Week 7 Notes (Chapters 8, 9)
Week 7 Notes (Chapters 8, 9) Bio 1510
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This 11 page Class Notes was uploaded by Nausheen Zaman on Sunday October 18, 2015. The Class Notes belongs to Bio 1510 at Wayne State University taught by Dr. Nataliya Turchyn in Summer 2015. Since its upload, it has received 120 views. For similar materials see (LS) Bas Life Mch in Biology at Wayne State University.
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Date Created: 10/18/15
Chapter 8 Cont A Closer Look at Light Reactions 0 O O Occur in the thylakoid membrane Called lightdependent reactions because they depend on sunlight Steps 1 H20 donates 2 lowenergy e to Photo2 es always move from P2 to P1 0 H2O oxidizes to O2 2 P2 receives lowenergy es es absorb photons with 680 nm energy become excited move to higher energy levels 3 High energy es then donated to plastoquinone PQ Q mobile electron carrier carries high energy es from P1 gt b6f complex 0 B6f very similar to bc1 in mito membrane acts as H pump 0 More H in thylakoid space than in stroma b6f complex acts as H pump by pumping H ions from stroma to thylakoid space upagainst concentration gradient using active transport only accepts e energy to move H up concentration gradients gt creates H gradient needed to make ATP synthase work to make ATP 0 When H ions rush through ATP synthase from the thylakoid space to stroma down the concentration gradients using passive transport facilitated diffusion gt ATP synthase rotates to combine ADP with Pi to make ATP chemiosmosis 0 ATP produced in the stroma floating around because ADP and Pi are floating in the stroma as well 3 b6f complex donates e to plastocyanin mobile e carrier 4 Plastocyanin delivers low energy e to P1 which then absorb photons with 700 nm energy 5 Low energy es become excited again as they go through P1 where they are picked up by Ferredoxin Fd carries e from P1 a NADP reductase 6 Delivered to NADP reductase enzyme reduces NADP by receiving 2e combines with H and reduced to NADPH 0 H2O oxidized to O2 NADP reduced to NADPH o E carried by pQ more energy than e carried by pC but less energy than e carried by Fd e pC lt e pQ lt e Fd o NADP final e acceptor in photosynthesis light reactions 0 SUMMARY H2O donates electrons to Photo2 gt pQ plastoquinone gt b6f complex gt pC plastocyanin gt Photo1 gt Fd Ferridoxin gt NADP productase gt NADP 2e H reduced to NADPH I Products ATP NADPH both produced and released in stroma 02 released in thylakoid space exergonic reaction 3 differences in P1 and P2 I P2 receives 680 nm light P1 receives 700 nm light I H20 donates 2e to P2 while plastocyanin donates 2e to P1 I P2 uses high energy e to make ATP P1 uses high energy e to make NADPH O o Photosynthesis vs Cellular Respiration Function in opposite directions 0 System 3 uw ill 0 Why HotDry Weather is a Problem for Some Plants 0 Under hot arid conditions leaves lose H20 by evaporation through stomata o Stomata close up as a response but 02 concentration increases in plants I When 02 instead of C02 binds to RuBP photorespiration occurs 0 Photorespiration I Requires sunlight I Like aerobic respiration uses 02 to produce C02 and H20 I Unlike aerobic respiration it uses ATP endergonic instead of Making ATP I Wasteful process for plants 0 They instead use C4 pathway to save energy 0 C4 Pathway Sugarcane and Corn 0 When inorganic C is incorporated into 4C organic compound oxaloacetate o Rubisco only found in bundle sheath cells of C4 plants 0 Works by separating processes into two different cells carbon fixation mesophyll and Calvin Cycle bundlesheath cells 30 ATP needed to make 1 glucose Called C4 pathway because the PEP is turned into an 4C oxaloacetate gt converted to malate gt travels through plasmodesmata gt bundle sheath cells gt goes through decarboxylation to be made into C02 used by rubisco in calvin cycle to make GBP gt glucose and pyruvate gt Pyruvate travels back into mesophyll thru plasmodesmata to be converted back into PEP o Majority of plants are C3 plants carry out C3 pathway ONLY and don t have C4 pathway 0 C3 Pathway o Occurs only in mesophyll cells 0 Rubisco and chloroplasts found in mesophyll cells of C3 plants 0 18 ATP to make 1 glucose Calvin Cycle only needs 18 ATP as well 0 C4 pathway although overcoming problems of photorespiration does have a cost 0 6 C02 needed to make 1 glucose 2 ATP needed to move 1 C02 in malate form from mesophyll gt bundle sheath cells 0 Spend an additional 12 ATP compared to Calvin Cycle I C3 plants use only 18 ATP to make 1 glucose carry out Calvin Cycle ONLY 0 C4 photosynthesis is advantageous in hot dry climates where photorespiration would remove more than half of C fixed by usual C3 pathway alone o CAM Plants Pineapples and Cacti 0 found in extremely hot dry environments 0 Have both pathways that occur in mesophyll cells but happen at different times of the day