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Energy in biochem
Uni of Notts, core skills in biochemistry, first year
| Term | Definition |
|---|---|
| Chemotroph | An organism that obtains energy by oxidising electron donors & using these electrons to build vital compounds. Some organisms use organic compounds (chemoorganotroph) or inorganic (chemolithotroph) |
| Endergonic reactions | Processes which aren't thermodynamically viable in the conditions they're required to occur in |
| How organisms perform vital endergonic reactions | Either alternate reaction pathways (catalysis) or being coupled with a very exergonic reaction (e.g., sodium ion co-transporters moving a substance against its concentration gradient |
| Role of Gibbs free energy (ΔG) in cells | It's a measure of useable energy in a system. If a reaction has a negative ΔG value then it's spontaneous, otherwise it must be catalysed or paired with a much more exergonic reaction |
| Principle of additive Gibbs free energy | The ΔG energy of consecutive reactions is cumulative. As long as the net charge is negative then the reaction is favourable. Cells can intentionally pair highly exergonic reactions with endergonic ones |
| How coupled reactions work | 1 reaction is chemically linked to the next by a shared intermediate. A reaction which spontaneously produces an intermediate very close to part of another reaction can transfer bond energy to it, forcing an unfavourable reaction. Enzymes can trigger this |
| Function of ATP in cells | Very thermodynamically unstable molecule, will spontaneously dephosphorylate. Is coupled with reactions fusing a phosphate to a molecule & lowers the ΔG until the reaction can occur in temperatures compatible with life |
| Gibbs free energy in metabolic pathways | Metabolic pathways are a system of coupled reactions, such large energy inputs make the reaction almost always reversible & endergonic steps are usually unidirectional even if they have an overall -ΔG |
Created by:
Beech47
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