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Catabolism is the part of the metabolism responsible for breaking down complex molecules into smaller molecules. Anabolism, the other part of the metabolism, builds simple molecules into more complex ones. Catabolism can be defined as a process which is the action of the set of metabolic pathways that breaks down molecules into smaller units that are either used in other anabolic reactions or are oxidized to release energy.
Key Terms: Catabolism, Metabolism, Anabolism, Metabolic Pathways, Energy, Catabolic Hormones, Glucose
What is Catabolism?
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Catabolism can be defined as the breakdown of complex molecules or substances into their constituent parts that form substrates for metabolic pathways.
There are two major parts to the process of Metabolism:
- Anabolism
- Catabolism.
Catabolism breaks down large and complicated molecules into smaller parts to produce energy, which is released as an outcome of the destructive branch of metabolism.
Catabolism
Read More: Carbohydrate Metabolism
Examples of Catabolic Processes
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Some of the catabolic processes are
- Citric acid cycle
- Glycolysis
- Lipolysis
- Oxidative deamination
- Muscle tissue breakdown
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Catabolism in Various Organisms
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The nature of catabolic reactions that occurs varies from organisms to organisms. The catabolic reactions can be classified based on their sources of energy and carbon as follows-
- Organotrophs: They use organic sources as a source of energy.
- Lithotrophs: They use inorganic substrates.
- Phototrophs: They use sunlight as chemical energy.
Stages of Catabolism
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The process of Catabolism can be broken down into three major stages:
- Stage 1: Digestion Stage
In this stage, the large organic molecules such as lipids, proteins, and polysaccharides, are digested into their smaller components outside the cells. This stage works upon cellulose, proteins, or starch, that cannot be absorbed directly by the cells.
- Stage 2: Release of Energy
Once the molecules are broken down, they are then taken up by cells and converted to yet smaller molecules, generally, acetyl coenzyme A, which leads to the release of some energy.
- Stage 3: Storage of Energy
The energy thus released is then stored by reducing coenzyme nicotinamide adenine dinucleotide into NADH.
The process of catabolism provides the chemical energy necessary for the growth and maintenance of cells. Some of the most common examples of catabolic processes are the citric acid cycle, glycolysis, the breakdown of muscle protein to use the amino acids as substrates for breaking down the fat present in adipose tissue to fatty acids, gluconeogenesis, and oxidative deamination of neurotransmitters with monoamine oxidase.
Read More: Difference between Lipids and Fats
Importance of Catabolic Pathways
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The importance of catabolic pathways can be listed as follows, which it is also given as catabolic pathways examples.
- In the process of Glycolysis, 6 carbon glucose is degraded into 3 carbon pyruvates. So, this pyruvate is used in the synthesis of different other components (catabolism takes place inside the cell).
- In the intestine (catabolism in the intestine), the digestive juices act upon the proteins and convert them into peptones, that can be easily degraded to amino acids and absorbed easily into our bloodstream.
- When we lack glucose in the blood, the conversion of Glycogen (a branched polymer of glucose) to glucose occurs. (catabolism primarily in the liver-blood medium).
Besides these, there is much more importance of catabolic pathways. Anabolism and catabolism maintain a constant and definite concentration of nutrients in our bodies.
Difference between Catabolic and Anabolic Pathways
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Catabolism is the part of the metabolism that breaks complex molecules into simpler ones, whereas the other part of metabolism, anabolism is the metabolic pathway that builds complex molecules up from the simpler ones.
One good example of catabolism is the breakdown of glucose into lactic acid. Many of these pathways release energy and generate ATP (Adenosine triphosphate).
Gluconeogenesis, the conversion of lactic acid back to the liver's glucose, is an anabolic pathway. It needs an ATP input like most anabolic pathways to do.
Catabolic and Anabolic Pathways
Read More: Difference Between Catabolism and Anabolism
Things to Remember
- Metabolism can be described as the chemical reactions or rates at which the body consumes calories to maintain the cells in an organism's living state.
- Catabolism and Anabolism are two subcategories of metabolism.
- Catabolism is defined as the breakdown of complex or large molecules such as proteins, polysaccharides, and fats into small molecules like amino acids, monosaccharides, and fatty acids.
