Cell Respiration
Cell respiration as a system for producing ATP
- Cell respiration is the controlled release of energy from organic compounds to produce ATP
- Respiration is a series of chemical reactions that happens in every cell
- Its purpose is to release energy in usable forms from chemical energy stored in food e.g. glucose
- Respiration is a catabolic process
- Glucose is the main respiratory fuel used in cells
- Lipids and proteins can also be used but they must undergo several changes before they can enter the respiratory pathway
- Glucose can enter glycolysis directly which makes it easier to oxidise than lipids and proteins
- Since proteins are primarily structural molecules, they will only be used as a respiratory fuel in conditions where glucose and lipids are not available
- Organic food substances contain a lot of chemical energy
- This energy cannot be released in one, uncontrolled step in cells, which would cause cell damage and tissue death
- Enzymes control the release of energy through a series of chemical reactions called a pathway
- This ends in the production of ATP (adenosine triphosphate)
- To make ATP, a phosphate group is linked to adenosine diphosphate (ADP)
- This process requires energy which comes from the breakdown of organic molecules
- The energy that is released is used for
- Fuelling anabolic processes
- Muscle contraction
- Fuelling active transport
- Moving molecules around the cell
- Generating heat to maintain body temperature in warm-blooded animals
Exam Tip
Respiration is often confused with gas exchange, but remember that respiration is a chemical process while gas exchange involves the exchange of carbon dioxide and oxygen at the alveoli or cells