1 All enzymes have an optimum functioning temperature. In humans this is at around 40degC, hence our body temperature is maintained at 37degC. There is a small buffer, because above a certain temperature the enzyme is destroyed in a process called denaturation.
Below this optimum temperature, the cooler the environment in which the enzyme is trying to work, the slower it works. So for instance if enzyme A is used to break down starch and you put a set amount of the enzyme into a set concentration of a starch solution at a given temperature at 30degC you can measure the amount of starch broken down into glucose. If I exactly repeat the experiment at 20degC then I can measure the amount of starch produced and see it will be less.
The relationship between the two amounts is called Q10 and for most mammals the relationship is that for every 10degC increase in the temperature of the environment, we can see that double the amount of work has been done by the enzyme. In biology, this would be expressed as Q10 = 2. The 2 means that 2 times as much work has been done (i.e. 2 times as much starch has been broken down).
2 Temperature affects enzyme activity because enzymes are made of proteins and as the temperature raises, the protein's molecular structure will be more and more unstable until it denatures and breaks apart. The pH works essentially the same where the enzyme will denature if it is in too acidic or too basic of an environment. Cofactors are molecules that will fit into the active site of an enzyme and active/deactivate. Enzyme inhibitors are little molecules that will fit into an enzyme and prevent the cofactor from reaching it and activating it.
3 At a low temperature the enzyme activity is dependent on it. In other words, it is less than optimal. If you slowly raise the temperature, the enzyme activity will increase. At room temperature the activity will be optimal. If you increase the temperature further by 10...