genetic information is stored inside the nucleus as DNA.compartmentalization: nuclear membrane / nuclear envelope surrounds the nucleus.Nucleus (compartmentalization, storage of genetic information).Eukaryotes divide by mitosis (all them chromosomes line up and stuff), prokaryotes undergo binary fission (no chromosomes, just a circular ring of DNA, no need for complex mitosis).Eukaryotes have membrane-bound organelles (ER, Golgi, lysosomes, mitochondria), prokaryotes don't.Eukaryotes have a true nucleus (membrane-bound), while prokaryotes don't.Defining characteristics = what sets eukaryotes apart from prokaryotes.Defining characteristics (membrane bound nucleus, presence of organelles, mitotic division).Membrane-Bound Organelles and Defining Characteristics of Eukaryotic Cells They are organized for mechanical strength, not an impermeable barrier. desmosomes: connects two cells together by linking their cytoskeleton.A series of cells with tight junctions also effectively forms an impermeable barrier. tight junctions: stitches/glues two cells together, and does not allow stuff to flow through between the cells.gap junctions: connects two cells, and allows stuff to flow through between the cells.Exocytosis and endocytosis: exo = getting stuff out, endo = taking stuff in.Action potential along muscle cell membrane causes contraction.Action potential along neurons propagates and cause release of neurotransmitters into synapse.Electrical signaling = change in membrane potential triggers change in cell.Chemical signaling = chemical binding to receptor triggers a change inside cell.Contact signaling = physical contact triggers a change inside cell.Second messengers cause a change inside the cell (through a protein kinase cascade).Receptor binding triggers the production of second messengers.Many hormones can't cross the plasma membrane, so they bind to membrane receptors on the outside.Membrane receptors, cell signaling pathways, second messengers.Membrane potential: the resting potential of the cell membrane is negative because of the sodium-potassium pump.Membrane channels: lets ions through the cell membrane.Thus, the cell maintains a negative resting potential. Sodium-potassium pump: 3 sodium (NA +) out, 2 potassium (K +) in.Active transport = ATP needed = sodium/ptassium pump = up/against a concentration gradient.Passive transport = no ATP needed = channels, facilitated diffusion = direction of movement is down a concentration gradient.Passive and active transport: things that can't readily diffuse across the membrane are transported across the membrane either without energy (passive) or with energy (active).Too much osmotic pressure, and the cell will lyse (eg: if you put animal cells in water).The bigger the difference in solute concentration, the bigger the osmotic pressure.Osmotic pressure = pressure exerted by solvent via osmosis = counter pressure needed to prevent osmosis.Solvent will move as to dilute the component with more solute dissolved (given a semipermeable membrane that lets solvent pass but not the solutes).Colligative properties depend on the number of solute dissolved in solvent.Osmosis: water diffuses freely across the membrane, but not ions.Therefore, ions can't pass through the lipid bilayer without assistance from channels/pumps.Mixing a charged ion with hydrophobilic lipid bilayer is thermodynamically unfavorable by entropy.Let's things through: small nonpolar molecules, others by the aid of channels or pumps.Changes shape: chemotaxis with the aid of changes in cytoskeleton.Invaginates to take things in: phagocytosis, pinocytosis, endocytosis.Fluid mosaic model: the fluid mosaic model basically describes the membrane as protein boats floating in a sea of lipids.Protein components: receptors, channels, transport proteins. Steroids, cholesterol (provide more fluidity).
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