Question

Describe the structure and roles of enzymes in metabolic pathways. Include in your answer: a. the structure of proteins, enzyme function, and the roles of coenzymes, cofactors and allosteric regulators b. a description of coupled reactions that drive metabolic pathways and the reasons that some molecules are unstable c. a description of the structure of ATP, the reasons for which it is unstable, and the role(s) of the phosphate group once transferred to another molecule.

Answer 1

a]  Enzymes are made up of amino acids which are linked together via peptide bonds in a linear chain to form a primary structure of protein; this assists in break down of foods into a usable form for cells through different chemical reactions. They lower the energy barrier to chemical reactions so that they can act upon the substrates and cause the reactions. Each enzyme in our body is characterised to specfic substrate. For instance, the enzymes that help break down of fatty-foods are not useful in breaking down carbohydrates, or vice versa. Cofactors are inorganic substrates, some of which are required to produce chemical reaction between enzyme and substrate, while others increase the rate of catalysis only. Some cofactors are attach to the enzyme, while others loosely bound. Coenzymes are organic molecules, which are needed by certain to enzymes bind to the substrate to cause a reaction, they are not specific to the enzymes they assist. Allosteric regulators include the activator/ inhibitor molecule (effector) that binds at a specific regulatory site on the enzyme inducing conformational changes which either enhance or reduce enzymatic activity.

b] Cells uses a strategy called reaction coupling to use the energy released by ATP hydrolysis to power other reactions in our body where an favorable energetic reaction (like ATP hydrolysis) is directly linked with an unfavorable energetic (endergonic) reaction; this linking often happens through a shared intermediate (a product of one reaction is used as a reactant in the second reaction). The two coupled reactions can be added together to give an overall reaction, where ΔG of the reaction will be the sum of the ΔG values of the individual reactions.  Structural instability of enzymes is a visible in High temperatures and extreme pH values; eventually causing the enzymes to denature (changing of its natural properties).

c]  Adenosine triphosphate, or ATP is a small, simple molecule which is thought of as the main energy currency of cells. ATP is structurally an RNA nucleotide which bears a chain of three phosphates; its center have a five-carbon sugar- ribose, which is attached to nitrogenous base adenine in one side and to the chain of three phosphates in the other side. The ATP is made unstable by the three adjacent negative charges in its phosphate tail, which very badly want to get further away from each other.  ATP powers cellular processes by transferring a phosphate group to another molecule by a process called phosphorylation; his transfer is carried out by special enzymes that releases energy from ATP's conversion to ADP.