Metabolites: Overview, Definition, Meaning Examples, Types

What are Metabolites?

Metabolites have very important functions in the cell including energy generation, signaling and the control of diverse metabolic pathways. They are of two types- Primary and Secondary Metabolites. These are carbohydrates, lipids, amino acids, nucleic acids and many other organic compounds that contribute to maintaining the body’s normal metabolism or disturb it if in excess or lacking. Hence, metabolites form an essential part of the myriad of interactions that occur within the biochemical organizational framework for existence.

Types of Metabolites

There are two types of metabolites:

Primary Metabolites

A primary metabolite is directly involved in the normal growth, development and reproduction. Examples include carbohydrates, proteins, lipids and nucleic acids.

Secondary Metabolites

A secondary metabolite is not directly involved in the processes but usually has important ecological functions. Examples include antibiotics, mycotoxins, etc.

Primary Metabolites

The primary metabolites are discussed below:

Definition and Functions

Primary metabolites are the substances that the cells of an organism produce and use for their day to day activities such as growth, development and reproduction. It is often associated with basic metabolic processes which are pivotal for the mere existence of the organism.

Importance in Growth and Development

Primary metabolites are essential compounds directly involved in an organism’s growth, development, and reproduction. These provide energy, structural components, and genetic material for cellular processes. Their continuous synthesis is vital for maintaining normal metabolism and physiological functions.

Examples and Roles

Carbohydrates: Function as the powerhouse and skeleton of cells. Glucose, for example, takes part in cellular respiration, and its major role is to provide energy in the form of ATP.

Proteins: Involved in metabolism as catalysts (enzymes), components of the matrix of various tissues (e.g., collagen in connective tissue), and hormones and receptors as controllers of metabolic processes.

Lipids: Used as energy reserves such as triglycerides, structural components in cell membranes such as phospholipids and signalling molecules such as steroids.

Nucleic acids: Include encodes the genetic information (DNA) required for heredity and act as carriers of genetic information and structural and functional components for the synthesis of proteins (RNA).

Secondary Metabolites

The secondary metabolites are given below-

Definition and Functions

Secondary metabolites are those organic compounds, which do not uphold any roles in growth, development, or reproduction, but are extremely essential biological and chemical entities involved in a range of ecological processes and defence mechanisms. In most cases, they help add to the ability of organisms to exist and live in the systems of the ecosystem.

Roles in Ecological Interactions and Defence

Derived metabolites work as a way of attracting pollinators, as well as discouraging herbivores and competing microorganisms. Hence affecting the plant and microbial communities.

These metabolites play the role of protecting an organism from being eaten, getting infected or having adverse conditions affecting its survival.

Examples and Biological Importance

Alkaloids: Found in plants, ingested by animals, alkaloid chemicals serve to discourage herbivory and predation. For instance, caffeine is a stimulant used in plants and nicotine is used as an insecticide.

Terpenoids: Some of these compounds are used in defence such as oils found in plants, appeal such as pheromones, and shieldlike sunscreen found in plants.

Phenolics: Found in plants, work as antioxidants, UV protection and antimicrobial agents. Flavonoids are commonly found in petals. Other examples of secondary metabolites include tannins, which are astringent compounds, found in leaves and barks.

Metabolism and Metabolic Pathways

The pathways are summarised below-

Overview of Metabolism

When in a specified environment, metabolism speaks to the aggregate of activities constituting existence within a living organism. In simple words, metabolism is the sum of an organism’s chemical reactions. It is an emergent property of life that arises from interactions between molecules within the cell.

Anabolism vs Catabolism

It can be categorized into two main processes: Anabolism and Catabolism are also closely related.

• Anabolism involves the building up of large molecules from small ones and mostly it demands energy. This process involves protein synthesis, development of nucleic acids and other cell structures required for growth and/or replacement.

• Catabolism entails the process of dismantling large structures into simpler ones and in the process liberating energy. It entails the process of glycolysis, the Krebs cycle, and lipids/protein catabolism for the production of ATP energy.

Key Metabolic Pathways

The key metabolic pathways are given below-

Glycolysis: Taking place in the cytoplasm but using mitochondrial enzymes, glycolysis involves the breakdown of glucose to pyruvate, producing a trifling quantity of ATP and NADH. This is a core transport route for aerobic and anaerobic respiration.

Krebs Cycle: Occurring in the mitochondrial matrix, the Krebs cycle finishes the oxidation of glucose-derived pyruvate to ATP, NADH and FADH2 but feeds the latter two into the ETC for oxidative phosphorylation.

