Chapter 8: Metabolism Flashcards
Metabolism
all of an organism’s chemical reactions
metabolic pathway
specific molecule is altered in a series of defined steps to form a specific product. each step is catalyzed by a specific enzyme
catabolic pathway
metabolic pathway that breaks down molecules and releases energy
anabolic pathway
metabolic pathway that builds complex molecules and consumes energy
kinetic energy
energy of motion
thermal energy
energy associated with random movement of atoms/molecules
potential energy
energy due to location or structure
chemical energy
potential energy available for release in a chemical reaction
thermodynamics
study of energy transformations in a collection of matter
isolated system
unable to exchange matter/energy with surroundings
open system
energy and matter can be exchanged with surroundings (ex: organisms)
first law of thermodynamics
energy can be transferred and transformed, but it cannot be created or destroyed (principle of conservation of energy)
entropy
measure of disorder/randomness
heat
thermal energy. can be used for work only when heat flows from a warm to a cold location.
second law of thermodynamics
every energy transfer or transformation increases the entropy of the universe
spontaneous process
process that occurs without input of energy and approaches equilibrium. ∆G must be negative (not 0).
free energy
portion of system’s energy that can perform work when temperature and pressure are uniform throughout the system (like a cell). also a measure of instability
∆G equation
∆G = ∆H - T∆S
equilibrium
state of maximum stability. free energy decreases as systems approach equilibrium.
exergonic reaction
spontaneous; proceeds with net release of free energy (-∆G)
endergonic reaction
nonspontaneous; absorbs free energy from surroundings
energy coupling
use of exergonic reaction to drive endergonic reaction
ATP
3 phosphate groups (negative charge), ribose sugar, and adenine.
ATP hydrolysis
terminal phosphate bond of ATP is broken with water, resulting in inorganic phosphate, ADP, and energy. releases energy because reactants have higher energy than products. (due to the repulsion of negatively charged phosphate groups that causes high instability).
glutamic acid -> glutamine
ATP phosphorylates glutamic acid to form an instable compound. ammonia replaces the phosphate group to form glutamine. (∆G = -3.9 kcal)
phosphorylated intermediate
molecule with phosphate group covalently bound to it, making it more reactive than original molecule. important for energy coupling.
ATP cycle
- ATP hydrolysis to ADP + P yields energy for cellular work (∆G = - 7.3 kcal/mole)
- ATP synthesis from ADP + P requires energy from catabolism
enzyme
macromolecule that acts as a catalyst. lowers activation energy for a reaction, but does not change ∆G.
catalyst
chemical agent that speeds up a reaction without being consumed by the reaction
activation energy
amount of energy required to start a reaction (contorts reactant molecules so the bonds can break)
transition state
unstable state of reactants that have absorbed enough energy for its bonds to break
substrate
reactant an enzyme acts on. held in place by weak interactions (hydrogen bonds, ionic bonds)
enzyme substrate complex
enzyme bound to its substrate
sucrase
enzyme that catalyzes hydrolysis of sucrose (disaccharide) into glucose + fructose (monosaccharides)
active site
region of enzyme that binds to substrate
induced fit
change in active site of enzyme to bind more snugly with substrate
enzyme catalysis
Catalysis carried out by R groups of amino acids in active site. It catalyzes either the forward or reverse reaction (to approach equilibrium).
enzyme mechanisms to lower activation energy/speed up reaction
- active site acts as template to arrange substrates in proper orientation
- stretches substrate molecules towards transition state (stresses/bends chemical bonds)
- active site provides proper microenvironment (ex: lower pH)
- direct participation of active site in chemical reaction
saturated
substrate concentration where all enzymes have their active sites engaged, so the rate of reaction is determined by the speed of reactant-product conversion.
effect of temperature
substrates collide with active sites more frequently at higher temperatures. Too high temperatures can cause protein to denature
optimal conditions
optimal pH and temperature
cofactors
nonprotein helpers for enzymes
coenzyme
cofactors that are organic molecules
competitive inhibitors
competes with substrate to bind with active site
noncompetitive inhibitors
binds to protein (not at the active site) and causes a shape change that makes active site less effective
β-galactosidase
breaks lactose into glucose and galactose
allosteric regulation
protein’s function at one site is affected by binding of regulatory molecule at another site
allosteric site
site on protein where activating/inhibitory regulatory molecule binds
allosteric activator
stabilizes active form of enzyme (ex: ADP activates catabolic enzymes)
allosteric inhibitor
stabilizes inactive form of enzyme (ex: ATP inhibits catabolic enzymes)
cooperativity
substrate molecule binds to an active site, triggering shape change in the other subunits of the enzyme that increases their catalytic activity
feedback inhibition
metabolic pathway switched off by inhibitory binding of its end product to an enzyme in the beginning of the pathway
