A&P Chapter 4

The cell is structural and functional unit of life
cells are the smallest unit of life
all cell come from preexisting cells
organisms activites depend on individual and collective cell activites.
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The cell is structural and functional unit of life
cells are the smallest unit of life
all cell come from preexisting cells
organisms activites depend on individual and collective cell activites.
the cell theory
how many cells are in the body
50-100 trillion
200 types
irregular-shaped
nerve cells
biconcave disc
red blood cells
cube-shaped
kidney tubule cells
column-shaped
intestinal lining cells
spherical
cartilage cells
cylindrical
skeletal muscle cells
maintain integrity and shape of a cell
obtain nutrients and form chemical building blocks
dispose of wastes
cell division (only some cells)
cells functions
separates the inside of cell from outside
-forms a stable barrier between 2 aqueous compartments
plasma membrane (cell membrane)
largest structure in cell contains genetic material, DNAnucleuscellular contents between plasma membrane and nucleus includes: cytosol and organellescytoplasmforms phospholipid bilayer in plasma membranephospholipids (75%)lipid with carbohydrate attached in plasma membraneglycolipids (5%)steroid with attached hydroxyl group. scattered with phospholipid bilayer strengthens and stabilizes membranecholesterol (20%)phosphate head is ______polar (hydrophilic)lipid tails are _______nonpolar (hydrophobic)carbohydrate group is hydrophilic; lipid portion hydrophobic appears only in the layer that faces extracellular fluid; one reason 2 layers are asymmetricglycolipidmembrane protein with a carbohydrate group attached carbohydrate part on extracellular surface onlyglycoproteinglycol (sugar) portion acts like molecular "signature" for cell-to-cell recognition also enables cell attachmentglycocalyxproteins are firmly embedded transmembrane: span the entire bilayer hydrophobic and hydrophilic regionintegralprotein are more loosely associated with external or internal membraneperipheralmost common functional categories of membrane proteinstransport protein and receptormost membrane lipids and proteins easily rotate and move sideways in bilayer allows for -easy reassembly of membrane, cell movement, growth diuison, secretionfluid mosaic modelfluidity is increased by (less stable)increased # of double bonds in fatty acid tails of lipids decreased amount of cholesterol in membranepermeability of lipid portion of the plasma membraneselectively permeablewhen some substance get through while others do notsemipermeablewhat substances can easily pass through plasma membranenonpolar: fatty acids, vitamins (A, D, E, K), steroids, oxygen, carbon dioxide, waterwhat substances can not pass through the plasma membranepolar, charged, large. Ions: Na+, K+, Ca2+, H+ polar molecules: polysaccharides, amino acids, glucose, nucleic acidscan act as channels and transporters increase permeability are very selective with each being specific to particular particlestransmembrane (integral) proteinsa difference between concentrations on each side of membrane can be chemical or be electricconcentration gradientcreated by different concentrations of chemicals and charges across membraneelectrochemical gradientsrequires no cellular energy ex) diffusion and osmosispassive processrequire cellular energy (ATP) substances generally move "uphill" against gradient ex) transporter proteins, endocytosis, exocytosisactive processesrandom mixing of particles in solution substance move down concentration gradient particles eventually become even distributed and can occur across membranediffusionsleepness of the gradient temperature mass of diffusing substance surface area diffusion distancefactors that influence diffusionmove freely through bilayer -oxygen, carbon dioxide, nitrogen gases, fatty acids, steroids, fat-soluble vitamins (A, E, D, K), small alcohols, ammonianonpolar, hydrophobic moleculespassive process diffusion of water across a selectively permeable membrane from high concentration of water to lower concentration moves toward higher solute concentrationosmosisforce of pressure against membrane the pressure that the fluid exerts on the walls of its container blood pressurehydrostatic pressurepressure exerted by the movement of water across a semipermeable membrane due to a difference in solution concentration the sleeper the gradient, the higher the osmotic pressureosmotic pressureinterstitial fluid is the same concentration as cytosol no net movement of waterisotonic solutioninterstitial fluid is less concentrated that cytosol water enters cellhypotonic solutioninterstitial fluid is more concentrated that cytosol water leaves cellhypertonic solutionsolutes moving against concentration gradient need energy: can be driven by ATP use or via energy stored in ionic concentrationactive transportactive transport proteins that move ions across membrane eg) calcium pumps or sodium/ potassium pumpsion pumpsno ATP use needed energy stored in ion concentration used to drive other substances across membrane against concentrations -usually sodium or hydrogen ionssecondary active transport1) receptor mediated 2) phagocytosis 3) pinocytosis or bulk-phaseendocytosis