Chapter 8 Review Guide 8 1 Sugars can be converted to amino acids that are linked together into proteins when needed and when food is digested proteins are dismantled into amino acids that can be converted to sugars Cell extracts supplies energy to perform work Energy light bioluminescence Metabolism totality of an organism s chemical reactions turns matter into energy manages the material and energy resources to the cell Metabolic pathway begins with a specific molecule resulting in a certain product Each step is catalyzed by an enzyme Catabolic pathways make energy after breaking down large molecules ex Cellular respiration Anabolic pathways consume energy to build complex molecules from simpler ones ex Photosynthesis greater potential energy in product Energy capacity to cause change Kinetic energy energy associated with motion Heat Thermal energy kinetic energy associated with the random movement of particles Potential energy energy that is not kinetic matter possesses this energy because of location or structure Chemical energy potential energy available for release in a chemical reaction Thermodynamics study of energy transformations Isolated systems are unable to exchange either energy or matter with its surroundings Open systems are able to transfer energy and matter organisms First law of Thermodynamics energy can be transferred transformed but never destroyed Second law of Thermodynamics every energy transformation increases the entropy randomization disorder of the universe OR for a process to occur spontaneously it must increase the entropy of the universe Spontaneous processes a process that occurs without the input of energy happen automatically Living systems increase the entropy of their surroundings Cells create ordered structures from less organized starting materials this ultimately increases the universe s entropy but they also take in organized forms of matter and energy from the surroundings and replace them with less ordered forms Energy comes into an ecosystem as light and leaves as heat 8 2 Free energy the portion of a system s energy that can perform work when temperature and pressure are uniform throughout the system as in a living cell o Once we know the value of change of free energy for a process we can use it to predict whether the process will be spontaneous Only processes in which delta G is negative are spontaneous Delta G can only be negative when the process involves a loss of free energy o Free energy is a measure of a system s instability more stable lower G o As a reaction proceeds towards equilibrium the free energy of the mixture of reactants and products decreases Exergonic reactions proceed with a net release of energy ex Cell respiration Energy outward negative delta G spontaneous o Free energy decreases while stability increases o The breaking of bonds does not release energy potential energy is released when new bonds are formed after the original bonds break Endergonic reactions absorb free energy ex Photosynthesis In a closed system equilibrium is reached and then work ends in an open system there is a constant flow even after equilibrium 8 3 8 4 A cell does three main types of work 1 Chemical work ex Glycolysis 2 Transport work ex Proton pump 3 Mechanical work ex Flagella Energy coupling the use of an exergonic process to drive an endergonic one ATP is responsible ATP sugar ribose nitrogenous base adenine and a chain of three phosphate groups Bonds of ATP are broken with hydrolysis and energy is released from ATP when the third phosphate group in broken comes from chemical change to a state of lower free energy This energy can be used to drive endergonic reactions ATP drives endergonic reactions by phosphorylation transferring a phosphate group to some other molecule Enzyme a macromolecule that acts as a catalyst a chemical agent that speeds up a reaction without being consumed by the reaction They lower activation energy the initial investment of energy for starting a reaction All reactions involve the breaking and forming of bonds Substrate the reactant an enzyme works on enzyme substrate enzyme substrate complex The substrate only fits into the active site Induced fit brings chemical groups of active site into positions that enhance their ability to catalyze reactions Active Site Lowers Activation Energy by 1 Orienting substrates correctly 2 Straining substrate bonds 3 Providing a favorable microenvironment 4 Covalently bonding to substrate Enzymes work at an optimal pH and temperature 70 degrees C Cofactors nonprotein helpers for catalytic activity Coenzyme organic cofactor Competitive inhibitors reduce the productivity of enzymes by blocking substrates from entering active sites can be overcome by increasing the concentration of substrate so that as active sites become more available more substrate molecules than inhibitor molecules are around to fain entry to the sites Noncompetitive inhibitors do not directly compete with the substrate to bind to the enzyme at the activation site but instead impede enzymatic reactions by binding to another part of the enzyme causing the enzyme to change its shape in such a way that the active site becomes less effective at catalyzing the conversion of substrate to product Toxins and poisons are often irreversible inhibitors Mutations in genes lead to changes in amino acid sequences of enzymes and may alter their substrate specificity 8 5 Chemical chaos results if a cell s metabolic pathways aren t regulated done by switching on off genes that encode specific enzymes or by regulating the activity of enzymes Allosteric regulation inhibits or stimulates enzymes activity occurs when a regulatory molecule binds to a protein at one site and affects the protein s function at another site Enzymes have active and inactive forms The binding of an activator stabilizes the active form while the binding of an inhibitor stabilizes the inactive form Cooperativity allosteric regulation that can amplify enzyme activity affects catalysts in a different active site while binding to an other active site Feedback inhibition negative feedback a metabolic pathway is switched off by the inhibitory binding to prevent cells from wasting chemical resources by synthesizing more than what it needs