Post on 18-Jan-2018
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METABOLISM
ENERGY AND LIFE
METABOLISM
The totality of an organisms chemical processes.
CATABOLIC PATHWAYS
Degradative Processes
ANABOLIC PATHWAYS
Building Processes
Complexity ofComplexity of
MetabolismMetabolism
Bioenergetics – study of how organisms manage energy
THERMODYNAMICS
• 1ST Law of Thermodynamics – Energy can be tranferred or transformed, but it can be neither created or destroyed.
• 2nd Law of Thermodynamics – Every energy transfer or transformation increases the entropy (disorder or randomness) of the universe.
Organisms live at the expense of free energy
• Chemical reactions may be classified based on free-energy changes. They are either
– Exergonic – proceeds with a net release of free energy
– Endergonic – absorbs free energy from its surroundings to proceed
ATP Powers Cellular Work
• A cell does three main kinds of workMechanical - beating of cilia, muscle
contraction, chromosome movementTransport – crossing a membrane
against the concentration gradientChemical – building of polymers
What is ATP? The nitrogenous base adenine with a
chain of three phosphates groups attached to the ribose.
• When the terminal phosphate bond is broken, ATP becomes ADP. This is an exergonic reaction releasing 7.3kcal of energy per mole of ATP
The ATP Cycle
ENZYMES• Catalytic proteins• Substrate-specific • Lock and Key fit• Initiate chemical reactions without being
used in the reaction ( reused)• Named for their substrate usually and
have the suffix (-ase)
The Catalytic Cycle of an Enzyme
• Enzymes use a variety of mechanisms that lower activation energy and speed up a reaction.
• Enzymes allow reactions to take place at lower temperature ( body temperature).
Factors that affect enzyme activity• Temperature
– Up to a point, the velocity of the reaction increases with the increase in temperature
– Most enzymes function optimally around body temperature (between 35o-40oC)
– Above the optimal temperature, the hydrogen bonds of the enzyme disrupt and the enzyme is denatured
• pH– The optimal pH is between 6 and 8
Other Factors Affecting Enzyme Activity
• Cofactors – nonprotein helper– If it is organic, then
it is a coenzyme– Most vitamins are
coenzymes• Enzyme inhibitors
– Competitive site– Noncompetitive site