Lecture 26 Flashcards
What forms can energy be changed to at a molecular level? What does gibbs free energy amount mean in regards to reaction movement?
Energy can be converted between forms such as chemical bonds, heat or mechanical. If Gibbs free energy is below 0 then the reaction is spontaneous/energetically favourable, if gibbs energe is 0 the reaction is at equilibrium under standard conditions. If Gibbs energy is greater than 0 the reaction is not spontaneous/is energetically favourable.
What is energy coupling and what is a key example in the cells?
energy coupling is taking a reaction which has a negative gibbs energy change and coupling it with one with a positive gibbs energy change. by coupling them we can get the unfavourable reaction to occur. The overall value when combined must lead to a negative gibbs energy change. The production of ADP into ATP requires energy input (positive delta G 30.5 kJ mol-1 under standard conditions with pH at 7). Likewise the reverse reaction releases energy which can be used for cellular work via energy coupling.
What process is coupled with ATP production and why is this not instant?
Oxidation of fuels like carbohydrates and lipids is coupled with the production of ATP in order to make the reaction favourable. The ATP may be generated by substrate level phosphorylation (directly via glycolysis and CAC) and oxidative phosphoryation (indirectly via reduction of co-enzymes). This oxidation is done in steps via the body in order to ensure almost all energy is captured for ATP production rather than converting into heat. At the same time co enzymes get reduced.
What do biological redox reactions often involve and what are the enzymes called?
Biological redox reactions often involve the transfer of hydrogen (including the electron). The coenzymes NAD and FAD interact with various enzymes to accept and donate the hydrogens/electrongs (enzymes involved in this are often called dehydrogenases).
What are coenzymes and what are the main examples in biological systems? (in detail)
Coenzymes are a subclass of co-factors which are small organic molecules with low concentration in cells. They act as carriers and are able to exist in two forms. The main examples for metabolism are NAD (nicotinamide adenine dinucleotide, accepts hydrogens and electrons from glycolysis, fatty acid oxidation and CAC, it undergoes a two electron reduction (1H+ and 2E- come in changing it from NAD+ to NADH)) and FAD (flavin adenine dinucleotide, its synthesised from riboflavin and accepts hydrogens from fatty acid oxidation and CAC, they are tightly bound to the proteins with which they interact (flavoproteins), it undergoes a two electron reduction from FAD to FADH2). Coenzyme A is also important, it is derived from pantothenic acid (B5), it is a carrier of acyl groups (carbon chains). It has two forms, free CoA (CoASH) or AcCoA with an acyl group attached.
