Cell: The Unit of Life Cheat Sheet

This unit explores the cell as the fundamental structural and functional unit of all living organisms, covering cell theory, prokaryotic and eukaryotic cell structures, and the functions of various organelles.

Core Principles

• All living organisms are composed of cells and their products.
• All cells arise from pre-existing cells (Cell Theory).
• Cells vary in shape, size, and function, adapted to their roles.
• Eukaryotic cells possess a membrane-bound nucleus and organelles; prokaryotic cells lack these.
• Organelles within eukaryotic cells perform specific, coordinated functions, often within an endomembrane system.
• The plasma membrane regulates the passage of substances into and out of the cell.
• The cell wall provides structural support and protection in plant cells and fungi.
• Mitochondria are the powerhouses of the cell, generating ATP through respiration.
• Chloroplasts in plant cells are responsible for photosynthesis.
• Ribosomes are responsible for protein synthesis.
• The nucleus controls cellular activities and contains genetic material (DNA).

Key Terms

• Cell Theory: The fundamental biological theory stating that all living organisms are composed of cells and all cells arise from pre-existing cells.
• Prokaryotic Cell: A cell lacking a membrane-bound nucleus and other membrane-bound organelles.
• Eukaryotic Cell: A cell possessing a membrane-bound nucleus and various membrane-bound organelles.
• Plasma Membrane: The selectively permeable outer boundary of animal cells and inner boundary of plant cells, regulating transport.
• Cytoplasm: The semi-fluid matrix filling the cell, enclosing organelles and being the site of many cellular activities.
• Nucleus: The organelle containing the cell's genetic material (DNA) and controlling cellular activities.
• Mitochondrion: The 'powerhouse' of the cell, responsible for cellular respiration and ATP production.
• Chloroplast: The organelle in plant cells responsible for photosynthesis.
• Ribosome: The cellular machinery responsible for protein synthesis.
• Endomembrane System: A network of organelles (ER, Golgi, lysosomes, vacuoles) involved in coordinated cellular functions like transport and synthesis.
• Fluid Mosaic Model: The accepted model describing the structure of the plasma membrane as a fluid bilayer of lipids with embedded proteins.
• Centromere: The region on a chromosome that holds sister chromatids together and attaches to spindle fibers during cell division.

Timeline

• 1831: Robert Brown discovers the nucleus.
• 1838: Matthias Schleiden proposes that all plants are composed of cells.
• 1839: Theodore Schwann proposes that all animals are composed of cells.
• 1855: Rudolf Virchow states that cells arise from pre-existing cells.
• 1950s: Detailed structure of the cell membrane studied with electron microscopes.
• 1972: Singer and Nicolson propose the fluid mosaic model of the cell membrane.