really good notes from jenny
10/21/04
Chapter 6 Notes continued
The free energy (G) in a system is related to the total energy (H) and it’s entropy (S) by this relationship:
G= H-TS (where T is temperature in Kelvin units)
The greater the decrease in free energy, the greater the maximum amount of work that a spontaneous process can perform
Catabolic reactions more spontaneous greater release of energy, delta G is negative in catabolic reactions
For a system to be spontaneous the system must either give up energy (decrease in H); give up order (decrease in S), or both
At equilibrium delta G = 0 and the system can do no work
A system @ equilibrium is @ maximum stability
In a chemical reaction @ equilibrium, the rate of forward and backward reactions are equal and there is no change in the concentration of products or reactants
Chemical reactions can be classified as either exerginic or endergonic based on free energy
Exergonic reactions- proceed with a net release of free energy and delta G is negative (catabolic) (products have less energy so that’s why G is negative)
The magnitude of delta G for an exergonic reaction is the maximum amount of work the reaction can perform
For the overall reaction of cellular respiration
C6H12O6+ 6O2->6CO2=6H2o
Delta G= -686 kcal/mol
Endergonic reactions- absorb free energy from their surrounding
Delta G is positive
Non-spontaneous
Delta G= 686 kcal/mol
Through this reaction, 686 kcal have been made available to do work in the cell
A catabolic process in a cell releases free energy in a series of reactions not in a single step
3 main kinds of work a cell does:
1. Mechanical Work
- Beating of cilia, contraction of muscle cells, movement of chromosomes
2. Transport Work
- Pumping substances across membranes against the direction of spontaneous movement
3. Chemical Work
- Driving endergonic reactions such as the synthesis of polymers from monomers
Most cases ATP powers it
- (Adenosine triphosphate)
- Nucleotide consisting of the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate
- Breaks down into a diphosphate- ADP (adenine diphosphate)
- The bonds between phosphate group can be broken by hydrolysis
- Hydrolysis of the end phosphate group forms adenosine diphosphate (ATP-> ADP+ Pi) and releases 7.3 kcal of energy per ATP molecule
- In the cell the energy from the hydrolysis of ATP is coupled directly to endergonic processes by transferring the phosphate group to another molecule
i. This molecule is now phosphorylated
ii. This molecule is now more reactive
ATP is a renewable resource that is continually regenerated by adding a phosphate group to ADP
- The energy to support renewal comes from catabolic reactions in a cell
- Regeneration, an endergonic process requires investment of energy: delta G= 7.3 kcal/mol.
Chemical reactions between molecules involve both bond breaking and bond forming
- No such thing as an inorganic enzyme
Activation energy is the amount of energy necessary to push the reactions over an energy barrier
- Enzymes do not change the delta G
It hastens reactions that would occur eventually
Enzymes are selective
The determine which chemical processes will occur @ any time
Enzymes speed reactions by lowering EA
The transitions state can then be reached even @ moderate temperatures
A substrate is a reactant which binds to an enzyme
Active site of enzymes
Pocket of groove on the surface of the protein in which the protein fits
The specifity of an enzyme is due to the fit between the active site and substrate
Induced fit- As a substrate binds, the enzyme changes shape leading to a tighter induced fit, bringing chemical groups into positions to catalyze the reaction
Chapter 6 Notes continued
The free energy (G) in a system is related to the total energy (H) and it’s entropy (S) by this relationship:
G= H-TS (where T is temperature in Kelvin units)
The greater the decrease in free energy, the greater the maximum amount of work that a spontaneous process can perform
Catabolic reactions more spontaneous greater release of energy, delta G is negative in catabolic reactions
For a system to be spontaneous the system must either give up energy (decrease in H); give up order (decrease in S), or both
At equilibrium delta G = 0 and the system can do no work
A system @ equilibrium is @ maximum stability
In a chemical reaction @ equilibrium, the rate of forward and backward reactions are equal and there is no change in the concentration of products or reactants
Chemical reactions can be classified as either exerginic or endergonic based on free energy
Exergonic reactions- proceed with a net release of free energy and delta G is negative (catabolic) (products have less energy so that’s why G is negative)
The magnitude of delta G for an exergonic reaction is the maximum amount of work the reaction can perform
For the overall reaction of cellular respiration
C6H12O6+ 6O2->6CO2=6H2o
Delta G= -686 kcal/mol
Endergonic reactions- absorb free energy from their surrounding
Delta G is positive
Non-spontaneous
Delta G= 686 kcal/mol
Through this reaction, 686 kcal have been made available to do work in the cell
A catabolic process in a cell releases free energy in a series of reactions not in a single step
3 main kinds of work a cell does:
1. Mechanical Work
- Beating of cilia, contraction of muscle cells, movement of chromosomes
2. Transport Work
- Pumping substances across membranes against the direction of spontaneous movement
3. Chemical Work
- Driving endergonic reactions such as the synthesis of polymers from monomers
Most cases ATP powers it
- (Adenosine triphosphate)
- Nucleotide consisting of the nitrogenous base adenine, the sugar ribose, and a chain of three phosphate
- Breaks down into a diphosphate- ADP (adenine diphosphate)
- The bonds between phosphate group can be broken by hydrolysis
- Hydrolysis of the end phosphate group forms adenosine diphosphate (ATP-> ADP+ Pi) and releases 7.3 kcal of energy per ATP molecule
- In the cell the energy from the hydrolysis of ATP is coupled directly to endergonic processes by transferring the phosphate group to another molecule
i. This molecule is now phosphorylated
ii. This molecule is now more reactive
ATP is a renewable resource that is continually regenerated by adding a phosphate group to ADP
- The energy to support renewal comes from catabolic reactions in a cell
- Regeneration, an endergonic process requires investment of energy: delta G= 7.3 kcal/mol.
Chemical reactions between molecules involve both bond breaking and bond forming
- No such thing as an inorganic enzyme
Activation energy is the amount of energy necessary to push the reactions over an energy barrier
- Enzymes do not change the delta G
It hastens reactions that would occur eventually
Enzymes are selective
The determine which chemical processes will occur @ any time
Enzymes speed reactions by lowering EA
The transitions state can then be reached even @ moderate temperatures
A substrate is a reactant which binds to an enzyme
Active site of enzymes
Pocket of groove on the surface of the protein in which the protein fits
The specifity of an enzyme is due to the fit between the active site and substrate
Induced fit- As a substrate binds, the enzyme changes shape leading to a tighter induced fit, bringing chemical groups into positions to catalyze the reaction