University:
Boston University
Course:
CAS BI 203 | Cell Biology
Academic year:

2022
Views:

113

Pages:

10
Author:

rezancuk2j

Osmosis (Diffusion of water) • Osmosis is the diffusion of water through a selectively permeable membrane down its concentration gradient • From an area of high water concentration to an area of lower water concentration How Osmosis works  A substance is solute dissolved in solvent.  Water is the solvent in the cell.  Concentration increase when the amount of solvent decrease. Osmotic Solutions • Isotonic concentrations of solute and solvent are equal. • Hypertonic- higher concentration of solutes. • Hypotonic- lower concentration of solutes Active Transport • • • • Movement against a concentration gradient Requires Energy (ATP) Allows for stockpiling One direction • Types: – Molecular Transport (Protein Pumps) – Bulk Transport (Endocytosis and Exocytosis) Active Transport Uses specialized transport proteins and protein pumps Sodium- Potassium ATPase Pump Protein pumps Use the ATP energy to move ions or large molecules across the plasma membrane. Molecules are moved against their concentration gradient. Importance of Sodium and Potassium ions Consuming too little potassium and too much sodium can raise your blood pressure Sodium- Potassium ATPase Pump The sodium–potassium pump is an enzyme found in the membrane of all animal cells For every ATP molecule that the pump uses, three sodium ions are exported and two potassium ions are imported Transport of Large Particles • Some substances are too large to move through the plasma membrane by diffusion or transport proteins and must get inside the cell by different Process. 1- Endocytosis how materials ENTER the cell 2- Exocytosis how materials EXIT the cell Endocytosis The process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing (swallow) it with their cell membrane Exocytosis A cellular process where cells eject waste products or chemical transmitters (such as hormones) from the interior of the cell. • Exocytosis is similar in function to Endocytosis but works in the opposite direction.