Introduction to
Metabolism Energy
& Enzymes
Ms. Napolitano
Honors Biology
11/22 – Do Now
• Please get your clickers!
• Think about and answer the following questions:
What is energy?
Why do we, as humans, need energy?
What are some different types of energy?
What is the 1st and 2nd Laws of Thermodynamics?
Metabolism
• Metabolism – total of all chemical reactions that take
place within an organism
• Metabolic/biochemical pathway – series of chemical
reactions, catalyzed by enzymes
• The product of one reaction becomes the reactant of the
next reaction
Types of Metabolic Pathways
• Catabolic pathways – break down complex
molecules into simpler molecules
• E released
• Anabolic pathways – build complicated
molecules from simpler molecules
• E consumed
Physics Review
• Energy
•
•
•
•
Kinetic
Thermal
Potential
Chemical
• The Laws of Thermodynamics
• 1st Law
• 2nd Law
Chemical Reactions Absorb or
Release Energy
• Exergonic reactions release
free energy
• Activation Energy (Ea) is the
E required to start the
reaction
Chemical Reactions Absorb or
Release Energy
• Identify A, B, C, D
• Endergonic reactions
absorb free energy
Catalyst
• Catalyst – reduces the activation energy to
speed up the chemical reaction
• Enzyme – catalytic protein
• Specific substrate binds to active site on enzymes...
called induced fit
• Enzymes reduce Ea
• Reaction occurs, products are formed
• Enzyme can be reused
Enzyme-Substrate Complex
Effect of Enzymes on Reaction
Rate
External Factors can Affect
Enzyme Activity
• Factors that affect enzyme shape will
affect its function
• Different enzymes have different
optimal conditions
Adenosine Triphosphate (ATP)
• Unstable molecule
• E coupling uses exergonic
process to power an
endergonic process
• Mediates most E coupling
by providing E to power
cell work
• E coupled by transferring
PO4- to another molecule
(phosphorylated)
Cofactors
• Cofactors – non-protein helpers that bind to
enzymes
• Inorganic vitamins
• Ex: Zn, Cu, Fe
• Coenzymes – organic cofactors
• Ex: Vitamins A, B12, C
Cofactors
Enzyme Inhibitors
• Inhibitors prevent an enzyme
from catalyzing a reaction
• Competitive inhibitors – block
substances from entering active
sites
• Noncompetitive Inhibitors –
bind to another part of the
enzyme, causing the enzyme to
change shape and become
inactive
• Regularly present to regulate
activity
Allosteric Regulation
• Allosteric Regulation – controls metabolic pathways,
so they are not always “on” or always “off” in
enzymes without quaternary structure
• Activators – stabilize active site
• Inhibitors – stabilize inactive form of active site
• Cooperativity – amplifies enzyme activity (allows
additional substrate)
• Feedback inhibition – the product binds to an
enzyme early in the metabolic pathway inhibiting
the enzyme
The chemical equation for cellular respiration is:
C6H12O6 + O2  CO2 + H2O + Energy
This is an example of an anabolic process. F
Which of the following statements is NOT correct?
A metabolic pathway...
A. Has an orderly sequence of reaction steps
B. Is mediated by only one enzyme that starts it
C. May be anabolic or catabolic
D. All of the above are incorrect
An enzyme...
A. Is a protein
B. Lowers the activation energy of a reaction
C. Is destroyed by the reaction it catalyzes
D. 1 and 2
What happens to an enzyme when it denatures?
A. The activation energy of the reaction is doubled
B. The activation energy of the reaction is lowered
C. It’s optimal conditions for temperature of the enzyme are
doubled
D. The shape of the enzyme molecule is changed
The chemical equation for cellular respiration is:
C6H12O6 + O2  CO2 + H2O + Energy
This is an example of an exergonic process. T