General Biology Lecture
General Biology Lecture BIOL 1A
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This 21 page Class Notes was uploaded by Nettie Herzog on Thursday October 22, 2015. The Class Notes belongs to BIOL 1A at University of California - Berkeley taught by Staff in Fall. Since its upload, it has received 26 views. For similar materials see /class/226652/biol-1a-university-of-california-berkeley in Biology at University of California - Berkeley.
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Date Created: 10/22/15
Terminator Technology Having invested considerable resources into the production of genetically engineered plants it is often beneficial to prevent the formation of viable seeds that contain the genetically engineered genes This can be illustrated by examining the production of soybean seeds For example the company Monsanto has developed glyphosate resistant soybean plantsseeds Glyphosate is an herbicide that kills plants by inhibiting the plantversion of Enol Pyruvate Synthase EPS which is needed for the production of some of the aromatic amino acids The bacterial version of EPS is not inhibited by glyphosate or certainly not as much as the plant version Monsanto has made transgenic soybean plants that contain the bacterial version of Enol Pyruvate Synthase EPS They were made available in 1996 and within less than 10 years over 85 of all soybean fields in the US were planted with glyphosate resistant seeds A farmer buys the seeds plants the seed and then at harvest time they harvest the bean kernelsseeds These seeds are glyphosate resistant and rather than buy new seeds from Monsanto next season the farmer could simply plant some of this year s crop next season unless some special modification was taken to prevent those seeds from being able to germinate Remember Monsanto is in the business of selling seeds A farmer buys seeds and plants the crop Consider those plants to be the F1 generation These plants produce seeds that are the F2 generation lfthe F2 seeds were viable then the farmer could plant some of their harvest and they would have glyphosate resistant plants You don t want to affect seed production in the parental plants since it is the soybean seed that is harvested and sold by the farmer You need to find a way to allow seed production so the farmer can sell their harvest yet prevent seed germination if the farmer were to plant their harvested seeds Terminator technology is the general term used to describe this approach As illustrated in lecture it can be complicated Monsanto must control the technology to prevent seed germination by the farmer It would be relatively easy to kill developing plants but Monsanto must also be able to grow their own plants to produce the seeds they sell then make sure the farmer cannot do the same Thus they need to design a system that automatically prevents germination in the farmer s harvested seed yet allows Monsato to produce seeds to sell The general approach is diagrammed below There will be three components to the system The first component that will be discussed is the mechanism that prevents seed germination ie termination The second component that will be discussed is the system that controls when termination occurs The final component is a system that allows Monsanto to control the timing of termination so they can generate seeds that they can sell Refer to the following diagram Plea FRT FRT RIP Plea stands for a promoter that is activated late in embryonic development Don t forget that when the seed develops there is an embryo inside it FRT represents a specific DNA sequence that is recognized by a specific DNA recombinase this enzyme will be discussed later RIP is a gene that encodes a Ribosome Inhibiting Protein If RIP is expressed within a cell the cell dies and hence in this case the developing embyro dies However Plea must be adjacent to the RIP gene for RIP to be expressed This was not made clear in lecture Without recombination RIP is not expressed due to the large intervening sequence between the FRT s If a specific recombinase that recognizes FRT is present then there is INTRAMOLECULAR recombination This recombination removes the large intervening sequence between the FRT s Notice that the recombination is NOT occurring during meioisis but occurs during the mitiotic cell cycle This is illustrated below in two illustrations The arrows indicate the position of recombination before recombination Note the placement of the promoter after recombination Plea FRT FRT RIP Before recombination Plea gtFRT RIP m