1 The Cell Membrane Gateway to the Cell

2 Cell Membrane flexible, not rigid The cell membrane is flexible, not rigid

3 Homeostasis Maintaining a stable internal environment despite external conditions; also called equilibrium Maintained by cell membrane controlling what enters & leaves the cell

4 Functions of Cell Membrane Protective barrier Regulate transport in & out of cell (selectively permeable) Allow cell recognition Provide anchoring sites for filaments of cytoskeleton

5 Structure of the Cell Membrane

6 Membrane Components

7 Phospholipids Make up the cell membrane Contains 2 fatty acid chains that are nonpolar Head is polar

8 Fluid mosaic model FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. FLUID MOSAIC MODEL

9 hydrophilic Polar heads are hydrophilic “water loving ” hydrophobic Nonpolar tails are hydrophobic “water fearing” Cell Membrane

10

11 Solubility Materials that are soluble in lipids can pass through the cell membrane easily

12 Small non-charged molecules move through easily. Examples: O 2, and CO 2 Semipermeable Membrane

13 Ions, and large molecules such as glucose and amino acids do not move through the membrane on their own. They must use transport proteins Semipermeable Membrane

14 Passive Transport NORequires NO energy HIGH to LOWMolecules move from area of HIGH to LOW concentration

15 Active Transport  Requires energy or ATP  Moves materials from LOW to HIGH concentration AGAINST the concentration gradient

Levels of Organization Atom -> Element -> Molecule -> Organelle -> Cell -> Tissue -> Organ -> Organ System -> Organism 16

Scientist Review Hooke – 1 st coined the term “cell” Schleiden – all PLANTS are made up of cells Schwann – all ANIMALS are made up of cells Leeuwenhoek – created the 1 st microscope Virchow – contributed “all cells arise from pre-existing cells” to the Cell Theory 17

Endosymbiotic Theory The idea that mitochondria were once Prokaryotic cells living outside of the Eukaryotic cell due to the existence of its own DNA. 18 Lynn Margulis