Chapter 5

1. Chapter 5 Bioenergetics: Fundamentals of Human Energy Transfer

2. First Law of Thermodynamics • Conservation of energy • Dictates that the body does not produce, consume, or use up energy; rather, it transforms it from one form into another as physiologic systems undergo continual change

3. The 6 forms of Energy • Light (sun) • Mechanical • Electric • Nuclear • Heat (solar) • Chemical (fuel, oil)

4. What is Photosynthesis? • The process by which plants, use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the "fuel" used by all living things. • The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. • Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive.

5. What is the equation for the chemical reaction of photosynthesis? CO2 + H2O  Glucose + O2 6CO2 + 6H2O  C6 H12O6 + 6O2 What do muscles use for energy? • Glucose (sugar) + O2 + Insulin for work • Muscle  muscle cells (trillions) – made up of nucleus, cytoplasm, mitochondria, organelles, etc.

6. Exercise Physiology – muscles act on the bones to transform chemical energy (ATP) into mechanical energy and motion. Photosynthesis creates sugar, cellular respiration breaks down sugar Organisms transform the chemical energy into a form it can use.

7. Redox Reactions • Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions • Redox reactions for short • The loss of electrons during a redox reaction is called oxidation • The acceptance of electrons during a redox reaction is called reduction

8. Oxidation [Glucose loses electrons (and hydrogens)] Glucose Oxygen Carbon dioxide Water Reduction [Oxygen gains electrons (and hydrogens)]

9. Key Point • The limits of exercise intensity ultimately depend on the rate that cells, extract, conserve, and transfer chemical energy in the food nutrients to the contractile filaments of skeletal muscle

10. Bioenergetics • Bioenergetics is the subject of a field of biochemistry that concerns energy flow through living systems. • It is the study of the metabolic processes that can lead to the production and utilization of energy in forms such as ATP molecules. • “How we break down energy nutrients into usable energy (ATP)”

11. Bioenergetics • Potential energy • Energy associated with a substance’s structure or position. • Kinetic energy • Energy of motion. • Potential energy and kinetic energy • The total energy of any system • Releasing potential energy (in the bonds of macronutrients) transforms it into kinetic energy of motion.

12. Some of the ways we transfer energy through bioenergetics • Anabolic – build up • requires ATP • Catabolic – break down • yields ATP

13. CHAPTER 6 Energy Transfer in the Body

14. 3 ways a muscle cell can produce ATP • ATP/PCr system • Anaerobic glycolysis (cytoplasm of muscle cell) • Lactate shuttle • Without enough oxygen, muscle cells break down glucose to produce lactic acid • Lactic acid is associated with the “burn” associated with heavy exercise • If too much lactic acid builds up, your muscles give out • Aerobic glycolysis (mitochondria of muscle cell) • Glycolysis • The Krebs cycle • Electron transport

16. Some Definitions • Glucose – simple sugar. The energy required of muscles to do work. • Glycolysis – the degradation of glucose. • Aerobic glycolysis • Anaerobic glycolysis • Glycogenolysis – the process of carbohydrate degradation when the starting substrate is stored glycogen. • Lipolysis – the degradation of fats (lipids) • All ‘ysis’ reactions require the work of enzymes to catalyze (speed up) their reactions.

17. Glycolysis occurs in the cytoplasm (the water medium of a cell)

18. HIGH-ENERGY PHOSPHATES • Adenosine Triphosphate – the energy currency • Powers all of cell’s energy requiring processes • Potential energy extracted from food • Energy is stored in bonds of ATP • Body stores 80-100g of ATP at any one time • If it’s there it gets used quickly (1-3 seconds of explosive all-out exercise) • Energy is transformed to do work

21. HARNESSING ATP’s POTENTIAL ENERGY • ADP forms when ATP joins with water (hydrolysis) • Outermost phosphate is released • Catalyzed by the enzyme ATPase • Limited currency • Low ATP levels in cells create sensitivity to ATP/ADP

22. At the onset of exercise, ATP is split into ADP + Pi to provide energy for muscular contraction. The increase in ADP stimulates creatine kinase to breakdown PCr to resynthesize ATP.