After recombination Note RIP is now under the control of Plea Since the promoter is specific for late embryonic development the seed develops fine but the embryo does not Thus you don t affect seed development much except for the absence of a viable embryo Also note that this change is permanent the piece of DNA containing the intervening sequence is lost during cell division it lacks an origin of replication and centromere and it is impossible for it to reinsert into the chromosome Controlling the activity of recombinase There is a second genetic locus that encodes a recombinase that is under the control of a specific promoter PreC When the promoter is active the recombinase gene is transcribed the mRNA is translated and the protein product recom binase can function by catalyzing intramolecular recombination at FRT sites There are several possible approaches for controlling the promoter If the promoter is constituitive then recombinase is constitutively produced Monsanto however needs to inactivate the recombinase when they are producing seed so that the seeds they produce have viable embryos Monsanto could apply a chemical that binds to the promoter and blocks transcription of recombinase However this would require that they apply this chemical at every generation ifthey forgot to do so they would never be able to recover the line again it would be dead The approach they used was to introduce an additional gene that produces a repressor that binds at the Prec The repressor is under the control of constitutive promoter PC Therefore the repressor protein is made constituitively no recombinase is made and no recombination occurs and seeds are produced with viable embr os This allows Monsanto to produce as many seeds as they want to continue their line HRepressor Recombinase F rec PC When Monsanto is ready to sell seeds they need to activate the recom binase by treating their harvested seeds with a chemical that turns on the recombinase in the seed being sold to the farmer The chemical blocks the repressor from binding to the Prec Thus when those seeds grow into plants they contain cells that contain DNA which has no intervening sequence between Plea and RIP due to recombination The plants grow fine and make fairly normal developed seeds but the seeds produced by that plant do not have viable embryos Why Because only the Plea has the RIP gene and that promoter is active only in embryonic cells and only during late embryonic development Hence the seeds develop fairly normal but lack viable embryos The farmer can sell their crop but the seeds are not viable To summarize because the Plea promoter driving the RIP gene is active late in seed development but before embryo development is complete Monsanto can treat fully developed seeds with the chemical to allow the recombination event to occur but RIP will NOT be expressed in those seeds because the time for Plea expression is over for that generation When those seeds are planted they grow into healthy adult plants which contain cells that have undergone intramolecular recombination When it comes time for the plants to produce seed the RIP gene is expressed Seeds develop fine except for the absence of a viable embryo Because the recombination is permanent there is nothing the farmer can do to make the seeds viable On a side note I imagine there is currently research being conducted to generate glyphosate resistant cocoa cannabis poppy plants etc as glyphosate is quite commonly used to eradicate these plants This research if being done is probably not widely advertised Specialized organs exchange materials with the environment Circulatory systems ensure that substances rapidly reach all cells of the body from these organs Gills and lungs exchange gasses Alimentary canal exchanges nutrients Liver and kidneys exchange wastes Ultimately exchange must occur at the cellular level There are several types of internal transport systems in animals 1 Gastrovascular cavities 2 Open circulation 3 Closed circulation Gastrovascular cavity is continuous with the aqueous environment Water is drawn into the mouth and circulates around the cavity Open circulatory system arthropods most mollusks Circulatory fluid escapes the vasculature and bathes organs directly hemolymph Heart pumps hemolymph Heart out to sinuses through vessels 4s Hemolymph in sinuses surrounding organs fl Tubular f rl A Anterior Lateral vessel vessels O t When the heart relaxes hemolymph returns to heart through pores ostia Closed circulatory system earthworms squids octopuses vertebrates Blood is confined