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CHAPTER 4: CELL METABOLISM 1 METABOLIC PROCESSES all chemical reactions that occur in the body Two (2) types : Anabolism • Larger molecules are made from smaller ones • Requires energy Catabolism • Larger molecules are broken down into smaller ones • Releases energy 2 CONTROL OF METABOLIC REACTIONS Enzymes • Control rates • Not consumed in chemical reactions • Substrate specific: Shape of active site determines substrate Substrate molecules Product molecule Active site Enzyme molecule (a) Enzyme-substrate complex (b) (c) Unaltered enzyme molecule 3 ENZYME ACTION Metabolic pathways • Series of enzyme-controlled reactions leading to formation of a product • Each new substrate is the product of the previous reaction Substrate 1 Enzyme A Substrate 2 Enzyme B Substrate 3 Enzyme C Substrate 4 Enzyme D Product • Enzyme names commonly reflect the substrate • Have the suffix – ase • Examples: sucrase, lactase, protease, lipase 4 Cofactors • Make some enzymes active • Non-protein component • Ions or coenzymes Coenzymes • Organic molecules that act as cofactors • Vitamins 5 FACTORS THAT ALTER ENZYMES • Heat • Radiation • Electricity • Chemicals • Changes in pH 6 RELEASE OF CHEMICAL ENERGY • Chemical bonds are broken to release energy • We burn glucose in a process called oxidation (combustion) 7 4.5: CELLULAR RESPIRATION Occurs in a series of reactions: 1. Glycolysis 2. Citric acid cycle (TCA or Kreb’s Cycle) 3. Electron transport system 4. Produces ATP 8 Includes: • Anaerobic reactions (without O2) – produce little ATP • Aerobic reactions (requires O2) – produce most of ATP needed 9 SUMMARY OF CELLULAR RESPIRATION Glycolysis no O2 High-energy electrons (e–) 2 ATP Glycolysis Cytosol 6-C sugar 2 3-C sugars 2 ATP 1 Glucose Pyruvic acid Pyruvic acid Citric Acid Cycle 2 High-energy electrons (e–) CO2 Mitochondrion Produces acetyl coenzyme A (CoA) 2 turns of cycle 3 2 ATP O2 Acetyl CoA Citric acid Oxaloacetic acid Citric acid cycle High-energy electrons (e–) 2 CO2 2 ATP Electron Transport Chain Electron transport chain 4 34 ATP formed 32–34 ATP 2e– and 2H+ O2 H2O 10 SUMMARY OF CATABOLISM Breakdown of large macromolecules to simple molecules Food Proteins Carbohydrates Fats Amino acids Simple sugars Glycerol Fatty acids (glucose) Glycolysis ATP Pyruvic acid Formation of CoA and 2 ATP Acetyl coenzyme A Citric acid cycle Complete oxidation, production of most of the ATP CO2 ATP High energy electrons carried by NADH and FADH2 3 Electron transport ATP chain 2e– and 2H+ –NH2 ½ O2 H2O Waste products CO2 4.6: Nucleic Acids and Protein Synthesis • Genetic information – instructs cells how to construct proteins; stored in DNA • Gene – segment of DNA that codes for one protein • Genome – complete set of genes • Genetic Code – method used to translate a sequence of nucleotides of DNA into a sequence of amino acids 12 TYPES OF RNA MOLECULES Messenger RNA (mRNA): Making of mRNA (copying of DNA) is transcription Transfer RNA (tRNA): • Carries amino acids to mRNA • Carries anticodon to mRNA • Translates a codon of mRNA into an amino acid Ribosomal RNA (rRNA): • Provides structure and enzyme activity for ribosomes 13 4.7: CHANGES IN GENETIC INFORMATION Only about 1/10th of one percent of the human genome differs from person to person Inborn Errors of Metabolism • Occurs from inheriting a mutation that alters an enzyme • Creates a block in a biochemical pathway 14 NATURE OF MUTATIONS Mutations – change in genetic information May or may not change the protein Code for glutamic acid Result when: Repair enzymes: correct mutations P T P S Direction of “reading” code • Extra bases are added or deleted • Bases are changed P P S A S C P S (a) T S T P Code for valine Mutation C S (b) 15 16 ANIMATION: HOW ENZYMES WORK Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 17 ANIMATION: DNA STRUCTURE Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 18 ANIMATION: DNA REPLICATION Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 19 ANIMATION: STAGES OF TRANSCRIPTION Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 20 ANIMATION: HOW TRANSLATION WORKS Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 21 ANIMATION: PROTEIN SYNTHESIS Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 22