Chapter 4 Metabolism Part 2

Chapter 4 Metabolism Part 2 - Ch 4: Cellular Metabolism -...

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Unformatted text preview: Ch 4: Cellular Metabolism - Part 2 Ch s Energy as it relates to Biology s Enzymes s Metabolism s Catabolism (ATP production) s s Glycolysis and the TCA Cycle Anabolism (Synthetic pathways) s Protein Synthesis Metabolism Metabolism s Definition = “All chemical reactions that take Definition place within an organism.” place s Metabolic pathways = network of linked reactions s Basic feature: coupling of exergonic rxs with endergonic rxs. (direct vs. indirect coupling) (direct Review: Review: s Energy = capacity to do work s s Usually from ATP Enzymes = biological catalyst s Lower activation energy s Return to original state s Opportunity for control Metabolism p 101 101 Catabolism → Energy Anabolism → Synthesis Energy transferred commonly measured in calories: 1 cal = ↑ 1 g of H2O by 1° C 1 Kcal = ↑ temp. of 1L H2O by 1o C. = Calorie (capital C) Energy released in catabolic reactions is trapped in Energy 1) Phosphate bonds 1) 2) Electrons Metabolic pathways: Network of interconnected chemical reactions interconnected Linear pathway Intermediates Circular pathway Branched pathway Control of Metabolic Pathways Control (Chapter 6) 1. Enzyme concentration (already Enzyme covered) covered) 2. Enzyme modulators Enzyme - Feedback- or end product inhibition inhibition - Hormones - Other signaling molecules 1. Different enzymes for Different reversible reactions reversible 2. Enzyme isolation 3. Energy availability (ratio of Energy ADP to ATP) ADP Catabolic Pathways: ATP-Regeneration ATP Amount of ATP produced reflects on usefulness of metabolic pathways: Aerobic pathways Anaerobic pathways Different biomolecules enter pathway at different points ATP = Energy Carrier of Cell (not very useful ATP for energy storage) ATP Cycle ATP : ADP ratio determines status of ATP synthesis reactions Glycolysis Glycolysis s From 1 glucose (6 carbons) to 2 From pyruvate (3 carbons) molecules pyruvate s Main catabolic pathway of cytoplasm s Does not require O2 ⇒ common for (an)aerobic catabolism (an)aerobic s Starts with phosphorylation of Starts Glucose to Glucose 6-P Glucose s (“Before doubling your money you first (“Before have to invest!”) have The Steps of The Glycolysis Glycolysis Net gain? Pyruvate has 2 Possible Fates: Anaerobic catabolism: Pyruvate Lactate Aerobic catabolism: Pyruvate Citric Acid Cycle Citric Acid Cycle Citric Other names ? Takes place in ? Energy Produced: 1 ATP 3 NADH NADH 1 FADH2 FADH Electron transport System Waste – 2 CO2 Waste Energy Yield of Krebs Cycle NADH See Fig. 4-24 NADH NADH FADH2 Final step: Electron Final Transport System s Chemiosmotic theory / oxidative phosphorylation s Transfers energy from NADH and FADH2 to ATP (via e- donation and H+ transport) (via donation s Mechanism: Energy released by movement of e- through transport system movement is stored temporarily in H+ gradient is s NADH produces a maximum of 2.5 ATP NADH FADH2 produces a maximum of 1.5 ATP FADH s 1 ATP formed per 3H+ shuttled through ATP Synthase Fig 4-25 Summary of CHO catabolism Cellular Respiration Respiration Maximum potential yield for aerobic glucose metabolism: 30-32 ATP synthesized from ADP H2O is a byproduct Protein Catabolism?? Protein s s s Proteases Peptidases Deamination (removal Deamination of the NH3) of s s NH3 becomes urea becomes Pyruvate, Acetyl CoA, Pyruvate, TCA intermediates are left. left. Lipid Catabolism?? Lipid s Lipolysis s s Lipases break lipids Lipases into glycerol (3-C) into Glycerol enters the Glycerol glycolytic pathway glycolytic s Called β-oxidation Called Synthetic Pathways Synthetic Anabolic reactions synthesize large Anabolic biomolecules biomolecules Unit molecules Glucose Amino Acids Macromolecules nutrients & energy required Polysaccharides Lipids DNA Protein Glycogen Synthesis Glycogen Made from glucose Stored in all cells but especially in s Liver (keeps 4h glycogen reserve for between meals) Liver (keeps s Skeletal Muscle → muscle contraction Skeletal Gluconeogenesis Glycolysis in reverse Glycolysis From glycerol, aa and lactate From All cells can make G-6-P, only liver and All Kidney can make glucose Kidney Protein Synthesis Proteins are necessary for cell functions Proteins Protein synthesis is under nuclear direction Protein ⇒ DNA specifies Proteins DNA ? DNA DNA mRNA ? Protein How can only 4 bases in DNA bases encode > 20 different aa in protein? encode 1 lletter word: 1 base = 1 aa etter 2 letter word: 2 bases = 42 = 16 aa letter 3 letter word: 3 bases = 43 = 64 aa 3 letter words = base triplets or codons codons Redundancy of Genetic Code (p 115) A combination of three bases forms a codon 1 start codon start 3 stop codon 60 other codons for 60 19 aa 19 Transcription Transcription DNA is transcribed into complementary mRNA mRNA by RNA Polymerase + nucleotides + Mg2+ + ATP Gene = elementary unit of inheritance Compare to Fig. 4-33 mRNA Processing (Fig. 4-33) Protein synthesis fig 4-27 fig Translation Translation mRNA is translated into string of aa (= polypeptide) (= mRNA 2 important components ?? mRNA + ribosomes + tRNA meet in cytoplasm Anticodon pairs with mRNA codon ⇒ aa determined Amino acids are linked via peptide bond. Fig 4-34 Primary Structure Post – Translational protein modifications: Folding, cleavage, additions ⇒ glyco- , lipo- proteins Protein Sorting Protein s No signal sequence ⇒ protein stays in cell protein No s Signal sequence ⇒ protein destined for translocation Signal into organelles or for export for For “export proteins”: Signal sequence For leads growing polypeptide chain across ER membrane into ER lumen membrane Modifications in ER Modifications Transition vesicles to Golgi apparatus for further Golgi modifications modifications Transport vesicles to cell Transport membrane membrane DNA Replication s SemiSemiconservative conservative s DNA DNA polymerase polymerase ...
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This note was uploaded on 12/24/2011 for the course STEP 1 taught by Professor Dr.aslam during the Fall '11 term at Montgomery College.

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