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Metabolism: You are a product of what you ate! 4/21-23 CH26

Metabolism: You are a product of what you ate! 4/21-23 CH26. How do we defecate? How much energy does carbohydrate, protein and fat contain? Why do we prefer to metabolize glucose in the cytosol? How does glycolysis work in the cytosol?

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Metabolism: You are a product of what you ate! 4/21-23 CH26

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  1. Metabolism: You are a product of what you ate! 4/21-23 CH26 • How do we defecate? • How much energy does carbohydrate, protein and fat contain? • Why do we prefer to metabolize glucose in the cytosol? • How does glycolysis work in the cytosol? • How does the Citric Acid Cycle work in the mitochodria? • How does oxidative phosphorylation work in the mitochondria? • How do we metabolize fats with beta-oxidation? • How do we transport cholesterol in the blood? • Why do we produce urea from ammonia?

  2. Odds and Ends,,,,of colorectal physiology • Dietary Fiber helps treat constipation because it increases the water content of the fecal material due to hydrogen bonded water…..watch to see what comes out more easily…..dry feces or those with a higher water content! • The microflora of the large intestine is important in actually producing some vitamins! • What happens during an appendicitis? Why is it often fatal? • What happens when flora use undigested food (polysacchrides in beans) to generate volatile fatty acids? • Hello “Flattus” or gas! • Why are colorectal cancers so common? • Why does fiber help reduce the risk? • What are colorectal polyps?

  3. Like the micturition reflex, the defecation reflex also uses local connections in the sacral roots (weak control). However, primary control of defecation is from higher CNS centers in the brain.

  4. Cliff Notes to Metabolism: CH 26How is metabolic or chemical energy measured? Energy Content: ability to heat water or do work (chemical or physical) Chemical Calorie (cal)= 1 cal raises temp of 1 ml 1o C Dietary Calorie (Cal)= 1 Cal raises 1,000 ml by 1o C Typical Person needs about 1,800 to 2,000 Cal/day This energy comes from diet (food) or stored reserves (fat/glycogen) Total = Basal Metabolic Rate + Energy for the “extras” Sedentary Lifestyle: Caloric needs go DOWN Active Lifestyle: Caloric needs go UP Aging: after the age of 40 your Basal Metabolic Rate decreases a few percent per year! This is why we gain weight after 40.

  5. How many calories per gram can the three nutrient types provide?“Nutrient”: dietary element required for health. There are 3 nutrient types: 1) Carbohydrates (sugars): 4 Cal/gram-water soluble • Easy to digest/store • Common in environment 2) Lipids (fat): 9 Cal/gram- not water soluble • Easy to digest/store • Common in environment 3) Protein (nitrogen): 45-60 grams/day 4 Cal/gram-variable water solubility • Difficult to digest/ inefficient to store for energy • Essential AAs are required in diet • Protein may not be common in environment Alcohol is not a nutrient: 7 Cal/gram and must become ATP or FAT Alcohol cannot be converted to sugars!

  6. WHY ARE CARBOHYDRATES (sugars) THE BEST ENERGY SOURCE FOR THE BODY?: Types: MonosaccharidesDisaccharidesPolysaccharides • Carbohydrates are the energy source of choice! • 1) Water Soluble-easy transport in blood! • 2) Storage forms-glycogen in muscle/liver! • 3) Ease of digestion-break down saliva or intestine! • 4) Ease of oxidation: burn very cleanly (CO2)! • 5) Channels for absorption: Co-transport or Uni-transport • Glucose is the carbohydrate of choice! • Some enter metabolic pathways as galactose or fructose! • Starches/Glycogen are broken down into glucose for use in the body!

  7. Glucose is metabolized by tightly controlled chemical reactions. The Goal is to produce energy (ATP) and CO2!Pathway: GlucoseGlycolysisCitricAcidCycleElectronTranpsort

  8. GLYCOLYSIS “Glucose Breakup” Occurs Only in Cytosol! 1 GLUCOSEIF O2-PRESENT YIELDS: 2 PYRUVATE, 2ATP, and 2 NADH Hypoxia Causes Fermentation: YIELDS DROP: 2 LACTIC ACID 2 ATP NO NADH!!!! This allows NAD+ regeneration….So Glycolysis continues at very low efficiency and ATP yield.