CAM plants keep stomata slightly open at night to make C4 function C02 PEP gt oxeloacetate gt malate stored in cell C4 decarboxylated gt C02 pyruvate rubisco gt calvin cycle gt G3P gt glucose 0 CAM plants spend more ATP to make glucose than C3 plants but probably don t indicate how much ATP is used in CAM plants same amount of ATP as C4 plants O O 0 Chapter 9 Cell Communication 0 Cell Talk 0 Signaling cell sends signals blue dot signalsligand can be protein peptide amino acid fatty acid steroid hormone or dissolved gases 0 Target cell receives signals only receives signals with a receptor attaches to the signal sent out by signaling cell only when it has RECEPTOR cell 0 Receptors can be found in the plasma membrane or inside the cell I Plasma membrane cellsurface receptors I Inside the cell intracellular receptors o How Do Cells Know What s Going On Around Them Signal transduction pathway converts info from signal into a cellular response often studied by pharmaceutical companies Ligands are usually hydrophilic like water bind to cell surface receptor protein peptide or polar amino acid Ligands that are hydrophobic hate water bind to intracellular receptors via simple diffusion to move across plasma membrane fatty acid steroid hormone dissolved gas 0 0 Different Types of Signaling Direct contact contactdependent O O O 0 When molecule on plasma membrane of one cell contacts receptor molecules on adjacent cell with gap junctions Facetoface conversation Important in early development where tissues that have similar properties begin to take on different functions Gap junctions formation of gaps made of connexons form between plasma membrane of adjacent animal cells allowing them to exchange inorganic ions amino acids and simple sugars NO PROTEINS too big to pass through gaps Animal cells only plants have plasmodesmata Paracrine signaling Para near Signaling cell releases shortlived ligands into extracellular fluid that affects several nearby target cells Target cells located very near signalling cell but do not touch each other Shortlived ligands crossfactors proteins that stimulate cell division and growth Involved in wound healing if you are injured cross factors tell nearby cells to increase in number and stimulates nearby cells to regrow and heal the wound Endocrine signaling I Signaling cell releases longlived ligands hormones that travel through bloodstream to induce changes in far reaching target cells Both animals and plants use this mechanism extensively Endocrine cells found in endocrine glands ie when glucose level increases pancreatic beta cells release insulin into blood delivered to cells that have insulin receptors only liver cells skeletal muscle fat cells and they convert excess glucose to glycogen liverskeletal fatty acids that react with glycerol to make fats fat cells Synaptic signaling O I Nerve cell releases shortlived ligands neurotransmitters into the gap synapse when forms between nerve and target cells Autocrine signaling I Auto cell I Cell sends signals to itself I Signaling cell produces ligands that bind to receptors on the same cell causing the cell to respond to its own signalsligands I Plays a very important role in immune response Tcells help destroy harmful antigens produces cross factors produces a signal to a cross factor gt binds to receptor on tcells gt tcells begin to divide quickly and this increases the defense response in tcells o Intracellular Receptors O O lntra inside Ligands for intracellular receptors are hydrophobic pass through membrane by simple diffusion Steroid hormone testosterone estrogen cortisol adrenal glands fatty acids dissolvable gases hydrophobic ligands Steroid hormone uses simple diffusion to move across plasma membrane and binds to steroid hormone receptor nuclear receptors cause changes in transcription in the nucleus eukaryotes only Transcription is part of gene expression gt when gene is transcribed and translated When steroid hormone binds to receptor receptor becomes active conformational change Hormone receptor complex moves into nucleus through nuclear pore binds to DNA turning transcription of specific gene on or off Stewital hurmuml t i li39 i ll fmrl estrogen membrane and blind to cytoplasmic recEplore W 7 39 L47 39 Y f l 2 Hormone binding alters receptor conformation so it no longer tingle inhibitor Gellular response is a change in gene expression 41 DNAbinding I site Exposed RH 7 gt UNAbinding eite HQEl d 3 Hormone receptorquot 7 complextranslocates i m mama fill transcription i 39I39i Er 139 villiquot quotill u 397 r r inhibitor Transcri ptfien activating domain in 9 Jr 43 Hormone receptor complex binds to DINJEL Thi uaually turns on transcription but can also turn it off Nitric Oxide Signaling O O Intracellular receptor found inside cell NO nitrate oxide gas hydrophobic ligand binds to nitric oxide receptor guanylyl cyclase Nerve terminal releases neurotransmitter