reactions that enables us to explain how an organism converts a given reactant to a desired end product • Stage II • Conversion of subunits to a form that can be completely oxidized • Acetyl-CoA • Enzyme used in many biochemical pathways • Starting material for biosynthesis of lipids

13. Sec. 24.4The Kreb’s Cycle • Kreb’s Cycle • Stage III of catabolism • AKA citric acid cycle, tricarboxylic acid cycle • Produces ATP, NADH, FADH2, and metabolic intermediates for the synthesis of needed compounds during the cycle • Occurs in mitochondria of the cell • Essential for the breakdown of glucose and other simple sugars • Very complex • Utilizes condensation, dehydration, hydration, oxidation, decarboxylation, and hydrolysis reactions • Each reaction is catalyzed by an enzyme

15. Kreb’s Cycle Con’t http://www.johnkyrk.com/krebs.html Starts when pyruvate produces Acetyl-CoA 1. Acetyl-CoA is the starting reactant—supplies the 2 carbons needed Acetic acid molecule linked to coenzyme A 2. Acetyl-CoA condenses with oxaloacetate to produce citrate (citric acid cycle)

16. Kreb’s Cycle Con’t 3. Isocitrate is reduced to NAD which leads to the NADH (nicotinamide adenine dinucleotide) (NADH used by Electron Transport Chain to create further ATP) 3 total NADH produces per 1 Acetyl-CoA 4. Alphaketogluterate produced—more NAD and acetyl-CoA added to produce two more NADH+ along with succinyl CoA 5. GTP is produced from GDP when another phosphate group is added. GTP (guanosine triphosphate) is easily converted to ATP…1=1 ratio

17. Kreb’s Cycle Con’t 6. FAD (flavin adenine nucleotide) added to succinate which readily accepts and transfers electron pairs to Electron Transport Chain where FADH2which is converted to ATP…each FAD yields 2 ATP 7. Water added to fumerate to produce malate. NAD added, electrons are transferred to produce NADH+ and oxaloacetate 8. Two more pyruvate are added to start the Kreb’s Cycle all over again

18. Sec. 24.5Cellular Respiration Occurs in mitochondria Mitochondria Power plants of the cell 100 to 5000 in a particular cell Outer and inner membranes that are folded into a series of ridges known as cristae Contains all of the enzymes and coenzymes needed for the Kreb’s cycle

19. The Electron Transport Chain Sequence of enzymes used to oxidize coenzymes and transfer the resulting electrons to oxygen Coenzymes involved: NADH and FADH2 Closely linked to the Kreb’s cycle Very little ATP actually produced in Kreb’s Aids in oxygen participation Assists significantly in ATP production ETC consists of four complexes (I, II, III, IV) Each complex contains several enzymes, other proteins, and metal ions that each have different tasks

20. Electron Transport Chain Con’t CoQ (coenzyme quinone, or ubiquinone) Mobile electron carrier that acts as an electron shuttle between Complexes I and II and Complex III Reactions of the ETC are a series of oxidation/reduction reactions involving cytochromes Cytochromes: iron-sulfur proteins and other molecules that ultimately reduce oxygen to water in Complexes III and IV Passes electrons through a series of protein complexes, moving towards increasing electron potential Electrons flow from molecules that easily transfer electrons to those that easily accept them Reduction Potential

21. Oxidative Phosphorylation Metabolic pathway that uses energy released by the oxidation of nutrients to produce ATP Tightly coupled with ETC Used by almost all forms of life Highly efficient way of storing energy NADH and FADH2 only work if ADP is phosphorylated to ATP

22. Oxidative Phosphorylation Con’t Electrons are transferred from electron donors to electron acceptors such as oxygen, in a redox reaction Reactions release energy, which is used to form ATP http://www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.htm

24. Theoretical Yields

25. ATP and Fibromyalgia Fibromyalgia Chronic pain in muscular system Afflicts 7-10 million Americans Mainly women ages 20-50 (3.4% of all women in US) Possible Cause: Unable to process ATP and abnormally low levels of ATP

26. Sec. 24.6Muscle Power Exercise Prolongs life Lowers chance of disease Makes muscles stronger, more flexible, more efficient in use of oxygen Muscles 600 in human body Strong muscles can do more work than weak Heart is a muscle…exercise pulse and blood pressure usually decline Training Effect Person who exercises regularly is able to do more physical work with less strain

27. Muscle Power Con’t Muscle stimulation and contraction requires energy (ATP) Two proteins that play important roles in muscle movement Actin Myosin Acts as an enzyme for removal of phosphate group from ATP Directly liberates the energy required for contraction Actomyosin Contractile protein of which muscles are made

28. Muscle Power Con’t Aerobic In presence of oxygen Respiration is aerobic under usual conditions and during moderate exercise Anaerobic Absence of oxygen Oxygen debt Not enough oxygen available during strenuous exercise Energy obtained from carbohydrates through the breakdown of glycogen and anaerobic glycolysis

29. Muscle Power Con’t Muscle Tissues Slow twitch (Type I) Light and moderate activity Respiratory capacity is high Can provide much energy via aerobic pathways Geared to oxidative phosphorylation High myoglobin Heme-containing protein in muscle that stores oxygen obtained from hemoglobin Needs high levels of oxygen Many mitochondria in Type I muscle cells Long, sustained activities (marathon runners)

30. Muscle Power Con’t Muscle Tissues Con’t Fast-twitch (Type IIB) Opposite characteristics of slow twitch Low respiratory capacity Low myoglobin levels Fewer mitochondria Generates ATP rapidly Short bursts of activity, muscles fatigue rapidly Sprinters, weightlifters

31. Muscle Power Con’t Training Endurance Increases size and number of mitochondria Increases level of enzymes required for transport and oxidation of fatty acids, the Kreb’s cycle, and oxidative phosphorylation Doesn’t increase muscle size significantly Strength No increase in mitochondria Causes neovascularization which increases efficiency of lactic acid removal Lactic acid inhibits ATP production and use

32. Creatine Phosphate Storage form of energy in muscles of vertebrates As ATP is utilized, creatine phosphate reacts with ADP to produce more ATP and creatine Concentration limited—used up after about 10-15 seconds of strenuous exercise Found in high amounts in meat and fish Naturally produced in body in synthesis of arginine Creatine supplements may increase muscle performance and body mass