Lecture Notes: Prokaryotic Cells

Introduction

• Prokaryotic cells are the simplest and most primitive form of cells.
• Originated billions of years ago.
• First living organisms on Earth were unicellular and prokaryotic.

Key Features of Prokaryotic Cells

Plasma Membrane

• Acts as a barrier between the cell and its environment.
• Composed of a phospholipid bilayer with proteins.
• Selectively permeable: allows intake of food and energy, expels waste.

Cell Wall

• Most prokaryotes have a rigid cell wall.
• Made of peptidoglycan (polymer of sugars and amino acids).
• Provides structural support and shape.

Cytoplasm and Cytosol

• The interior of the cell is called cytoplasm.
• Cytosol is the fluid component within the cell membrane.
• Jelly-like substance where cellular components reside.

Nucleoid

• Region containing genetic information.
• Consists of chromosomes, large DNA molecules.
• DNA is composed of genes, which code for proteins.

Ribosomes

• Complex macromolecules made of RNA and proteins.
• Site of protein synthesis through transcription and translation.

Enzymatic Functions

• Enzymes copy DNA and perform metabolic functions.
• Metabolic processes produce energy for movement and reproduction.

Cell Size

• Cells have a high surface area to volume ratio.
• Efficient exchange of materials with the environment.
• Typical size: around a hundredth of a millimeter in diameter.

Comparison to Eukaryotic Cells

• Prokaryotic cells are unicellular (e.g., bacteria and archaea).
• Eukaryotic cells are found in multicellular organisms like humans.
• Human cells are eukaryotic, not prokaryotic.

Conclusion

• Prokaryotic cells, although simple, are extremely numerous and vital to life on Earth.
• Eukaryotic cells will be discussed next as they form larger, multicellular organisms.