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Biology – Kevin Dees
Chapter 8
Introduction to Metabolism
Biology – Kevin Dees
____________
• Defined as the sum total of the chemical
reactions that occur in a living thing.
Think of metabolism as a road map of
thousands of different chemical reactions
_____________ regulate metabolism
A B C D
ENZYME 1
ENZYME 3
ENZYME 2
Biology – Kevin Dees
There are two basic metabolic
processes
1. ___________________ pathways
– Degradation reactions
– breakdown large molecules into smaller
ones
– Releases energy
– i.e aerobic cellular respiration
C6H12O6 + O2 CO2 + H2O
Biology – Kevin Dees
There are two basic metabolic
processes
2. ________________ pathways
– Building reactions
– Form large molecules from smaller ones
– Consume energy
– i.e photosynthesis
CO2 + H2O C6H12O6 + O2
Biology – Kevin Dees
The key is understanding
ENERGY!!
• ________________ can be defined as the capacity to cause change – WORK!!!
• Energy is fundamental to all metabolic processes
Biology – Kevin Dees
• _______________________– “moving energy” – Energy associated with relative motion
– Heat is also kinetic energy
– Thermal energy
• ____________________– “stored energy” – energy because of location or structure
– Chemical energy can be potential energy because of the energy stored in chemical bonds
Biology – Kevin Dees
Biology – Kevin Dees
Energy changes forms!!!!
• The study of energy transformations is
known as _____________________
• There are two laws of thermodynamics
that govern energy transformations in
organisms and all other collections of
matter
Biology – Kevin Dees
The first law of thermodynamics (principle of conservation of energy)
• The amount of energy in the universe is ______________;
• energy can be transformed and transferred, but cannot be
created or destroyed.
– Plants converting light into sugar
– Food particles being converted into kinetic energy of movements of
animals
Biology – Kevin Dees
The second law of thermodynamics (principle of entropy)
• Every energy transformation or transfer
increases the entropy in the universe.
_____________ = measure of disorder
• As energy transformations or transfers
occur some energy is converted into an
unusable form
– Body heat
Biology – Kevin Dees
Biology – Kevin Dees
Cellular work
• There are three types of cellular work
– Mechanical work • motility
• Cilia beating; contraction of muscle cells
– Transport work • Active transport mechanisms
• Na-K pump
– Chemical work • Driving reactions to proceed
• Joining of amino acids to form polypeptides
Biology – Kevin Dees
In most cases, cells’ energy demands
needed to do work is ion the form of
• Adenosine triphosphate (ATP)
Biology – Kevin Dees
Energy is released why ATP is
hydrolyzed
Biology – Kevin Dees
How is this
energy used
by a cell?
• To perform the
three types of
cellular work
• A phosphate is
removed
• The recipient of
the phosphate is
said to be
phosphorylated
Biology – Kevin Dees
ATPs are used constantly by a cell
• You use about 45kg of ATP a day
• At any given instant there is <1 g present
in your cells
• Why???
Biology – Kevin Dees
Biological catalysts - enzymes
• Catalysts speed up reactions by lowering
activation energy
– The amount of energy needed to initiate a
reaction
• Enzymes are organic catalysts – proteins!!
– Typically end in –ase
– Enzymes regulate metabolism!!
Biology – Kevin Dees
Substrate specificity of enzymes
• Enzymes are very specific as regards the
reactions they participate in.
• In order for an enzyme to work, the reactants
(called substrates) bind to the enzyme forming
an enzyme-substrate complex
• The site on the enzyme where the substrates
bind is known as the active site
– Recall that proteins are large 3-D molecules and
shape plays a significant role in their function!!!
Biology – Kevin Dees
Biology – Kevin Dees
Substrate
Active site
Products
Biology – Kevin Dees
The enzymatic activity is affected
by the environment
– pH – most have optimal range
– Temperature – most have optimal range
– Cofactors – non-protein helpers
– Coenzymes – organic helpers – vitamins
– Inhibitors – compete for active sites with substrates
• Nerve gas – sarin – blocks actylcholinesterase - disrupts the nervous system
• Pesticides
• Penicillin
