ENERGY & ENZYMES
LIFE PROCESSES
REQUIRE
ENERGY
• Energy = the ability to move or change
matter.
What are some forms of
energy?
• Light
• Heat
• Chemical
• Electrical
From food webs to the life of a cell
energy
energy
energy
Flow of energy through life
 Life is built on chemical reactions

transforming energy from one form to another
organic molecules  ATP &
organic molecules
sun
solar energy 
ATP & organic molecules
organic molecules 
ATP & organic molecules
Chemical Reactions
• Process in which bonds between
atoms are broken, and new ones are
formed.
• This produces one or more different
substances.
Chemical Equations
Reactants: The starting materials for a
chemical reaction.
Products: The substances that form
after the reaction.
Follow a specific format
• Reactants
• NaCl
Products
Na + Cl+
Metabolism
All of the chemical reactions that
occur within an organism.
Metabolism
 Chemical reactions of life

Bond must form between molecules
 Occurs through dehydration synthesis
 Dehydration synthesis: A chemical reaction that
builds up molecules by losing water molecules.
 Anabolic reactions – Building up molecules from
smaller units - Requires an input of energy
That’s why
they’re called
anabolic steroids!
Metabolism

Bonds also must break between molecules
 Occurs through hydrolysis
 Hydrolysis: chemical reaction that breaks
down molecules by adding water molecules
e.g. starch into glucose
 Digestion
 Catabolic reactions – Breaking down of
molecules into smaller units
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Chemical reactions & energy
 Some chemical reactions release energy

exergonic
digesting molecules=
LESS organization=
lower energy state
 Some chemical reactions require
input of energy

endergonic
building molecules=
MORE organization=
higher energy state
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Energy is needed to start a
chemical reaction
ENERGY
• Activation Energy: The energy
needed to start a chemical reaction.
Enzymes help reactions
occur
• Enzymes: substances that increase
the speed of chemical reactions.
• http://www.youtube.com/watch?v=XT
Um-75-PL4
Enzymes:
• are Proteins
• are Catalysts
• are in YOUR cells catalyzing reactions RIGHT
NOW
• Help you maintain homeostasis
• Are specifically shaped by type
• Work on substrates
• Substrate: substance upon which enzymes
work
• Have active sites (part the substrate fits into)
Some common enzymes:
• Amylase
• Catalase
• Sucrase
• DNA Polymerase
• Lipase
• Protease
Naming conventions
 Enzymes named for reaction they catalyze
sucrase breaks down sucrose
 proteases break down proteins
 lipases break

down lipids
 DNA polymerase builds DNA
 adds nucleotides
to DNA strand

pepsin breaks down
proteins (polypeptides)
Activation Energy with and
without an enzyme
How does an enzyme work?
• Step 1: Enzyme attaches to its specific substrate
(sucrase attaches with sucrose)
• Step 2: At the active site, the enzyme and the
substrate interact in a way that reduces activation
energy of the reaction
• Step 3: The reaction is complete when products form.
The enzyme is now free and goes an acts on a new
substrate.
Lock and Key model
 Simplistic model of
enzyme action

substrate fits into 3-D
structure of enzyme’
active site
 H bonds between substrate &
enzyme

like “key fits into lock”
Some things can make enzymes work
FASTER or NOT AT ALL
• Temperature: Enzymes work at optimal temperatures.
If the temperature is too high or too low, it may change
the shape of the enzyme so it won’t work.
• pH: Values outside of the preferred range of enzymes
may cause bonds to break and then the enzyme can’t
work.
Temperature
reaction rate
What’s
happening here?!
37°
temperature
Enzymes and temperature
 Different enzymes function in different
organisms in different environments
reaction rate
human enzyme
hot spring
bacteria enzyme
37°C
temperature
70°C
(158°F)
pH
What’s
happening here?!
trypsin
reaction rate
pepsin
pepsin
trypsin
0
1
2
3
4
5
6
pH
7
8
9
10
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