Cellular Structure and Functions

Hypotonic solution-has a lower concentration of solutes and a higher concentration of water relative to the cytoplasm of the cell;thus, the solution has less tone, or osmotic pressure, than the cell-water moves by osmosis into the cell, causing it to swell; if the cell swells enough, it can rupture, a process called LysisIsotonic solution-concentrations of various solutes and water are the same on both sides of the cell membrane-cell therefore neither shrinks nor swells Hypertonic solution-has a higher concentration of solutes and a lower concentration of water relative to thecytoplasm of the cell-water moves by osmosis from the cell into the hypertonic solution, resulting in cell shrinkage, or crenation

Facilitated diffusion-carrier-mediated transport process that moves substances across the cell membrane from an area of higher concentration to an area of lower concentration of that substance

Active transport-carrier-mediated process that moves substances across the cell membrane from regions of lower concentration to those of higher concentration against a concentration gradientExample:

Sodium-Potassium Pump

Moves Na+ out of cells and K+ into cells. The result is a higher concentration of Na+ outside the cell and a higher concentration of K+ inside the cell.

Secondary Active Transport-involves the active transport of one substance, such as Na+, across the cell membrane, establishing the concentration gradient;diffusion of that transported substance down its concentration gradient provides the energy to transport a second substance, such as glucose, across the cell membrane

Endocytosis and ExocytosisEndocytosis-uptake of material through the cell membrane by the formation of a vesicle-the cell membrane invaginates (folds inward) to form a vesicle containing the material to be taken into the cell;the vesicle then moves into the cytoplasmReceptor-mediated Endocytosis-cell membrane contains specific receptor molecules that bind to specific subtances;when a specific substance binds to the receptor molecule, endocytosis is triggered, and a substance is transported into the cell.

Cholesterol and growth factors are examples of molecules that can be taken into a cell by this process

Phagocytosis-often used for endocytosis when solid particles are ingested-part of the cell membrane extends around a particle and fuses so that the particle is surrounded by the membrane;that part of the membrane then pinches off to form a vesicle containing the particle;the vesicle is now within the cytoplasm of the cell, and the cell membrane is left intactWhite blood cells and some other cell types phagocytize bacteria, cell debris, and foreign particles;Phagocytosis is an important means by which white blood cells take up and destroy harmful substances that have entered the bodyPinocytosis-smaller vesicles are formed and contain liquidExocytosis-membrane-bound sacs called secretory vesicles accumulate materials for release from the cell;they move to the cell membrane, where the membrane of the vesicle fuses with the cell membrane, and the material in the vesicle is eliminated from the cell

Example:Secretion of digestive enzymes by the pancreas and the secretion of mucus by the salivary glands