Lecture 6 - Metabolism and Energy PDF

Lecture 6 - Metabolism and energy Chapters 8 and 9 Concept 8.3-8.4,9.1-9.4 CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers CONCEPT 9.1 Catabolic pathw...

Lecture 6 - Metabolism and energy Chapters 8 and 9 Concept 8.3-8.4,9.1-9.4 CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers CONCEPT 9.1 Catabolic pathways yield energy by oxidizing organic fuels CONCEPT 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate 182 CONCEPT 9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules CONCEPT 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions ATP contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups (the triphosphate group) bonded to it The bonds between the phosphate groups of ATP can be broken by hydrolysis. The reaction is exergonic and releases energy the cell’s proteins harness the energy released during ATP hydrolysis in several ways to perform the three types of cellular work—chemical, transport, and mechanical. ATP hydrolysis causes changes in the shapes and binding affinities of proteins. ← example transporter protein ATP is a renewable resource that can be regenerated by the addition of phosphate to ADP. The free energy required to phosphorylate ADP comes from exergonic breakdown reactions (catabolism) in the cell CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers A spontaneous chemical reaction occurs without any requirement for outside energy, but it may occur so slowly that it is imperceptible An enzyme is a macromolecule that acts as a catalyst, a chemical agent that speeds up a reaction without being consumed by the reaction. G = -29.3 kJ>mol), The initial investment of energy for starting a reaction—the energy required to contort the reactant molecules so the bonds can break—is known as the free energy of activation, or activation energy The reactant an enzyme acts on is referred to as the enzyme’s substrate. Only a restricted region of the enzyme molecule actually binds to the substrate. This region, called the active site, is typically a pocket or groove on the surface of the enzyme the active site catalyze the reaction and the product is released. The enzyme is then free to take another substrate molecule most enzyme reactions are reversible Many enzymes require non protein helpers or Cofactors for catalytic activity, often for chemical processes like electron transfers that cannot easily be carried out by the amino acids in proteins. heme in hemoglobin If the cofactor is an organic molecule, it is referred to, more specifically, as a coenzyme Enzyme Inhibitors selectively inhibit the action of specific enzymes. They can be competitive or noncompetitive 3. What happens if the product of an enzymatic reaction is an inhibitor of the enzyme itself? CONCEPT 9.1 Catabolic pathways yield energy by oxidizing organic fuels Metabolic pathways that release stored energy by breaking down complex molecules are called catabolic pathways six CO2 molecules In a redox reaction, the loss of electrons from one substance is called oxidation, and the addition of electrons to another substance is known as reduction. Oxidation and Reduction with respect to Hydrogen Oxidation and Reduction with respect to Oxygen Transfer Transfer Oxidation is the loss of hydrogen. Oxidation is the gain of oxygen. Reduction is the gain of hydrogen. Reduction is the loss of oxygen. CONCEPT 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis, which occurs in the cytosol, begins the degradation process by breaking glucose into two molecules of a compound called pyruvate. In eukaryotes, pyruvate enters the mitochondrion and is oxidized to a compound called acetyl CoA, which enters the citric acid cycle. The citric acid cycle is also called the tricarboxylic acid cycle or the Krebs cycle Hans Krebs ~1930 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules The hydrogen atoms are not transferred directly to oxygen, but instead are usually passed first to an electron carrier, a coenzyme called NAD+ Dehydrogenases are enzymes that remove a pair of hydrogen atoms from the substrate, thereby oxidizing it. The electron transport chain is a series of proteins that pass electrons from NADH to Oxygen, while accumulating protons (H+ ions) across a membrane. The end result of the ETC is the accumulation of proton in between the two membranes of the mitochondria electron transport chain https://www.youtube.com/watch?v=nmoLoiFakxY&t ATP synthase uses the energy of an existing ion gradient to power ATP synthesis. like a water mill The power source for the ATP synthase is a difference in the concentration of H+ on opposite sides of the inner mitochondrial membrane. Protons move through here → H + ATP synthesis happens here → ADP + Pi + squeezing force = ATP ATP synthase https://www.youtube.com/watch?v=OT5AXGS1aL8 summary CONCEPT 8.3 ATP powers cellular work by coupling exergonic reactions to endergonic reactions CONCEPT 8.4 Enzymes speed up metabolic reactions by lowering energy barriers CONCEPT 9.1 Catabolic pathways yield energy by oxidizing organic fuels CONCEPT 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate 182 CONCEPT 9.3 After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules CONCEPT 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis