Bioelements, Biomolecules, and Cellular Nutrition: A Comprehensive Look
Bioelements and Biomolecules
Bioelements are the chemical elements that constitute the material of living things. Biomolecules are formed when bioelements combine to create the molecules of living things.
Properties of Water
- Solvent Power: Water is a great solvent for many substances, allowing them to be transported throughout the body or incorporated into cells in a dissolved state.
- Chemical Reactivity: Water provides the H+ and OH- required for hydrolysis reactions, as well as O2 and H2 in oxidation-reduction reactions.
- High Specific Heat: Water absorbs large amounts of heat without a significant increase in temperature, acting as a thermal buffer in living things.
- High Heat of Vaporization: Evaporation of liquid water absorbs much heat, allowing living beings to lower their temperature through evaporation, such as sweating.
Carbohydrates
Carbohydrates are molecules composed of C, H, and O. They perform energy and structural functions in cells. They are classified as:
- Monosaccharides: Simple sugars that are the basic units of carbohydrates, made of a single sugar molecule (e.g., glucose, fructose, ribose, and ribulose).
- Disaccharides: Composed of two monosaccharides linked by a covalent bond (e.g., maltose, lactose, and sucrose).
- Polysaccharides: Long chains of hundreds or thousands of monosaccharides (e.g., starch, cellulose).
Lipids
Lipids are formed by C, H, O, and P. They are divided into two groups: saponifiable and unsaponifiable.
- Aciglicerides: Molecules formed by a glycerol and 1, 2, or 3 fatty acids. They function as long-term energy reserves, provide thermal insulation, and protect organs.
- Phospholipids: Two types: phosphoglycerides and sphingolipids.
- Glycolipids: Saponifiable lipids that have carbohydrates in their composition.
- Waxes: Apolar lipids used for waterproofing or protection against dryness.
- Steroids: Unsaponifiable lipids derived from steranes, such as cholesterol.
- Terpenes: Molecules that occur in plants, such as carotenoids.
Proteins
Proteins comprise C, H, O, N, and sometimes P and S. They are macromolecules formed by the union of amino acids. Protein functions include structural support, reserve, transport, hormonal regulation, contractile movement, and defense.
Nucleic Acids
Nucleic acids are molecules composed of three subunits: a pentose sugar, a phosphate group, and a nitrogenous base (C, H, O, N, P, S…). Examples include DNA and RNA.
Endosymbiotic Theory
The endosymbiotic theory, proposed by Lynn Margulis, suggests that eukaryotic cells evolved when larger prokaryotic cells engulfed smaller prokaryotic cells. Instead of being digested, the smaller cells survived and became symbiotic, eventually evolving to perform useful functions, leading to the development of mitochondria and chloroplasts.
Viruses
Viruses are primarily protein structures that contain genetic material inside. Other non-cellular entities include viroids and prions.
Nutrition
Nutrition is the set of processes by which organisms exchange matter and energy with their environment to maintain their internal organization and perform vital functions. These processes are carried out by cells in three phases:
- Input of materials into the cell
- Use of matter and energy
- Excretion of waste products
Input Materials to the Cell
Nutrients enter cells via controlled transport mechanisms. Food or organic molecules are subjected to digestion into simpler forms and converted into molecules that can be used intracellularly or extracellularly.
Using Material and Energy
Cell metabolism involves the synthesis of cellular substances and the obtaining of energy.
Excretion of Waste Products
This involves removing unused nutrients and waste products of cell metabolism.
Cell Types of Nutrition
- Autotrophic: Cells can synthesize organic matter from simple inorganic nutrients.
- Heterotrophic: Cells derive organic matter from the environment, either directly or through the ingestion and digestion of food.
Small Molecule Transport
- Passive Transport: Occurs without energy consumption. Diffusion mechanisms include simple and facilitated diffusion.
- Active Transport: Molecules or ions move against concentration gradients, from areas of lower to higher concentration (e.g., sodium-potassium pump).