Metabolism
Basic Concepts and Design
Metabolism


What is metabolism?
 all the chemical reactions that take place in
cells
 series of energy transformations
Why do living organism require energy?
 to synthesize large molecules from small ones
 to move substances in and out of cells
 muscle contraction and cell movement
Metabolism
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
What is the difference between phototrophs and
chemotrophs?
 phototrophs obtain energy from sunlight
 chemotrophs obtain energy from breaking
chemical bonds
What is the difference between anabolic and
catabolic reactions?
 catabolic – fuels degraded to release useful
energy
 anabolic – energy used to synthesize
biomolecules
Metabolism

Why are reactions often coupled in metabolic pathways?
 to insure that the overall free energy change is negative

a reaction that requires energy may be paired with
one that releases energy
Glucose
2ADP + 2Pi
2Lactate
G°' = -184.5 kJ mol -1
2ATP + 2 H2 O G°' = +61.0 kJ mol -1
Glucose + 2ADP + 2Pi
2Lactate + 2ATP + 2 H2 O
G°' = -123.5 kJ mol -1
Metabolism
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What is the role of ATP in cells?
 donor of free energy in energy requiring
reactions
Why is ATP an energy rich molecule?
Metabolism

What are the factors that contribute to the
large amount of energy released when ATP
is hydrolzed?
 resonance stabilization
 electrostatic repulsion
 ease of hydration
Metabolism
Metabolism
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What do we mean by
phosphoryl transfer
potential?
 ability to donate a
phosphate group
What molecules
besides ATP can
transfer PO4 groups?
Metabolism

How is ATP
regenerated in cells?
Metabolism

The oxidation of which of these two molecules
will produce more ATP and why?
Metabolism
•
How do molecules with high phosphoryl
transfer potential couple the oxidation of
carbon to the synthesis of ATP?
 glyceraldehyde-3-PO4 + NAD+ + HPO4
1,3 biphosphoglycerate + NADH + H+
 1,3 biphosphoglycerate + ADP  3phosphoglyceric acid + ATP
Metabolism
Metabolism

What is happening at
each stage of
catabolism?
Metabolism

While ATP is an activated carrier of
phosphoryl groups, what molecule(s) is
(are) activated carrier(s) of electrons during
oxidation?
 nicotinamine adenine dinucleotide
(NAD)
 flavin adenine dinucleotide (FAD)
Metabolism
Metabolism
O
CNH2
N+
Ad
+ H+ + 2 e -
NAD +
(oxidized form)
H O
CNH2
H
N
Ad
NADH
(reduced form)
Metabolism

One H is transferred to NAD with 2 electrons and
the other H goes into solution as a proton.
Metabolism
Metabolism
Metabolism

What activated carrier for electrons is used in most
biosynthetic reactions or the reaction shown
above?
 NADPH
Metabolism

Why is coenzyme A an important molecule in
metabolism?
 carrier of acyl groups
Metabolism
Metabolism

While metabolism consists of thousands of
reactions, each reaction falls into one of six
categories.
Oxidation-Reduction Reaction
Ligation Reaction
Isomerization Reaction
Group Transfer Reaction
Hydrolytic reaction
Addition or Removal of
Functional Groups
Regulation of Metabolism

What are the three basic ways in which metabolic
reactions are regulated?
 controlling amount of enzyme
 influencing rate of transcription
 altering catalytic activity
 allosterically
 covalent modification
 controlling accessibility of substrates
Regulation of Metabolism
How do hormones influence metabolism?
 alteration of enzyme activity
 glucagon and glycogen phosphorylase
 What other factors influence metabolism?
 compartmentalization
 energy status of cell

Metabolism

What do ATP, NADH, FAD and coenzyme
A have in common and what does this
indicate about these molecules?
 adenosine diphosphate
 evolved from early RNA catalysts