Molecular Biology

 Enzymes are globular proteins that work as catalysts  Catalysts speed up chemical reactions without being altered themselves  Enzymes are often called “biological catalysts” because they are made by living things and speed up biochemical reactions

 Substrates are the substances that enzymes convert into products.  A general equation for an enzyme- catalyzed reaction is: substrate enzyme product

 Thousands of reactions occur in cells. Nearly all of which need to be catalysed.  Enzymes only catalyze one biochemical reaction.  This is called Enzyme-substrate specificity

Enzymes have an active site to which specific substrates bind  Substrate (or substrates) bind to a specific region on the surface of the enzyme called the Active Site  The shape and chemical properties of the substrate and active site match each other

Stages of enzyme activity: 1. Substrate(s) binds to the active site. 2. Substrate is converted to products while bound to the active site. 3. The products are released, leaving the site available to catalyse another reaction.

 Gerty and Carl Cori Data Analysis Question  p97 in text

Enzyme catalysis involves molecular motion and the collision of substances with the active site

 A substrate molecule can only bind to the active site if it moves close to it  The coming together of substrate and active site is known as a Collision

 Water is in a liquid state… water particles and dissolved particles are in contact with each other and in continual motion  Collisions between substrate and enzyme occur because of these random movements  Successful collisions require the substrate and active site to be correctly aligned

Enzymes can be denatured  Enzymes are proteins and, like other proteins, their structure can be irreversibly altered by certain conditions  When the enzyme has been denatured its active site can no longer bind the substrate. What conditions will denature an enzyme?

Predict what factors might affect enzyme activity.  Temperature  pH  Substrate concentration

Why would temperature affect the rate of enzyme activity?

Temperature affects enzyme activity in 2 ways:  Molecules of substrate and enzyme move faster and the chance of collisions increases  Enzyme molecules can become denatured and no longer able to catalyse reactions

Why would pH affect the rate of enzyme activity?

pH affects enzyme activity  Most enzymes have an optimum pH. This level is not the same for all enzymes.  At higher or lower pH the structure of the enzyme is altered

Why would concentration affect the rate of enzyme activity?

Substrate concentration affects enzyme activity  Substrate-enzyme collisions take place more frequently with more molecules present  When the active site is occupied it is not available to bind other substrates The rate of increase decreases as concentration increases