Explain that enzymes lower the activation energy of the chemical reactions that they catalyse.

Exergonic (exothermic) and endergonic (endothermic) reactions.

Explain the difference between Non/Competitive Inhibition with reference to one example of each type

·         Competitive inhibition

a.      When a molecule is so similar to the substrate molecule that it binds to the active site and prevents the actual substrate from binding with the enzyme.

b.      Examples

c.      Sulfonamide Prontosil inhibits folic acid synthesis in bacteria

·         Non-competitive

a.      When a molecule, an inhibitor molecule, binds to an enzyme, NOT its active site, and changes the conformation of the active site resulting in a change in activity.

b.      Example

c.      Lisinopril lowers high blood pressure by inhibiting the enzyme ACE

Explain the role of allostery with respect to feedback inhibition and the control of metabolic pathways

a)     Allostery

i)        allosteric interactions are mechanisms by which an enzyme may be temporarily activated or inactivated.

ii)      It is a form of non-competitive inhibition. An allosteric interaction occur among enzymes that have at least two binding sites

(1)  one for active site

(2)  one for allosteric effector

(a)  this changes the shape of the enzyme molecule and either activates or inactivates it.

b)     Feedback inhibition

i)        Common means of biological control

(1)  One of the last products acts as an allosteric effector, inhibiting the function of one of the enzymes, often the first in the series.

c)     Metabolic Pathways

i)        In a reaction that may take one of two directions, the effector may act to shunt the reactions along another pathway.

Other Notes in this Category

1. Cell Respiration
2. Enzymes
3. Membranes
4. Photosynthesis
5. Proteins

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