Anabolic and Catabolic Reactions, Cell Metabolism and Homeostasis


What are anabolic and catabolic reactions? Information about cell metabolism and homeostasis.


Each organism has the ability to detect and respond to stimuli from the environment. The growing of the root deep into the ground, the growing of the stem in the opposite direction of gravity, you taking your hand away immediately when you touch a very hot object, even a small Paramecium running away from acidic liquid dropped into the microscope slide is a response given to stimulating changes in the environment. What is the purpose? Why do we feel thirsty? Why do we feel hungry? The answer is “homeostasis“. As we mentioned before, homeostasis means balanced, equal state in Latin. Each organism works very hard to protect the internal balance. Homeostasis often involves internal feedback mechanisms. When we feel cold, we shiver, so that with the rapid contraction of the muscles we produce energy and warm up. When we feel hot, we sweat, so that excess energy is given out by the evaporation of water.

There are two types of reactions in the cell that help keep homeostasis. These are anabolic and catabolic reactions.

a) Anabolic Reactions

These reactions are the reactions which result in synthesis of polymers from monomers.

  • Synthesis of starch from glucose molecules
  • Synthesis of glycogen from glucose molecules
  • Synthesis of proteins from amino acids
  • Production of blood and muscle cells from proteins
  • Synthesis of glucose from carbon dioxide and water.

In the process of anabolic reactions, the cell mainly spends energy, and water is produced.

b) Catabolic Reactions

These reactions are the reactions which result in the breaking down of polymer molecules into their monomers.

  • Breaking down of starch into glucose molecules.
  • Breaking down of glycogen into glucose molecules
  • Breaking down of proteins into amino acids
  • Breaking down of tissue proteins
  • Breaking down of photosynthesis into carbon dioxide and water.

In the process of catabolic reactions, water is used and energy is released. Not only us, multicellular, highly developed organisms, but unicellular ones also work very hard to survive! Many protists that live in pure water (hypotonic environment) have the risk of taking in too much water and swell. The contractile vacuoles collect and remove excess water, thereby helping to achieve homeostasis, a stable inner environment.

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