4.5 Lesson 5: Enzymes
- Enzymes are mostly protein molecules that act as catalysts, that is, they either speed up or slow down cellular reactions. Some enzymes speed up a reaction to more than a million times faster than if the enzyme was not present!
- Enzymes are highly specific in terms of the substrate (reactant) with which they react. For instance, enzymes that help build the keratin protein of hair from many amino acids, only do that ‘job’.
- In order to do its work, an enzyme must unite — even if briefly — with at least one of the substrates. Due to the specificity of the enzyme/substrate reaction, they bind to each other like a lock and key. If the shape is not exact, they will not react.
- There are two parts to an enzyme:
- the apoenzyme (the protein portion) and
- the cofactor (or coenzyme) which is a non-protein portion (often a vitamin)
- Many enzymes are inserted in cell membranes so that they can interact more efficiently within the cell.
- Enzymes usually end in the suffix “-ase” and are named for the types of chemical reactions they catalyze, ex. lipase enzymes break down lipids.
- The speed of enzyme action depends on pH, temperature, and amount of enzyme or substrate present. If the temperature or pH is not right, the enzyme will become permanently denatured (change shape) and so be unable react.
- Enzymes are vital for the building and the breaking down of macromolecules that the cells need to function. This will be discussed in a later Lesson.
