Fluid mosaic model has proteins embedded in fluid lipid bilayer Membranes Cellular membranes have 4 components Phospholipid bilayer Transmembrane integral proteins Interior peripheral protein network Cell surface markers Phospholipids membranes foundation Membranes have organized structure that spontaneously form bilayers Nonpolar interior impedes the passage of water soluble substances key property of lipid bilayer Membranes picky about what passes through Phospholipid bilayer is fluid Hydrogen bonding of water holds the two layers together Phospholipids and unanchored proteins can move through the membrane Membrane fluidity can change based on composition and temperature Saturated fatty acids makes membranes less fluid unsaturated fatty acids Cholesterol can either increase or decrease membrane fluidity depending on the temperature Theres polar end and non polar ends on cholesterol molecules Membrane proteins Transporters Enzmes Cell surface receptors Cell to surface identity markers Cell to cell adhesion proteins Attachments to the cytoskeleton Structure relates to functions Diverse functions arise from the diverse structures of membrane proteins have common structural features related to their role as membrane proteins Anchoring molecules are modified lipids with nonpolar regions and domains linked to proteins Integral membrane proteins have at least one transmembrane domain that spans the lipid layer Pores Nonpolar regions within a transmembrane protein can create a pore Interior is polar and allows water and small polar molecules to pass Passive transport across membranes No energy is required Molecules move due to a concentration gradient Diffusion is movement of molecules from high concentration to low concentration Barrier hydrophobic interior that repels polar molecules Nonpolar molecules move until the concentration is moved Facilitated diffusion involves channel and carrier proteins Membrane is selectively permeable Osmosis net diffusion of water across a me membrane toward a higher solute concentration Channel proteins Open gate Hypertonic higher solute concentration Hypo lower solute concentration Isotonic same osmotic Aquaporin s facilitate osmosis Maintaining osmotic balance Extrusion contractile vacuoles Isosmotic Regulations marine organisms adjust internal concentration to match sea water terrestrial animals circulate isotonic fluid Turgor pressure plant cells and cells walls Example sodium potassium pump Animal cells have low internal concentration of Na and high external concentration To maintain the pump move na and K against their concentration gradient ATP energy Coupld transport Uses ATP indirectly Endocytosis Exocytosis Glucose NA transporter captures the energy from Na diffusion to move glucose against the concentration gradient Co transports Na and glucose Bulk transport occurs through vesicles and requires energy Moving large amounts of products through the lipid membrane is problematic Human genetic disease familial hypercholesterolemia the LDL receptors lack tails 0ne long continuous double strand fiber In the nondividing nucleus some expressed and some not expressed Typical human chromosome 140 million nucleotides long or 2 inches 9 30 13 Chapter 10 how cells divide Binary fission bacterial cell division one chromosome Septation production of septum separates cells other components begins with formation of ring FtsZ proteins Eukaryotic chromosomes Every species has a different amount chrom Humans have 23 pairs 46 chromosomes Chromatin Structure Nucleosome complex of DNA and histone proteins Promote and guide coiling of DNA DNA duplex coiled around 8 histone proteins every 200 Wrapped into higher order coils Karyotype array of chromosomes in an individual organism Humans are diploid 2 completes of chrom Haploid 1 set 23 chrom Pairs of chrom Are homologous each one is a homologue 5 phases of Eukaryotic cell cycle M phase mitosis and cytokinesis G1 S G2 Interphase Duartion of cell cycle varies Fruit fly embryos 8 minutes Mature cells take longer to grow Most variation in length of G1 resting phase G0 cells spend more or less time here M phase Mitosis 5 phases Prophase Prometaphase Metaphase Anaphase Telophase Prophase Promatphase Chromosomes condense spindle apparatus assembles and nuclear envelope breaks down Transition occurs after disamebly of nuclear envelope Chromosomes attach to the spindle Metaphase Alignment of chromosomes at equator Anaphase centromeres split sister chromatids separate 2 forms of movement chromosomes move toward poles poles move apart Telaphase spindle apparatus disassembles Nuclear envelope forms nucleolus appears in each new nucleus Cytokinesis cleavage of the cell into equal halves animal cells cleavage furrow Plants cells cell plate forms Fungi and some protists just weird Cell dicides to divide Primary point for external signal influence Control cell cycle Metaphase anaphase G1 S G2 M s G2 m Cell makes a commitment to mitosis Assesses success of DNA replication Late metaphase spindle Cyclin Dependent Kinases Enzymes that phosphorlate proteins cyclins group of regulatory proteins CDKS group of enzymes Cells insures that all chromosomes are attached to the spindle Partner with the different proteins cyclins at different points in the cell cycle CDK cyclin complex called mitosis promoting factor MPF Activity of cdk is controlled by the pattern of phosphorylation Anaphase Promoting checkpoint APC At the spindle checkpoint presence of all chromsomes at the metaphase plate and the tension on the microtubbles between poles Growth factors act by triggering intracellular signaling systems Growth factors can override cellular controls otherwise inhibit cell division Unrestrained uncontrolled growth of cells Failure of cell cycle Two kinds of genes can disturb the cell cycle when they are mutated Cancer Tumor suppressor genes proto oncogenes Tumor suppresser genes P53 plays a key role in G1 checkpoint 53 proteins monitors intergrity of DNA Function prevent mutated cells from going through the cell cycle P53 is absent or damaged in many cancerous cells Retinoblastoma susceptibility gene predisposes in Inheriting a single mutated copy of Rb one good copy Rb proteins binds important regulatory proteins and prevent stimulation of cyclin Proto ongenes Normal celleur genes that become on when mutated can cause cancer Only one copy needs to undergo Some encode receptors for growth factors If receptor is mutated in on cell no longer