Essential Functions and Structures of Living Organisms

Vital Functions of Living Beings

Nutrition

The function by which living beings utilize food substances to produce energy.

Relation

The function by which all living beings relate to the environment and respond to stimuli.

Reproduction

The function by which every living being is capable of producing similar beings.

Chemical Composition of Living Beings

Bioelements

These are the chemical elements that form part of living beings.

Classification by Abundance

They are preferentially classified as:

• Fundamental Bioelements
• Secondary Bioelements
• Trace Elements (Oligoelements)

Biomolecules

These are the molecules that form part of living beings. They can be:

• Organic: Large molecules characterized by long chains of carbon atoms.
• Inorganic: Small molecules that do not contain carbon (Note: This is a simplification; some inorganic molecules like CO2 contain carbon, but the key distinction often relates to C-H bonds and complexity).

Cell Types: Prokaryotes vs. Eukaryotes

Prokaryotes

• Appeared ~3.5 billion years ago; more primitive and smaller.
• Typical examples: Bacteria.
• DNA is a single circular chromosome, not enclosed by a membrane.
• Do not have membrane-bound organelles.

Eukaryotes

• Appeared much later, ~2 billion years ago.
• Typical examples: Animal cells, plant cells, protozoa, algae.
• DNA is organized into multiple linear chromosomes located within a nucleus (membrane-bound).
• Possess various membrane-bound organelles, each with specific functions.

Cell Types: Animal vs. Plant

Animal Cells

1. Have varied shapes; generally lack a rigid cell wall.
2. Do not have chloroplasts.
3. Possess centrioles (involved in cell division).
4. Have multiple small vacuoles, if any.

Plant Cells

1. Typically have a prismatic shape due to a rigid cell wall.
2. Contain chloroplasts, responsible for photosynthesis.
3. Generally lack centrioles.
4. Usually have one or two large central vacuoles.

Metabolic Processes: Nutrition Types

Autotrophic Nutrition

A process where organisms use carbon dioxide from the air, water, and mineral salts to synthesize glucose, releasing oxygen. This process requires light energy (photosynthesis) or chemical energy (chemosynthesis). Typical examples: algae, plants, some bacteria.

Heterotrophic Nutrition

Consists of the cell taking ingredients from the external environment, including glucose, to oxidize them and produce energy, releasing carbon dioxide and water. Typical examples: animals, protozoa, fungi, most bacteria.

Cell Reproduction Mechanisms

Bacterial Reproduction (Binary Fission)

Bacteria reproduce by binary fission, involving several phases:

1. The DNA duplicates, creating two identical copies.
2. Each copy moves to opposite poles of the cell.
3. The cell divides in the middle, forming two daughter cells.

Mitosis

Consists of the division of the cell's nucleus (in eukaryotes).

Cytokinesis

Consists of the division of the cytoplasm, distributing it between the two daughter cells formed from the mother cell.