BS 161 1st Edition Exam 3 Study Guide Lectures 18 28 Lecture 18 Finishing up cell respiration fermentation regenerate NAD so that glycolysis can continue even without oxygen produces 2 ATP per glucose molecule 2 kinds alcohol and lactic acid human muscles use lactic acid fermentation when there is a lack of oxygen Photosynthesis photosynthesis the process that converts solar energy into chemical energy autotrophs producers of the biosphere heterotrophs consumers of the biosphere chloroplasts similar and likely evolved from bacteria have their own circular DNA and bacteria like ribosomes similar to the mitochondria in animal cells leaves are the major location of photosynthesis get their green color from chlorophyll stomata pores that allow oxygen to exit and carbon dioxide to enter mesophyll interior tissue of leaves contain chloroplasts thylakoids connected sacs in chloroplast contains chlorophyll stacked in columns called grana stroma dense fluid in chloroplasts oxygen comes from splitting the water molecules photosynthesis is a redox process water is oxidized carbon dioxide is reduced light reactions energy capturing reactions calvin cycle carbon fixing reducing reactions wavelength difference between crests or troughs of waves determines type of electromagnetic energy photosynthesis is only concerned with visible light 400 700nm light consists of discrete particles called photons or quanta pigments molecules that absorb visible light Lecture 19 green light is reflected and transmitted by chloroplasts all other wavelengths of light are absorbed absorption spectrum graph plotting a pigment s absorption vs wavelength action spectrum profiles the relative effectiveness of different wavelengths of radiation in driving a process when a pigment absorbs light it goes from a ground state to an excited state fluorescence when electrons fall back to ground state photons are given off photosystem consists of reaction center complex surrounded by light harvesting complexes light harvesting complexes funnel the energy of photons to the reaction center primary electron acceptor accepts an excited electron from chlorophyll a occurs in the thylakoid membrane z scheme aka linear electron flow transfer of electrons primary pathway produces ATP and NADH using light energy goes from photosystem II to photosystem I photosystem II best at absorbing wavelength of 680 nm photosystem I best at absorbing wavelength of 700 nm Chl ground state chlorophyll Chl excited chlorophyll Chl electron deficient chlorophyll H2O is split be enzyme replenishes electrons for electron deficient chlorophyll diffusion of protons H drives ATP synthesis cyclic electron flow uses only photosystem I and produces ATP but not NADPH Lecture 20 Calvin Cycle regenerates its starting material after molecules enter and leave the cycle builds sugar from smaller molecules second phase of photosynthesis carbon enters cell as CO2 leaves as sugar called glyceraldehyde 3 phosphate G3P cycle has to take place 3 times fixing 3 molecules of CO2 to make one G3P calvin cycle has 3 phases 1 carbon fixation catalyzed by rubisco 2 reduction requires a lot of energy reduces acid to a sugar opposite reaction glycolosis of 3 regeneration of CO2 receptor ribulose bisphosphate RuBP C3 plants first compound with fixed C is 3C C4 plants perform photorespiration doesn t produce ATP or sugar uses the enzyme PEP carboxylase release CO2 in bundle sheath cells some plants use crassulacean acid metabolism CAM open their stomata at night Lecture 21 main idea through signaling one cell can control what another cell is doing example epinephorine fight or flight epinephorine is hydrophilic and impermeable to the cell glycogen phosphorylate is not activated directly by epinephrine a signal ligand is received by a receptor transduced through the receptor then the cytoplasm and a cell type specific response is made paracrine one cell makes it a different cell responds to it autocrine same cell makes and responds gap junctions are very small pores not a lot can pass between cells proteins can t pass between hydrophilic ligands need a plasma membrane receptor know what hydrophilic and hydrophobic molecules look like Lecture 22 hydrophobic ligands have a receptor within the cell ex steroids gases and lipids two types of chemical ligands have different receptor sites nonpolar is inside the cell polar is outside the cell on the transmembrane receptor four types of receptor proteins g protein coupled receptor binds to g protein tyrosine kinase receptor kinase function is activating after binding ion channel receptor bind the ligand then increase decrease a specific ion entry to the cell intracellular receptor within the cytoplasm become activated transcription factors able to directly affect transcription Lecture 23 second messengers small nonprotein molecules or ions they amplify the signal examples cAMP IP3 DAG calcium Ca2 cyclic AMP cAMP made from ATP by an enzyme called adenylyl cyclase activates protein kinase A know what a kinase cascade looks like and does picture in book and on slide 38 from lecture a kinase cascade causes amplification glucose 1 phosphate doesn t exit the cell because the phosphate causes it to be charged and it doesn t look enough like glucose to pass through the membrane IP3 and DAG are made from membrane phospholipids by the enzyme phospholipase C they act to open up calcium channels in the endoplasmic reticulum scaffolding protein complexes of proteins look like three proteins linked together different cells can respond differently to the same signal if they have different intracellular transduction pathways cell cycle the life of the cell until it divides cell division cell reproduction cell proliferation chromosome replication starts at one ori origin of replication later a cell wall forms between separated nucleoids Lecture 24 interphase when the cell grows DNA is replicated mitosis division of the nucleus cytokinesis division of the cell growth must be coordinated with DNA replication check points ensure coordination different cells divide at different rates Gap 1 G1 cell gets signals and decides whether they are the right signals prepares for DNA synthesis check point here called start most important one DNA synthesis S replicated DNA takes 8 12 hours Gap 2 G2 doubles amount of DNA and prepares to condense chromosomes Mitosis M nuclear envelope is lost chromosomes are freely mixed in the cytoplasm spindle prepares chromosomes for