pH
An explanation of pH in terms sufficient for A-level biology would be something like this.
Substances that are acidic are easily able to release a Proton (H+). Substances that are alkaline donate hydroxyl ions (OH-).
In terms of their effect on enzymes both protons and hydroxyl ions have the effect of breaking Hydrogen bonds that help hold the tertiary structure of the enzyme in shape. As with temperature, this results in a change in the shape of the active site and the loss of the enzyme function - it is again, denatured.
As with temperature, different enzymes have different optimum pH's. As the diagram above shows, Pepsin (a protease enzyme found in the stomach) works best at a pH of around 2. Salivary amylase works at its optimum in the near neutral conditions found in the mouth. (we will consider these more in Unit 2 when we study digestion)
As the pH moves away from the optimum the enzyme becomes increasingly denatured and less active.
Substances that are acidic are easily able to release a Proton (H+). Substances that are alkaline donate hydroxyl ions (OH-).
In terms of their effect on enzymes both protons and hydroxyl ions have the effect of breaking Hydrogen bonds that help hold the tertiary structure of the enzyme in shape. As with temperature, this results in a change in the shape of the active site and the loss of the enzyme function - it is again, denatured.
As with temperature, different enzymes have different optimum pH's. As the diagram above shows, Pepsin (a protease enzyme found in the stomach) works best at a pH of around 2. Salivary amylase works at its optimum in the near neutral conditions found in the mouth. (we will consider these more in Unit 2 when we study digestion)
As the pH moves away from the optimum the enzyme becomes increasingly denatured and less active.
Buffers
You don't need to get hung up on how buffers work, you just need to know they exist and can be added to a solution in order to make sure the pH does not change during an experiment.
It is particularly important if you expect your product to be acidic or alkaline. Fore example, when triglycerides are digested by lipase they release fatty acids and the solution would become acidic. Sometimes this can be utilised by using a pH indicator and using the time taken to change as an indicator of rate. However, if the pH changes too much that would potentially alter the shape of the enzyme. It introduces a variable that is not controlled.
In simple terms buffers are able to accept H+ ions and then release them again. This counteract the effect of any H+ released from acids present.
It is particularly important if you expect your product to be acidic or alkaline. Fore example, when triglycerides are digested by lipase they release fatty acids and the solution would become acidic. Sometimes this can be utilised by using a pH indicator and using the time taken to change as an indicator of rate. However, if the pH changes too much that would potentially alter the shape of the enzyme. It introduces a variable that is not controlled.
In simple terms buffers are able to accept H+ ions and then release them again. This counteract the effect of any H+ released from acids present.