Diffusion and Osmosis

The Cell Membrane Protective barrier for the cell “Selectively permeable” – controls what can go in and what can go out Made up of two layers of phospholipids (a type of fat): “phospholipid bilayer” Contains other types of molecules essential for cell function such as proteins, carbohydrates and other types of fats.

Phospholipids Contains a head and a tail Head is hydrophilic: “water-loving” Tail is hydrophobic: “water-fearing” Cells are bathed in mostly water, so phospholipids arrange themselves to have heads facing the water and tails facing away from it = creates a nice barrier!

Diffusion Our bodies always strive for equilibrium and a steady state as part of homeostasis. Cells can take in molecules as part of this process (across a membrane or within the cell). Diffusion: Random movement of molecules from high concentration to low concentration to reach equilibrium.

Osmosis Movement of water across a membrane from high concentration to low concentration to achieve equilibrium. Water moves across the cell membrane through special protein channels called aquaporins.

What will happen in the diagram? “less water, more solute” “more water, less solute” “equal” Isotonic Hypotonic Hypertonic H2O

What happens when an animal cell is placed in a hypotonic solution? What happens when an animal cell is placed in a isotonic solution? What happens when an animal cell is placed in a hypertonic solution?