Biology 123 Test 2
Three types of work cells do
1) chemical work 2) transport work 3) mechanical work
glycolysis and the krebs cycle produce only
4 ATP molecules per glucose molecule
How does an enzyme catalyze a reaction?
By lowing the Ea barrier
Delta G
G (final state) - G (initial state)
what accounts for most of the energy extracted from the glucose?
NADH and FADH2
Can an enzyme change delta G of a reaction?
No
feedback inhibition
a metabolic pathway switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway
spontaneous process
a process that can occur without an input of energy
reduction
addition of electrons from one substance
cooperativity
amplifies the response of enzymes to substrates
Allosteric regulation
any case in which a protein's function at one sit is affected by the binding of a regulatory molecule to a separate site
catabolic pathway
breakdown pathways
Induced fit
brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
energy
capacity to cause change
electron transport chain
consists of a number of molecules, mostly proteins, built into the inner membrane of the mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.
anabolic pathways
consume energy to build complicated molecules from simpler ones
A cell at equilibrium is _
dead
noncompetitive inhibitors
do not directly compete with the substrate to find to the enzymes at the active site
oxidizing agent
electron acceptor
reducing agent
electron donor
redox reactions
electron transfers
endergonic
energy inward
potential energy
energy matter possesses
exergonic
energy outward
activation energy
energy required to start the reaction
induced fit
enzyme changes shape slightly when it binds to substrates
second law of thermodynamics
every energy transfer or transformation increases the entropy of the universe
The rate of an enzymatic reaction increases with
increasing temperature
What pH do enzymes work best at?
it varies, each enzyme is different
heat or thermal energy
kinetic energy associated with the random movement of atoms or molecules
oxidation
loss of electrons from one substance
entropy
measure of disorder, randomness
selective inhibition
molecules naturally present in the cell often regulate enzyme activity by acting as inhibitors.
aerobic respiration
most prevalent and efficient, when oxygen is consumed as a reactant
Cofactors
nonprotein helpers
Coenzyme
organic molecule cofactor
The optimal pH values for most enzymes fall in the range of
pH 6-8
fermentation
partial degradation of sugars or other organic fuel that occurs without the use of oxygen
active site
pocket or groove on the surface of the enzyme where the catalysis occurs
Free energy
portion of a systems energy that can perform work when temperature and pressure are uniform throughout a system
chemical energy
potential energy available for release in a chemical reaction
chemiosmosis
process where energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work, such as the synthesis of ATP
alcohol fermentation
pyruvate is converted to ethanol in two steps. 1) releases co2 from pyruvate which is converted to acetaldehyde. 2) acetaldehyde is reduced by NADH to ethanol
lactic acid fermentation
pyruvate is reduced directly by NADH to form lactate as an end product with no release of CO2
competitive inhibitors
reduce the productivity of enzymes by blocking substrates from entering active sites, can be overcome by increasing the concentration of the substrate.
kinetic energy
relative motion of objects
negative delta G
spontaneous process, for delta G to be negative delta H must be negative or t delta s must be positive
Why is ATP useful to the cell?
the energy it releases on losing a phosphate group is greater than the energy most other molecules could deliver
Enzyme-substrate complex
the enzyme binds to its substrate
Substrate
the reactant an enzyme acts on
bioenergetics
the study of how energy flows through living organisms
metabolism
the totality of an organism's chemical reactions
energy coupling
use of an exergonic process to drive an endergonic one
