Exam 3 Review Chapter 8 Photosynthesis 8 1 Overview Overall chemical reaction for photosynthesis o 6CO2 6H2O C6H12O6 6O2 Redox considerations o Oxidation of H2O electron donor light reactions o Reduction of CO to form higher energy carbohydrate Calvin cycle Chloroplast structure thylakoid membrane lumen stroma Photosynthetic electron transport chain compare to mitochondrial ETC o Photosynthetic ETC electron excited by light energy in PS II transferred to PS I captured in NADPH at end of chain electron in water molecule replaces excited electron protons accumulate in lumen used to drive ATP synthesis o Aerobic Resp ETC NADH is oxidized proton is moved across membrane oxygen is final electron acceptor proton gradient gives ATP synthase energy to synthesize ATP 8 2 The Calvin Cycle Takes place in the stroma what are the inputs and outputs o CO2 reduced by NADPH and incorporated into a carb molecule what is the role of ATP and NADPH o ATP phosphorylates 3 PGA is required for regeneration of RuBP o NADPH transfers 2 high energy electrons to 3 PGA what is the function of rubisco o Carboxylation addition of CO2 to the 5 carbon compound RuBP 8 3 Capturing Sunlight into Chemical Forms Chlorophyll poor at absorbing green wavelengths light absorbing head containing magnesium atom at its center and hydrocarbon anchoring tail Reaction center light energy is converted into electron transport electron energy are transferred from one reaction center to the next Photosystem II supplies electrons to beginning of ETC pulls electrons from water Photosystem I energizes electrons with a 2nd input of light energy Z scheme use of water as electron donor requires input of light energy at 2 places in ETC electrons used to reduce NADP Production of NADPH and ATP o NADPH receives electron at end of ETC is reduced by PS I NADP o ATP synthesized by ATP synthase using proton electrochemical gradient in reductase lumen Ferredoxin NADP reductase catalyzes a chemical reaction that produces reduced NADPH at end of ETC Be able to compare ETC of mitochondrial inner membrane with photosynthetic ETC on thylakoid membrane where electrons come from where they end up similarities and differences between the two 8 4 Challenges to Photosynthetic Efficiency Why how photosynthesis can generate damaging ROS reactive oxygen species o When NADP is in short supply absorbed light energy OR the energy associated electron can be transferred to O2 o O2 superoxide anion 2 peroxide o O2 o O2 O2 Role of antioxidants SOD H2O2 CAT H2O O2 o Neutralize reactive oxygen species o Beta carotene ascorbate vitamin C Chapter 12 DNA Replication 12 1 Overview Semiconservative replication each strand acts as a template one parental strand one newly synthesized strand New strands grow in 5 to 3 direction bases added to 3 end Replication fork s site where parental strands separate typically many along each chromosome Leading strand synthesized as one long continuous polymer 3 end pointed toward replication fork versus lagging strand initiated at intervals Okazaki fragments DNA polymerase o Can only function in 5 to 3 direction o Can only elongate the primer o Lagging strand must be replicated in fragments going backwards away from replication fork Okazaki fragments RNA primase primer needed to initiate DNA polymerization DNA polymerase has a proofreading function can correct its own errors Helicase unwinds parental double helix at replication fork Single stranded binding proteins bind the single stranded regions of DNA to prevent the template strands from coming back together Topoisomerase II works upstream from the replication fork to relieve the stress on the double helix 12 2 Replication of chromosomes Replication bubbles multiple origins along a chromosome replication fork on each side Telomerase replaces lost telomere repeats o Telomere shortening on lagging strand during each round of cell division o Addition of telomere repeats capping 12 3 Isolation Identification and Sequencing of DNA Fragments Polymerase Chain Reaction PCR targeted region of DNA is amplified o Denaturation heating so DNA strands separate breaking of hydrogen o Annealing cooling so primers bind o Extension optimal temperature for DNA polymerase each primer is o Needed in tube template DNA DNA polymerase two RNA primers bonds elongated nucleotide bases Taq polymerase remains active at high temperatures DNA polymerase would need to be replaced after each cycle PCR controlled DNA replication 3 stages Taq polymerase hundreds of DNA strands produced versus natural DNA replication occur on its own 2 segments of DNA produced Gel Electrophoresis determine size of DNA fragments electric current passed through molecules negatively charged move toward the positive pole move according to size bands made visible by dyes that bind to DNA Chapter 11 Cell Division 11 1 Cell division Eukaryotic cell cycle o M phase parent cell divides into 2 daughter cells Mitosis separation of chromosomes into 2 nuclei Cytokinesis division of the cell itself into 2 separate cells o Interphase time between 2 successive M phases G1 phase specific regulatory proteins are made activated S phase replication of entire DNA content G2 phase preparation for M phase G0 phase perform specialized functions liver nerve brain some permanently 11 2 Mitotic cell division Karyotype chromosome condensation compaction representative of a species Key terms related to chromosomes portrait formed by the number and shapes of chromosomes o Homologous chromosomes 2 of the same type of chromosome both o Haploid versus diploid numbers one complete set of chromosomes versus carrying the same set of genes 2 complete sets o Sister chromatids 2 identical copies in each chromosome o Centromeres hold together sister chromatids o Kinetochore structure on chromatids where spindle fibers attach o Mitotic spindle microtubules pull chromosomes into separate daughter cells Steps of mitotic division o Prophase chromosomes are visible centrosomes radiate microtubules o Prometaphase microtubules attach to chromosomes o Metaphase chromosomes align in the center of the cell o Anaphase sister chromatids separate and move to opposite poles o Telophase nuclear envelope reforms and chromosomes decondense 11 3 Meiotic Cell Division Meiosis I separates homologous chromosomes sister chromatids do not 2 daughter cells are now haploid but each chromosome consists of two identical sister chromatids Meiosis II like mitosis number of chromosomes stays the same
View Full Document
Unlocking...