to vessels and is not in direct contact with tissue cells Blood is distinct from interstitial fluid Dorsal vessel main heart Auxiliary Ventral In each organ hearts vessels Interstitial Small branch vessels lluld Blood exchanges materials with the interstitial fluid which bathes the cells Vertebrate Hearts Closed circulatory system composed of a heart and vessels cardiovascular 3Q 1 or 2 atria chambers which receive blood returning to the heart 1 or 2 ventricles chambers which pump blood out of the heart Veins return blood to the heart Arteries leave the heart Capillaries are tiny vessels where exchange with tissues occurs Two chambered heart shes Three chambered heart 39ogs amphibians many reptiles Glll ca lllarles Lung and skin capillaries Systemic capillaries Loss of BP during passage through gill capillaries decreases BP in systemic capillaries Double circulation ensures vigorous ow of blood to the brain muscle and other organs because blood is umped a second time after it loses ressure in the lungs This limits O2 delivemto tissues and limits maximum metabolic rate P P Four chambered heart crocodilians birds mammals 2 atrium 2 ventricle Lung caplllaries The heart keeps oxygen rich blood completely separated from oxygen poor blood This enhances delivery of O2 to all parts of the body and restores pressure after blood passes through the lungs Systemic aplllarles Mammalian Cardiovascular System Right atrium Right ventricle Pulmonary arteries rs mic Pulmonary capillaries Pulmonary veins Left atrium quotquotquotm quot Leftventricle Systemic arteries Systemic capillaries Systemic veins Right atrium F Pullimml HS 7 All mgan am ussua 1174 Man Mg Phases of the Cardiac Cycle Systole contraction of ventricle amp ejection of blood from ventricle Diastole relaxation of ventricle ventricular filling amp atrial contraction 3 How do we maintain constant unidirectional flow Structure of the Heart 3 layers 1 Simple squamous epithelium endothelium amp CT 2 Cardiac muscle 3 CT amp simple squamous epithelium Structure of blood vessels 3 layers 1 Simple squamous epithelium endothelium amp CT 2 Smooth muscle amp elastic sheets 3 CT Cardiac muscle contractile cells Striated involuntary specialized 7 to contract rhythmically quot Specialized junctions Intercalated discs Parallel to cross striations anchor cells together Cardiac muscle fibers encircle the heart chambers wringing action to empty chambers 1 m Ep Largest arteries next to the heart maintain constant blood flow Large amount of elastic tissue in smooth muscle layer Walls distend during contraction systole as they fill with blood Elastic walls recoil during relaxation diastole Valves ensure one way flow 2 atrioventricular valves 2 semilunar valves Semilunai vaivc UQE H 394 ml i u fili39 ii Systole Ventricle starts to contract Ventricular pressure becomes greater than atrial pressure AV valve closes Ventricular pressure becomes greater than aortic blood pressure Aortic semilunar valve opens Semilunarvalvroboe Diastole Ventricle muscle relaxes l Ventricular pressure becomes less than aortic blood pressure Aortic semilunar valve closes l Ventricular pressure becomes less than atrial pressure AV valve opens Rapid filling of ventricle begins In late diastole get atrial contraction Heart sounds 1st sound closing of AV valves at the beginning of systole 2nd sound closing of semilunar valves at the beginning of diastole How do we maintain appropriate timing of atrial and ventricular contractions Gapjunctions 39 cwh 39 Conduct electrical impulses from a cell to cell allowing cardiac cells to contract in unison l t 4 mum JJ twp it m lntarcalatsd disk mum Cardiac muscle conducting cells Not contractile specialized for generation and conduction of electrical impulses in a rhythmic pattern pacemaker cells Sinoatrial SA node Cardiac pacemaker Spread through atria via gap junctions Atrioventricular AV node Delay Ventricular conducting fibers to apex of ventricle Spread through ventricle via gap junctions N 0 5 U1 Electrocardiogram ECG EKG a p ven mubr venumubr depobnza on deplanza on repobnzanon node conduc on Stroke volume and cardiac output Amount of blood ejected with each cycle stroke volume Total volume of blood ejected per unit time cardiac output Cardiac output stroke volume x heart rate CO SV x HR CO SV x HR At 70 beatsminute and a stroke n volume of 75 mlbeat cardiac output 52 literminute All of blood volume is pumped through the circuit each minute Takes just seconds for O2 and nutrients to reach all tissues Symemm cucumuon CO can increase to 35 litermin during exercise