BS 161 1st Edition Exam 2 Study Guide Lectures 10 17 Lecture 10 Fundamental units of life all organisms are made of cells the cell is the simplest collection of matter that can live cell structure is correlated to cellular function All cells arise from pre existing cells Prokaryotic cells that don t have a nucleus bacteria Archaea lumped together with prokaryotes bacteria and example organisms that live in extreme environments Eukaryotic cells with a nucleus Protists single celled eukaryotes Composition of a cell Wet weight 70 water 25 macromolecules 5 ions and small molecules Dry weight 60 proteins 25 nucleic acids 10 carbohydrates 5 lipids Majority of nucleic acids in a cell are RNA The logistics of carrying out cellular metabolism sets limits on the size of cells The surface area to volume ratio is critical As the surface area increase by a factor of n2 the volume increases by a factor of n3 Basic features of all cells 1 Small want a high surface area to volume ratio 2 Obtain energy from environment Autotrophs Self feeders plants convert light into chemical energy Heterotrophs feed on other things everything other than plants 3 Selective in what comes in goes out membrane allows passage of certain materials selective permeability 4 Use genetic material to reproduce DNA The plasma membrane is a selective barrier that allows sufficient passage of oxygen nutrients and waste to service the volume of every cell Hydrophobic molecules ex Hydrocarbons can dissolve in the lipid bilayer and pass through the membrane rapidly Polar molecules ex sugars do not cross the membrane easily If a molecule cannot easily pass through but is needed transport proteins are used to convey it through a space within a dedicated Tran membrane protein Five types of transport across membranes 1 Passive transport movement of a permeable molecule across the membrane in unaided diffusion 2 Osmosis the passive diffusion of water across a membrane which has impermeable molecules 3 Facilitated transport net diffusion movement of an impermeable molecule across the membrane using a transporter 4 Active transport movement of an impermeable molecule from low to high concentration sides using energy 5 Bulk transport carrying the impermeable molecule across in a vesicle phagocytosis Lecture 11 Osmosis net diffusion of water net water movement across a membrane from high to low water concentration until it reaches equilibrium Goes until isotonicity a water balance is achieved Hypotonic if the solute concentration is lower outside vs inside the cell water will rush in causes cell to swell burst Hypertonic if the solute concentration is higher outside vs inside the cell water will rush out causes cell to shrivel Isotonic if the solute concentration is the same outside and inside the cell there is no net water movement the cell is normal Facilitated diffusion impermeable weakly permeable molecules go from a high concentration to a low concentration through a transmembrane aka integral protein energy is not required Ion channel proteins change conformation to move the ion Active transport change in the shape of transmembrane proteins using energy to transport molecules against a concentration gradient uses ATP hydrolysis to change transporter shape required for ion movement Membrane potential all cells generate one Helps bring in cations and expel anions Membrane proteins can change if their charge is made different can lose function Energy can be stored in an electric gradient of H Prokaryotic cells no nucleus DNA held in nucleoid no membrane bound organelles cytoplasm bound by the plasma membrane E coli has 5 x 106 base pairs circular Gram stain Positive is purple Negative is red Biodiversity more bacterial species being discovered due to advances in DNA sequencing and many species being unculturable Lecture 12 Antibiotics kill bacteria but don t kill animal cells because they do not react with animal cell components Eukaryotic cells Has DNA in a nucleus that is bounded by a nuclear envelope nuclear membrane Has membrane bound organelles mitochondria and chloroplast Has cytoplasm in the region between the plasma membrane and nucleus The nucleus Contains the cell s genetic material Enclosed by the nuclear membrane separates it from the cytoplasm Nuclear membrane is a double membrane inner and outer nucleus membrane each membrane consists of a lipid bilayer Pores regulate entry and exit of molecules Shape is maintained by nuclear lamina protein Nuclear matrix similar to cytoskeleton of cytoplasm Proteins get into the nucleus by being specifically transported there importin binds to NLS and brings specific proteins to nucleus Chromatin in the nucleus made of DNA and proteins Condenses to form chromosomes 23 pairs in humans Nucleolus located in the nucleus the site of rRNA synthesis and ribosomal subunit assembly 3 RNA polymerases in eukaryotes Pol I rRNA 90 of cellular RNA Pol II mRNA 3 Pol III tRNA 7 Ribosomes particles made of rRNA and protein Free ribosomes in the cytosol synthesis of intracellular proteins Bound ribosomes on the outside of endoplasmic reticulum synthesis of membrane and secreted proteins Lecture 13 Endomembrane system consists of nuclear envelope endoplasmic reticulum ER Golgi apparatus GA lysosomes plasma membrane Vesicles small membrane enclosed transport things around the cell can fuse with membranes or other vesicles ER biosynthetic factory Smooth ER lacks ribosomes synthesizes lipids metabolizes carbohydrates detoxifies proteins Rough ER ribosomes stud its surface ribosomes synthesize glycoproteins proteins covalently bonded to carbohydrates distributes transport vesicles is a membrane factory for the cell Signal peptide stretch of amino acids that serve as zip code for protein tells it where to go Signal Recognition Particle SRP recognizes signal peptide GA consists of cisternae flattened membranous sacs modifies products of the ER adds sugar to proteins sorts and packages materials into transport vesicles Cis face receiving side inside Trans face shipping side outside Flow of materials through endomembrane system ER transport vesicles cis golgi stack transition vesicles trans golgi stack transport vesicles fusion with plasma membrane Phagocytosis cell eating some cells engulf other cells forms a food vacuole defense mechanism cells try to rid the body of bacteria and viruses Autophagy lysosomes use enzymes to recycles the cells own organelles and macromolecules Pinocytosis cell drinking all