  9. NAD+ IS REQUIRED FOR GLYCOLYSIS TO PROCEEDMOST OF YOUR NAD+ IS PRODUCED IN THE MITOCHONDRIA IF OXYGEN IS AVAILABLE! • Some cells (red blood cells) lack mitochondria entirely and some have very few (neurons) • These cells prefer (need) to use glucose for energy • These cells are typically insulin insensitive! • Sometimes cardiac or skeletal muscle itself is hypoxic and fermentation is needed (i.e. LDH and HEART ATTACK) • Fermentation is back-up energy supply! • Lactic Acid makes the muscles SORE! • Fermentation: lactic acid ends up in the blood and passes to the liver where it is recycled back into pyruvate and glucose. • This is very costly to the body/liver

  10. When pyruvate is produced by glycolysis, it may be oxidized to acetate, CO2 and NADH. Acetate then enters the mitochondrial “Citric Acid Cycle” where it is fully oxidized to carbon dioxide (CO2) that we exhale!The NADH and FADH2 let oxidative phosphorylation make ATP. Please don’t try to memorize this…ok? Just look at the NADH (3) and FADH (1)produced!

  11. Remember: oxygen must be available in mitochondria at the end of the chain to accept the electrons brought to it on NADH and FADH2. This reaction makes “metabolic water” when ATP is produced. Otherwise (no oxygen) THINGS back up and lactic acid fermentation must occur to make ATP! THIS IS OXIDATIVE PHOSPHORYLATION because you make ATP by phosphorylating ADP (ADP+ Pi + energy ATP)

  12. Summary of energy producing catabolic reactions that use glucose as the primary energy input:#1Glycolysis, #2Citric Acid Cycle, #3Electron Transport! Electron-transport chain is also called oxidative phosphorylation, it occurs inside a mitochondria IF the cell HAS mitochondria and oxygen.

  13. HOW DO WE GENEREATE ATP FROM FATS?FATTY ACIDS THEN UNDERGO “BETA-OXIDATION” TO YIELD Acetate, NADH, FADH2, CO2 , tremendous amounts of ATP and a few toxins like ketones and acetone. First Step: The enzyme LIPASE converts storage triglycerides into free fatty acids Second Step: Mitochondria converts FA into acetyl-CoA and NADH/ FADH2 (16 carbon Fatty acid>>>8 Acetyl-CoA) (1 glucoseonly 2 acetyl-CoA) Third Step: Send Acetyl-CoA to the Citric Acid CycleNADH and FADH2 Fourth Step: NADH and FADH2 drive oxidative phosphorylation (ATP produced) Fats and carbohydrates share the citric acid cycle for acetyl-CoA oxidation Do you see why triglycerides can store so much energy? (4 Cal/g glucose verses 9 Cal/g fat). Fat has a Problem: we must have oxygen and mitochondria present in the cell to use NADH, otherwise no ATP produced. Problem: sometimes we oxidize fatty acids and accidentally make acetone and ketones that are toxic! This occurs in uncontrolled diabetes.

  14. Review: How are lipids transported by blood to/from the body? Plasma Albumen: free fatty acid solubility in blood very limited! Chylomicrons of gut> carry digested TG Lymphatics carry chylomicrons through lymphatic vessels that dump into blood at the subclavian vein Very Low Density Lipoproteins (VLDL) Deliver fatty acids to body and carry cholesterol VLDL made by liver and becomes LDL when Triglycerides are removed LDL(BAD) deliver remaining cholesterol of particle to body HDL(GOOD) produced by liver and pick up cholesterol in body and recycle it back to the liver.

  15. The problem with using amino acids for energy in the body is that they invariably produce toxins like ammonia and/or ketones.However, if you are starving you may have no choice! 

  16. You try to convert toxic ammonia molecules into the less harmful urea for excretion in the urine! However, if ammonia production is greater than urea production and removal we can poison our body. This is why amino acids from protein are poor choices for energy production.

  17. Some good lecture review questions (CH 26: Metabolism) 1) Where do the glycolytic reactions occur and what happens to glucose as a result of these reactions? 2) What are the products of glycolysis in the presence of oxygen and in conditions of hypoxia? 3) What does the citric acid cycle do and where in a cell does it occur? 4) What is the name of the chemical reactions in the mitochondria that use the high-energy electrons of NADH and FADH2 to produce ATP? 5) Name two places in the body where one could find cells that cannot use the citric acid cycle or electron transport and are dependent upon glucose and fermentation? 6) Lipase breaks a triglyceride into free fatty acids. Fatty acids are broken down into acetyl-CoA. What enzyme system helps fat oxidizing cells use acetyl-CoA from either glucose or fat? 7) What are two potential toxins created in a cell by beta-oxidation? 8) Where is cholesterol synthesized? How is it carried to the body? How is cholesterol in the body returned to the liver? 9) What nitrogen-containing toxin is produced when we have to burn amino acids from protein as the primary energy source during starvation? 10) Glucose is oxidized without making toxins, and both fats and amino acids can create toxins, this is why our bodies prefer carbohydrates (glucose) for energy.

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