Cell

🧫 CELL STRUCTURE REVIEWER

Prokaryotic vs. Eukaryotic Cells

🔬 TWO TYPES OF ORGANISMS ACCORDING TO CELL STRUCTURE

Prokaryotes

• These are single-celled organisms.

• They do not have a membrane-bound nucleus.

• They lack mitochondria and other membrane-bound organelles.

• Examples: Bacteria and Archaea

Eukaryotes

• These are organisms whose cells contain a true nucleus enclosed by a membrane.

• They have membrane-bound organelles such as mitochondria, Golgi apparatus, ER, etc.

• Examples: Plants, Animals, Fungi, Protists

🧱 PARTS AND FUNCTIONS OF A PROKARYOTIC CELL

• Nucleoid – Region that contains the cell’s DNA.

• Ribosome – Responsible for synthesizing proteins.

• Cell Wall – Provides structure and protection; made of peptidoglycans in most bacteria.

• Cell Membrane (Plasma Membrane) – Controls the movement of substances in and out of the cell.

• Capsule – A sticky layer that helps the cell attach to surfaces.

• Flagella (Flagellum) – Tail-like structures that help the cell move.

• Pili – Rod-like structures used for attachment and transfer of DNA.

• Fimbriae – Hair-like structures that help in attaching to surfaces.

🧬 PARTS AND FUNCTIONS OF A EUKARYOTIC CELL

• Nucleus – Stores DNA and controls cellular activities such as replication and transcription.

• Ribosome – Synthesizes proteins for the cell.

• Cell Wall – Provides support and protection; found in plant and fungi cells.

• Cell Membrane – Semi-permeable membrane that regulates what enters and exits the cell.

• Mitochondria – Known as the "powerhouse of the cell"; produces energy (ATP).

• Endoplasmic Reticulum (ER)

Rough ER – Has ribosomes; produces and transports proteins.

Smooth ER – Lacks ribosomes; produces lipids and detoxifies substances.

• Vacuole – Stores water, nutrients, and waste; large in plant cells.

• Lysosome – Breaks down waste, damaged organelles, or harmful invaders.

• Golgi Apparatus – Modifies, sorts, and packages proteins and lipids for transport.

🔗 SIMILARITIES BETWEEN PROKARYOTIC AND EUKARYOTIC CELLS

• Both have DNA as their genetic material.

• Both contain ribosomes that make proteins.

• Both have cytoplasm, the jelly-like fluid that fills the cell.

• Both are surrounded by a plasma membrane that regulates what enters and exits.

⚖ DIFFERENCES BETWEEN PROKARYOTIC AND EUKARYOTIC CELLS

• Prokaryotic cells are small (0.1 to 5.0 micrometers) and simple in structure, while eukaryotic cells are larger (10 to 100 micrometers) and more complex.

• Prokaryotes do not have a nucleus. Their DNA is circular and found in the nucleoid. Eukaryotes have a nucleus containing linear DNA.

• Prokaryotic cells lack membrane-bound organelles. Eukaryotic cells contain organelles such as mitochondria, ER, Golgi bodies, etc.

• Prokaryotes are always unicellular. Eukaryotes may be unicellular or multicellular.

• Cell division in prokaryotes occurs through binary fission, conjugation, transformation, and transduction. In eukaryotes, it occurs through mitosis (and meiosis for sexual reproduction).

• The genetic material in prokaryotes is circular, double-stranded, and has a single origin of replication. In eukaryotes, DNA is linear, double-stranded, and has multiple origins of replication.

• In prokaryotic cells, transcription and translation happen at the same time in the cytoplasm. In eukaryotic cells, transcription occurs in the nucleus and translation occurs in the cytoplasm.

• Prokaryotes reproduce asexually. Eukaryotes mostly reproduce sexually, though some can reproduce asexually.

• Prokaryotic cells are the oldest and most abundant types of cells on Earth. Eukaryotic cells are believed to have evolved from prokaryotic ancestors.

📌 KEY TAKEAWAYS

• Prokaryotes are ancient, simple, and always unicellular.

• Eukaryotes are newer, complex, and can be unicellular or multicellular.

• The presence of a true nucleus and membrane-bound organelles is the main difference.

• Despite differences, both cell types share essential structures like DNA, ribosomes, cytoplasm, and plasma membrane.