Learning Outcomes BIOL1081 - 10/1

Describe allosteric regulation, drawing a picture of an allosteric enzyme and its important sites, and drawing a diagram of feedback inhibition.

Allosteric regulation: enzymes can exist either as active or inactive known as an allosteric enzyme. Noncompetitive enzymes bind to an allosteric site. This is a portion of the enzyme that acts as an on/off switch. Binding to this site can switch the enzyme between active and inactive. This substance that binds to the allosteric site and reduces enzyme activity is called an allosteric inhibitor. Substance that binds to allosteric site and puts enzyme in the active configuration is called allosteric activator, thus increasing enzyme activity. Feedback inhibition: Control mechanism where an increase in the concentration of some molecules inhibits the synthesis of that molecule. The end product of a biochemical pathway binds to an allosteric site on the enzyme that catalyzes the first reaction in the pathway.

Define what it means to catalyze a reaction, contrasting the course of a reaction with and without a catalyst.

Catalyze reaction: influence chemical bonds to lower activation energy, thus speeding up the reaction. In biological systems, the catalyst is most commonly an enzyme. The shape of an enzyme allows it to stabilize the association between substrates. When two substrates are brought together in a correct orientation or by stressing bonds of substrate by an enzyme, the enzyme lowers activation energy required for new bonds to form. This then causes the reaction to proceed faster than if it did not have an enzyme.

Describe the composition and structure of enzymes including cofactors, coenzymes, and multi enzyme complexes.

Different types of cells contain different types of enzymes. These structural and functional differences are often the determinants of the function of the cell. Enzymes are 3D shape and highly specific. Most enzymes are proteins with pockets on their surface called active sites. These active sites are where the substrate will bond to the enzyme. Cofactors: nonprotein chemical components required by enzymes to function. Cofactors are usually metal ions found in the active site participating in catalysis. Coenzyme: nonprotein organic molecule that plays an accessory role in enzyme-catalyzed reactions by acting as a donor or acceptor of electrons. Multi-enzyme complexes: several enzymes catalyzing different steps in a sequence of reactions. Closer proximity of enzymes means a faster process, making functions more efficient.

Explain how enzymes bind to their substrates including enzyme specificity and changes in enzyme structure.

Enzymes are proteins with pockets called active sites. This active site is where the substrate binds to the enzyme. The substrate must fit perfectly within the active site for catalysis to occur. Once the substrate binds to the enzyme it can cause the enzyme to shift its shape through induced fit. This change to induced fit can open the enzyme to bind with other substrates. One substrate "activates" the enzyme. Enzymes are sensitive to specific substances that bind to an enzyme and cause it to change its shape. This allows cells to regulate which enzymes are active and inactive at a particular time. This regulation allows for increased efficiency and control of changes of characteristics during development.

List the types of enzyme inhibitors that affect enzyme activity, comparing and contrasting the mechanisms of inhibition.

Inhibitor: substance that binds to enzyme and decreases its activity. Competitive inhibitor: compete with a substrate for the same active site, occupying the active site and preventing substrates from binding. Noncompetitive inhibitor: bind to enzyme in location other than active site, changing the shape of the enzyme making it unable to bind to the substrate.

Define metabolism, catabolism, and anabolism.

Metabolism: sum of all chemical processes occurring within a living cell or organism Catabolism: molecules are broken down into smaller components and energy is released. Anabolism: energy is used to build up molecules.

Describe how substrate concentration, temperature, and pH affect enzyme activity.

Temperature: Within an enzyme-catalyzed reaction, the rate of reaction increases with increase in temperature but only up to optimum temperature. Below this temperature, hydrogen bonds/hydrophobic interactions not strong enough to support induced fit needed for catalysis, and above temperature the enzyme will denature. pH: Enzymes are sensitive to hydrogen ion concentration of fluid the enzyme is dissolved in. Changing concentration shifts balance between positively and negatively charged amino acid residues. Enzymes have an optimum pH between 6 and 8. Substrate concentration: Rate of enzyme-catalyzed reaction is affected by concentration of both enzymes and substrate. Increasing the substrate concentration will increase the rate of reaction (more substrate molecules colliding with enzyme molecules).