All organs and tissue DlhE man lungs Regulation of heart rate and stroke volume 1 Neural 2 Hormonal Heart rate Regulation alters the rhythm of the SA node and can increase or decrease HR from the resting value Stroke volume Regulation alters the strength of contraction of cardiac muscle and can increase or decrease stroke volume lnverse relationship between heart rate and the size of an animal Related to the higher metabolic rate of the smaller animals and their increased need to deliver 02 Elephant 25 beatsmin Mouse 700 beatsmin Blood Flow Medium arteries Lead to organs or regions Extensive amount of smooth muscle Walls constrict and dilate to regulate distribution of blood flow Arterioles Lead to capillary beds Small vessels but extremely numerous Overall they have a large surface area and contribute to V n resistance to blood flow Walls constrict and dilate to g regulate blood pressure 7 High pressure pressure 39 Hydrostatic pressure energy forces blood to flow Hydrostatic pressure is higher at the aorta due to contraction of ventricles and high elastic recoil of aorta wall Blood flows down the pressure gradient towards veins Friction along vessel walls causes resistance to flow Loss of pressure energy due to overcoming this resistance Friction along vessel walls causes resistance to flow Loss of pressure energy due to overcoming this resistance Pressure mm Hg v I m I ca In to g 5 s 2 g 2 s gt lt g 8 2 E g S q a lt c a gt a lt I o d gt High pressure LOW pressure Flow delta P R Flow high pressure low pressure resistance to flow of entire circuit low pressure about 2 mmHg high pressure mean arterial pressure MAP about 95mmHg delta P about MAP resistance to blood flow of entire circuit total peripheral resistance TPR Flow C0 5 Mean arterial pressure MAP MAP CO X TPR BP changes with SV HR and TPR Regulation of mean arterial pressure Baroreceptors are arterial receptors that sense changes in blood pressure A decrease in blood pressure causes increased HR increased SV and increased TPR All of which will increase MAP Caraiid sinus Am baruracaplors TPR increases in response to constriction of arterioles Why must we regulate blood pressure Regulation of blood volume Fluid moves across capillary walls by bulk flow Driving force for bulk flow pressure gradient Filtration movement of water and substances from the lumen of the capillary to the interstitial space A 3 quotV Reabsoerion movement of water amp substances from the interstitial 39i 7 space to the lumen of the capillary wall Capillary h drostatic pressures P V Filtration pressure 30 mm Hg Filtration pressure 2 mm Hg Hydrostatic pressure gradient falls but still favors filtration entire length of capillary Water moves from capillary to interstitial compartment due to hydrostatic pressure Capillary oncotic osmotic pressures 73625 quotK Oncotic pressure is constant and favors reabsorption along entire length of capillary Water moves from interstitial to capillary compartment due to oncotic pressure Respiratory medium sources of 02 for organism 1 Air for terrestrial animals Atmosphere 21 02 easier to ventilate air 2 Water for aquatic animals 02 varies considerably always less than air Advantage keeps respiratory surface moist Respiratory surfaces include 1 Entire surface area of animal every cell is close to the respiratory medium 2 Entire outer skin dense network of capillaries just beneath the skin 3 Respiratory organs 1 Gills 2 Tracheae 3Lungs Gills Outfoldings of the body surface total surface area of the gills is much greater than of the body Oxygempoor cm 39 arch Direction 39 322mmh of water V quot0 r V a b Vquot WNW 39 vessel V 3 t r Water flow Gill filaments Gills in bony fish are ventilated by the continual current of water entering the mouth and exiting at the back of the gill cover Exchange by diffusion always down concentration Countercurrent ow of blood and water ensure maximum exchange Blood 90 saturated with 02 Water flow OVel39 Blood flow lamellae through ShOWing lamellae 02 showing 02 cnmmwem n n is in as n Without countercurrent maximum loading would be to equilibrium or 50 saturated at most Terrestrial animals 1 O2 and 002 diffuse much faster in air than in water so respiratory surfaces do not have to be as well ventilated Less energy is expended on ventilation 2 Respiratory surfaces continually lose water to evaporation Decrease evaporative loss by folding W inside body Tracheal systems Insects Air tubes branch throughout the insects body Largest tubes tracheae Finest branches extend all the way to surfaces of most cells Body wall Air sacs near organs that require large supply of 02 Lungs most terrestrial vertebrates Lungs are restricted to one location A circulatory system is required for gaseous transport throughout the body internal mantle of land snails book lungs of spiders lungs of terrestrial vertebrates Respiratory Circulatory System SlStem Lungs composed of 1Respiratory passages respiratory surface epithelium where gaseous exchange occurs alveoli 2Conducting passages bring air to and from the respiratory passages A dense network of capillaries is immediately adjacent to the epithelium of the respiratory surface quot 39 1 150 million alveoli per lung in humans Mammalian Respiratory System Conducting passages Nose nasal cavities Pharynx Larynx Trachea Bronchi Bronchioles Respiratory passages Respiratory bronchioles Alveoli Airblood diffusion barrier 1 Fluid lining alveolus 2 Alveolar cell 3 Interstitial space 4 Endothelial cells of capillary About 02 microns thick 75 square meters surface area Gaseous exchange A steady state is maintained The rate of O2 consumption by cells rate added to blood at lungs The rate CO2 produced by cells rate CO2 leaves blood at the lungs Partial pressure of a gas Component of gas pressure exerted by an individual gas Sum of all gas pressures atmospheric pressure 760 mm Hg at sea level Po2 760 mmHg x 21 02 160 mmHg Inhaled Hr Exhaled alr Egg uvawR Egg Aligum E 39 T lms quot2 W cell c 53 quot Concentration rm r gradientdrives the diffusion of 02 from WWW alveoli to blood and quot39M from blood to tissues Pulmmuy urlurlea Concentration mm gradients drive quot quotWquot diffusion of CO2 from tissues to blood and from blood to alveoli Syslamll veins Ventilation Delivers O2 to the alveolus and increases plasma OZ Removes COZ from the alveolus and decreases plasma C02 Hypoventilation HypoVentil ation decreased ventilation 302 C02 for metabolic rate Hyperventilation Hyperventilation increased ventilation for metabolic rate 1P02 coz Transport of Oxygen in Blood Respiratory pigments proteins with metal atoms built into their structure Hemocyanin in arthropods and many mollusks OZ binding component is copper blue coloring Dissolved in plasma not found in cells Hemoglobin in almost all vertebrates OZ binding component is iron red coloring Packaged into cells allowing higher concentration without altering osmotic properties of plasma 98 02 carried on hemoglobin in humans Red Blood Cells V 7 About 45 of volume of blood About 25 trillion in 5 liter of blood 7 micron diameter biconcave discs Hemoglobin lls the cytoplasm 13 of mass of cell 0 mitochondria rough ER etc High surface to volume ratio aids in diffusion of gasses throughout the cell Energy by glycolysis Transport of 02 1 Dissolved in plasma 2 2 Reversiny combined with hemoglobin 98 oxygenation Hemoglobin has 4 identical subunits each with a heme group containing iron Hb can carry 4 O2 molecules Heme group Iron atom 02 loaded lnlungs b 0 unloaded m tissoes Polypepude ham Oxygenation of hemoglobin exhibits cooperativity Binding of each oxygen molecule makes it easier for the next to bind Release of each oxygen molecule makes it easier for the next to release easy on difficult off amp 5 100 lt E l 393 so i O 39 O 7 39 WmMammal in WWW mmmmmmmmmmmmmm gs e g so g I easy off 2 40 difficult g 1 on DISSOCIatIOl i curve 3quot 20 for hemoglobin O I I l 0 l l 39 Po mm Hg Dissociation curve for hemoglobin 100 E I O unloaded from 5 hemoglobin during E 30 normal metabolism E O reserve that can 2 60 1 be unloaded from 5 I hemoglobin to g i tissues with high 3 4 metabolism I I 39 3 39 39 a 20 N l l O o I t I 1 139 Po2 arterial blood 0 20 40 60 80 100 A T i 100 mmHg Tissues Tissues Lungs during at rest Po2 venous blood exermse Pomm Hg 40 mmHg Transport of CO2 in venous blood 1 Dissolved in plasma 10 2 Bound to proteins especially hemoglobin 30 3 As bicarbonate ions 60 nco In arterial blood 90 of CO2 is transported as bicarbonate ions Enzyme carbonic anhyd rase CO2 H20 HZCO3 HCOa39 H co smrcell a rampart V min Issue 50 W A V r I Interstitial co gratinm Hco U j 39 Hemoglobin 939 releases co2 and H lluld T Caplllary wall Hemoglobin picks up 02 and H coa Alvlolm space In lung co2 H20 H2003 HCO339 H Ventilating Lungs Breathing Frogs Frogs have balloonlike lungs Positive pressure breathers push air into lungs 1 Lower floor of mouth to enlarge cavity full of air 2 Close mouth and nostrils raise floor of mouth to force air down the trachea 3 Elastic recoil in walls of lungs and contraction of body walls forces air back out
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