Biology Class 9: Fundamental Unit of Life

Primary Function of the Cell Membrane

• The cell membrane regulates the entry and exit of substances, maintaining homeostasis.
• It provides a barrier that separates the internal environment of the cell from the external environment.
• The membrane is selectively permeable, allowing specific ions and molecules to pass while blocking others.

Prokaryotic vs Eukaryotic Cells

• Prokaryotic cells lack a nucleus and organelles, while eukaryotic cells possess both.
• Prokaryotes are typically smaller and simpler in structure compared to eukaryotes.
• Both types of cells have DNA, ribosomes, and a plasma membrane, but their organization and complexity differ significantly.

Role of Ribosomes

• Ribosomes are essential for protein synthesis, translating messenger RNA (mRNA) into polypeptide chains.
• They can be found either free-floating in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER.
• Ribosomes are composed of ribosomal RNA (rRNA) and proteins, playing a crucial role in the cell's overall function.

Cellular Structure for Energy Production

• Mitochondria are the organelles primarily involved in energy production through a process called cellular respiration.
• They convert glucose and oxygen into adenosine triphosphate (ATP), the energy currency of the cell.
• Mitochondria possess their own DNA and double membrane, indicating an evolutionary relationship to prokaryotic cells.

Function of the Cytoplasm

• The cytoplasm is the gel-like substance within the cell membrane, facilitating the movement of materials and organelles.
• It provides a site for biochemical reactions, including metabolic processes crucial for cell survival.
• The cytoplasm contains cytosol, organelles, and various molecules, contributing to the cell's structural integrity and functionality.