Introduction to Metabolism Cell Structure and Function

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1 Introduction to Metabolism Cell Structure and Function Cells can be divided into two primary types prokaryotes - Almost all prokaryotes are bacteria eukaryotes - Eukaryotes include all cells of multicellular organisms, and many single-celled organisms such as the yeasts and the protists.

2 Introduction to Metabolism - Origin of Eukaryotes

3 Introduction to Metabolism - Cell Structure and Function Anatomy of a Typical Animal Cell The differences between prokaryotes and eukaryotes lie in their internal organization and modes of reproduction. In eukaryotic cells, many of the cellular macromolecules a r e p a c k a g e d i n t o organelles, s u b c e l l u l a r structures surrounded by their own membranes. Prokaryotes lack this internal organization.

4 General Functions of Metabolism Obtain energy in a chemical form by degradation of nutrients Convert a wide variety of nutrient molecules into the central precursor molecules needed to build proteins, carbohydrates, nucleic acids, and lipids Synthesize cell molecules. Modify and repair the biomolecules necessary for specific functions in specialized cells or both

5 Catabolism vs Anabolism

6 Catabolism vs Anabolism Catabolism Biochemical degradation of energy containing compounds. 1. Capture of the energy in new chemical forms. (ATP, GTP, NADH, NADPH, FADH2) 2. Conversion of energy containing compounds into a small number of simpler molecules. Pyruvate, acetate, Krebs cycle intermediates Anabolism Biosynthesis of biomolecules from simple components. 1. Glucose other monosaccharides and polysaccharides 2. Acetate fatty acids 3. Glycerol + fatty acids triacylglycerols 4. Amino acids hormones, alkaloids, porphyrins, neurotransmitters, proteins 5. Nucleotides ATP, coenzymes, nucleic acids Ion and biological transport across membranes.

7 Stages of Catabolism 1 Nutrient molecules are degraded to lower-molecular mass components. 2 The products of stage 1 are converted into one simple molecule: Acetyl-S-CoA. 3 Acetyl-S-coenzyme A is oxidized to CO2 and H2O by the Citric Acid Cycle. 4 Reduced coenzymes are oxidized through the Electron Transport Chain to yield ATP.

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9 Nutrients New Forms of Energy During the second and third stages of catabolism, important compounds are formed that fuel anabolism: Adenosine triphosphate (ATP) Carrier of energy. Nicotinamide adenine dinucleotide (NADH) Carrier of reducing power Nicotinamide adenine dinucleotide phosphate (NADPH) Carrier of reducing power Flavin adenine dinucleotide (FAD) Carrier of reducing power Flavin adenine mononucleotide (FMN) Carrier of reducing power

10 ATP NAD(P) +

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12 Synthesis of ATP Substrate level phosphorylation: Direct transfer of a phosphate group from a high energy phosphate compound to adenosine diphosphate Adenosine-O--P--P Adenosine-O--P--P--P R--P Nutrients

13 Synthesis of ATP Oxidative phosphorylation: Direct addition of inorganic phosphate to ADP during the simultaneous oxidation of reduced cofactors by the electron transport chain Adenosine-O--P--P Adenosine-O--P--P--P P Energy High energy electrons

14 Use of ATP ATP PO 4 3- Energy H2O ADP Energy is used to Fuel Anabolic Processes: Biosynthesis Active transport Muscle contraction Transcription, translation H 2 O PO4 3- Energy AMP

15 Reduction and Oxidation of Coenzymes Certain cofactors link metabolic oxidations to metabolic reductions. These oxidations and reductions are better described as dehydrogenations and hydrogenations, the removal and addition of hydrogen ions and electrons. AH 2 Coenzyme (oxidized) BH 2 A Coenzyme-H 2 (oxidized) B

16 Reduction and Oxidation of Coenzymes AH 2 Coenzyme (oxidized) BH 2 A Coenzyme-H 2 (oxidized) B Coenzyme As an oxidizing agent As a reducing agent Nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide phosphate NAD+ NADP+ NADH/H+ NADPH/H+ Flavin adenine dinucleotide FAD FADH2 Flavin adenine mononucleotide FMN FMNH2

17 Reduction and Oxidation of Nicotinamide Cofactors NAD + NAD + serves as an oxidant by accepting a hydride ion (H: - ) from a reductant to form NADH. This reduced form is later reoxidized by passing its electrons to molecular oxygen through the electron transport chain in the mitochondria. H:-, H+ H H+ + H + NADH/H +

18 Reduction and Oxidation of Flavin Cofactors FAD FAD serves as an oxidant by accepting two hydrogen atoms from a reductant to form FADH2. CH2 OH - - This reduced form is later reoxidized by passing its electrons to molecular oxygen through the electron transport chain in the mitochondria H, H FADH 2

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20 Stages of Catabolism