Metabolism (Lecture 1)
Microorganisms Require Energy: because they work against entropy
They require entropy for growth and multiplication including the synthesis of new cellular
materials. They also require energy for mobility – the flipping of flagella required ATP. It is
also required for active transport of materials into cell and repair cellular damage.
Production of Energy
The energy is from the nutrients in their environment.
Metabolism is the sum of all chemical reactions within a living cell
Metabolism reactions can be categorised as:
- Catabolic (breaking down molecules)
- Anabolic (building up molecules)
NB: Catabolic reactions are used to get energy out of food and anabolic reactions are used
for growth and multiplication of microbes and the synthesis of new cellular molecules of
Chemotroph Breaking down complex molecules using
oxidation –reduction reactions
Phototroph Use light to produce food
Heterotroph Small organic compound molecules are
taken in from the outside to be utilised
Autotroph Use carbon dioxide to fix into sugars
Most bacteria, all fungi, protozoa and animals are chemoheterotrophs: they use organic
molecules and them oxidise them.
This is where complicated organic molecules are broken down into simple molecules that
can be utilised by the microorganism. They are degradative reactions.
They are generally hydrolytic reactions so use water to break bonds. Energy is released
through the breaking of these bonds (exergonic).
- the larger the compound the higher the energy content
- sugars are broken down into carbon dioxide and water Metabolism Notes
These are examples of biosynthetic reactions that are often dehydration synthesis reactions
that release water. These reactions consume energy (endergonic).
During these reactions simple substances are built up to complex organic substances
Simple Substance Complex Organic Substance Bonds Formed
Amino Acids Proteins Peptide Bonds
Nucleotides Nucleic Acid Phosphate Bonds
Sugars Polysaccharides/Starches Glycosidic Bonds
All these simple substances undergo polymerisation to form the complex organic substances
Most organisms Link the Reactions
- the catabolic reactions drive the anabolic reactions
The energy is achieved by Adenosine Triphosphate (ATP), which is how energy is conserved
During catabolic reactions ATP is synthesised and during anabolic reactions ATP is
Driving a Cell’s Metabolism
Most metabolism reaction rates are too slow at room temperature, therefore catalysts are
used to speed up the reaction.
Enzymes are biological catalysts that are made of proteins. They lower the activation energy
of biological reactions to speed up the rate. The function and specificity of the enzyme is
related directly to the protein structure.
Some specific RNA molecules, ribozymes are also catalytic. Metabolism Notes
Four Levels of Protein Structure
Primary The amino acid sequence