Download ATP and Energy, Enzymes - Jocha

ATP and Energy, Enzymes
SOME BASIC ENERGY CONCEPTS
 Energy makes the world go around.
 But what is energy?
 Energy is defined as the capacity to perform work.
 Kinetic energy is the energy of motion.
 Potential energy is stored energy.
2 basic types of energy
 Machines and organisms can transform potential
energy stored in matter to kinetic energy.
•Swimming motion of sperm
•Muscles producing contraction
•Solar radiation is converted to chemical energy in green
plants forming sugars
 In all such energy transformations, total energy is conserved.
 Energy cannot be created or destroyed.
 This is the principle of conservation of energy.
Energy conversions
 Every energy conversion releases some randomized energy in the form of heat
which increases the entropy or randomness of the universe.
 Heat is a
 Type of kinetic energy (energy of movement)
 is always a “waste” product of all energy conversions
Fuel
Energy conversion
Waste products
25% of
energy is
actually
used!
40% of
energy is
actually
used
(humans)
1
ATP and Energy, Enzymes
How do living things manipulate energy?
Sunlight
Plants store
Animals store
(radiant energy)
(chemical energy)
(chemical energy)
ATP used in
metabolic
processes
Heat as waste
product
Conversion to
carbohydrates
by
Photosynthesis
Sunlight
 One of the types of
Conversion to ATP during
cellular respiration
radiant or
electromagnetic energy
coming from the sun
 Plants, algae, and
some cyanobacteria are
able to use by mean of
photosynthesis
ATP used in
metabolic
processes
Heat as
waste
product
Conversion to ATP during
cellular respiration
Chemical Energy
 Potential energy stored in matter, is released or stored
when molecules are changed from one type to another
 All living things use chemical energy to stay alive… in
a process called “cellular respiration”, the energyreleasing chemical breakdown of fuel molecules, that
provides energy for cells to do work
What units we use to measure chemical energy?
Calories (Cal or Kcal)
 A calorie is the amount of energy that raises the temperature of one gram of
water by 1 degree Celsius.
 Food Calories are kilocalories, equal to 1,000 calories.
 The average Calories needed by a human being are 2,000
2
ATP and Energy, Enzymes
ATP and Cellular Work
 ATP works like an
energy shuttle
 It is a short
term storage
place for energy
obtained from
food
 Releases it
later as needed
Transport work (cell transport)
 ATP energizes other molecules by
transferring phosphate groups, this
energy helps cells perform…
Mechanical work (muscles)
Chemical work (enzymatic reactions)
The ATP Cycle
 Cellular work spends ATP.
 ATP is recycled from ADP and a phosphate group through cellular respiration.
 A working muscle cell spends and recycles about 10 million ATP molecules per
second.
Food (animals, fungi, protozoa, most bacteria)
Sunlight + CO2 + H2O (plants, algae, cyanobacteria)
3
ATP and Energy, Enzymes
ENZYMES
 Metabolism is the total of all chemical reactions in an organism.
 Most metabolic reactions require the assistance of enzymes, special proteins that
speed up chemical reactions.
Why do we need to speed up reactions using enzymes?
Activation Energy (Ea)
Synthesis and breakdown of molecules and energy
conversion processes requires energy to initiate the
breakdown of nutrients
(octet rule… chemical bonds… remember?)
Extra energy required to destabilize existing chemical bonds and initiate a chemical reaction
between two or more molecules
Enzymes reduce the energy of activation!
Without enzymes
With enzymes
How Enzymes Work…
 Every enzyme is very selective, catalyzing a specific reaction.
A
reactants
B+C
products
 Each enzyme recognizes only one substrate, a specific reactant molecule.
 The enzyme fits to the substrate, and the enzyme changes shape slightly.
 This interaction is called induced fit.
Enzymes are substrate specific!
Enzymes remain unchanged!
 Enzymes can be
reused billions of
times, one single
enzyme can convert
millions of substrate
molecules per second!
ACTIVE SITE:
 Is the part of the
enzyme, where the energy
of activation is lowered by
the enzyme so the reaction
can happen
4
ATP and Energy, Enzymes
Factors that affect the enzymes activity…
1) Temperature
 Optimum (temperature range at which
the speed of product generation is
maximum)
 The speed of the reaction, or the
number of molecules of substrate that
one enzyme can react with in a given
time, decreases as temperature moves
right or left from the optimum range.
 At higher or lower temperatures than the optimum, Enzymes can lose their
configuration (be completely unfolded and only retain the primary structure) and be
no longer active
Enzyme
Denatured
Enzyme
(1ry structure =
sequence of
amino acids)
Denaturation
Loss of the structures of a protein, only the
primary structure remains
2) pH
 Is important in defining the final shape of proteins
 each enzyme reaches it maximum activity level at a given pH
 Changes in pH determine
the number of H+ ions
available in the enzyme
environment
 these H+ may interact with
exposed side-chains of the
polar enzyme molecule
 enzyme activity changes
Denaturation
3) Enzyme-Substrate concentration
Loss of the structures of a
protein, only the primary
structure remains
 With all other variables fixed
 Rate of product formation is defined by the enzyme characteristics
 With huge amounts of substrate present
 the rate of product generation can only be increased by adding more
enzymes!
5
ATP and Energy, Enzymes
Enzyme Inhibitors…
 Enzyme inhibitors can prevent metabolic reactions by binding to the active site.
Enzymes regulation…
Negative feedback
 Is a regulatory mechanism in which a 'stimulus' causes an opposite 'output' in
order to maintain an ideal level of whatever is being regulated
 The amount of one or more products in the sequence of reactions regulate
the activity of an enzyme in a previous reaction of the sequence
6