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
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 2Lactate G°' = -184.5 kJ mol -1
2ADP + 2Pi 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
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
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 3-
phosphoglyceric 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 O
H H
CNH2 CNH2
+ H+ + 2 e -
N+ N
Ad
Ad
NAD + NADH
(oxidized form) (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