Cell Membrane Diffusion and Water

Membrane structure Made up of Phospholipids, proteins, and carbohydrates The membrane creates the protective outer layer of the cell Creates boundaries in a watery environment Hydrophilic head Phosphate group Symbol Hydrophobic tails

Phospholipid bilayer The cell membrane is called a bilayer because it has two layers together to create the boundary Due to the hydrophobic nature of the lipids, the center of the membrane hates water and charged molecules Hydrophilic heads Hydrophobic tails Water

Membrane Proteins Membrane proteins are found embedded in the membrane and have specific function:  Communicate  Transport materials  Enzyme activity

Messenger molecule Receptor Activated molecule TransportSignal transductionEnzyme activity ATP

Extracellular matrix Glycoprotein Carbohydrate Plasma membrane Microfilaments of cytoskeleton Phospholipid Cholesterol Proteins Cytoplasm Glycolipid

Diffusion Molecules inside of cells are in constant motion (Brownian motion) The result of Brownian motion is diffusion Diffusion= movement of particles from high concentration to low concentration Diffusion leads to equilibrium

LE 5-14 Molecules of dyeMembrane Equilibrium

Passive transport Selectively permeable membrane= allows some (small, non-polar) substances across. Passive transport = When there is movement (diffusion) across a membrane without energy.

Molecules of dye Membrane Equilibrium

Facilitated diffusion Some molecules (larger, polar) can not pass through the membrane without help Facilitated diffusion= movement of larger, or polar molecules through a membrane protein (tunnel)

LE 5-15 Solute molecule Transport protein

Active transport Some molecules are needed in high concentrations in the cell. These molecules go against diffusion and need help Active Transport= The movement of molecules across the membrane using energy and a protein to move against diffusion.

LE 5-18a Transport protein Solute Solute binding Phosphorylation ATP ADP P

Osmosis Water is in constant movement Osmosis= The movement of water across a selectively permeable membrane. Water moves from high concentration to low concentration.

LE 5-16 Water molecule Selectively permeable membrane Solute molecule H2OH2O Lower concentration of solute Higher concentration of solute Equal concentration of solute Solute molecule with cluster of water molecules Net flow of water

Tonicity Solute= substance being dissolved Solvent= Substance dissolving Hypertonic= a solution with a higher concentration of solute Hypotonic= a solution with a lower concentration of solute Isotonic= a solution with equal amounts of solute

LE 5-17 Isotonic solution Hypotonic solution Hypertonic solution H2OH2O H2OH2O (1) Normal (2) Lysed H2OH2O H2OH2O H2OH2O H2OH2O Animal cell Plant cell (4) Flaccid(5) Turgid(6) Shriveled (plasmolyzed) (3) Shriveled Plasma membrane H2OH2O H2OH2O

Movement of molecules Endocytosis= materials being engulfed into the cell  Endocytosis=Enter Exocytosis= materials being released from the cell.  Exocytosis=Exit

LE 5-19 Vesicle Fluid outside cell Protein Cytoplasm Vesicle forming

(a) Molecules cross cell membranes polar molecules and ions (e) (b) (d) (c) of uses by passive transport may be moving down moving against requires diffusion transport proteins