AQA GCSE FOUNDATION Biology: Eukaryotes and Prokaryotes

Eukaryotes vs. Prokaryotes: A Crash Course in Cell Structure

This tutorial explores the fundamental differences between eukaryotic and prokaryotic cells, two major categories of living organisms. Understanding these distinctions is crucial for comprehending the diversity of life on Earth.

What's the Difference?

The primary distinction lies in the presence or absence of a nucleus, a membrane-bound organelle that houses the cell's genetic material (DNA).

• Eukaryotic cells possess a true nucleus, providing a separate compartment for DNA replication and transcription. They also boast other membrane-bound organelles that specialize in various functions.
• Prokaryotic cells lack a nucleus and other membrane-bound organelles. Their DNA is located in a region called the nucleoid, which is not enclosed by a membrane.

Key Differences in a Nutshell:

Examples of Cell Types:

• Eukaryotic cells:
  • Animal cells: Muscle cells, nerve cells, blood cells.
  • Plant cells: Root cells, leaf cells, flower cells.
  • Fungal cells: Yeast cells, mushroom cells.
• Prokaryotic cells:
  • Bacteria: E. coli, Salmonella.
  • Archaea: Methanogens, halophiles.

Prokaryotic Cell Structure

While lacking a nucleus, prokaryotic cells still possess essential components:

• Cell Wall: Provides structural support and protection.
• Plasma Membrane: Regulates the passage of substances into and out of the cell.
• Cytoplasm: The gel-like substance within the cell, containing various enzymes and molecules.
• Ribosomes: Responsible for protein synthesis.
• Nucleoid: The region containing the cell's DNA.

Eukaryotic Cell Structure

Eukaryotic cells are more complex, with a vast array of organelles, each performing a specialized function:

• Nucleus: Contains the cell's DNA, controls cellular activities.
• Mitochondria: Powerhouses of the cell, responsible for energy production (ATP).
• Endoplasmic Reticulum (ER): Network of membranes involved in protein and lipid synthesis.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Digest cellular waste and debris.
• Chloroplasts (in plant cells): Sites of photosynthesis.

Understanding the Evolutionary Significance:

Prokaryotic cells are considered to be the earliest forms of life on Earth. Eukaryotic cells likely evolved from prokaryotes through a process called endosymbiosis, where one prokaryote engulfed another, eventually leading to the development of organelles like mitochondria and chloroplasts.

Key takeaway:

Understanding the fundamental differences between eukaryotes and prokaryotes is crucial for comprehending the diversity of life, from single-celled bacteria to complex multicellular organisms. These differences reflect the remarkable evolutionary journey of life on Earth.