Chapter 24 sp24 (2).pptx

Chapter 24: Metabolism Objectives 1. Define metabolism. Explain how catabolism and anabolism differ. 2. Summarize important events and products of glycolysis, the citric acid cycle, and electron transport. 3. Compare the metabolic pathway of carbohydrates and lipids and their products. 4. Summ...

Chapter 24: Metabolism Objectives 1. Define metabolism. Explain how catabolism and anabolism differ. 2. Summarize important events and products of glycolysis, the citric acid cycle, and electron transport. 3. Compare the metabolic pathway of carbohydrates and lipids and their products. 4. Summarize the events in carbohydrate metabolism, and fatty acid metabolism and relate them back to how we utilize each as an energy source. Part 2 – Metabolism Metabolism: sum of all biochemical reactions inside a cell involving nutrients Anabolism: the reactions that build larger molecules from smaller ones (synthesis) Catabolism: The reactions that break down larger molecules into smaller ones. (Decomposition) © 2016 Pearson Education, Inc.  Role of Carbohydrates, Lipids, and Proteins Carbohydrates Dietary sources Primarily from plants, such as starch (complex carbohydrates) in grains and vegetables Sugars (mono- and disaccharides) © 2016 Pearson Education, Inc. Carbohydrates (cont.) Uses in body Glucose: fuel most used by cells to make ATP C6H12O6 Excess glucose is converted to glycogen or fat, then stored Fructose and galactose are converted to glucose by liver before entering circulation Metabolized through glycolysis © 2016 Pearson Education, Inc. Lipids Dietary sources Triglycerides (neutral fats): most abundant form Found in saturated fats in meat, dairy foods, tropical oils, or hydrogenated oils (trans fats) Unsaturated fats found in seeds, nuts, olive oil, and most vegetable oils Cholesterol found in egg yolk, meats, organ meats, shellfish, and milk products Liver makes ~85% cholesterol © 2016 Pearson Education, Inc.  Metabolized through Lipids (cont.) lipolysis Uses in body Adipose tissue offers protection, insulation, fuel storage Phospholipids essential in myelin sheaths and all cell membranes Cholesterol stabilizes membranes; precursor of bile salts, steroid hormones Major fuel of skeletal muscle © 2016 Pearson Education, Inc. Proteins Dietary sources Animal products (eggs, milk, fish, most meats), as well as soybeans, are considered complete proteins Contain all needed essential amino acids Legumes, nuts, and cereals contain incomplete proteins (lack some essential amino acids) © 2016 Pearson Education, Inc. Proteins (cont.) Uses in body Structural materials Example: keratin (skin), collagen and elastin (connective tissue), and muscle proteins Functional molecules Example: enzymes and some hormones Three factors help determine whether amino acids are used to synthesize proteins or burned as fuel: 1. All-or-none rule All amino acids needed must be present for protein synthesis to occur; if not all are present, then amino acids are used for energy © 2016 Pearson Education, Inc. Proteins (cont.) Uses in body (cont.) 2. Adequacy of caloric intake Protein is used as fuel if insufficient carbohydrate or fat is available 3. Hormonal controls Anabolic hormones (GH, sex hormones) accelerate protein synthesis and growth Adrenal glucocorticoids (released during stress) promote protein breakdown and conversion of amino acids to glucose © 2016 Pearson Education, Inc. Anabolism and Catabolism Anabolism: synthesis of large molecules from small ones (example: synthesis of proteins from amino acids Catabolism: hydrolysis of complex structures to simpler ones (example: breakdown of proteins into amino acids) Cellular Respiration A Collection of catabolic reactions that allows us to use food as energy Done through 3 processes: Glycolysis Citric Acid Cycle Oxidative phosphorylation (Electron Transport Chain) Cellular Respiration cont. - Glycolysis Glycolysis ("sugar splitting"): Utilized by carbohydrates only Glucose is made up of 6 carbons bonded together The group of carbon will break apart = two, 3-carbon fragments. Each carbon fragment gives 2 ATP. Need 2 ATP molecules to do this. Occurs in cytosol of cells Anaerobic (can occur without oxygen present) Converts glucose to pyruvic acid Produces a net of 2 ATP for every glucose molecule Cellular Respiration – Citric acid cycle After glucose is turned into pyruvate, and oxygen is present the pyruvate moves to the citric acid cycle. If no O2 is present, the pyruvic acid is turned to lactic acid We now enter from the cytoplasm to the mitochondria For each turn of the citric acid cycle we get: 1 molecule of ATP, NADH & FADH2 Cellular Respiration – Electron Transport Chain Carries out the final catabolic reactions that occur. We are still inside the mitochondria We have to have O2 present for this process to occur. Uses hydrogen combined with oxygen to make a large amount of ATP. Net of about 28 ATP. Cellular Respiration SO- We have 2 ATP molecule from glycolysis 2 ATP from citric acid cycle 28 ATP from ETC = About 32 ATP are produced from one glucose molecule  Stage 1: GI Tract Nutrients are: Digested into absorbable units. Absorbed into the blood and Figure transported to tissue cells. PROTEINS CARBOHYDRATES FATS 24.3 Three Amino acids Glucose and other sugars Glycerol Fatty acids stages of Stage 2: Tissue Cells Anabolism or catabolism: Proteins Glucose Glycogen Triglycerides metabolis In anabolism, nutrients are Glycolysis built into macromolecules. In catabolism, nutrients are m of broken down to pyruvic acid and acetyl CoA. Glycolysis is the major NH3 energy- Pyruvic acid catabolic pathway. containing Acetyl CoA nutrients. Stage 3: Mitochondria Oxidative breakdown of stage 2 products: Citric CO2 is released. acid The H atoms removed are ultimately Infrequent cycle CO2 delivered to molecular oxygen, forming water. O2 Some of the energy released is used to form ATP. The citric acid cycle and oxidative Oxidative phosphorylation phoshorylation are the major pathways. H H2O (in electron transport chain) Catabolic reactions ATP ATP ATP Anabolic reactions © 2016 Pearson Education, Inc.  Figure 24.11 Energy yield during cellular respiration. Mitochondrion Cytosol 2 NADH + H+ Electron 2 NADH + H+ 6 NADH + H+ 2 FADH2 shuttle across mitochondrial membrane Glycolysis Citric Electron transport 2 acid chain and oxidative Pyruvic Acetyl Glucose cycle phosphorylation acid CoA (4 ATP – 2 ATP 10 NADH + H+  2.5 ATP used for activation Lactic 2 FADH2  1.5 ATP energy) Acid Net +2 ATP +2 ATP + about 28 ATP by substrate-level by substrate-level by oxidative phosphorylation phosphorylation phosphorylation –2 ATP (average shuttle cost) Fate of pyruvic acid depends on Typical About ATP yield if there is oxygen present. If no 30 ATP per glucose oxygen, pyruvic acid is made into lactic acid. If there is oxygen present, we continue to the next step. © 2016 Pearson Education, Inc. Metabolism of triglyceride Remember – triglyceride is made of a glycerol backbone, and three fatty acids. To break down the glycerol has to be broken from the fatty acids Glycerol backbone goes through glycolysis as mentioned above. Fatty acids will undergo lipolysis Lipid metabolism cont. Is key for long-term energy storage and release. Process is utilized when there isn’t enough glucose available. After fatty acids are liberated they are converted to acetyl CoA, and enter the citric acid cycle to be made into ATP. Each fatty acid is used to make ATP = higher net ATP are produced during lipolysis (verses 1 glucose molecule) 1-20 chain fatty acid = 144 ATP Metabolism of proteins Not an efficient use to energy Takes a very long time, and uses a lot of ATP, not as much net ATP as lipid metabolism. Proteins are used as a last resort Figure 24.19 Proteins Carbohydrates Fats Interconversio n of Proteins Glycogen Triglycerides carbohydrate s, fats, and Glucose proteins. Amino acids Glycerol and Glucose-6-phosphate fatty acids Glyceraldehyde 3-phosphate Keto acids Pyruvic acid Lactic acid NH3 Acetyl CoA Urea Ketone bodies Citric Excreted acid in urine cycle © 2016 Pearson Education, Inc.