2 Plasma membrane of cell selectively permeable (allows some substances to cross more easily than others)Made mostly of proteins and lipids (phospholipids).Phospholipids and proteins create unique physical environment (fluid mosaic model)
29 Organism does not have rigid walls must have ability to osmoregulate and maintain internal environment.Plant cells expand when watered causing pressure to be exerted against cell wall.Allows plant to stand up against gravity (turgid cell); not watered, plant will begin to wilt (flaccid cell).
33 Charged particles that cannot pass through membrane - proteins to pass through (facilitated diffusion - diffusion of substance down it’s [ ] gradient with help of transport protein)Some channel proteins (gated channels) open/close depending on presence/absence of physical or chemical stimulus.
34 In this case, the protein actually rotates to dump the materials to the insideof the cell.
35 Sometimes materials need to be moved against [ ] gradient (active transport) Active transport requires energy of cell to move substances from an area of low [ ] to an area of high [ ] (i.e. sodium-potassium pump in animal cells)
44 Materials leave membrane through lipid bilayer or through transport proteins. Exocytosis - transport vesicle buds from Golgi apparatus - moved by cytoskeleton to plasma membrane.When membranes meet - fuse - material is let out to outside of cell.
45 Endocytosis - cell brings in macromolecules and matter by forming new vesicles from plasma membrane. Membrane is inwardly pinched off and vesicle carries material to inside of cell.
51 3Receptor-mediated endocytosis - specific in transported substances. Extracellular materials bind ligands (receptors) - causes vesicle to form.Allows materials to be engulfed in bulk (i.e. cholesterol in humans)