Biological Processes: Nutrition, Metabolism, and Digestion Systems

Fundamentals of Nutrition and Metabolism

Defining Key Biological Concepts

Nutrition: The set of processes by which living things incorporate foreign substances to obtain matter and energy.

Food (Alimentos): Substances consumed by living beings.

Feeding (Alimentación): The process of taking food. Food is composed of substances called nutrients.

Types of Nutrition

Nutrition is classified based on how organisms obtain organic matter:

• Autotrophs

  Capable of producing their own organic matter from simple inorganic substances. They require an energy source:

  • Photosynthetic: Obtain energy from sunlight (e.g., algae, plants, and photosynthetic bacteria).
  • Chemosynthetic: Use energy released by specific chemical reactions (e.g., determined bacteria).

• Heterotrophs

  Use biomolecules produced by other living beings as a source of organic matter (e.g., protozoa, fungi, animals, and many bacteria).

Processes Involved in Nutrition

In Animals

• Digestive Process: Conversion of food into simpler substances.
• Gas Exchange: Oxygen uptake.
• Transportation: Distribution of oxygen and nutrients.
• Metabolism: Nutrient utilization.
• Excretion: Elimination of waste material.

In Plants

• Absorption: Inorganic nutrient uptake.
• Transport: Inorganic nutrients.
• Evapotranspiration: Water loss through the leaves.
• Gas Exchange.
• Photosynthesis.
• Transport of Organic Substances.
• Metabolism and Cellular Respiration.
• Elimination.

The Digestive Process and Its Phases

The digestive process includes phenomena occurring in the digestive system, enabling the uptake of food, transforming it into substances useful to the body, and expelling waste. It consists of four phases:

1. Ingestion

   Taking food from the outside environment.

2. Digestion

   Food processing into nutrients.

   • Intracellular Digestion

     Carried out within the cell (common in unicellular and primitive multicellular organisms).

   • Extracellular Digestion

     Occurs outside the cells, often in the digestive tube. It can be:

     • External: Outside the body (e.g., arachnids).
     • Internal: Within the body (e.g., many invertebrates and all vertebrates).

     In extracellular digestion, food undergoes mechanical transformation (fragmentation) and chemical transformation.

3. Absorption

   Passage of nutrients from the digestive tract into the blood.

4. Egestion

   Elimination of undigested waste material (feces).

Types of Digestive Systems

• Gastrovascular Cavity

  A sac lined with cells, communicating with the outside via a single orifice that serves as both mouth and anus (e.g., Sponges and Polyps).

• Gastrointestinal Tract

  A tube starting at the mouth, where food enters, and ending at the anus, where waste is expelled.

Examples of Digestion Types

• Sponges: Intracellular digestion (gastrovascular cavity).
• Cnidarians: Extracellular digestion (gastrovascular cavity).
• Mollusks: Extracellular digestion (digestive tube).
• Arthropods: External digestion and gastrointestinal tract.

Vertebrate Digestive Process

Digestion is extracellular, occurring along the digestive tube, which consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. Attached glands also exist.