Question

Consider the structure and function of each of these four biological macromolecules. How does the structure of each molecule affect its function? For example, in complex carbohydrates, why would long chains of glucose be more effective for energy storage than single glucose molecules? How do the four levels of protein structure affect the shape of enzymes and why is this important for enzyme function? Explain the "lock and key" model of enzyme function using the terms substrate, active site, and product.

Answer 1

Macromolecule like carbohydrates are used up by the organisms for energy production to carry basic life processes. Carbohydrates are regarded as the fuel for living organisms. In addition to carbohydrates sometimes, animals uses fats and proteins for energy production but the priority among three macromolecules is the order of carbohydrates > fats > proteins. Means carbohydrates are used first, then fats and In last proteins for energy production. Which macromolecule Produces more energy, depends upon the structure of the compound. Let us see why would long chains of glucose be more effective for energy storage than single glucose molecule. The energy of a compound is stored in its bonds. Each kind of a bond has a different bond energy. Here is the bond energy of different kinds of bond.

Which compound have more energy depends upon

1) the type of bond that compound have and

2) the number of that particular bonds.

If the molecule or compound has more the number of that particular bonds, will have more stored energy which is produced on oxidation. Same is the case with glucose ( a simple carbohydrate) having 7 C-H bonds, 5 C-C bonds, 5 C-OH bonds and 1C =O bond, but the complex carbohydrates like oligosaccharides or polysaccharides like Starch, Glycogen, Cellulose etc. with long chains of glucose have lots of bond in which more energy is stored as compared to single glucose.

Lock and Key Hypothesis

Substrate  is an organic compound at which an enzyme binds to carry out a biochemical reaction at extreme higher rate.

active site is a site or portion on the substrate having a special cavity like structure at which an enzyme binds.

product is the desired compound which is formed from enzyme substrate complex after a biochemical reactions.

In order to explain why enzymes have such a high level of specificity, Emil Fischer in 1894 suggested that both a substrate and an enzyme have specific geometric shapes that fit exactly into each other. This idea of both substrates and enzymes having a natural geometric fit has been called the lock and key hypothesis.

The problem with this hypothesis is that it doesn’t explain the stabilization of the enzyme. When an enzyme has a substrate enter into its active site, the enzyme will change its shape slightly to match the substrate. If the enzymes were to be specifically designed to fit a substrate, then there would be no need for it to have to adjust its shape.

In 1958, another scientist named Daniel Koshland suggested a slight modification to the lock and key hypothesis. Koshland’s suggestion was that since enzymes were so flexible, the active site is constantly being reshaped by its interaction with the substrate.

Koshland suggested that substrate doesn’t bind to an active site as if it were specifically the right shape, but that the amino acid side-chains that are a part of the active site are molded into a specific position. This position allows the enzyme to start the catalyzing process. Koshland’s modified suggestion has been called the induced fit theory.