TEM picture of a real cell membrane. Cell Membranes All cells have a cell membrane Controls (regulates) what comes in and out of the cell to maintain an internal balance called homeostasis Provides protection and support for the cell TEM picture of a real cell membrane.

Lipid Bilayer -2 layers of phospholipids Cell Membranes Structure of cell membrane Lipid Bilayer -2 layers of phospholipids Phosphate head is polar (water loving) Fatty acid tails non-polar (water fearing) Proteins embedded in membrane Phospholipid Lipid Bilayer

Cell Membranes Cell membranes have pores (holes) in it Selectively permeable: Allows some molecules to pass and keeps other molecules out Sometimes referred to as semi-permeable The structure helps it be selective! Pores

Fluid Mosaic Model Proteins Polar heads love water & dissolve. Each individual cell exists in a fluid environment and the cytoplasm within the cell also has a fluid environment. The presence of a liquid makes it possible for substances (oxygen, nutrients, and waste products) to move in and out of the cell. Non-polar tails hide from water. Carbohydrate cell markers Proteins

Structure of the Cell Membrane Outside of cell Carbohydrate chains Proteins Lipid Bilayer Transport Protein Phospholipids Inside of cell (cytoplasm)