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Energy Basics
AP Biology
Energy
• The ability to do work
• Used in metabolism,
which is the cell’s
capacity to acquire
energy and use it to
build, break apart,
store, and release
substances.
Potential vs. Kinetic
• Potential energy is stored;
may be chemical ( as in
storage molecules such as
lipids, starch, and
glycogen)
• Most energy available to
cells is in covalent bonds
• Kinetic is energy of
motion; potential energy is
transformed into kinetic
Metabolism
• Chemical reactions
• Catabolic: larger to
smaller; energy yield
• Anabolic: smaller to
larger; require energy
• Cell must balance
energy requiring
reactions with energy
yielding reactions
st
1
Law of Thermodynamics
• The amount of
energy in the
universe is
constant
nd
2
Law of Thermodynamics
• Energy can be
transformed
• The 2nd state will have
less energy than the
first state
• Some usually escapes
as heat
Breaking up Glucose
• Cells (using enzymes)
break the covalent bonds
in glucose
• Left are six molecules of
CO2 and six molecules of
H20
• This releases energy,some
in the form of ATP
• The rest is lost as heat
• Usable energy is less than
what was in glucose
Energy in Reactions
• Exergonic: ends in a
net loss in energy
• Energy is released
during the reaction
• Occurs continually in
living cells: supplies
energy (breakdown of
glucose)
• Endergonic: ends in a
net increase in energy
• Requires energy to
make it happen
• Synthesis
• Uphill climb
• Less likely to run
spontaneously
Chemical equilibrium
• Nearly all reactions
are reversible
• Which way it runs
depends partially on
ratio of reactants to
products
ATP
• Adenosine triphosphate
• Composed of ribose,
adenine, and three
phosphate groups
• ADP is adenosine
diphosphate
• Breaking or transferring a
phosphate group yields a
large amount of usable
energy
ATP
• A phosphate group
transfer from ATP to
another molecule is
called phosphorylation
• If covalent bonds are
stable, why does this
phosphate group given
up so easily?
ATP
• The arrangement of
the phosphates puts
lots of negative
charges close together
• The negative charges
repel each other
• Getting rid of a
phosphate groups
stabilizes (and lowers
energy)
Renewable ATP
• ATP is energy
currency
• Constantly used
and remade
• ADP + P makes
ATP
(endergonic)
• ATP-P makes
ADP (exergonic)