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Metabolic Basis For Living | CBSE Class 11 Biology Chapter 9

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Biomolecules are the fundamental building blocks of all living things. They work together to promote various biological processes that are required for life. They differ in structure and size. Hydrogen and oxygen are the two most abundant elements in biomolecules. Within the body, living systems synthesize four types of biomolecules. They are as follows:

It is also important to understand that the major types of biomolecules are basically polymers of simple elements. For example, amino acids are the building blocks of proteins. Phosphate, sugar, and nitrogen for nucleic acids For lipids, fatty acids and glycerol are used. Carbohydrates are simply sugar. Some biomolecules can also be combined to form specialized molecules. For instance: Glycoproteins contain protein and carbohydrates. Lipoproteins contain protein and lipids. Lipids and carbohydrates in glycolipids

Metabolic Basis for Living


The collection of chemical processes occurring within an organism’s cells is referred to as metabolism. All metabolic changes occur in a series of events along a specific pathway known as the metabolic pathway. In a sequence of processes along this metabolic route, biomolecules are both made and broken down. In other words, metabolic processes lead to the formation of either simple macromolecules from complex molecules or complex compounds from simple molecules. By breaking molecules, metabolic processes extract energy that is then used to create the building blocks. Anabolism and catabolism are the two stages of the metabolic process. Anabolic pathways are metabolic processes that convert simple molecules into more complex ones. It is sometimes referred to as the biosynthetic pathway since it involves the synthesis of metabolites. For instance, proteins are made of amino acids. Another metabolic mechanism that converts a more complex structure into simple molecules is the catabolic pathway. The catabolic pathway is illustrated by the process of glycolysis, which transforms a more complex 6-C glucose molecule into a 3-C pyruvic acid. Energy is used during anabolism; hence, anabolic pathways both require and expand energy. Energy is released during catabolism. Lactic acid is produced when glucose is broken down, releasing energy. The released energy packets are retained and stored in living creatures for future use. Adenosine triphosphate, a form of stored energy used by living systems, is used for mechanical work, anabolism, and other processes (ATP).

Any of the countless chemicals created by cells and living things is a biomolecule. Proteins, lipids, nucleic acids, and carbohydrates are the four main categories of biomolecules. The unique role of storing the genetic code of an organism is performed by nucleic acids. The transporters that carry nutrients and other chemicals into and out of cells are proteins, which are also important structural components of cells.

Similarly, carbohydrates, which are among the most common macromolecules on Earth and are generally composed of molecules with carbon, hydrogen, and oxygen atoms, are crucial energy sources and structural elements of all life. They are made up of oligosaccharides, polysaccharides, oligosaccharides, and four different types of sugar units. Another essential biomolecule found in living things is called a lipid, which also serves as a chemical messenger and a repository of stored energy. Additionally, they create membranes that divide and compartmentalize cells’ interiors, allowing higher (more sophisticated) organisms to develop organelles like the nucleus and mitochondrion.

  • In another example, DNA, which is a very long molecule-in humans, the combined length of all the DNA molecules in a single cell stretched end to end would be about 1.8 meters (6 feet), whereas the cell nucleus is about 6 μm (6 10-6 meter) in diameter-has a highly flexible helical structure that allows the molecule to become tightly coiled and looped.
  • This structural feature plays a key role in enabling DNA to fit in the cell nucleus, where it carries out its function in coding genetic traits.

Metabolism and The Living State 

Every living thing, including prokaryotes and eukaryotic fungus, is made up of thousands of macromolecules and metabolites. However, the ratio fluctuates. One biomolecule’s concentration within an organism might be higher or lower than that of another biomolecule. Additionally, the metabolites’ non-equilibrium condition maintains their steady state. “Systems at equilibrium cannot perform work,” as the saying goes. A living system can never be in equilibrium since it constantly uses and releases energy through metabolism. For organisms to remain in a non-equilibrium steady state and be alive, metabolism is necessary. We can infer that a non-equilibrium state is necessary for life to exist.

FAQs on the Living State

Question 1: The ability to conduct work requires a non-equilibrium steady-state, which is the alive state.


The concentration of each biomolecule, which is in metabolic flux, defines the steady state in which living things live. Any physical or chemical phenomenon follows equilibrium in a parallel fashion. Living things are constantly working, thus they can never establish homeostasis. As a result, the living state is in a non-equilibrium steady state since it needs the energy produced by metabolism to conduct activities.

Question 2: Describe the various lipid forms using some examples.


Lipids can exist as simple fatty acids and are not soluble in water. A fatty acid has an R-group, which can be methyl, ethyl, or a higher number of -CH2 groups, coupled to a carboxyl group. For instance, although palmitic acid has 16 carbon atoms total, including carboxyl carbon, phosphatidic acid has 20 carbon atoms total. Both unsaturated and saturated fatty acids may be present. Glycerol or trihydroxy propane is an additional lipid. In several number of lipids, fatty acids are combined with glycerol to form diglycerides, triglycerides, and monoglycerides, which are referred to as oils or fats depending on their melting point.

Question 3: What are the primary roles that carbohydrates?


The principal jobs that carbohydrates do are:

  • Control of blood sugar.
  • Contributes to the metabolism of fat and prevents ketosis.
  • Give the body and nervous system food and energy.
  • Serves as the fundamental element of food, comprising sugars, starches, and fiber.
  • They serve as the main energy source. subsequently participates in the conversion of proteins into glucose and the breakdown of carbohydrates to create energy for metabolism

Question 4: Is it possible to classify rubber as a main or secondary metabolite? 


It comes from the rubber tree and is a secondary metabolite ( Hevea brasiliensis). The highly specialized phloem cells known as laticifers in the rubber tree as latex are responsible for its production. Rubber is a terpenoid that is employed in a variety of sectors due to its strong tensile strength, plasticity, and elasticity. It is a polymeric material that conducts electricity well.

Question 5: What exactly are Saturated Fatty Acids?


There is no double bond between the carbon atoms in these fatty acids. Palmitic acid, butyric acid, and hexanoic acid are a few examples. Short-chain fatty acids, medium-chain fatty acids, long-chain fatty acids, and very long-chain fatty acids are the four types. Coconut and palm oil, dairy fat, peanuts, dry fruits, fibers, lauric acid, acetic acid, and other sources of such fatty acids are common. The hydrocarbon chain in saturated fatty acids is straight and contains only single bonds. It has a long shelf life and low rancidity. Saturated fatty acids should account for 10% of the total calories in the human body. They are healthy (when consumed in moderation), but excessive consumption can lead to heart disease and other diseases.

Question 6: Describe glycolipid.


They contain carbohydrate and nitrogen molecules in addition to fatty acids. They are mostly found in the brain’s White Matter and the nervous system as a whole. These biomolecular structures are in charge of cellular recognition and help to maintain proper immunological functions.

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Last Updated : 08 Nov, 2022
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