Transcript Energy and Enzymes

Energy and Enzymes
• What is energy?
Energy is the
capacity to do work.
Cells continually
use energy to
develop, grow,
repair, reproduce,
etc.
Forms of Energy
• Kinetic energy
▫ Motion
▫ All moving objects have kinetic
energy
• Potential energy
▫ Stored
• Chemical energy
▫ Food
▫ Contains potential energy
• Mechanical energy
▫ Muscle movement.
▫ Chemical energy needed
First law of thermodynamics
• Law of Conservation of Energy
• Energy cannot be created or
destroyed, but it can be changed
from one form to another.
• Example:
▫ Photosynthesis converts solar
energy into chemical energy.
Second law of thermodynamics
• Energy cannot be changed from one form into another without a loss
of usable energy.
• Heat is a form of energy
that dissipates into the
environment
• Heat can never be
converted back to
another form of energy.
ATP: Energy for Cells
• Adenosine triphosphate
(ATP) is the energy currency of
cells.
• When cells need energy, they
“spend” ATP.
• ATP supply is maintained by
breakdown of glucose during
cellular respiration.
Adenosine Triphosphate
• ATP is a nucleotide.
• Adenosine
• Ribose- sugar
• Three phosphate groups
• ATP is an energy carrier for
many different types of
reactions.
ATP to ADP
• When ATP is converted into
ADP (adenosine
diphosphate) when one
phosphate group is removed.
• About 7.3 kcal of energy is
released per mole of ATP.
Metabolic Reactions
• Metabolism is the sum of all
the biochemical reactions in a
cell.
• Reactants are substances that
participate in a reaction.
• Products are substances that
form as a result of a reaction.
2 Types of Metabolic Reactions
Catabolic
• Breakdown of larger molecules to
produce energy
Anabolic
• energy‐consuming synthesis of
cellular components from smaller
molecules
Exergonic reactions
• The products have less free
energy than reactants
• Reaction will occur
spontaneously.
• Tend to be catabolic
Endergonic reactions
• Products have more energy than
reactants;
• Reactions can only occur with an
input of energy.
• Tend to be anabolic
Energy of Activation
• Reactions often require
activation.
• The energy of activation (Ea)
is the energy that must be added
to cause molecules to react.
• For metabolic reactions to occur
in a cell, an enzyme must
usually be present.
Enzymes
• Proteins and catalysts
• Speed chemical reactions.
• Every enzyme is specific in its
action and catalyzes only one
reaction or one type of
reaction.
• Control the rate of chemical
rxns by weakening bonds, thus
lowering the amount of
activation energy needed for
the reaction
Enzyme-Substrate Complex
• Enzymes lower the energy of
activation by forming a complex
with their substrate(s) at the
active site
• Substrates are the reactants
• Active site is a small region on
the surface of the enzyme where
the substrate(s) bind, then
change in shape facilitating the
reaction.
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Enzyme + Substrate = Product
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How the Enzyme Works
Enzymes
are
reusable!!!
Active site
changes
SHAPE
Called
INDUCED
FIT
Factors Affecting Enzymatic Speed
• Substrate concentration.
• Optimal pH
• Temperature
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Denaturating Proteins
Changes in temperature & pH can
denature (unfold) a protein so it no
longer works
Cooking denatures
protein in eggs
Milk protein separates into
curds & whey when it
denatures
Enzymes in Everyday Life
http://youtu.be/E90D4BmaVJM