Metabolism, Energy and
Enzymes
6.1 Energy
• Energy: Ability to do work.
• Allows cells to carry out essential
life processes.
• Kinetic Energy: Energy of motion.
• Potential Energy: Stored energy.
• Food (chemical energy) has
potential energy.
• Movement = Mechanical energy.
6.1 Energy
• Metabolism: Sum of all of
the chemical reactions that
occur in a cell.
• Reactants: Substances that
participate in the reaction.
• Products: Substances that
are formed as a result of the
reaction.
6.1 Energy
•Exothermic Reactions: Reactions that release
energy.
• Cellular Respiration
•Endothermic: Require an input of energy to
occur.
• Photosynthesis
6.2 Enzymes
• Enzyme: Protein molecule
that functions to speed a
chemical reaction. The
enzyme is unaffected.
6.2 Enzymes
• Typically end in “ase”
• Name usually relates to
substrate.
• Two main functions:
• Join molecules together.
• Break molecules down.
• Reusable
6.2 Enzymes
• Substrate: Reactants of enzymatic reaction.
• Active Site: Location on enzyme that comes into direct contact with
substrate.
• Enzyme-Substrate Complex: Intermediate formed when substrate and
enzyme attach at active site.
• Product: Molecule that is produced, different from substrate.
6.2 Enzymes
• Specificity
• Enzymes are specific to
certain substrates.
• Based on structure of
enzymes and substrate.
• Similar to a key in a lock
6.2 Enzymes
• Induced Fit
• When substrate initially
binds with enzyme, not a
perfect match.
• Both substrate and
enzyme will change shape
to join together more.
6.2 Enzymes
• Energy of Activation: The
energy needed for molecules to
react with one another.
• Catalyst: Substance that
increases the rate of a chemical
reaction without itself
undergoing any permanent
chemical change.
6.3 Factors that Influence Reaction Rate
• Substrate Concentration
• As you increase the amount of
substrate, more product can be
produced by the enzyme.
• Ticket Puncher
• Punches a ticket every 2 seconds.
• If 10 people come within 1 minute, no
problem.
• As more and more people come, there
will be a limit to the number of people
who can get in.
6.3 Factors that Influence Reaction Rate
• Temperature
• As temperature increases, more
collisions with the enzyme will occur.
• Ticket Puncher:
• Too cold, slows process down.
• Warmer, just right.
• Too hot, stops working.
6.3 Factors that Influence Reaction Rate
• Optimal pH
• pH can regulate structural configuration
of enzyme.
• Each enzyme has an optimal pH.
• Ticket Puncher
•
•
•
•
pH = Hungry.
Starving, nothing gets done.
Sick from overeating, nothing gets done.
Just right, optimal conditions.
6.3 Factors that Influence Reaction Rate
• Denatured: Proteins bond’s begin to break if temperature/pH rises
past a certain point.
6.3 Factors that Influence Reaction Rate
• Enzyme Inhibition: Occurs when a
molecule binds to an enzyme and
decreases activity.
• Competitive Inhibition: Inhibitor
binds with active site and competes
with substrate.
• Amount of product is regulated.
• Enzyme is usually not destroyed.
• Ticket Puncher: A person gives the
ticker holder a ticket that jams the
ticker puncher. The ticket puncher
can’t punch anymore tickets for
people to get in.
6.3 Factors that Influence Reaction Rate
• Non-Competitive Inhibition: Inhibitor binds with site on enzyme
called the allosteric site.
• This reaction changes the active site, regulating the enzyme reaction.
• Ticket Puncher: The ticket puncher breaks their leg and has to use a
crutches. Since they can’t use their hands, they can’t punch tickets.
6.3 Factors that Influence Reaction Rate
•Allosteric Activation
• Occurs when the binding
of one ligand enhances
the attraction between
substrate molecules and
the active site.
6.4 Compartmentalization
•Metabolic Pathway: Series of link reactions.
E1
E2
E3
E4
E5
E6
A→B→C→D→E→F→G
6.4 Compartmentalization
• Feedback Inhibition
• Product produced by an enzyme binds to enzyme's active site.
• When product is abundant, product forms with allosteric site which changes the
active site. Enzyme activity drops.
• When product is used up, inhibition is reduced and more product is produced.
6.4 Compartmentalization
• Smaller spaces within a large whole
allow for cells to have specific
functions assigned to organelles.
• Optimize the efficiency of the process.
• Focus all energy into one small area
instead of larger area.
• Prokaryotes don’t have membrane
bound organelles, but still
compartmentalize in different regions
of the cell.
6.4 Compartmentalization
• Metabolic Pathway Disease: Mutation on gene that creates
one of the enzymes in a pathway creates an enzyme that
doesn’t work.
• Substrate starts to accumulate.
• End product isn’t made.
E1
E2
E3
E4
E5
E6
A→B→C→D→E→F→G
6.5 Redox Reactions
• Oxidation-Reduction
Reaction: Transfer of
electrons from one molecule
to another.
• Redox Reaction
• Oxidation: Loss of electrons.
• Reduction: Gain of electrons.
6.5 Redox Reactions
•OIL RIG
•Oxidation is Losing
•Reduction is Gaining