Metabolism
Metabolism refers to all the chemical reactions taking place in a cell.
There are thousands of these in a typical cell, and to make them easier to
understand, biochemists arrange them into metabolic pathways. The
intermediates in these metabolic pathways are called metabolites.
Reactions that release energy (usually breakdown reactions) are
called catabolic reactions (e.g. respiration)
Reactions that use up energy (usually synthetic reactions) are
called anabolic reactions (e.g. photosynthesis).
Photosynthesis and respiration are the reverse of each other, and you
couldn’t have one without the other. The net result of all the
photosynthesis and respiration by living organisms is the conversion of
light energy to heat energy
Cellular Respiration
The equation for cellular respiration is usually simplified to:
glucose + oxygen react to form carbon dioxide + water (+ energy)
, But in fact respiration is a complex metabolic pathway, comprising at
least 30 separate steps. To understand respiration in detail we can break it
up into 3 stages:
Above Summary:
The different stages of respiration take place in different parts of
the cell. This allows the cell to keep the various metabolites
separate, and to control the stages more easily.
The energy released by respiration is in the form of ATP.
Since this summarises so many separate steps (often involving
H+ and OH- ions from the solvent water), it is meaningless to try to
balance the summary equation.
The release of carbon dioxide takes place before oxygen is
involved. It is therefore not true to say that respiration turns
oxygen into carbon dioxide; it is more correct to say that
respiration turns glucose into carbon dioxide, and oxygen into
water.
Stage 1 (glycolysis) is anaerobic respiration, while stages 2 and 3
are the aerobic stages.
Metabolism refers to all the chemical reactions taking place in a cell.
There are thousands of these in a typical cell, and to make them easier to
understand, biochemists arrange them into metabolic pathways. The
intermediates in these metabolic pathways are called metabolites.
Reactions that release energy (usually breakdown reactions) are
called catabolic reactions (e.g. respiration)
Reactions that use up energy (usually synthetic reactions) are
called anabolic reactions (e.g. photosynthesis).
Photosynthesis and respiration are the reverse of each other, and you
couldn’t have one without the other. The net result of all the
photosynthesis and respiration by living organisms is the conversion of
light energy to heat energy
Cellular Respiration
The equation for cellular respiration is usually simplified to:
glucose + oxygen react to form carbon dioxide + water (+ energy)
, But in fact respiration is a complex metabolic pathway, comprising at
least 30 separate steps. To understand respiration in detail we can break it
up into 3 stages:
Above Summary:
The different stages of respiration take place in different parts of
the cell. This allows the cell to keep the various metabolites
separate, and to control the stages more easily.
The energy released by respiration is in the form of ATP.
Since this summarises so many separate steps (often involving
H+ and OH- ions from the solvent water), it is meaningless to try to
balance the summary equation.
The release of carbon dioxide takes place before oxygen is
involved. It is therefore not true to say that respiration turns
oxygen into carbon dioxide; it is more correct to say that
respiration turns glucose into carbon dioxide, and oxygen into
water.
Stage 1 (glycolysis) is anaerobic respiration, while stages 2 and 3
are the aerobic stages.
