Membrane and Transport Notes

Review: Prokaryotic vs. Eukaryotic

Plasma membrane – thin flexible selectively permeable bilayer Structure – lipids, proteins, and carbohydrates in a fluid mosaic model 1. Lipid – phospholipid

2. Proteins – embedded in the phospholipid bilayer Enzymes Cell recognition Cell signaling Transport

3. Carbohydrates – attached to embedded proteins or phospholipids Cell recognition Cell adhesion

There are two main types of transport across a membrane Passive Active

Passive Transport the movement of molecules across a membrane without the use of energy (ATP)

Diffusion Molecules move down a concentration gradient (from a high conc. to a low conc.)  Simple diffusion  Facilitated diffusion  Osmosis

Facilitated diffusion The passage of large or charged molecules down a concentration gradient through a carrier protein Large or charged molecules can not pass through the membrane so they must pass through a carrier protein to get inside or out

Active Transport When a cell expends energy to move molecules or ions across a membrane Usually occurs from low to high (opposite)

1. Hypertonic – the solution with a higher concentration of solute compared to the cell in it 2. Hypotonic – the solution with a lower concentration of solute compared to the cell in it 3. Isotonic – solutions in which the concentration of solute are equal to the cell in it Solutions are referred to as one of the following: