– Catabolism and anabolism are two types of metabolic processes that occur in living cells. Metabolism is the sum of all the chemical reactions that allow an organism to maintain its life functions, such as growth, development, repair, and adaptation.

– Catabolism is the type of metabolism that involves breaking down complex molecules into simpler ones, releasing energy in the process. Catabolism is also called "destructive metabolism" because it destroys the chemical bonds in larger molecules and produces smaller molecules.

– The energy released by catabolism can be used for various purposes, such as performing work, generating heat, or synthesizing new molecules. Catabolism is usually faster and more spontaneous than anabolism.

– Anabolism is the type of metabolism that involves building up complex molecules from simpler ones, using energy in the process. Anabolism is also called "constructive metabolism" because it creates new chemical bonds and produces larger molecules.

– The energy used by anabolism comes from the catabolic reactions or from external sources, such as food or sunlight. Anabolism is usually slower and less spontaneous than catabolism.

🔅 Examples of catabolic reactions are:

Glycolysis

– This is a pathway that converts glucose (a six-carbon sugar) into pyruvate (a three-carbon molecule), producing ATP (the main energy currency of cells) and NADH (an electron carrier) in the process. Glycolysis occurs in the cytoplasm (the fluid inside cells) and does not require oxygen. Glycolysis is the first step of cellular respiration, which is the process of extracting energy from organic molecules.

Beta-oxidation

– This is a pathway that breaks down fatty acids (long chains of carbon atoms with a carboxyl group at one end) into acetyl-CoA (a two-carbon molecule that can enter the citric acid cycle), producing ATP and FADH2 (another electron carrier) in the process. Beta-oxidation occurs in the mitochondria (the organelles that produce most of the energy in cells) and requires oxygen. Beta-oxidation is the main way of metabolizing fats for energy.

Proteolysis

– This is a process that hydrolyzes (splits with water) proteins (large molecules made of amino acids) into amino acids, producing water and ammonia in the process. Proteolysis occurs in various locations in cells, such as lysosomes (organelles that digest waste materials), ribosomes (organelles that synthesize proteins), or proteasomes (complexes that degrade damaged or unwanted proteins). Proteolysis is important for regulating protein levels and quality in cells.

🔅 Examples of anabolic reactions:

Gluconeogenesis

– This is a pathway that produces glucose from non-carbohydrate sources, such as amino acids, lactate, or glycerol. Gluconeogenesis occurs mainly in the liver (the organ that regulates blood sugar levels) and requires ATP and NADH. Gluconeogenesis is important for maintaining glucose levels when carbohydrates are scarce or during fasting.

Lipogenesis

– This is a pathway that synthesizes fatty acids from acetyl-CoA and malonyl-CoA (a three-carbon molecule derived from acetyl-CoA). Lipogenesis occurs mainly in the cytoplasm of liver and adipose tissue (fat cells) and requires ATP and NADPH (another electron carrier). Lipogenesis is important for storing excess energy as fat.

Protein synthesis

– This is a process that forms proteins from amino acids, using mRNA(messenger RNA) as a template and tRNA (transfer RNA) as a carrier. Protein synthesis occurs mainly in the cytoplasm on ribosomes and requires ATP and GTP (another energy currency). Protein synthesis is important for creating new proteins for various functions in cells.