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Chapter 8 notes. An Introduction to Metabolism. Concept 8.1. Metabolism : the totality of an organism’s chemical reactions A metabolic pathway begins with a specific molecule and is altered into a product - each step is catalyzed by an enzyme. Concept 8.1.
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Chapter 8 notes An Introduction to Metabolism
Concept 8.1 Metabolism: the totality of an organism’s chemical reactions A metabolic pathway begins with a specific molecule and is altered into a product - each step is catalyzed by an enzyme
Concept 8.1 Catabolic pathway: release energy in the breaking down of complex molecules into simpler compounds - ex. glucose CO2 + H2O Anabolic pathway: consume energy to build complicated molecules from simpler ones - ex. amino acids proteins
Concept 8.1 Energy: the capacity to do work Reactions (Rxns.) are either exergonic (energy outward) or endergonic (energy inward)
Concept 8.2 Exergonic rxns. proceed with a net release of energy - occur spontaneously Endergonic rxns. absorb free energy from their surroundings - nonspontaneous
Concept 8.2 Cells do three kinds of work: - mechanical work (ex. contraction of a muscle cell) - transport work (ex. pumping of substances across a memebrance) - chemical work (ex. synthesis of polymers from monomers)
Concept 8.3 Energy coupling: the use of an exergonic process to drive an endergonic one ATP is the energy source used in most rxns. - contains a ribose (sugar), adenine (base), and 3 phosphate molecules
Concept 8.3 Energy is released from ATP when the terminal phosphate bond is broken ATP ADP + Pi + Energy - work is accomplished by phosphorylation - the transferring of the Pi to another molecule (ex. channel protein)
Concept 8.3 ATP is regenerated in the cell by phosphorylating ADP through an exergonic rxn. in the cell - in a muscle cell 10 million ATP are consumed and regenerated per second per cell
Concept 8.4 Spontaneous rxns. May occur at very slow rates - sucrose glucose + fructose - if an enzyme is added, the same rxn. can completed in seconds Catalyst: a chemical agent that speeds up reaction w/out being consumed
Concept 8.4 Enzyme: a biological catalyst Activation energy, the energy needed to begin a rxn, prevents many rxns from occurring quickly Heat is used to speed up rxns b/c it increases the speed of reactant molecules (to collide more often)
Concept 8.4 In biological systems heat alone would not work - too much heat denatures proteins and kills cells An enzyme (catalyst) lowers the amt. of activation energy needed - enzymes are very selective
Concept 8.4 The reactant an enzyme binds to is called the substrate - binds to the active site of the enzyme - the enzyme converts the substrate to product - the product is released Enzyme animation
Concept 8.4 Up to a point, the rate of an enzymatic reaction will increase with temperature - eventually it will drop because of thermal agitation and protein denaturing
Concept 8.4 Most human enzymes function best at 35-40 oC. - some bacteria that live in hot springs have proteins that work best at 70 oC. Most human enzymes also work best at 6-8 pH. - pepsin in the stomach work best at PH 2
Concept 8.4 Certain chemicals can selectively inhibit the activity of specific enzymes Competitive inhibitors: reduce enzyme activity by blocking the substrate from binding to the active site - can be overcome by increasing [substrate]
Concept 8.4 Noncompetitive inhibitors: impede the reaction by attaching to another part of the enzyme, thus changing its shape - ex. toxins and poisons
