BIOC 212 Lecture Notes - Lecture 36: Covalent Bond, Enzyme Catalysis, Hydrolysis

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Thermodynamics & Equilibrium I
!
Energy in Biology
Cells organized into tissues, which are organized into organism
o To maintain organization, need energy
Keeping a system organized requires energy
o To maintain structures of proteins, organelles, etc.
o To create & re-create building blocks (i.e. aa for proteins)
o To reorganize/adapt to circumstances
i.e. cells divide or die in response to signals
All these require energy
Second Law of Thermodynamics
Energy is governed by thermodynamics
o Relates to order and disorder of system
Second law: in isolated systems (or universe), the degree of disorder only
increases
Entropy: (S) measure of disorder within a system
o Positive entropy change spontaneously favors a reaction
Counter to what happens in biology since need to maintain structures
o In biological systems, this usually translates into the release of heat into the
sea surrounding the system
Need to increase disorder somewhere to maintain order in biology
Takes input of energy to actively maintain ordered state
Cell is not a closed system, it exists in the body which exists in the environment
If can maintain order/structure within a cell, then must increase disorder outside
the cell
o Disorder in terms of molecular motion = heat
o One of major by-products in biology is heat generation
o Conservation of second law of thermodynamics
Metabolism
Metabolism is how cells maintain order without breaking second law
Cells & organisms use energy to live and grow
Catabolic pathways break down molecules of food
o Result of breakdown releases energy that can be stored as chemical bonds
Useful energy stored as chemical bonds
o Building blocks (metabolites) for biosynthesis
Breakdown molecules to simple components that can be re-used
o Heat released in environment (disorder)
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