Chapter 8: Energy and Enzymes

coupling reactions

energy obtained from exergonic reactions (food) to power endergonic needs

first law of thermodynamics

energy is neither created nor destroyed but can be transformed

second law of thermodynamics

the amount of disorder in a system increases over time

kinetic energy

energy of motion

thermal energy

energy of moving molecules

potential energy

energy stored in position or configuration

chemical energy

energy stored in chemical bonds that can be transferred to other bonds or taken from other bonds with weaker bonds with higher potential energy than stronger bonds

gibbs free energy

composite of heat/bond energy and entropy effects and determines whether a reaction is spontaneous or not

spontaneous

when gibbs is less than 0 and reaction does not require energy input to occur

exergonic

energy output

endergonic

energy output

nonspontaneous

when gibbs is greater than 0 and reaction requires energy input to occur

energetic coupling

process between exergonic and endergonic reactions allows chemical energy released from one reaction drive another via redox or transfer of phosphate groups

oxidization

loss of electrons

reduction

gain of electrons

ATP hydrolysis

process in which ATP’s terminal phosphate is broken off to ADP adding energy to the system which can be coupled to endergonic reactions to make them spontaneous

substrates

reactants that undergo a chemical reaction by binding to an enzyme at the active site to allow proper orientation

conformational change

when enzyme does not fit substrate until substrate makes contact with it

specificity

characteristic of enzymes in which each enzyme only works with specific substrate

saturation

characteristic of enzymes in which active sites of all enzymes become filled up at a threshold concentration of substrate

saturation kinetics

characteristic of enzymes in which the speed of reaction reaches maximum

competition

characteristic of enzymes in which sometimes there are molecules that are similar enough to the substrate that they bind to the active site, reducing the reaction rate

cofactors

inorganic ions such as Zn2+, Mg2+, Fe2+ that reversibly react with enzymes and detach easily

coenzymes

organic molecules such as NADH and FADH2 that interact with enzymes and detach easily (include vitamins)

prosthetic groups

non amino acid atoms or moleecules permanently attached to enzymes

regulating molecules

regulate cell’s enzymatic activity that may change enzyme’s structure, ability to bind to its substrate, or may either activate or deactivate an enzyme’s function

competitive inhibition

reversible regulatory reaction where molecule competes with the substrate for the active site

allosteric regulation

reversible regulatory reaction molecule binds at a location other than the ctive site, causing a change to enzyme’s shape, and can activate or deactivate the enzyme

phosphorylation

most common form of covalent modifcation in which kinases covalently add phosphate groups to their substrates to active or phosphatases take it off to deactivate

kinases

enzymes that phosphorylate

phosphatases

enzymes that dephosphorylate (remove covalently linked phosphate groups from substrate

peptide cleavage

the enzymatic hydrolysis of peptide bonds to release smaller peptide fragments or amino acids

proteolytic cleavage

process where proenzyme takes off something covering the active site to make it accessible

feedback inhibition

as concentration becomes abundant it feed back to stop reaction and amount of initial substrate is not depleted and stored or used for other reactions

temperature graph

pH graph

substrate concentration graph