Credit to STEPHEN ESPOSITO 2011 BSC2010 Stroupe UNIT TWO LECTURE 7 phosphate group on its 3rd OH They are Before we start remember what a phospholipid consists of 2 Fatty acids on a Glycerol a 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 a prokaryotes DNA is in the nucleoid area of the cell not bound by a 1 DNA membrane than bacterial cells 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 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 toxins III 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 can not pack as closely so they are more fluid at moderate temperatures the activity of the cell a cis unsaturated lipids are bent more than trans unsaturated lipids so they 1 Cis lipids are more bent than Trans lipids b cholesterol a steroid limits lipid movement so it rigidifies membranes c when the temperature drops membranes stop moving and this can affect 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 regions Credit 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 ER Credit 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 e vesicles fuse with the membrane and contents end up outside of the cell II Selective Permeability A The cell communicates with its surroundings through the membrane either passively without help from the cell or actively with help from the cell 1 this is important because a if the cells ionic strength becomes uncoupled from its
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