23. PHOSPHOCREATINE – THE ENERGY RESEVOIR • Anaerobic resynthesis of ATP • ADP + PCr  ATP + Cr • Hydrolyzed by the enzyme creatine kinase • ADP is phosphorylated to ATP • Creatine may be phosphorylated back to PCr • Cells store ~4-6 times more PCr than ATP • Gee, why is there so much hype over creatine supplements?

24. IMPORTANT BY-PRODUCTS • If ATP is constantly being broken down we must be talking about continuous movement (i.e., exercise), therefore hydrolysis and phosphorylation stimulate: • Glycogenolysis • Glycolysis • Respiratory pathways of mitochondria • If glycolysis moves into mitochondria, we must be talking about aerobic glycolysis! • Anaerobic glycolysis occurs in the cytoplasm only.

27. The Krebs Cycle • animation

28. ENERGY RELEASE FROM FOOD • Carbohydrate • Glycolysis • Occurs in cytosol • Series of chemical reactions • The breakdown of Glucose to pyruvate to acetyl CoA • If pyruvate is broken down into acetyl CoA we are talking about aerobic glycolysis (aerobic respiration) – where??? • If pyruvate is not broken down into acetyl CoA it is reformulated into lactate – meaning we are talking about which type of glycolysis (aerobic or anaerobic?) • Limited quantities of ATP are generated • Glucose is cleaved into 2-pyruvate molecules • See page 187 in text

29. In the Cytoplasm of the Cell

30. Aerobic Glycolysis In the Mitochondria of the Cell

31. Aerobic Glycolysis

32. Aerobic Glycolysis

33. Aerobic respiration is divided into two processes: the Krebs cycle, and the Electron Transport Chain, which produces ATP through chemiosmotic phosphorylation. The energy conversion is as follows: C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy (ATP) muscular work

34. LACTATE FORMATION • Pyruvate may be reduced to form lactate • Occurs in an anaerobic state • Lactate dehydrogenase drives this reversible reaction • Oxidation of glucose, which causes protons to be released into solution • pH drops as proton concentration rises • What does a lowered pH mean? • Reduction of pyruvate to lactate helps to buffer the solution

35. LACTATE IS NOT A WASTE PRODUCT • Blood lactate potential uses: • Lactate shuttle • Converted to pyruvate and oxidized as an energy source in another cell • Gluconeogenesis • Converted back to glucose in the liver in Cori Cycle

38. GLYCOGENESIS • Metabolism of glucose to glycogen • Is this an anabolic or catabolic reaction? • Regulation of glycogen metabolism • Glycogen Synthase drives the reaction

39. GLYCOGENOLYSIS • Metabolism of glycogen to glucose • In the liver • Glycogen Phosphorylase drives the reaction • Glucose released into blood • Maintains blood glucose levels • Epinephrine stimulates Glycogen Phosphorylase

40. ENERGY RELEASE FROM FOOD • Citric Acid Cycle • Also known as Krebs Cycle • Continues oxidation of: • Carbohydrates following glycolysis • Fatty acids following beta oxidation • Some amino acids following deamination • What’s the purpose of the krebs cycle? • See page 189

41. The Krebs Cycle • animation

46. TOTAL ENERGY TRANSFER FROM GLUCOSE CATABOLISM Ok, decent

47. ENERGY RELEASE FROM FAT • Adipocytes • Site of fat storage and mobilization • Fat is stored primarily as triglycerides • Mobilization • First step in utilizing fatty acids is Lipolysis • Triglycerides are split into fatty acids and glycerol • Hormone Sensitive Lipase drives lipolysis

49. FATTY ACIDS FROM LIPOPROTEINS • Lipoproteins also transport triglycerides • What are the 2 common lipoproteins? • Lipoprotein Lipase (LPL) catalyzes hydrolysis of these triglycerides • LPL is located on surface of surrounding capillaries

50. OXIDATION OF FAT • Beta Oxidation • Cleaves two-carbon compounds from fatty Acetyl CoA molecule • Two-carbon acetyl groups enter Citric Acid Cycle • Oxidation produces NADH (an enzyme)