Lecture 13 Flashcards
Gibbs energy variable
Thermodynamic potential of the system
Maximal work a system can perform
Enthalpy
H
Total heat content of the system
Temperature
T
Measurement of the avg kinetic energy of a system
Entropy
S
Tendency of energy to become dispersed or
Measure of order of randomness in a system
Gibbs free energy formula
Delta G= delta H - T deltaS
Endothermic rxn
Absorb energy in the form of heat
Exothermic rxn
Release energy in form of heat
Spontaneous rxn
Process that can occur without a constant input of energy
Rxn will tend to be spontaneous if what
They are exothermic
Products have less energy than reactants
Or
If entropy of products is greater than entropy of reactants
Combustion of glucose formula
Rxn of glucose with oxygen to form CO2 and water
C6H12O6 + 6O2 -> 6CO2 + 6H2O
Rxn releases a significant amount of heat (delta H is less than zero) and is spontaneous (negative delta G)
Exothermic Exergonic rxn
Condition of glucose
Exothermic and Endergonic rxn
Freezing of water
EndothermicEndergonic rxn
Photosynthesis
6 CO2 + 6H2O + light energy -> C6H12O6 + 6O2
Since second law of thermodynamics is that entropy must increase do cells violate this law?
No
Living systems are open (therefore they can maintain highly organized state)
Living systems being in both energy and matter from surroundings and use them to maintain an organized state
They real ease energy and disordered molecules into the environment
One way to identify life
Life consumes energy and converts it to work that decreases local entropy
Metabolic pathways
Metabolism
Catabolic pathway
Anabolic pathway
Metabolism
Collection of all chemical rxns present within a cell or organism
Catabolic pathway
Energy released by the breakdown of complex molecules to simpler compounds
Anabolic pathway
Energy consumed to build complicated molecules from simpler ones
Metabolic pathways AKA
Biosynthetic pathways
Energy coupling
Coupling of an Endergonic reaction to an Exergonic reaction
Hydrolysis of ATP
Exergonic rxn that can be coupled to make otherwise Endergonic reactions proceed spontaneously
Coupling reactions require what
Enzymes
How do enzymes facilitate reactions
They are catalysts that lower activation energy
How do enzymes work
Bring molecule’s together
Expose reactant molecules to altered charge environments that promote catalysis
Enzymes change the shape of substrate molecules
Active site enzymes
In a biochemical reaction the active site of an enzyme combines briefly with reactants (substrates) and is released unchanged
Temperature and pH effect on enzymes
Most enzymes have an optimal temperature and pH where it operates at peak efficiency
At temp and ph levels above or below these optimal level the rxn rates drop off
Ph about 7 usually
Enzymes secreted from cells may have pH where
Further away from neutrality
Changes is pH in terms of enzyme
How does it work
Affect the charged groups in the amino acids of the enzyme
How does temp affect an enzyme
As temp rises rate of reactions increase
High temperatures denature proteins including enzymes and reduce the rate of reactions
Enzyme cofactors
Non protein groups that bind precisely to an enzyme
Necessary for catalysis to occur
Cofactors
Often metallic ions (iron. Copper. Zinc. Manganese)
Mg essential for ATP dependent rxns
Fe present in hemoglobin and cytochromes. Involved in electron transport
Coenzymes
Organic molecules. Such as vitamins
NAD+ (nicotinamide adenine dinucleotide)
Involved in redox rxns. Carrying electrons from one rxn to another
FAD (flaxen adenine dinucleotide).
Another electron carrier used in redox rxns
Concentration dependence of enzymatic rxns
In the presence of excess substrate. The rate of catalysis is proportional to the amount of enzyme
When substrate concentration is low
Vs high
Rxn rate slows
Enzymes and substrates collide infrequently
Vs
Enzymes become saturated with reactants
Rate of rxn levels off
Enzyme inhibitors
Non substrate molecules that can bind to an enzyme and decrease its activity
Competitive inhibition
Inhibitor competes with normal substrate for active site
No competitive inhibition
Inhibitor doesn’t compete with normal substrate for active site.
Instead combines with sites elsewhere on the enzyme
Feedback inhibition
A type of metabolic regulation
Product of a rxn inhibits its own synthesis
Helps conserve cellular resources
Redox rxns
Cells transfer energy by redox rxns. Usually energy can be transferred through the transfer of electrons
Usually involves the transfer of a hydrogen atom (containing an electron and a proton) rather than just an electron
Oxidation
Loses electrons
Gives up energy as it releases electrons
Reduction
Gain electron
Receives energy with the electron
Most common encountered acceptor molecules in a living cell include
NAD+ -NADH
Nicotinamide adenine dinucleotide
NADP+ -NADPH
nicotinamide adenine dinucleotide phosphate
FAD+ -FADH2
Flavin adenine dinucleotide
Each of these electron transfer agents can exist in a reduced state. In which it has more free energy, or in oxidized state which it has less energy
Which has less energy potential
Oxidized or reduced
Oxidized
Which has more energy potential
Oxidized or reduced
Reduced
