Evolution of Eukaryotic Cells: Organelles and Functions

The Evolution of Eukaryotic Cells

The evolution from prokaryotic to eukaryotic cells began with a series of changes.

Loss of the Cell Wall

The resulting cell possessed a single, flexible membrane containing many ribosomes, which serve to synthesize digestive enzymes.

The convolution of the cell membrane allowed the cell to increase in size through folds, providing a larger surface area for nutrient absorption. Subsequently, digestive enzymes break down material, which is then expelled from the cell.

Formation of the Nucleus

Digestion occurs both inside and outside the cell. The membrane invaginates to enclose the DNA, creating a precursor to the cell nucleus.

Development of Organelles

The first structures to appear were peroxisome precursors, which initiated the creation of the eukaryotic cell to manage destructive components created by oxygen levels. Mitochondria precursors developed the ability to generate more efficient molecules. The development of peroxisomes and mitochondria facilitated better adaptation for chloroplasts, which produce oxygen for photosynthesis. These organelles supplement certain cell types by utilizing solar energy.

Cell Organelles and Their Functions

• Mitochondria: A complex organelle responsible for cellular respiration: Glucose + O2 → CO2 + H2O + Energy (ATP).
• Ribosomes: Composed of RNA and proteins, these are the smallest organelles and are responsible for protein synthesis.
• Golgi Apparatus: Often described as the cell's "post office," it consists of 5 to 10 semicircular sacs. Its function is to store, modify, and transport proteins to their target organelles. It is also involved in the synthesis of certain carbohydrates.
• Centrioles: Their primary function is the formation and organization of filaments that constitute the spindle apparatus during nuclear cell division.
• Plasts and Chloroplasts: Found only in plant cells. If they lack chlorophyll, they are called plasts; if they contain chlorophyll, they are chloroplasts. They contain a stack of membranes called thylakoids. Groups of thylakoids form grana. The stroma stores energy.
• Vacuoles: Similar to vesicles but larger, vacuoles are primarily found in plant cells. Their function is to store substances; in plants, they contain water and occupy a significant portion of the cell.