UNIT TWO-LECTURE 7:Before we start, remember what a phospholipid consists of: 2 Fatty acids on a Glycerol + a phosphate group on its 3rd OH. They are: -Amphipathic (one side is hydrophobic and one side is hydrophilic). -In water, they self assemble so the lipid part sticks together and the phospho part points out. These are the source of the lipid bilayers that make up membranes.I.Cells are the basic unit of life A.Common features between prokaryotic and eukaryotic cells: 1.Plasma membrane- phospholipid bilayers that are embedded with proteins that are scattered all over it and inside of it. There are two separate bilayers (it is a double membrane that encapsulates the cell bits floating inside). a.the volume:surface area ratio of a cell matters because the cell communicates with its outside through the membrane (basically the membrane is its surface area). There is a max volume at which diffusion can’t support the cell. 2.cytosol- fluid inside of the plasma membrane 3.cytoplasm- the interior of the cell 4.chromosomes- compacted genetic DNA 5.ribosomes- biological macromolecules that make proteins 6.motility proteins called flagella are on the outside of the cell.Credit to: STEPHEN ESPOSITO, 2011, BSC2010 (Stroupe)B.Features that are DISSIMILAR: 1.DNA a.prokaryotes DNA is in the nucleoid (area of the cell not bound by a membrane). b.eukaryotes DNA is in the membrane bound nucleus 2.organelles- membrane bound compartments that are only found in Eukaryotes. 3.Bacteria(a type of prokaryote) are 1-5 nanometers in diameter, compared to eukaryotic cells which are typically 100 nanometers in diameter. (Eukaryotic cells are Larger than bacterial cells). 4.Plant cells, have more in common with human cells than bacterial cells.II.Mitochondria, Chloroplasts and Peroxisomes A.Mitochondria - found in ALL eukaryotic cells(also found in plant cells) - fuels cellular respiration (cellular respiration means making ATP) 1.1to10 nanometers long 2.double membrane with proteins in each bilayer 3.outer membrane is smooth 4.inner membrane has many folds called cristae so that there is a large inner membrane space. Between the membranes is the inner membrane space, and within the inner membrane is the mitochondrial matrix.Credit to: STEPHEN ESPOSITO, 2011, BSC2010 (Stroupe)5.folds are important to increase the surface area for increased respiratory efficiency. 6.Mitochondria contain their own DNA. B.Chloroplasts- these are specialized plastids in plants that work in photosynthesis (a plastid is a Plant Organelle) (plants have mitochondria too) 1.2 to 5 nanometers in size, shaped like a disk. 2.Double membrane with inter-membrane space between the inner and outer membrane and stroma (fluid inside the double membrane sac) 3.contains 3rd membrane that makes stacks called thylakoids 4.stacks of thylakoid membrane are called Granums. 5.chloroplasts contain their own DNA (found in the stroma, along with ribosomes :)) C.Peroxisomes- in mammalian and plant eukaryotes. 1.single membrane 2.catalyze H2 + O2 >> H2O2 3.used to break down fatty acids 4.in liver, also removes ethanol(beer, liquor, Four Loko, etc) and other toxinsIII.Cell membranes are fluid mosaics made of lipids, proteins and carbohydrates A.semipermeable membranes- some things pass more easily than others (compare to bouncers at the club--checks who enters just as semipermeable membrane checks what enters cell)Credit to: STEPHEN ESPOSITO, 2011, BSC2010 (Stroupe)1.lipids with charged head group and hydrophobic tail give the membrane amphipathic character that determines permeability. 2.many proteins within the membrane also affect its permeability 3.carbohydrates attached to the proteins and the lipids affect the extracellular qualities.IV.the Fluid Mosaic Model- phospholipid bilayer membranes are fluid. A.fluidity- the packed lipids are flexible but not liquid 1.the membrane is primarily held together by hydrophobic interactions 2.motion of the membrane is lateral(side to side) but Rarely do membrane-embedded objects flip from one side to another. 3.additives affect membrane behavior a.cis unsaturated lipids are bent more than trans unsaturated lipids so they can not pack as closely so they are more fluid. 1.Cis lipids are more bent than Trans lipids b.cholesterol (a steroid) limits lipid movement so it rigidifies membranes at moderate temperatures c.when the temperature drops, membranes stop moving and this can affect the activity of the cell. B.Mosaic comes from the proteins in the membranes 1.different proteins are found in different membranes 2.integral proteins are embedded in the membrane through hydrophobic regionsCredit to: STEPHEN ESPOSITO, 2011, BSC2010 (Stroupe)3.peripheral proteins are bound to the surface of the membrane and are more hydrophilic than integral proteins.LECTURE 8:I.Cell membranes are fluid mosaics made of lipids, proteins, and carbohydrates A.the word fluid comes from the proteins in the membranes (They move laterally, and RARELY flip sides: but still do sometimes!) 1.integral proteins are embedded within the membrane through hydrophobic regions 2.peripheral proteins are bound to the surface of the membrane and are more hydrophilic than integral proteins 3.there are 6 functions of membrane proteins a.transport b.enzymes c.signal transduction d.cell to cell recognition e.intracellular joining f.attachment to the cytoskeleton and the ECM B.Synthesis and sidedness (from ER to vesicles to Golgi Apparatus to vesicles to the plasma membrane 1.the process for sidedness goes as follows: a.lipids and membranes are made in the ERCredit to: STEPHEN ESPOSITO, 2011, BSC2010 (Stroupe)b.post-translational modifications on proteins happen in the ER (to make glycoproteins) 1.correctly glycosylated proteins are important for the following: a.cell to cell recognition b.immunity c.development(such as embryo tissue sorting) 2.glycoproteins are different in different species and also different in human blood types (A, B, and O). c.the ER sends these glycoproteins to the Golgi apparatus where they are further processed. Lipids are also glycosylated here as well. d.vesicles bud and are exported to the plasma membrane (this is how membrane proteins get to the cell surface---through vesicles budding!)
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