Question

define metabolism and enzyme. provide 2 examples of enzymes and explain how they are important for metabolism. give 2 examples of biomolecules that are not enzymes and define their roles in metabolism

Answer 1

Metabolism:

• The sum total of chemical activities occurring in a cellular system is called metabolism or metabolic activity.
• Metabolism involves anabolism or catabolism.
• Anabolism is a type of metabolism with involve synthesis of larger molecules from smaller molecules.

Anabolic (synthesis of glucose)

6Co₂ + 6H₂O -> C₆H₁₂ O₆ + 6O₂

• Breaking down of substances into smaller components, to release energy is described as catabolism or catabolic activity.

Catabolic (breakdown of glucose)

Enzymes in metabolism:

• Enzymes are molecules that help in catalyzing biochemical reactions, by binding substrates to their active or catalytic site.
• Two important enzymes of metabolism:

1. Phosphofructokinase

• Phosphofructokinase (PFK) plays the key role in the regulation of glycolysis, though hexokinase controls the initial glycolytic step.
• The first irreversible reaction in glycolytic pathway (the slowest and rate limiting step) is phosphorylation reaction mediated by PFK

2. Succinyl co A synthase

• The enzyme Succinyl co A (Co Enzyme A) synthase (SCS), also referred to as- Succinyl co A ligase, Succinate thiokinase.
• It is an enzyme of Citric acid cycle or TCA which reversibly catalyse the reaction: succinate to succinyl Co A.

Other bio-molecules in metabolism:

Apart from enzymes, other bio-molecules that play important role in metabolism may be co-enzymes, co-factors, etc.

1. Co-factor- Pyridoxal Phosphate- active form of vitamin B6.

2.

• NAD is Nicotinamide Adenine Dinucleotide and FAD is Flavin Adenine Dinucleotide.
• They act as electron carriers during several steps of respiration.