Cellular Processes and structure 03 Cell Structure Osmosis Cell Membrane Membrane Transport Eukaryotic cells

Cell Membrane AP Bio Framework: 2.A.2 Holtzclaw: 50-52 (7.1-7.2) Campbell: 7.1-7.3

Cells create and maintain internal environments that are different from their external environments. Cell membranes are selectively permeable due to their structure.

Cell membranes separate the internal environment from the external environment

Selective permeability is a direct consequence of membrane structure Fluid mosaic model - phospholipids slide around each other and are embedded with proteins

Selective permeability is a direct consequence of membrane structure Reactions in organelles are separated from the rest of the cell - which is separated from the rest of the environment - by a permeable membrane.

Cell membranes Structural framework phospholipid molecules glycerol attached to a phosphate and two carbon chains amphipathic embedded proteins can span membrane or face one side cholesterol adds structure, determines fluidity glycoproteins and glycolipids carbohydrate bound to a protein (or lipid) uses include signaling, structure, and protection

Cell membranes Structural framework phospholipid molecules embedded proteins cholesterol glycoproteins and glycolipids

Phospholipids are amphipathic Hydrophilic and hydrophobic ends. Hydrophilic phosphates face the aqueous environments (internal and external) Hydrophobic fatty acid portions face each other within the interior of the membrane itself.

Embedded proteins can be hydrophilic, or hydrophobic charged and polar side groups or hydrophobic nonpolar side groups.

Cell membranes are selectively permeable Small, uncharged or nonpolar molecules freely pass across the membrane N2, O2 Hydrophilic substances embedded channel and transport proteins large polar molecules and ions glucose, Na ions Water moves across membranes through channel proteins called aquaporins.

Cell walls provide a structural boundary permeability barrier for some substances

Plant cell walls Made of cellulose external to the cell membrane

Prokaryote cell walls Made of Peptidoglycan mesh of amino acids and sugars external to the cell membrane

Fungal cell walls Made of chitin external to the cell membrane

Be able to 2.10 Use representations and models to pose scientific questions about the properties of cell membranes and selective permeability based on molecular structure. 2.11 Construct models that connect the movement of molecules across membranes with membrane structure and function