Biol 120 Endomembrane System and Cell Structure & Function

Know the components of a cell.
Distinguish between a prokaryotic and eukaryotic cell.
Be able to describe the makeup and function of the structures and organelles that compose a cell, including:
- Cell membrane
- Nucleus
- Ribosomes
- Organelles part of the Endomembrane System
- Mitochondria
- Chloroplasts
- Peroxisomes
- Components of the cytoskeleton
- The role of the cell wall in cell communication in plants (plasmodesmata)
- Mechanisms of cell adhesion in animal cells (junctions and desmosomes)

All living cells share five fundamental elements:

All cells are surrounded by the plasma membrane.
It is a bilayer composed of phospholipid molecules with embedded protein molecules.
This bilayer consists of an inner leaflet and an outer leaflet.

Plasma membranes are semi-permeable, meaning they control the flow of substances into and out of a cell.
The lipid bilayer acts as a hydrophobic barrier to water-soluble substances.
Permeability of a synthetic lipid bilayer to different classes of molecules (from most to least permeable):
- Permeable: Small, nonpolar molecules (e.g., $O<em>2$ , $CO</em>2$ , $N_2$ , steroids).
- Partially Permeable: Small, uncharged polar molecules (e.g., water, urea, glycerol, ethanol).
- Restricted Permeability: Large, uncharged polar molecules (e.g., glucose, sucrose).
- Impermeable: Ions (e.g., $H^+$ , $Na^+$ ) and charged polar molecules (e.g., amino acids, ATP, proteins, polysaccharides, nucleic acids).
Mechanism of selective transport: Selected substances can penetrate cell membranes through transport protein channels.
Significance: Selective transport of ions and water-soluble molecules maintains the specialized internal environments required for cellular life.

Central Region: Contains DNA molecules, which store hereditary information (genes).
Cytoplasm: In eukaryotic cells, this term describes all material within the cell membrane, except for the nucleus.
- It encompasses the cytosol and various organelles suspended within it.
Cytosol: The aqueous portion of the cytoplasm, containing water, dissolved ions, and various organic molecules.
Cytoskeleton: Maintains cell shape and plays crucial roles in cell division and chromosome segregation.

Prokaryotes (domains Bacteria and Archaea):
- Bacteria
- Archaea
- Only organisms in these domains consist of prokaryotic cells.
Eukaryotes (domain Eukarya):
- Animals
- Plants
- Fungi
- Protists
- All consist of eukaryotic cells.