Exam 2 - Chapter 8 Flashcards
Energy
the capacity to do work
Work
any activity involving mental or physical effort to achieve a result
Kinetic energy
energy of motion
Potential energy
stored energy
Food is chemical energy
First law of thermodynamics
energy cannot be created or destroyed but it can be changed from one form to another
•Also called law of conservation of energy
Second Law of Thermodynamics
with each energy transformation, some energy becomes unable to perform work (usually lost as heat)
•Every energy transformation increases entropy
entropy
measure of randomness or disorder in a system
Energy transfers
- most energy lost as heat
- sun ultimate source of energy on Earth
- total amount of useable energy decreases as entropy increases
Metabolism
all chemical reactions taking place in a cell
Metabolic pathway
series of interconnected biochemical reactions which convert a substrate into a product through a series of stepwise reactions
Catabolic pathway
release energy by breaking down complex molecules, breaking bonds
Anabolic pathway
input of energy required to build up complex molecules from simpler ones, forming bonds
Gibbs free energy (G)
amount of energy available to do wor
Endergonic reaction
requires an input of energy
non-spontaneous
positive ∆G (energy to do work)
potential energy of products greater than reactants
Exergonic reaction
net release of free energy
spontaneous
negative ∆G (energy to do work)
potential energy of reactants is greater than products
Equilibrium
cells are open systems which require a constant input of energy, energy coupling between exergonic and endergonic reactions
cells will never reach equilibrium
Cellular Work
chemical (endergonic anabolic reactions)
transport (moving materials against chemical gradient)
mechanical (movement)
Activation energy (Ea)
- the minimum amount of energy required to get a chemical reaction started
- usually supplied in the form of heat from the surroundings
- The amount of heat that can be absorbed is usually the rate limitingstep of a chemical reaction
Transition state
contorted high energy unstable state which must be achieved before a chemical reaction proceeds
Enzymes
a catalytic protein that speeds up a reaction without being consumed by the reaction
are very specific
ends in -ase
how do enzymes work
by lowering activation energy barrier NOT by changing ∆G, or the energy of the reactants and products
Conditions that effect enzyme activity
- substrate concentration (enzyme saturation)
- temperature & pH (optimal ranges, extremes can cause denaturation)
- cofactors & coenzymes
Enzyme Activity Controlers
- Inhibitors
- Allosteric regulation
- Feedback inhibition
