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