3.3 Cell Membrane Updates: Homework: reading 3.3/29.6 Homeostasis and exercise lab due Tuesday Quiz begins Tuesday: 3.1

3.3 Cell Membrane LEQ: What is the structure and function of a cell membrane? Activator: – –What are the universal structures of all cells? – –What structures do eukaryotes have in addition to the universal structures? – –Make a 2 column chart or Y diagram to organize your answer (no writing just short and simple lines/listing) Key terms – plasma membrane, fluid mosaic model, selective permeability, receptor

3.3 Cell Membrane Cells evolved a plasma membrane with a unique chemical composition: –Phospholipids cells evolved unique, sustained chemical systems

3.3 Cell Membrane (b) Space-filling model (a)(c) Structural formula Phospholipid symbol Fatty acids Hydrophilic head Hydrophobic tails Phosphate Glycerol Hydrophobic tails Hydrophilic head Phospholipids: polar “heads” and nonpolar “tails”

3.3 Cell Membrane Structure - phospholipid bilayer: –Two sided w/ heads facing toward water; hydrophilic – –Fatty acid tails in middle; hydrophobic!

3.3 Cell Membrane Explain how the arrangement of phospholipids in a bilayer is like an oreo cookie. Use the following terms: hydrophobic, hydrophilic, polar and non polar

3.3 Cell Membrane The fluid mosaic model: membrane molecules interact in a fluid-like (oil) and flexible way to support membrane function The fluid mosaic model explained

3.3 Cell Membrane Membranes have two basic functions. Functions: physical barrier that surrounds and protects the cell Selectively permeable - controls (regulates) passage of chemicals

3.3 Cell Membrane Explain how the structure of a cell membrane supports the functions of being a physical barrier and selectively permeable transport.

3.3 Cell Membrane Cells interact with the environment and communicate using the plasma membrane Chemical signals (ligand) bind to a protein receptor: – –Lock-and-key fit

3.3 Cell Membrane Cells use special receptors to respond to hormones target cell hormone receptor not a target cell

3.3 Cell Membrane

Discuss with your group how your thermostat and furnace work together to heat your home. Write: How is the cold exposure/thyroid hormone loop like heating your house?

3.3 Cell Membrane

Summary: Why might different cells respond to different signals in their respective environments? How do they do this? Why do phospholipids form a bilayer when they are dissolved in water? If membranes solidified why would homeostasis be disrupted in a cell? – –How does this relate to the characteristics of organisms?

3.3 Cell Membrane What is quorum sensing? What adaptive advantage does it confer to a colony? According to the video, bacteria release two types of molecules. What different roles do these molecules play?

3.3 Cell Membrane