Cellular Nutrition: Autotrophs, Heterotrophs, and Respiration
Cells need organic substances for two main purposes:
- Building and Repair: To rebuild structures, grow, and reproduce.
- Energy Production: To carry out activities such as movement and exchanging substances with the environment.
Living organisms obtain nutrition in two primary ways:
Autotrophic Nutrition
Autotrophs are able to capture energy from sunlight and use it to produce organic matter from inorganic substances. They take in raw materials to construct their own nutritional matter.
Heterotrophic Nutrition
Heterotrophs are unable to produce their own organic matter from inorganic matter. They need to incorporate organic matter produced by other living beings. These foods serve as both building materials and a source of energy.
Photosynthesis
Photosynthesis is the process by which plants capture and use energy from sunlight to convert inorganic matter into organic matter. This organic matter is used partly for building their own structures, partly for energy to perform vital functions, and the rest is stored as a reserve substance.
Plants produce organic matter in areas that possess chlorophyll and are exposed to sunlight. The first organic substances produced are carbohydrates or sugars. The development of organic matter during photosynthesis is accompanied by the release of oxygen into the external environment.
The Process of Photosynthesis
- Water and mineral salts dissolved in water (sap) circulate in thin tubes, called woody vessels, up to the leaves.
- When it reaches the leaves, much of the water is released abroad through small holes called stomata. This process is called transpiration.
- Plants absorb atmospheric carbon dioxide through the stomata of the leaves.
- The organic matter produced in the leaves (sap) runs from the leaves to other parts of the plant through a duct called the phloem.
Animal Nutrition
The type of food animals eat defines their alimentary regime, which can be classified into:
- Herbivores
- Carnivores (predators, scavengers, and apex predators)
- Omnivores
Nutrition provides the nutrients for growth, tissue renewal, and energy. It involves four systems:
Digestive System
Captures food, and through digestion, breaks it down into soluble small molecules that cross the intestinal wall into the blood, which then transports them to all cells.
Respiratory System
Captures oxygen from the air and expels carbon dioxide that the blood carries.
Circulatory System
The blood carries nutrients and oxygen to all cells. It also carries waste substances and carbon dioxide to expel them.
Excretory System
Responsible for eliminating waste substances produced by cells.
Respiration
In animals, breathing occurs when gas exchange takes place: oxygen is retained, and carbon dioxide is expelled.
- Inspired air: 21% oxygen, 0.03% carbon dioxide, 78% nitrogen.
- Expired air: 16% oxygen, 4.5% carbon dioxide, 78% nitrogen.
In plants, oxygen in the air or dissolved oxygen in water can penetrate all parts of the plant, mainly through the stomata. Inside, the air goes through the spaces between cells, facilitating gas exchange. Oxygen is released, and carbon dioxide is collected.
Cellular Respiration
Energy is obtained through respiration. In the mitochondria of all cells, a process called cellular respiration occurs, in which:
- Organic matter is degraded and transformed into inorganic substances.
- Oxygen is consumed.
- Released energy is transformed into heat, but most of it can be used for cell division, growth, the construction of large molecules, muscle contraction, etc.
Cells use organic substances to build their own structures and get energy for their activity.