Metabolism

5 general principles governing metabolic pathways. A complex chemical transformation occurs in a series of separate, intermediate reactions that form a metabolic pathway.

5 general principles governing metabolic pathways. 2. Each reaction is catalyzed by a specific enzyme.

5 general principles governing metabolic pathways. 3. Most metabolic pathways are similar in all organisms, from bacteria to plants to humans.

5 general principles governing metabolic pathways. 4. In eukaryotes, many metabolic pathways are compartmentalized, with certain reactions occurring inside specific organelles.

5 general principles governing metabolic pathways. 5. Each metabolic pathway is controlled by key enzymes that can be inhibited or activated, thereby determining how fast the reaction will go.

Free energy Chemical energy available to do work Biochemical reactions may change the form of the energy, but not the net amount of energy. Exergonic reaction If it releases energy Endergonic Reaction If energy is needed.

ATP Formation Adenosine triphosphate Energy Currency Energy is captured in chemical bonds when ATP is formed.

ATP Hydrolysis ATP can be hydrolyzed at other sites in the cell. Active cells require millions of molecules of ATP per second. Yields free energy, ADP, and the organic phosphate ion

Energy Needs synthesis (biomolecules) reproduction active transport movement temperature regulation

ATP Molecule Nitrogen containing base Adenosine Ribose sugar Three phosphate group sequence

Redox Reactions One substrate transfers one or more electrons to another substance. Reduction = gain of one or more electron by an atom. Oxidation = Loss of one or more electrons.

Redox Reaction IN General, The more reduced a molecule is, the more energy is stored in its covalent bonds. Some energy is transferred from the reducing agent to the reduced product. Some energy remains in the reducing agent. Some energy is lost to entropy.

Nicotinamide Adenine dinucleotide NAD Exists in two distinct forms NAD+  one that is oxidized NADH  one that is reduced Reduction reaction involves the transfer of a proton (H+) and 2 electrons. Highly endergonic within the cell.

NADH Oxidation of NADH by O2. Larger Package of free energy than ATP. Highly exergonic Releasing -52.4 kcal/mol. Larger Package of free energy than ATP.

In order to carry out the many metabolic processes needed to sustain life, cells release and reuse the energy contained in chemical bonds.

Energy-coupling coenzymes In particular ATP and NADH Play vital role in the transfer of energy between cellular reactions that release energy (catabolism) and those that require energy (anabolism). Most of the energy-releasing reaction in the cell produce NADH, but most of the energy-consuming reactions require ATP.