Membrane Transport Guided Notes

Let’s review…

Structure of the Plasma Membrane Phospholipid Molecules – Description: Lipid polymer Has two distinct ends – Hydrophilic Head End: Water-loving Polar Glycerol and phosphate group – Hydrophobic Tail End: Water-fearing Nonpolar Fatty acid chains

Fluid Mosaic Model 1.Phospholipids form a bilayer (2 rows) 2.Polar heads on the outside 3.Nonpolar tails on the inside 4.Large proteins between layers, act as channels 5.Cholesterol helps stabilize the structure 6.Surface proteins and carbohydrate chains for recognition

So… Just how does a plasma membrane regulate what goes in and out – and WHY?

Let’s start with the “WHY?”… Plasma Membrane (PM) and Homeostasis: Homeostasis is the regulation of internal conditions to maintain functions. 1.PM is responsible for maintaining homeostasis 2.PM keeps the cell in balance 3.PM regulates products and wastes 4.PM regulates intake and output substances

Now…Let’s get to the “How?”

Diffusion Movement of particles from an area of higher concentration to an area of lower concentration Passive – no energy needed!

Concentration Gradient Measure of how concentration changes from one place to another

Osmosis Diffusion of water across semi-permeable membrane Depends on concentration of solute on either side of a membrane

Solute Part of a solution The substance dissolved by or into the solvent Example: Kool-Aid powder

Solvent Part of a solution The substance that does the dissolving Example: Water

Dynamic Equilibrium Result of diffusion where particles move in and out of the cell but overall concentrations stay the same

Isotonic Solution Solution where the concentration of solute OUTSIDE the cell is the same as the concentration of solute INSIDE the cell Water flows both ways

Hypertonic Solution Solution where the concentration of solute OUTSIDE the cell is HIGHER than the concentration of solute INSIDE the cell Water flows OUT OF the cell

Hypotonic Solution Solution where the concentration of solute OUTSIDE the cell is LOWER than the concentration INSIDE the cell Water flows INTO the cell

Passive Transport Movement of particles across a membrane by diffusion or osmosis No energy used

Facilitated Diffusion Passive transport across cell membrane that uses transport or carrier proteins to help move particles Think: Does this require energy?

Active Transport Transport of materials across a cell membrane against a concentration gradient Requires energy (ATP) Like swimming upstream!

Endocytosis Active transport process where a cell engulfs (“eats”) materials using the plasma membrane Releases materials into the cell

Exocytosis Active transport process where materials are excreted or expelled out of the cell through the membrane.

What is happening in each image?