into synaptic gap gt binds to target cell Synaptic signaling exists between nerve cell and endothelial cell gt endothelial cells found in our blood vessels produce nitric oxide gt outside of endothelial cells are smooth muscle cells arteries and veins only regulate the diameter of the arteries and veins by constrictingdilating when needed gt N0 gas diffuses through endothelial cells via simple diffusion gt NO binds to NO receptor found inside smooth muscle cells signaling between endothelial and muscle cells is paracrine gt smooth muscle cells relax and arteries and veins become wider dialate phasodialation gt blood flow increases Controlled by Viagra 1 Evtlii ll Elil iii nerve terminal ng 1 u neurotransmitter l ill bound to MD gimnfhil W Eln l Sitingtn muscle It l 739 EE39 arginine I 1 V V rm l I I elitism emanation V f quot ennui mrrusmrr V a license nEnBEiatiiES a is endothelial l 1r cell Viagra l I Used to treat erectile dysfunction in men when men cannot get erections Erections occur when smooth muscle cells in penal arteries relax allows increased blood flow into penis hardens o Nerve cells release neurotransmitter gt binds to receptor in membrane of endothelial cell gt endo cell produces N0 gas gt diffuses into several nearby smooth muscle cells in penal arteries gt gas binds to NO receptors guanylyl cyclase acts as an enzyme gt GC becomes active gt activates GTP to cGMP causes smooth muscle cells to relax and erections to occur 0 Erections inhibited by phosphodiesterase converts cGMP gt GMP men with erectile dysfunction has excess phosphodiesterase o Membrane Surface Cell Receptors o Majority of receptors are in plasma membrane 0 3 classes all use hydrophilic ligands I Do not cross cell membrane 0 Chemicallygated ion channels I Open to let specific ions such as NA K CA2 or CI to pass through membrane in response to the building of a ligand neurotransmitter I When neurotransmitter binds to receptor receptor behaves as an ion channel only specific ions pass through membrane acetylcolon receptor gt chem gated ion channel found in skeletal muscles and become active when acetylcolon shortlived ligand binds to receptor and receptor acts as a sodium ion channel allowing sodium ions to enter skeletal muscles allowing muscles to contract I Acetylcolon receptor is found in the cell membrane lICJ S EN K 39 0 Enzymatic receptors I Act likeassociate with enzymes found inside the cell I Become active when ligands bind to receptors gt cellular response 0 Almost all are protein kinases phosphorylate themselves andor other proteins O G proteincoupled receptors GPCRs Receptor Tyrosine Kinases RTKs Most common enzyme receptors Influence cell cycle cell migration cell metabolism and cell proliferationdivision Each RTK monomer is a single transmembrane protein that passes the plasma membrane only once as an alpha helix 2 different domains 0 Extracellular ligandbinding domain binds ligands gt can be crossfactors short lived or hormones long lived o Intracellular kinase domain consists of many tyrosines amino acid Dimerization coming together of two kinases activates kinases each kinase transfers one Pgroup from ATP gt tyrosine amino acid autophosphorylation gt phosphorylated tyrosine kinases interact with other proteins to elicit cellular responses Binding of ligands to RTKs gt come together to form dimer dimerization to associate together gt activates kinases gt each kinase transfers phosphate from ATP gt tyrosine of dimer partner autophosphorylation gt these phosphorylated tyrosine kinases phosphorylate other proteinsinteract with other proteins aiding in cellular response lnsulin Receptor Belongs to RTKs Activated by insulin and lowers blood glucose Hormone hydrophilic and longlived ligand lnsulin receptors found in skeletal muscle and liver cells E The xSubunit ef ene iar39ieuiini reeepter pheeeheryleiee the ether eil eeirig the ineulin reepenee preteins ie be eeiiaieieei Converting glucose to glycogen decreases glucose levels in out blood MmHil in i5quot lineuiirireeeeier 1 a 39il insulin hindst the extireeell ulet damein ell the u eu un l el ll ie I ineulin reeepteir a w a l ht iv 1 m in aquot g Dieul de bridge Insulin seeperiee preteirii Pheepmwl eied ineuliri veepWee preteine eelivate glyeegen emiiiiitl39ieee V 4i Elyeegen eyniheee mneerie glueeee inte glyeegen Kinases vs Phosphatases Protein kinases phosphorylate proteins turning their activities on or off Some proteins become active in phosphorylation while other proteins are turned off from it Divided into 2 groups 0 Tyrosine kinases phosphorylate tyrosines ONLY 0 Thryonine kinases phosphorylate either serines or thryonines ONLY cannot phosphorylate tyrosine Protein activated by phosphorylated is deactivated by dephosphorylation o Phosphatases enzymes that dephosphorylate phosphorylated proteins turning their activities on or off
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