Cellular Nutrition: Processes, Types, and Metabolism
Cellular nutrition consists of all the processes in which cells obtain matter and energy to perform their vital functions. Cells need energy to carry out their activities and matter to build their components.
Substance Interchange
- Osmosis: This is the normal way of interchanging water. Water passes through the cell membrane from a less concentrated solution to a more concentrated one, separated by a semi-permeable membrane, such as the plasmatic membrane of cells, which allows its passage but not the dissolved substances. Example: blood filtration in the kidneys.
- Diffusion: Small molecules soluble in water, such as mineral ions and gases like oxygen and carbon dioxide, pass through the plasmatic membrane by diffusion from an area of greater concentration to an area of lesser concentration. Diffusion takes place without using energy. Example: gas exchange in the lungs.
- Active Transport: This mechanism is used for the passage of larger molecules or when molecules pass in the opposite direction to the concentration gradient. This transport requires energy and the participation of transporting proteins of the plasmatic membrane. Example: glucose reabsorption in the nephron, where glucose moves from a low concentration area to a higher concentration area in the bloodstream.
- Endocytosis and Exocytosis: This kind of interchange occurs with large-sized particles and molecules, which are contained in vesicles. Endocytosis is the entrance of substances, and exocytosis is the exit of them.
Types of Cellular Nutrition
- Autotrophic: Beings that only take inorganic substances from the environment, such as oxygen, mineral salts, water, and carbon dioxide. Using an external source of energy, they obtain internal chemical energy (ATP) and transform the inorganic substances into organic matter.
- Heterotrophic: Beings that need, besides oxygen and water, to take in food from the environment. Food is always made up of organic matter formed by other organisms. Animals, protozoa, fungi, and bacteria are examples of this.
Metabolic Processes
- Catabolism: This is the set of chemical reactions by which cells degrade complex molecules into simpler ones, releasing useful energy for the cell.
- Anabolism: This is the set of reactions by which cells synthesize their own components or complex molecules from simpler substances or molecules, consuming chemical energy.
Autotrophic and Heterotrophic Nutrition
- Autotrophic Nutrition: Takes place in plants (photosynthesis). Metabolism in cells: cells can transform luminous energy into chemical energy (ATP). This takes place in chloroplasts.
- Heterotrophic Nutrition: Takes place in animals. There are four parts of the digestive apparatus involved in nutrition: digestive (for processing food), respiratory (for interchanging gases with the environment), circulatory (for transporting nutrients and gases throughout the body), and excretory (for eliminating toxic products). Metabolism in cells: they use the organic matter that they obtain from the medium to obtain energy through catabolic reactions.