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Lecture 3

BIOL 1201 Lecture Notes - Lecture 3: Atp Hydrolysis, Endergonic Reaction, Exergonic Process

Biological Sciences
Course Code
BIOL 1201
Moroney, James

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Study Guide #2 for Biology 1201, section 4 2013
Blaike Musso
**Phosphorylate- introduce a phosphate group into a molecule or compound.
Chapter 8, pages 142-161
Metabolism, metabolites
- Cells need an input of energy to stay alive, metabolism, breaks down molecules
- The totality of an organisms chemical reactions is called Metabolism- (change) an
emergent property of life that arises from orderly interactions between molecules
- Metabolism- the totality of organism’s chemical reactions, consisting of catabolic and
anabolic pathways, which manage the material and energy resources of the organism.
oCan be thought of as an elaborate road map of thousands of chemical reactions
that occur in a cell
oCatabolic pathways- release energy by breaking down complex molecules to
simpler compounds ( exergonic)
oAnabolic Pathways- consume energy to build complicated molecules from
simpler ones (endergonic)
- Metabolite - a substance formed in or necessary for metabolism
Where is energy required in the cell? This is a hard concept to grasp. It is needed to build the
cell, maintain the cell, make and keep ion gradients etc.
- Thermodynamics- just know endothermic ( energy is required) and Exothermic ( energy
is released)
o1st Law ( Law of the Conservation of energy) energy can be transferred or
transformed BUT energy cannot be created or destroyed
o2nd Law- energy transformation or transfer increases the disorder of the universe
(entropy). Living cells unavoidably convert forms of energy to heat.

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- ATP is responsible for mediating most energy coupling
in cells, and in most cases it acts as the immediate source
of energy that powers cellular work.
- Bonds bw the phosphate group and ATP can be broken
by hydrolysis ( the addition of water)
ATP cycle (Figure 8.11)
- An organism at work uses ATP continuously, but ATP is
renewable regenerated by addition of Phosphate to ADP.
Free energy comes from exergonic breakdown reactions in the cell (catabolism).
Catabolic (exergonic) pathways provide the energy for the endergonic process of making
How ATP drives chemical work and mechanical work (Figures 8.9 and 8.10)
- ATP powers cellular work by coupling exergonic and endergonic reactions
- a cell does 3 main kinds of work:
ochemical work- the pushing of endergonic reactions that would not occur
otransport work- the pumping of substances across membranes against the
direction of spontaneous movement

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omechanical work- such as beating of cilia, the contraction of muscle cells, and the
movement of chromosomes during cellular respiration
drives Transport
and Mechanical
work. ATP
hydrolysis causes
change in the
shapes and
binding affinities of proteins. This can occur (a) directly, by phosphorylation, as shown
for a membrane protein carrying out active transport of a solute or (b) indirectly, via
noncovalent binding of ATP and its hydrolytic products, as in the case for motor proteins
that move vesicles ( and other Organelles) along cytoskeleton “tracks” in the cell.
Enzymes, activation energy, catalysis (Figures 8.14 and 8.15)
- Enzyme- macromolecule that acts as a catalyst, a chemical agent that speeds up a reaction
without being consumed by the reaction.
oEnzymes and metabolism: enzymes are proteins, catalysts, depend on their shape
for activity
Enzymes LOWER activation energy
Substrate  ( added ezyme)  product
Sucrose = H2o  sucrose  glucose + fructose
Substrate binds on enzyme at activation site
Binding produces “ induced fit” to enzyme
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