Biol 120: Cell Structure & Function - Topic 2

All living cells share fundamental components critical for life:

Plasma Membrane (Cell Membrane): Surrounds the cell, acting as a selective barrier.
Cytoplasm: The entire content within the cell membrane, excluding the nucleus in eukaryotes.
Chromosome: Contains the cell's genetic material (DNA).
Ribosomes: Sites of protein synthesis.
Cytoskeleton: Provides structural support, maintains cell shape, and facilitates movement.

Basic Structure: A bilayer composed of phospholipid molecules with embedded protein molecules.
- Consists of an inner leaflet and an outer leaflet.
Function: Semi-permeable, controlling the flow of substances into and out of the cell.
- The lipid bilayer acts as a hydrophobic barrier to water-soluble substances.
- Selective Transport: Specific substances (ions, water-soluble molecules) penetrate membranes through transport protein channels.
- Maintains specialized internal environments necessary for cellular life.
- Permeability varies significantly for different molecule types: permeable (gases, small hydrophobic molecules), partially permeable (small uncharged polar molecules like water, ethanol), restricted permeability (larger uncharged polar molecules like glucose), impermeable (ions, charged polar molecules, macromolecules).

DNA: Located in a central region, stores hereditary information (genes).
Cytoplasm: All material within a eukaryotic cell enclosed by the cell membrane, excluding the nucleus. It is the region between the plasma membrane and the central DNA-containing region (nucleus or nucleoid).
Cytosol: The aqueous, jelly-like portion of the cytoplasm in an intact cell, containing water, dissolved ions, and various organic molecules.
Cytoskeleton: Maintains cell shape and plays crucial roles in cell division and chromosome segregation.