Ch 8 Flashcards
Metabolism
the totality of an organism’s chemical reactions
The beginning of the metabolic pathway
starting molecule or precursor
The end of the metabolic pathway
product
The middle steps of the metabolic pathway
intermediates
What if the enzyme that catalyzed the reaction that turned C into D was shut off?
buildup of C
Types of metabolic pathways
catabolic and anabolic
catabolic pathway
release energy by breaking down molecules
anabolic pathway
consume energy to build molecules
Define energy
the capacity to cause change
bioenergetics
the study of how energy flows through living organisms
kinetic energy
energy associated with the relative motion of objects
potential energy
energy that matter possesses because of its location or structure
heat energy
aka thermal, kinetic energy associated with random movement of atoms
light energy
powers photosynthesis
chemical energy
potential energy available for release in a chemical reaction
thermodynamics
study of the energy transformations that occur in a collection of matter
First Law of Thermodynamics
Principle of Conservation of Energy: energy can be transferred or transformed, but it cannot be created or destroyed
Second Law of Thermodynamics
Every energy transfer or transformation increases the entropy of the universe.
Entropy
measure of disorder or randomness
spontaneous process
process that can occur without an input of energy, increases the entropy of the universe
Gibbs free energy
portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system
Symbol for Gibbs free energy
G
Change in free energy equation (symbols)
Delta G = Delta H - T Delta S
Change in free energy equation (words)
change in free energy is equal to change in enthalpy minus temperature times change in entropy
enthalpy
total energy
In the delta G equation, temperature is measured in:
Kelvins
A spontaneous reaction has a _______ delta G
negative
exergonic reaction
net release of free energy, spontaneous, downhill
endergonic reaction
absorbs free energy, uphill
Exergonic reactions are more likely to occur because
they are spontaneous so don’t require energy
delta G at equilibrium
zero
What happens when a system reaches equilibrium?
no work can be done, cell would be dead
List types of work done by living cells
chemical work, transport work, and mechanical work
Chemical work
push of endergonic reactions that would not occur spontaneously
transport work
pumping of substances across membranes against direction of spontaneous movement
mechanical work
beating of cilia, contraction of muscle cells, and movement of chromosomes during cellular reproduction
energy coupling
downhill reactions can drive uphill reactions, one way cells manage energy resources
Delta G in STP and cellular conditions. Why are they so different?
Standard: -7.3 kcal/mol
Cell: -13 kcal/mol (78% greater)
So different because cells have greater reactant and product concentrations than 1 M
How do phosphorylated intermediates power otherwise impossible reactions?
A phosphorylated intermediate is formed when the phosphate group from an ATP transfers to another molecule like the reactant. The reaction that releases the energy is coupled with an endergonic reaction so that overall they are exergonic.
enzymer
macromolecule that acts as a catlyst
catalysts
chemical agents that speed up a reaction without being consumed
Every chemical reaction involves what two processes?
bond breaking and forming
What is activation energy (EA)?
the initial investment of energy required to start a reaction
What is activation energy also called and why?
Energy barrier because it is a hill that the reaction must get over
Heat or thermal energy is often sufficient to overcome activation energy of many reactions, but what makes heat inappropriate as a “catalyst” in living cells?
could denature the proteins/enzymes
What do enzymes do and what don’t enzymes do?
DO lower the activation energy barrier
DON’T change delta G
What are reactants called in enzymatic reactions?
substrates
Glucose and fructose have the same empirical formula but are very different compounds; these are called:
isomers
An enzyme binds to a substrate to form:
an enzyme-substrate complex
Where on the enzyme does the reaction take place?
active site
Describe enzyme interaction with substrate
induced fit: enzyme shapes itself to fit substrate, like a hand in glove rather than a lock and key
Mechanisms by which enzymes cause reactions to take place
- template for substrate orientation
- stretching and stressing substrates and stabilizing transition state
- provide favorable microenvironment
- direct participation in reaction
environmental conditions that affect enzyme activity
temperature (37C) and pH (7.4)
If environmental conditions reach extreme levels, then the enzymes could:
denature
cofactors
nonprotein helpers for catalytic activity (better orient substrates)
cofactor examples
metal ions: zinc, copper, iron, magnesium
coenzymes
organic molecules cofactors
coenzyme examples
vitamins
competitive inhibitors
block substrate from entering active site
noncompetitive inhibitors
bind to an allosteric site which changes the enzymes shape and makes it less effective
How can competitive inhibition be counteracted?
increasing substrate concentration
allosteric regulation
protein’s function at one site is affected (inhibited or stimulated) by the binding of a regulatory molecule to a separate site
How are allosteric regulation and noncompetitive inhibitors related?
both bind to an allosteric site to affect function
AR: stabilizes inactive form
NI: changes shape
feedback inhibition
metabolic pathway shut off by the inhibitory binding of its end product to an enzyme that acts earlier in the pathway
Compartmentalization for pathways
multi enzyme complex facilitates a sequence of reaction. often encased in a membrane to ensure that reactions don’t affect each other
What gives ATP its energy?
phosphate groups because the negative electrons are close together
ATP is a:
RNA molecule
