Enzymes: Need to Know

Study Notes

Enzymes are proteins that act as biological catalysts, accelerating chemical reactions without being consumed.
Each enzyme is specific to one substrate and produces only a specific set of products.
Made from long chains of amino acids linked by peptide bonds; their structure is folded into a unique 3D shape.

Some enzymes require additional molecules, known as co-enzymes, for optimal function.
Co-enzymes are organic, non-protein substances; vitamins B1 and B6 function in this role.
Enzyme names typically end with the suffix ‘-ase’.

Enzyme function is influenced by environmental conditions such as pH, temperature, concentration of enzymes, and substrates, as well as the presence of inhibitors.

Each enzyme has a specific pH range for optimal activity:
- Amylase: best at pH 7 (neutral).
- Pepsin: functions optimally around pH 2 (acidic), suited for the stomach.
- Lipase: works best at pH 10 (alkaline) in the small intestine.

Enzyme activity typically increases with temperature, peaking at around 40°C.
Above 40°C, enzymes rapidly denature, losing shape and function.
Human enzymes function optimally around 37°C but can become inactive above this temperature, particularly in the brain, risking seizures.
Plant enzymes thrive at an approximate optimum temperature of 25°C.

Denaturation refers to the loss of an enzyme's shape and activity, caused by several factors:
- High Temperature: Enzymes lose shape above 40°C; irreversible changes occur at temperatures exceeding 50°C. For example, egg whites transition from clear to stiff upon heating.
- pH Change: For instance, salivary amylase, which breaks down starch at pH 7-8 in the mouth, becomes inactive when exposed to the acidic environment (pH 1) in the stomach.
- Agitation: Physical mixing or beating can alter enzyme shape and activity, such as when egg whites are beaten, forming a thick mixture that traps sugar.

The active site is the specific region on the enzyme where the substrate binds and reactions occur.
The binding causes slight shape changes in both substrate and enzyme, forming an enzyme-substrate complex.
These transformations facilitate product formation and lower activation energy needed for the reaction.
Resulting products may form a substrate-product complex, allow the enzyme to revert to its original shape, ready to catalyze another reaction.

Anabolic Reactions: Create more complex products from simpler reactants; e.g., muscle formation.
Catabolic Reactions: Break down complex reactants into simpler products; oppositely, they release energy.