LIFE 120 Exam #2
Enzyme
catalytic protein (or ribozyme); allow reactions to occur on the time scale necessary for life processes; speed up reactions by lowering the activation energy providing an alternative pathway for the reaction
Oxidizing Agent
causes reduction, gains electrons
Reducing Agent
causes reduction, loses electrons
Anabolic Pathways
consume energy to build complex molecules from simpler ones
Spontaneous Reaction
energetically favorable, exergonic reaction
Kinetic Energy
energy associated with motion
1st Law of Thermodynamics
energy can be transferred and transformed, but it cannot be created or destroyed
Activation Energy
energy needed to reach transition state that comes from thermal energy and molecular collisions
Potential Energy
energy that matter possesses becuase of its location or structure
Negative Regulation
enzyme activity can be blocked by certain inhibitors
Substrate-level Phosphorylation
enzyme transfers a phosphate group from a molecule to ADP; occurs during glycolysis and the citric acid cycle
2nd Law of Thermodynamics
every energy transfer or transformation increases the entropy of the universe
Catabolic Pathways
release energy by breaking down complex molecules into simpler compounds
ATP Hydrolysis
releases free energy that can be used to do work
Reduction
substance gains electrons, becomes reduced
Oxidation
substance loses electrons, becomes oxidized
Endergonic Reactions
have a net gain of free energy +^G
Exergonic Reactions
have net loss of free energy -^G
Transition State
high energy state where molecules are able to react
Cellular Respiration
includes both aerobic and anaerobic respiration but it often used to refer to aerobic respiration
ATP
main source of energy to drive endergonic reactions
Metabolic Pathways
multistep reaction sequence that begins with certain reactants and ends with certain products; each step is typically catalyzed by a specific enzyme
Cellular Respiration
1. glycolysis 2. citric acid cycle 3. oxidative phosphorylation
Catalytic Cycle of an Enzyme
1. substrates enter active site 2. substrates are held in active site by weak interactions 3. substrates are converted to products 4. products are released 5. active site is available for new substrates
Reaction Coupling
allows the cell to use energy from ATP hydrolysis to drive energetically unfavorable reactions
Oxygen is Reduced
because it has a greater share of electrons in the final products
Carbon is Oxidized
because it has less of a share of electrons in the final products
Competitive Inhibitors
bind and block the active site
Noncompetitive Inhibitors
bind to a different location on the enzyme, but prevent the active site from functioning
Catalyst
chemical agent that speeds up a reaction without being consumed by the reaction
Oxidation-Reduction Reactions
chemical reactions that involve electron transfer
NAD+
functions as a high energy electron shuttle during cellular respiration; maintains electrons in a high energy state for use later in cellular respiration
Cellular Respiration
glucose+oxygen--->carbon dioxide+energy
Thermal Energy
kinetic energy associated with random movement of atoms or molecules
Chemical Energy
potential energy available for release in a chemical reaction
Chemical Reactions
proceed in both directions; drive the processes of life
Chemical Equilibrium
reached when the rate of the forward reaction is equal to the rate of the reverse reaction; concentrations of the reactants and products remain essentially stable
Substrate
reactant molecule
Oxidative Phosphorylation
redox reactions of the electron transport chain are coupled to addition of free phosphate to ADP; occurs during last phase of respiration
Active Site
shape allows enzymes to be very specific for a single reaction
Positive Regulation
some enzymes must bind to other factors or be modified in some way in order to be active
Energy
the capacity to cause change
Entropy
the disorder in a system
Free Energy
the portion of a system's energy that can do work
Thermodynamics
the study of energy transformations
Metabolism
the totality of an organism's chemical reactions
Heat
thermal energy in transfer from one object to another