As the food enters your body, it gets broken down into molecular components so that you can actually use the nutrition these molecules provide. All of the physical and chemical activities in your body that convert or use energy are called metabolism. These include things like breathing, digesting food, and circulating blood.

But metabolism is a pretty broad term, and it includes all of the chemical activities in your body. We can think of metabolism in two separate forms: catabolism and anabolism. 


Catabolism involves all of the metabolic processes that tear down biomolecules, while anabolism is all of the metabolic processes that build biomolecules.

Metabolic and Catabolic Processes

Metabolism is the set of chemical reactions that occur in living organisms to sustain life. It involves various processes that can be categorized into two main types: metabolic and catabolic processes.

Metabolic Processes:
Metabolic processes refer to the chemical reactions that build molecules and store energy within an organism. These processes are essential for the growth, maintenance, and reproduction of cells. Here are some key metabolic processes:

1. Anabolism: Anabolism is the process of synthesizing complex molecules from simpler ones. It requires energy input and is responsible for the growth and repair of tissues. Examples of anabolic processes include protein synthesis, DNA replication, and the formation of glycogen from glucose.

2. Photosynthesis: Photosynthesis is a metabolic process that occurs in plants and some microorganisms. It converts sunlight, carbon dioxide, and water into glucose and oxygen. This process is vital for the production of food and oxygen in the ecosystem.

3. Cellular Respiration: Cellular respiration is the process by which cells break down glucose and other organic molecules to release energy in the form of ATP (adenosine triphosphate). It occurs in the mitochondria of eukaryotic cells and generates energy required for cell functions.

4. Assimilation: Assimilation is the process of incorporating nutrients into the body after digestion. During assimilation, the body absorbs essential nutrients from food and transports them to various cells and tissues.

Catabolic Processes:
Catabolic processes involve the breakdown of complex molecules into simpler ones, releasing energy in the process. These processes provide the necessary energy for an organism to perform various activities. Here are some key catabolic processes:

1. Glycolysis: Glycolysis is the initial step of cellular respiration and occurs in the cytoplasm of cells. It breaks down glucose into pyruvate, generating ATP and NADH in the process.

2. Protein Degradation: Catabolism of proteins involves the breakdown of amino acids into simpler compounds. This process occurs when the body requires energy and lacks other fuel sources. The amino acids released from protein degradation can be used to synthesize new proteins or converted into glucose or fatty acids for energy production.

3. Lipolysis: Lipolysis is the breakdown of triglycerides (fat) into glycerol and fatty acids. This process mainly occurs in adipose tissue and provides energy during times of fasting or low glucose availability.

4. Glycogenolysis: Glycogenolysis is the breakdown of glycogen, a stored form of glucose, into glucose molecules. It is an essential process in maintaining blood glucose levels during fasting or increased energy demands.

In summary, metabolic processes involve building complex molecules and storing energy, while catabolic processes break down complex molecules, releasing energy. These processes are interrelated and crucial for the functioning of living organisms.