Nutrition and Metabolism in Living Organisms
We say q is the flow of cyclic matter, but it loses energy, degrading to heat in the environment without apparently recovering it. The energy flow is unidirectional: solar energy is transformed by plants into chemical energy, and only about 10% of the stored energy is returned to the environment as heat. Only stored energy goes to the next trophic level.
ITEM 5. NUTRITION AND METABOLISM
5.1. Concept of Nutrition
Autotrophic and Heterotrophic Nutrition: This refers to the exchange of materials and energy that every living thing needs to perform with the external environment to carry out its vital activity.
- Autotrophic: Organisms take free energy and inorganic substances and synthesize organic substances. They take the necessary substances directly through absorption.
- Photosynthesis: Uses light energy and chlorophyll (only in plants).
- Chemosynthesis: Uses oxidation reactions (some bacteria).
- Heterotrophic: Organisms cannot capture free energy or synthesize organic matter from mineral substances. They need organic matter (matter + energy) (animals, plants without chlorophyll, and some bacteria). They can take oxygen, water, and mineral salts directly, but organic compounds must be broken down through digestion into their essential components.
5.2. Concept of Metabolism
Metabolism is the set of chemical reactions conducted in living organisms, specifically inside the cells. These include:
- Anabolism: Processes of assimilation or elaboration of immediate principles.
- Catabolism: Processes of dissimilation or decomposition of immediate principles.
Respiration
Respiration is defined as the oxidative phase of catabolism, through which living organisms obtain the energy needed to perform their vital activities. It is, therefore, the energy metabolism of living beings. All organisms need respiration to perform all activities. In the respiratory apparatus, organic matter is oxidized and dehydrogenated, losing electrons and protons. These are gained by other reduced substances. Respiration is a redox process: a process of oxidation-reduction. Depending on the involvement of free oxygen, two types of respiration are distinguished:
- Aerobic: Complete oxidation, transforming into inorganic material with low energy content.
- Anaerobic: Incomplete oxidation. Energy efficiency is higher than with aerobic respiration, being an organic substance with energy potential. It is also called intramolecular respiration.
Fermentation
Fermentation is the decomposition of organic matter by anaerobic organisms, which take in external organic matter and return it through the respiratory process. Different types include:
- Alcoholic: Produces ethanol.
- Acetic: Produces acetic acid.
- Lactic: Produces lactic acid.
- Butyric: Produces butyric acid.
- Putrefaction: Fermentation of proteins.
Photosynthesis
Also called the chlorophyll function of nutrition, photosynthesis is the process by which organisms, using carbon dioxide and water, and incorporating light energy, are able to synthesize sugars and other organic substances, releasing oxygen. Photosynthesis allows for the capture of light energy from the sun and its transformation into chemical energy, the only energy useful for any metabolic route. The energy is used for the synthesis of molecules and is not stored in energy molecules. The transformation process of solar energy into chemical energy takes place in the chloroplast. For light energy to be useful in a living being, it must be captured by molecules capable of absorbing it. These light-capturing substances are called pigments and are located in the thylakoids of chloroplasts. These pigments can be: chlorophylls, xanthophylls, carotenoids, etc. Photosynthesis comprises two phases:
- The light-dependent phase, which takes place in the grana of the thylakoids of chloroplasts.
The electrons are released by the incidence of light.