Photosynthesis: In plants and some bacteria photosynthesis is the process by which light energy is converted to chemical energy (glucose) from carbon dioxide and water. Implies a process that takes place in chloroplasts and results in the formation of oxygen as the waste product.

Fermentation: In unfavourable anaerobic conditions, fermentation is possible through which NAD + can be regenerated from NADH formed through glycolysis. It has different final products like lactic acid in animals, ethanol and C02, in yeast and bacteria through which, ATP production is accomplished without the use of oxygen.

How to increase metabolism?

Metabolism can be increased by focusing on lifestyle habits.

Muscle Building and Exercise

Unlike fat tissues, muscles consume calories, hence increasing metabolic rate. This can be achieved through weight training. It is important to stay active by taking a walk, jogging, cycling etc as these exercises help to increase the metabolic rate during the exercises and after the exercises.

Diet and Hydration

Protein has a higher thermic effect on food as compared to carbs or fats. Therefore, it helps to increase metabolic rate when ingested. Skipping meals is one of the causes of the decrease in the metabolic rate. Ideally, one should follow a fixed timetable of meals and snacks to ensure that the metabolic rate remains high all day.

Water is important to metabolism and can for a while even raise the basal metabolic rate if the water is for example served icecold.

Sleep and Stress Management

Lack of quality sleep affects metabolism and the balance of hormones and other chemicals in the body. Achieving and maintaining 7 to 9 hours of sleep performance for the night positively affects the metabolism process of the body.

If stress is prolonged constant, it has to take its toll on hormones and hence metabolism could slow down. To enhance metabolism, the healthcare professional will need to recommend stress-reducing activities such as mindfulness or yoga

Metabolites NEET MCQs (With Answers & Explanations)

Important topics for NEET exam are:

• Primary Metabolites

• Secondary Metabolites

• Catabolism vs Anabolism

Practice Questions for NEET

Q1. Secondary metabolites such as nocotine, strychnine, and caffeine are produced by plants for their:

1. Nutritive value

2. Growth response

3. Defence action

4. Effect on reproduction

Correct answer: 3) Defence action

Explanation:

Secondary metabolites in plants help in defense action. These have toxic, repellent, or antimicrobial properties, helping to prevent damage to the plant and increase survival. Secondary metabolites in plants, such as alkaloids, terpenoids, and phenolics, play a crucial role in defense mechanisms. They deter herbivores, inhibit the growth of competing plants (allelopathy), and protect against pathogens. Additionally, these compounds can attract pollinators or seed dispersers, aiding in plant reproduction.

Hence, the correct answer is option 3) defense action.

Q2. From the following groups, select the one that has only secondary metabolites.

1. Arbrin, cellulose, originine, tyrosine

2. Glycine, gums, serine, diterpenes

3. Carotenoids, phenylalanine, curcumin, rubber

4. Conclavin-A, Morphine, Codeine, Vinblastine

Correct answer: 4) Conclavin-A, Morphine, Codeine, Vinblastine

Explanation:

Primary metabolites are crucial organic substances that participate in the growth and development of organisms. These compounds are present in the cells of animals, plants, and microbes. They are integral to physiological functions. Notable examples include amino acids and sugars, which serve as the foundation of proteins and energy sources, respectively.

Secondary metabolites, on the other hand, are exclusively produced in certain cell types like those of fungi, plants, and bacteria. Unlike primary metabolites, they are not directly linked to an organism's primary metabolic pathways. However, they perform supportive roles. For instance, alkaloids deter parasitic organisms, flavonoids lure pollinators, and some contribute to UV protection and floral colouration. Additional examples encompass substances such as oils, rubber, and gums. These metabolites are often involved in ecological interactions and organism defence mechanisms.

Hence, the correct answer is option 4) Conclavin-A, Morphine, Codeine, Vinblastine.

Q3. In anabolic reactions, the formation of complex molecules takes place from simpler molecules and thus energy is

1. Destroyed

2. Produced

3. Stored

4. Transferred

Correct answer: 3) Stored

Explanation:

Simpler molecules like monosaccharides, amino acids, and nucleotides are combined in anabolic processes to form more complex structures like proteins, polysaccharides, and nucleic acids (DNA and RNA). For these metabolic processes, which often need an energy input to allow the creation of larger molecules from their smaller counterparts, adenosine triphosphate (ATP) is often the primary energy source needed. The significance of these molecules lies in their essential contributions to the development and upkeep of cells, which are vital for the overall health and functionality of tissues and organs in biological systems.

Hence, the correct option is (3) Stored.

Also Read:

• Metabolites and Their Types

• Proteins

• Applications of Enzymes

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