The Plasma Membrane Essential Questions: How does the structure of the plasma membrane allow it to function as a regulatory organelle and protective barrier for a cell?

Function: Plasma Membrane Maintains homeostasis by controlling substances entering & leaving the cell.

Think-pair-share What kinds of substances might need to enter or leave the cell?

A cell must take in and keep needed materials, such as glucose, while maintaining a balance with its surroundings.

A cell must remove wastes and keep harmful substances from entering.

Selective Permeability inside cell outside cell The property of a membrane that allows some materials to pass through while keeping others out.

Selective permeability allows different cells to carry on different activities within the same organism.

Structure of the Plasma Membrane

outside cell cytoplasm

Cholesterol Stabilizes the membrane by preventing phospholipids from sticking together

Proteins Transport-help move large molecules across the membrane Markers-helps chemicals recognize certain cells Enzymes

Proteins Transport Proteins Marker Proteins Enzymatic Proteins

Channel protein Provide a “tunnel” or channel for molecules to pass through the membrane

Carrier protein Protein that picks up a molecule and “carries” it across the membrane

Cell recognition protein Carbohydrate chain at the end of a protein and is used for cell to cell recognition and attachment

Phospholipids Phosphate head (glycerol +phosphate) 2 Fatty acid tails

Phospholipids Phosphate head polar hydrophilic “water-loving” Fatty acid tails nonpolar hydrophobic “water-fearing” “attracted to water” Fatty acid “repelled by water”

Phospholipids are arranged in a bilayer outside cell Polar Heads Non-polar tails Because there is water inside and outside of a cell, the phospholipids line up with the tails on the inside of the layer (away from the water) and the heads are on the outside of the layer (near the water). The phosphate group is soluble in water because it is polar and therefore attracted to water molecules. Fatty acid tails are not soluble in water because they are not polar and therefore not attracted to water molecules. inside cell

Think - Pair - Share Why do the phosphate heads point outward and the fatty acid tails point inward? Phospholipid molecule Polar head (includes phosphate group) Nonpolar tails (fatty acids) Section 2 Check

phospholipids move around The phospholipids can move sideways through their layer, but not from one layer to the other.

Name given to this model of the plasma membrane. Fluid because the phospholipids are free to move within the membrane. Mosaic because of the pattern it produces when viewed from above.

Plasma Membrane Talk to a Partner Carbohydrates, transport proteins, cholesterol, phospholipids, bilayer, cytoplasm, outside cell

QUESTIONS???

What does it mean that a cell membrane has a lipid bilayer?

What is the function of this structure?

What is the function of this structure?

What is the function of this structure?

Describe the 2 components of this structure

Which of the following best describes the plasma membrane's mechanism in maintaining homeostasis? A. protein synthesis B. selective permeability C. fluid composition D. structural protein attachment Section 2 Check

Explain why the model of the plasma membrane is called the fluid mosaic model. Section 2 Check

Cornell SummarY