Energy and Chemical
Reactions
Section 2-4
Energy
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Energy is the ability to move or change matter.
Many forms – light, heat, chemical, mechanical,
electrical
Can be converted to different forms
ex. Heat energy converted to mechanical energy
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Can be stored or released by chemical reactions
Chemical reaction – process during which chemical
bonds between atoms are broken and new ones are
formed, producing one or more different substances
Chemical Reactions
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How often do they occur in the body? A LOT!!!
This is your METABOLISM.
Start with REACTANTS and end with
PRODUCTS
REACTANTS → PRODUCTS
The arrow means changes to or forms.
Chemical Reactions absorb or release energy.
This happens when bonds are broken or
formed. FIGURE 2-13
2 H2O → 2 H2 + O2
Reactants – red
Products - blue
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Metabolism – term used to describe all of
the chemical reactions that occur within
an organism.
Where do we get our energy? Food
Activation Energy – the energy needed
to start a chemical reaction
exs. Heat from a flame to burn paper;
spark from spark plug to cause gas to
ignite – engine in car starts
Enzymes
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Help biochemical reactions to occur
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Biochemical reactions – reactions occurring in
cells
Require activation energy
Chemical reactions in cells occur quickly & at
relatively low temperatures because of the
action of enzymes
Enzymes – substances (proteins) that
increase the speed of chemical reactions
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Most enzymes are proteins.
They are catalysts – substances that
reduce the activation energy of a chemical
reaction
They speed up the reactions because they
decrease the activation energy.
Enzymes help organisms maintain
homeostasis. Without enzymes, chemical
reactions would not occur quickly enough
to sustain life.
Enzymes affect specific
substrates
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Substrate – a substance on which an enzyme
acts during a chemical reaction
Enzymes only react on specific substrates
Enzyme’s shape determines its activity
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Typically a large protein with one or more deep
folds on its surface
Folds form pockets – active site – where
enzyme’s substrate fits
Enzyme acts only on a specific substrate because
only that substrate fits into active site.
Factors that affect enzyme
activity
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Factors that change the shape of enzyme
affects enzyme’s activity
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Temperature – enzymes operate most efficiently
within a certain range of temperature
pH – most efficient within a range of pH
Enzymes active at any one time in a cell
determine what happens in that cell
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Many enzymes catalyze different chemical
reactions; specific enzyme for each reaction
Different cells – different enzymes