- Catabolism can be referred to as a metabolic condition that is destructive in nature. Both Glycolysis and the citric acid cycle are involved in this process.
- Catabolism is a breakdown feature, whereas Anabolism is a build-up feature of metabolism.
Previous Year Questions
- Calcium Metabolism In Birds Gets Disturbed Due To… [KEAM]
- One Mole Of Glucose On Metabolism Liberates How Ma
- A Molecule Of Atp Is Structurally Similar To A Mol
- The Limiting Factor In Nitrification Of Soil Is
- Metabolism Refers To The Sum Of Chemical Reactions
- Mark The Incorrect Statement About Atp
- Metabolism Can Be Best Defined As
- The Process Of Conversion Of Soil Nitrates Into Fr
- The Process Of Decay Of Dead Organic Matter Is Kno
- Mitochondria In Middle Piece Of Sperm Is Called
- In Which Part Of Mitochondria Does Atp Synthesis O
- Function Of Mitochondria Is
- With Janus Green Mitochondria Turn
- If A Biochemical Analysis Of Mitochondria Has To B
- Mitochondria Are Called Power Houses Of The Cell M
- The Functional Unit Of Mitochondria Is
Sample Questions
Ques. Does catabolism release energy? (3 Marks)
Ans. Catabolic Reactions help in breaking down the big organic molecules into smaller molecules, releasing the energy trapped in the chemical bonds. Not 100 per cent effective are these energy releases (conversions). The amount of energy that is released is less than the overall amount that the molecule contains.
Ques. Is respiration a catabolic process? (3 Marks)
Ans. Cellular breathing can be classified as a catabolic mechanism in which glucose is broken down to release a cell’s available energy. Cellular respiration, along with all catabolic processes, releases energy which can then be trapped and used in the cell through various other reactions.
Ques. What are some examples of catabolism in Eukaryotes? (3 Marks)
Ans. Catabolism leads to the breakdown of complex molecules such as proteins, polysaccharides, and fats into smaller ones like amino acids, monosaccharides, and fatty acids. Some of the catabolic reactions are:
- Citric acid cycle
- Glycolysis
- Lipolysis
- Oxidative deamination
- Oxidative phosphorylation
- Muscle tissue breakdown
In all the eukaryotic cells, several key catabolic reactions occur, including the citric acid cycle, oxidative deamination, glycolysis, lipolysis, and oxidative phosphorylation.
Ques. What are some examples of catabolism in Prokaryotes? (3 Marks)
Ans. Prokaryotes require energy and carbon to survive. Prokaryotes are chemoheterotrophs, as they obtain carbon and energy from other organisms, as a result of which, they meet their need by utilizing:
- Carbon Metabolism, i.e, the process of converting carbon into organic molecules within the body.
- Energy Metabolism: Essential for growth.
Ques. What is the catabolic and anabolic function in the Krebs cycle? (3 Marks)
Ans. The Krebs cycle has various reversible processes. The Krebs cycle consumes acetyl-CoA and generates NADH, CO2, proton, and other compounds when cycling clockwise, which is referred to as catabolism. Citrate can be collected and fluxed out of mitochondria, leading to the production of fatty acids. Also, Oxaloacetate is an important step in the gluconeogenesis process. Anabolism is the term used for those processes.
Ques. Can we say that all enzymes are catabolic? (3 Marks)
Ans. Catabolic reactions are typically energy-releasing, whereas, on other hand anabolic reactions are energy-demanding. Both catabolic and anabolic reactions need the use of enzymes.
Many enzymatic reactions use energy even though they are a part of the catabolic route, thus, we cannot classify enzymes as catabolic or anabolic enzymes. For instance, Phosphofructokinase I, is a glycolytic enzyme that transforms Fructose 6 Phosphate to Fructose 1,6 bisphosphate by transferring phosphate from ATP to Fructose 6 Phosphate and then using the energy obtained from ATP dephosphorylation.
Ques. Are the vitamin supplements catabolic? (3 Marks)
Ans. Most fat-soluble vitamins are only carried through the body by proteins that act as carriers. Foods that are high in fat-soluble vitamins are consumed. The acid present in the stomach acid breaks down the meal, which then goes through the small intestine, where it is further broken down. Bile is the essential requirement for fat-soluble vitamin absorption.
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