Biological Organization and Cell Theory Fundamentals

1. Formation of Living Organisms

The hierarchy of biological organization is as follows: Atom → Chemical Elements → Molecule → Macromolecule → Cell → Tissue → Organs → Systems → Body.

2. Cell Theory

A cell is the basic structural and functional unit of all organisms. All cells perform three vital functions:

• Nutrition: The set of processes that enables organisms to use and transform substances needed to stay alive.
• Interaction: Involves several systems and organs, including sensory organs, the nervous, endocrine, skeletal, and muscular systems.
• Reproduction: Ensures survival over time through male and female reproductive organs.

Note: All cells originate from pre-existing cells.

3. Cellular Differences and Similarities

Differences

• Number of cells: Unicellular (one cell) or Multicellular (more than one).
• Type of cells: Prokaryotes (without a nucleus) or Eukaryotes (with a nucleus).
• Type of nutrition: Heterotrophic and Autotrophic (both obtain nutrients from organic compounds).
• Type of reproduction: Asexual (creates an identical copy) or Sexual (does not produce an identical copy).

Similarities

All cells perform the three main functions and share a fundamental structure.

4. The Cell Structure

Cell Membrane

A fine layer that separates the cell from the outside environment.

• Small Molecules:
  • Diffusion: Passive transport where molecules move without energy. When the molecule is water, it is called Osmosis.
  • Active Transport: Requires energy (ATP) to move molecules across the membrane.
• Big Molecules:
  • Endocytosis: The membrane creates a vesicle to move molecules inside the cell.
  • Exocytosis: Vesicles are used to move molecules outside the cell.

Nucleus

Located in the center of the cell, it controls cellular functions. It is composed of nucleoplasm, chromatin, and the nucleolus.

Cytoplasm

A jelly-like substance that contains the following organelles:

• Mitochondria: Double-membrane organelles that produce energy through cell respiration.
• Ribosomes: Small organelles without a membrane that contain RNA and proteins.
• Endoplasmic Reticulum:
  • Rough: Contains ribosomes and works with proteins.
  • Smooth: Lacks ribosomes and destroys toxic substances.

5. Mitosis Phases

1. Interphase: 46 chromosomes.
2. Prophase: Chromosomes are doubled.
3. Prometaphase: The nucleus dissolves.
4. Metaphase: Chromosomes align in the middle.
5. Anaphase: Chromosomes are separated.
6. Telophase: Cell division begins.
7. Cytokinesis: Two daughter cells are created.