Bio Lab13 EnzymeActivity
Interactions
BigIdea
4
investigation 13
ENZYME ACTIVITY*
How do abiotic or biotic factors influence the rates of enzymatic reactions?
■■BACKGROUND
Enzymes speed up chemical reactions by lowering activation energy (that is, the energy needed for a reaction to begin). In every chemical reaction, the starting materials (the substrate(s) in the case of enzymes) can take many different paths to forming products.
For each path, there is an intermediate or transitional product between reactants and final products. The energy needed to start a reaction is the energy required to form that transitional product. Enzymes make it easier for substrates to reach that transitional state. The easier it is to reach that state, the less energy the reaction needs.
Enzymes are biological catalysts. They are large protein molecules, folded so that they have very specifically shaped substrate binding sites. These binding sites make substrates go into the transition state. To catalyze the reaction, several regions of the binding site must be precisely positioned around the substrate molecules. Any change in the shape of the overall folded enzyme molecule can change the shape of the binding site.
The optimum reaction conditions are different for each enzyme. The correct environmental conditions, proper substrates, and, often, particular cofactors associated with an enzyme are needed. In some instances, the optimum conditions can be deduced fairly accurately based on the following:
• The organism from which the enzyme is derived
• The part of the organism in which the enzyme functions
• The environmental conditions in which that organism lives
For example, this investigation mentions lactase, the enzyme that catabolizes the disaccharide sugar lactose into the two monosaccharides, glucose and galactose. In humans, lactase is found mostly in the small intestine, where the pH is around 7. It would be reasonable to hypothesize that human lactase is optimally active at pH 7 and at 37°C.
BigIdea
4
investigation 13
ENZYME ACTIVITY*
How do abiotic or biotic factors influence the rates of enzymatic reactions?
■■BACKGROUND
Enzymes speed up chemical reactions by lowering activation energy (that is, the energy needed for a reaction to begin). In every chemical reaction, the starting materials (the substrate(s) in the case of enzymes) can take many different paths to forming products.
For each path, there is an intermediate or transitional product between reactants and final products. The energy needed to start a reaction is the energy required to form that transitional product. Enzymes make it easier for substrates to reach that transitional state. The easier it is to reach that state, the less energy the reaction needs.
Enzymes are biological catalysts. They are large protein molecules, folded so that they have very specifically shaped substrate binding sites. These binding sites make substrates go into the transition state. To catalyze the reaction, several regions of the binding site must be precisely positioned around the substrate molecules. Any change in the shape of the overall folded enzyme molecule can change the shape of the binding site.
The optimum reaction conditions are different for each enzyme. The correct environmental conditions, proper substrates, and, often, particular cofactors associated with an enzyme are needed. In some instances, the optimum conditions can be deduced fairly accurately based on the following:
• The organism from which the enzyme is derived
• The part of the organism in which the enzyme functions
• The environmental conditions in which that organism lives
For example, this investigation mentions lactase, the enzyme that catabolizes the disaccharide sugar lactose into the two monosaccharides, glucose and galactose. In humans, lactase is found mostly in the small intestine, where the pH is around 7. It would be reasonable to hypothesize that human lactase is optimally active at pH 7 and at 37°C.