8.1 And 8.2 Metabolism

Question 1

What do metabolic pathways consist of and give examples?

Answer 1

They consist of cycles of enzyme, catalyzed reactions where the products of the one reaction becomes the reactants of the second reaction. An example would be glycolysis, which is a chain reaction or the Krebs and Calvin cycles which are cyclics reactions. 

Question 2

What is bioinformatics and how has it been used to identify new antimalarial drugs

Answer 2

By informatics is the development of methods and software to understand, biological data, often using large amounts of data from gene sequencing and other chemical databases. Malaria is caused by plasmodium parasites and has evolved resistance to drugs so comparison of parasites metabolic proteins with inhibitor databases can help to identify chemicals which inhibit parasitic metabolic enzymes, but not human ones

Question 3

What is activation, energy and what role do enzymes have in the chemical reactions that they catalyze?

Answer 3

Activation energy is the minimum energy required for reaction to take place because reactants need kinetic energy to move and collide, as well as to overcome inter or intramolecular forces to be positioned correctly. Enzymes lower activation energy bringing reactants together, so there is no need to increase temperature allowing reactions to occur at physiological temperatures. They also bond with reactants to force them into the correct orientation or activation energy allows reaction to happen faster

Question 4

What are enzyme inhibitors and what are the two main types? describe a certain model for substrate activation.

Answer 4

Inhibitors decrease the rate of enzyme control reactions, or they completely prevent them. The induced fit model is used to describe when a substrate binds to the active site of an enzyme. The enzyme changes shape which activates the substrate. The product is formed in released and the enzyme, returns to its normal shape.

1. There is competitive inhibitors, which are similar in shape to the substrate and compete with the substrate for the active site, preventing its binding. An example is the drug methotrexate which inhibits the synthesis of nucleotides, preventing DNA replication for cancer treatment.
2. Non-competitive buying to the enzyme at the allosteric site, which is the non-active site altering the enzymes shape and preventing substrate binding. For example, cyanide binds to cytochrome C oxidase in mitochondria to prevent ATP synthesis.

Question 5

Distinguish different types of inhibition from graphs show non-inhibitor, versus competitive inhibitor versus noncompetitive inhibitor.

Answer 5

1. With no inhibitor the substrate concentration is greater until the enzyme is completely saturated and plateaus.
2. Competitive inhibitor shows lower rate of reaction compared to no inhibitor. As substrate concentration increases substrate out, competes inhibitor the reaction can reach a maximum rate, but it needs a higher concentration of substrate.
3. Noncompetitive, inhibitor slower rate of reaction compared to no inhibitor. Even as substrate concentration increases some enzymes will always be inhibited reaction will never reach a max rate.

Question 6

How does end product inhibition control metabolic pathways? Describe its advantages.

Answer 6

The product of the last reaction inhibits the enzyme that catalyzes the first reaction.

Advantages
1. If end product levels are high, the pathways switched off so intermediate or products don’t build up.

2. If and product levels are low, the pathway is active, so intermediate or products can be made.

Question 7

Give an example of end product inhibition

Answer 7

Threonine is used to synthesize isoleucine, via multi step pathway, where the first enzyme in the pathway is threonine deaminase. When isoleucine levels are low, the pathway continues. When isoleucine levels accumulate it binds to the allosteric site and inhibits threonine deaminase.