Cellular Structures and Functions
Cell Wall
Presence: Not found in all cells (e.g., animal cells).
Location: Outside the plasma membrane.
Composition: Varies depending on the organism; common components include cellulose (plants), chitin (fungi), and peptidoglycan (prokaryotes).
Functions: Provides shape, strength, protection, and support.
Plant Cell Walls: Have primary and secondary walls with pores called plasmodesmata.
Cell Membrane
Presence: Found in all prokaryotic and eukaryotic cells.
Composition: Primarily composed of proteins and lipids, with small amounts of carbohydrates.
Structure: Fluid-mosaic model, with a lipid bilayer and embedded proteins.
Functions:
Semi-permeable barrier: Controls the movement of molecules in and out of the cell.
Cell recognition and signaling: Senses chemical messages and identifies other cells.
Organelle boundaries: Encloses organelles in eukaryotic cells.
Note: The next section will discuss the cytoplasm and cytoskeleton.
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