Metabolic Pathways
What you should learn:


The difference between Anabolic and
Catabolic metabolic pathways, and give
examples of each.
The importance of reversible, irreversible and
alternative pathways in the control of
metabolism.
The key role played by specific enzymes in
regulating rates of reactions.
Cell Metabolism is defined as :


The product of all the biochemical reactions
which take place in a living cell.
Cell metabolism involves a network of
interconnected and integrated chemical
pathways catalysed by enzymes.
Link to youtube lesson on metabolism
http://www.youtube.com/watch?v=iIW5SPY-vwI
Metabolic pathways fall into two categories:
Catabolic pathways lead to the breakdown
of complex molecules into simpler ones,
usually with the release of energy.
E.g aerobic respiration.

Anabolic pathways lead to the
(bio)synthesis of more complex molecules
from simpler ones (building blocks) –
requires energy.
E.g. protein synthesis
e.g. Amino Acids
Carbon Dioxide
ATP
+
Water
ENERGY TRANSFER
Catabolic – Aerobic
Respiration
Glucose
Anabolic – e.g.
Protein synthesis
Energy
+
Oxygen
Respiration
Catabolic
Energy
Energy
Energy
ADP
Protein molecule
+
Pi
Protein Synthesis
Anabolic
Another example:
glucose-1-phosphate
phosphorylase
starch
This reaction requires the input of energy to
proceed (anabolic reaction).
Another example:
starch
amylase
maltose
This reaction releases energy (catabolic
reaction).

Metabolic pathways can have reversible and
irreversible steps.
AND

Alternative pathways may exist that can
bypass steps in a pathway.

Example of
reversible/
irreversible
pathways

Example of
alternative
routes in
metabolism