Principles of METABOLISM Basic concepts

Metabolism purposes 1-Obtain energy 2-convert nutrient molecules into the cell’s own characteristic molecules 3-polymerize monomers precursors into macromolecules 4-synthesize and degrade biomolecules required for specialized cellular functions

Metabolism, the sum of all the chemical transformations taking place in a cell or organism, occurs through a series of enzyme-catalyzed reactions that constitute metabolic pathways.

Chemical reactions in metabolism Most of the reactions in living cells fall into one of five general categories: 1- oxidation-reductions; 2- reactions that make or break carbon–carbon bonds; 3- internal rearrangements, Isomerizations, 4- group transfers; and (5) free radical reactions.

1. Oxidation-reduction reactions

2. Reactions that make or break carbon–carbon bonds

3. Internal rearrangements, isomerizations, and eliminations

4. Group transfer reactions

5. Free radical reactions

Enzymes

Enzyme as biocatalist

Specify

Active site

kinetics

inhibition

Bioenergetics:The Role of ATP Biologic Systems Conform to the General Laws of Thermodynamics 1-The total energy of a system, including its Surroundings remains constant 2-The total entropy of a system must increase if ∆G<0 ΔG = ΔH− TΔS ΔG = ΔE − TΔS if ∆G<0 exergonic if ∆G>0 endergonic equilibrium if ∆G=0 ΔG0′ = −RT ln K ′eq When the reactants are present in concentrations of 1.0 mol/L, ΔG0 is the standard free energy change

Coupling reactions

ATP The nucleotide coenzyme adenosine triphosphate (ATP) is the most important form of chemical energy in all cells. Cleavage of ATP is strongly exergonic.

HIGH-ENERGY PHOSPHATES PLAY A CENTRAL ROLE IN ENERGY CAPTURE AND TRANSFER

Energy charge in cells

Main sources of ATP (1) Oxidative phosphorylation: The greatest quantitative (2) Glycolysis (3) The citric acid cycle

Oxidative phosphorylation

Chemiosmatic hypothesis(mitchell)

Redox potential

The Respiratory Chain Consists of Four Complexes: Three Proton Pumps and a Physical Link to the Citric Acid Cycle Electrons are transferred from NADH to O2 through a chain of three large protein complexes called NADH-Q oxidoreductase, Succinate dehydrogenase, Q-cytochrome c oxido-reductase, and cytochrome c oxidase

Electrons Flow from Ubiquinol to Cytochrome c Through Q-Cytochrome