Structure of Life: Cells, Systems, and Essential Nutrition
Biological Organization: From Tissue to Organism
Levels of Structural Organization
The body is organized hierarchically, starting from specialized cells:
- A tissue is a set of specialized cells of the same type that perform a particular function.
- The union of several tissues forms an organ.
- The set of several organs whose functions are related is an apparatus or system. We speak of a single system when a predominant tissue exists.
- The set of all apparatuses and systems constitutes a multicellular organism.
Tissues, Organs, and Systems
Tissues and Their Functions
Tissues are specialized for specific roles:
- Protection: Integument (skin), Mucosa.
- Reserve: Fat (Adipose tissue).
- Support: Bone tissue.
- Secretion: Glandular tissue.
- Union/Connection: Connective tissue.
- Movement: Muscular tissue.
- Communication: Nervous tissue.
Examples of Organs
Organs are structures composed of multiple tissues working together:
- Heart
- Stomach
- Muscle (as an organ)
Apparatuses and Systems: Vital Functions
These structures work together to perform the essential functions necessary for life:
1. Nutrition
Nutrition is the process by which we incorporate nutrients and oxygen to obtain energy and perform vital functions. Examples include the digestive apparatus, respiratory system, circulatory system, and excretory system.
2. Reproduction
Reproduction allows for the survival of the species. Examples include the male and female reproductive tracts.
3. Coordination and Relation
This function is achieved thanks to the existence of various systems, apparatuses, and organs that allow the organism to interact with its environment and regulate internal processes. Examples include sensory organs, the nervous system, the endocrine system, and the musculoskeletal system.
Understanding Nutrition and Essential Nutrients
Nutrition vs. Feeding
- Nutrition is the set of processes that allows organisms to use and transform nutrients to stay alive.
- Feeding is the process by which we obtain these external environmental nutrients.
Macronutrients and Micronutrients
Carbohydrates (Glucosides or Carbon Hydrates)
Carbohydrates are primarily energetic substances.
- Simple Carbohydrates or Sugars: These have a sweet taste, such as glucose or fructose (present in honey and fruit), sucrose (table sugar), and lactose (in milk).
- Complex Carbohydrates: These include starches and vegetable cellulose, which contains dietary fiber.
Lipids (Fats)
Lipids are highly energetic molecules. Fat is the main energy reserve.
- Saturated Fats: These molecules are highly energetic. Saturated fats typically come from animals.
- Unsaturated Fats: These typically come from vegetables.
Proteins
Proteins are primarily structural molecules. They are formed by the union of simpler molecules called amino acids, of which there are 20 different types.
Of the 20 existing amino acids, 12 can be manufactured from other amino acids (non-essential). The remaining 8 (essential amino acids) must be incorporated through food.
Vitamins
Vitamins are essential substances for the proper functioning of the body. Vitamins are easily destroyed by heat, light, and even the oxygen in the air.
- Fat-Soluble Vitamins: These accumulate in the liver. The best known are Vitamins A and D.
- Water-Soluble Vitamins: These do not accumulate and must be regularly replenished. Examples include B1, B2, B12, and C.
Minerals
Minerals are inorganic substances. Some are structural (e.g., calcium), they constitute an important part of the proper functioning of organs, and are involved in the regulation of cellular metabolic reactions.
Key minerals and ions include:
- Calcium (structural component)
- Potassium
- Carbonates
- Phosphates
- Other solids
Water
Water is the most abundant molecule in our body. Water acts as a solvent, is used as a transport system for substances, and helps regulate body temperature.
There is a crucial balance between the amount of water removed and the amount incorporated through food and drink.