Metabolism and Energy Transformation in Body Cells - Renata Armenakovna Petrosova 2004

Energy Metabolism
Stage One: Preparatory Phase

Energy is essential for the vital activity of any living Organism. Plants accumulate solar energy in Organic compounds through Photosynthesis. During METABOLISM/26.html">Energy Metabolism, these organic compounds are broken down, and the energy of their chemical bonds is released. Part of this energy is dissipated as heat, while another part is stored in ATP molecules. In animals, energy metabolism proceeds in three stages.

Food enters the body of animals and humans in the form of complex high-molecular-weight compounds. Before these substances can reach the Cells and Tissues, they must be broken down into low-molecular-weight compounds that are more readily assimilated by cells.

The First stage involves the hydrolytic degradation of organic substances in the Presence of Water. This process is driven by Enzymes within the digestive tract of Multicellular animals, inside the digestive vacuoles of unicellular organisms, and—at THE CELLULAR LEVEL—within Lysosomes.

Reactions of the preparatory stage:

Proteins + H2O

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Amino Acids + Q;

fats + H2O

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glycerol + Higher Fatty acids + Q;

Polysaccharides

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glucose + Q.

In mammals and humans, proteins are broken down into amino acids in The Stomach and duodenum through the action of enzymes known as peptidohydrolases (Pepsin, Trypsin, Chymotrypsin). The breakdown of polysaccharides begins in the Oral Cavity under the Influence of the enzyme ptyalin and continues in the duodenum through the action of amylase. Fats are also digested in the duodenum by lipase. All The energy released during these processes is dissipated as heat.

The resulting low-molecular-weight compounds enter the bloodstream and are transported to all Organs and cells. Within the cells, they are delivered to lysosomes or directly into the Cytoplasm. If the breakdown occurs at the cellular level inside lysosomes, the substances pass immediately into the cytoplasm. This stage serves to prepare the compounds for intracellular degradation.



Last update: 13/08/2026

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