Energy The coupling of anabolic and catabolic pathways catalyzed by enzymes, otherwise known as...
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Transcript of Energy The coupling of anabolic and catabolic pathways catalyzed by enzymes, otherwise known as...
EnergyThe coupling of anabolic and
catabolic pathways catalyzed by enzymes, otherwise known as
“Metabolism”
Metabolism and thermodynamics Metabolism includes all chemical reactions
in an organism Pathways are a sequence of ordered steps
each controlled by an enzyme Catabolic pathways release energy and
typically hydrolyze molecules Anabolic pathways require energy and
usually synthesize molecules
Forms of Energy Kinetic- energy of motion Thermal energy or heat is the measure of
kinetic energy Potential- energy of position or location,
stored Chemical energy is potential energy stored
in bonds of molecules
Thermodynamics 1st law- the total energy of the universe is
constant, it can only be transferred and transformed from one kind to another.
2nd law- energy transfer or transformation results in increasing disorder or entropy. Energy is often lost as heat during a reaction or motion of matter (friction)
Reactions An exergonic reaction proceeds with a net
release of free energy and is spontaneous An endergonic reaction is nonspontaneous
and must absorb free energy from the surroundings
ATP powers cellular work by coupling exergonic and endergonic reactions
Energy coupling: using exergonic reactions to power endergonic ones
ATP or adenosine triphosphate can be hydrolyzed to ADP and an inorganic phosphate molecule releasing ~ 13kcal/mol.
The phosphate is often transferred to another molecule in a process called phosphorylation
This molecule is more reactive (less stable) ex. Integral transport protein in the membrane
A cell regenerates the ATP during cellular respiration
The Hydrolysis of ATP to ADP + P
Enzymes are Catalyst Enzymes speed up chemical reactions by
lowering the EA, activation energy. Remember Enzymes are proteins and have
very specific shapes. They fit with the substrate(s) at the active site.
The result in an “induced fit” that creates the enzyme-substrate complex.
Enzyme Substrate Complex
Enzyme substrate complex
Activation EnergyEA
EA
The red line indicates the reaction with an enzyme.
Optimal temp and pHTable: pH for Optimum ActivityEnzyme pH OptimumLipase (pancreas)8.0Lipase (stomach)4.0 - 5.0Lipase (castor oil)4.7Pepsin1.5 - 1.6Trypsin7.8 - 8.7Urease7.0Invertase4.5Maltase6.1 - 6.8Amylase (pancreas)6.7 - 7.0Amylase (malt)4.6 - 5.2Catalase7.0
Enzyme activity Proteins are denatured at high temp, and low or
high pH, this is why buffers are so important to the maintenance of chemical reactions.
The rate of a reaction can be controlled or regulated in 3 ways Denaturing- interupts the 3D shape Competitve inhibitors- compete for active site Noncompetitive inhibitors- attach at allosteric site
Inhibitors
Enzyme helpers
Cofactors- nonprotein helpers for catalytic activity, bind to either the enzyme or the substrate ex. Zinc, iron, and copper
Coenzymes- are organic helpers and include most vitamins
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/coenzy_.htm