Metabolism and Enzymes Notes in Short/Conceptual Answers | Biology Class 9 BISE and Federal Boards

Maximize Your Biology Exam Success: Short answers of Chapter 6 "Enzymes" Notes for Grade IX Board and Entry Tests Preparation

    Bioenergetics is a crucial topic in the field of biology and a fundamental aspect of living organisms. It plays a vital role in shaping the fate of an organism and its survival. For students in grade IX and those preparing for entry tests or competitive exams, a solid understanding of bioenergetics is crucial for success. In this blog post, we present to you concise and conceptual answers to the essential sub-topics of bioenergetics including the definition of metabolism, types of metabolism, metabolic pathways, the role of enzymes in metabolism, and the mechanism of enzyme action. These topics have been presented in an easy-to-understand and well-structured manner to make learning and retaining the information easier.

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Class 9 level Biology Notes on Metabolism in short answers format
from Notes Library of H.E.S (Health, Education, and Skills) 

What do you mean by the term metabolism?

Metabolism

The Sum of all the chemical reactions taking place in the body of living organisms is called metabolism.

Explanation

• Inside living bodies, different types of chemical reactions take place every time. 
• Some of these reactions result in the formation of large molecules (constructive process), while others result in the breakdown of large molecules (destructive process). 
• So in other words we can say that the sum of constructive and destructive processes is known as metabolism.

What are the two types of metabolism?

Types of metabolism

    As metabolism is the sum of constructive and destructive processes, so there are following two types of metabolism.

a. Anabolism (Constructive process)

The type of metabolism in which small molecules combine to form large molecules is called anabolism.

• Inside living bodies, some reactions take place to build up large molecules from small units. For example inside our body amino acids (small units) combine large molecules of proteins, so the proteins form in our body due to anabolism.

b. Catabolism (Destructive process)

The type of metabolism in which large molecules break down to give small units is called catabolism.

• Some reactions in our body take place for the breakdown of large molecules into smaller ones. For example, due to physical exercise, muscles of our body break down fat into smaller units of fats called “Fatty acids” and “Glycerol”. So the fats burn because of a catabolic reaction.

Define metabolic pathways. 

Metabolic pathways

A series of reactions that proceed in an orderly step-by-step manner with the help of specific substances (enzymes) is called metabolic pathways.

Explanation

• The process of metabolism occurs in a step-by-step manner. For example, consider that a substrate-A (a product of the reaction) is converted into substrate-B then substrate-B will be converted into substrate-C, and then C into D, and so on. 
• But the important point to remember is that without the involvement of enzymes the conversion of one substrate into another will not favor normal reaction.

Define enzymes. 

Enzymes

The organic catalysts that speed up the rate of a biochemical reaction without being involved are called enzymes.

Explanation

    In chemistry, we use catalysts most often to speed up the chemical reaction without the involvement of itself. But inside the living bodies, there are some natural organic molecules that speed up the reactions of metabolic pathways. These organic molecules are known as enzymes. There are about 2000-3000 enzymes in a cell, while different cells have different enzymes.

Shortly discuss the role of enzymes in metabolism.

Role of Enzymes in Metabolism

• Enzymes are as much important in metabolism as we need oxygen. Without oxygen, we will not able to get energy from food. Similarly, without an enzyme, there will no chemical reaction occurs in living organisms.
• Enzymes play a critical role in metabolism by acting as catalysts to speed up chemical reactions in the body. 
• Without enzymes, many metabolic reactions would occur too slowly or not at all, disrupting normal cellular processes and leading to disease or death. 
• Each enzyme is specific for a particular reaction and helps to lower the activation energy needed for the reaction to occur, allowing it to proceed more rapidly. 
• Enzymes are vital for many metabolic pathways, including digestion, energy production, and the synthesis of biomolecules.

What do enzymes do in our bodies?

Role of enzymes in our body

• They are responsible for facilitating or speeding up, the thousands of chemical reactions that take place every second in our cells. 
• Without enzymes, these reactions would occur at a much slower rate.
• Enzyme catabolizes many substances, for example, digestive enzymes break down the food we eat into smaller molecules that can be absorbed and used by our cells for energy and other functions. Enzymes in our liver are also involved in the metabolism of drugs and toxic substances, helping to process and eliminate them from our bodies.
• By catalyzing chemical reactions, enzymes help to control the flow of energy and matter in our cells and ensure that they function properly
• Enzymes also play a role in regulating cellular activities, such as cell division and growth. 

Shortly discuss the mechanism of action of an enzyme.

Mechanism of enzyme's action 

• In order to understand the mechanism of action of enzymes and how they work? We have to first know what the“energy of activation” is?

Energy of activation

The energy needed to initiate (start) a chemical reaction is called as the energy of activation.

• Enzymes don’t take part in chemical reactions but only work on the energy of activation. 
• The greater the energy of activation more time will a reaction need to complete and vice versa. 
• Enzyme’s mechanism of action is that enzymes lower the energy of activation, so less time is needed for a reaction to take place and thus speeds up the chemical reaction.

Describe the mechanism of enzyme action with the help of the lock and key model

Mechanism of enzyme action (Lock and key model)

• The mechanism of enzyme action can be best explained with the help of a model known as the “lock and key model” which was proposed by German chemist Emil Fischer in 1894.
• According to the lock and key model, the enzyme should be considered as a key that combines with a substrate, which acts as a lock for its key. 
• As for every lock, there is its own key, similarly, every substrate (lock) has its specific enzymes (key) to act upon. When the substrate fits into the shape of the enzyme, chemical changes occur inside the substrate and thus the new product is formed which acts as a reactant for the next step of the metabolic pathway.
• For this reason, the enzyme must have the same shape to fit its substrate. After the completion of the reaction, the enzyme is freed and unchanged so it can be used repeatedly.