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