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Fundamentals Of Biology I

by: Verla Grady DDS

Fundamentals Of Biology I BSC 1010C

Marketplace > Valencia College > Biology > BSC 1010C > Fundamentals Of Biology I
Verla Grady DDS
GPA 3.95


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This 13 page Class Notes was uploaded by Verla Grady DDS on Thursday October 29, 2015. The Class Notes belongs to BSC 1010C at Valencia College taught by Staff in Fall. Since its upload, it has received 33 views. For similar materials see /class/231217/bsc-1010c-valencia-college in Biology at Valencia College.

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Date Created: 10/29/15
Photo synthesis Objectives Describe the roles played by light and pigments in photosynthesis Identify the pigments involved in photosynthesis by paper chromatography 3 Determine the wavelengths most useful for photosynthesis by determining the absorption spectrum of a pigment extract Nb l 4 Demonstrate the effect of changing light levels on electron transport in photosynthesis as measured by oxygen production 5 Describe an experiment that demonstrates that carbon dioxide is utilized during photosynthesis Introduction The equation for photosynthesis is COZ HZO CHZOn 02 In this equation CHZO represents the general carbohydrate Usually this equation is multiplied by six so that glucose C5H1205 is the end product of photosynthesis The equation is then written as follows 6COZ 6HZO gt C5H1205 602 Photosynthesis takes place in the chloroplasts In the last 40 years the details of chloroplast ultrastructure have been determined and this has helped explain the process The arrangement of thylakoid membranes in the grana is critical to energy harvesting The matrix or stroma has an important role in producing storage molecules The overall process of photosynthesis can be understood as two closely linked sets of reactions The light dependent reactions occur in the thylakoid membranes where electron transport produces NADPH and creates a hydrogen ion gradient across the thylakoid membrane that drives ATP synthesis by chemiosmosis ATP and NADPH are then used by the lightindependent reactions These occur in the stroma regions where carbon fixation is carried out by the enzymes of the Calvin cycle to convert COZ to carbohydrates such as glucose The driving force for photosynthesis is light absorption by the photosynthetic pigments of photosystems I and II Only the wavelengths of light absorbed by the photosystems can be used to drive photosynthesis Light energy drives the flow of electrons from water molecules which are split to form oxygen and hydrogen by a complex of proteins and metal ions associated with photosystem II through photosystem II along a chain of electron carriers through photosystem I and eventually to NADP The flow of electrons through the chain of electron carriers also creates a gradient of H that is used for the synthesis of ATP by chemiosmosis The entire process by which light energy is converted into chemical energy in the form of ATP and NADPH is called noncyclic photophosphorylation The process is so named because the flow of electrons is noncyclic from the source water to the destination NADPH The energy to drive the electron flow uphill comes from light photo ADP undergoes phosphorylation addition of a phosphate group carried out by the ATP synthetases in the thylakoid membrane using the energy provided by the proton H gradient Sometimes ATP alone is the product of some lightdependent reactions This is due to a process called cyclic photophophorylation in which the electrons pass through the electron transport carries but do not get passed to NADP Instead the electrons pass from photosystem I to the electron transport chain and back to photosystem I While passing through the electron transport chain they contribute to the size of the hydrogen ion gradient which increases the output of ATP Oxygen and NADPH are not products of this process In the lightindependent reactions of the Calvin cycle the chemical energy stored in ATP and NADPH is used to reduce COZ to carbohydrate an uphill or endergonic process Carbon fixation begins with carbon dioxide uptake and incorporation into an organic molecule a reaction catalyzed by the enzyme ribulose bisphosphate carboxylaseoxygenase The energy stored in the ATP and NADPH is then used to convert the low energy COZ to highenergy carbohydrates While these reactions are typically referred to as the lightindependent reactions in intact plants they are dependent on light as they are driven by ATP and NADPH which are the products of the lightdependent reactions As long as noncyclic photophosphorylation continues sufficient NADPH and ATP will be available for the Calvin cycle reactions COZ will be fixed and carbohydrate will be synthesized 1f light is removed or electron flow chemically blocked ATP and NADPH are quickly used up and the Calvin cycle stops working This is the mechanism of action of a number of popular herbicides 1n intact photosynthesis systems then light is necessary for the Calvin cycle as it is tightly linked to the synthesis of ATP and NADPH Recently it has been recognized that water is both a reactant and product of photosynthesis This realization has come about as biologist better understood the formation of oxygen as a product of photosynthesis It is now known that a total of 12 water molecules are required as reactants for photosynthesis 1n the space below write out a balanced equation for the synthesis of one glucose molecule from 6 carbon dioxide molecules and 12 water molecules Referring back to the equations at the beginning of the introduction should provide you with a clue for how this might work Identifying Plant Pigments by Paper Chromatography The primary photosynthetic pigment in most plants is chlorophyll a At the center of each photosystem are is pair of chlorophyll 1 molecules that are responsible for generating high energy electrons using light energy39 these are known as the reaction center chlorophylls Surrounding the reaction center chlorophylls are more chlorophyll 1 molecules together with chlorophyll I molecules carotenes and xantho hylls These pigments are known as secondary or ancillary pigments They also absorb light energy but funnel it towards the reaction center chlorophylls for use in making high energy electrons In this exercise you are going to use a technique called paper chromatography to separate out these four types of pigments Chromatography is a technique that separates molecules from each other on the basis of their solubility in particular solvents The more soluble the pigment is in the solvent the faster and farther it moves up the chromatography paper The size of the molecule also affects the rate it moves up the paper with smaller molecules progressing further up the paper than large molecules Procedure 1 Obtain a strip of chromatography paper taking care to hold it only by the top andor sides While the strips have been cut to the correct length you need to cut one end the bottom to form a pomt 2 Draw a faint horizontal line in pencil only about 2cm from the tip and place a small X in the center of the line 3 Use a capillary tube to apply a small amount of extracted spinach pigments to the Do this by barely touching the end of the capillary tube to the paper and then immediately withdraw it A small green spot should appear on the paper 4 Allow this drop to dry completely and then repeat step 3 Repeat this process at least 15 times The resulting spot should be small and very dark It may take 1015 minutes to achieve this 5 Obtain a large test tube containing a premeasured amount of chromatography solvent and place it in a test tube rack CAUTION Ether which is a part of the chromatography solution is toxic and extremely ammable Do not breathe the fumes or allow others to breathe the fumes Under no circumstance is the stopper to be removed from the test tube except to add or remove the chromatography strip Do not place the chromatography solution near a heat source 6 Carry the test tube rack and your chromatography strip to one of the porches outside the building Quickly remove the stopper attach your chromatography strip to the hook on the stopper and replace the strip and stopper in the test tube making certain the stopper is securely seated in the test tube Return the test tube rack and test tube to the lab 7 After about 2030 min the solvent will be close to the top of the strip and you must remove the strip immediately Carry the rack outside again remove the stopper remove the strip from the hook and replace the stopper securely in the test tube 8 Immediately mark the location of the solvent front edge of the part wet by the solvent with a pencil You will be unable to analyze your chromatogram if you fail to do this before the rapidly drying solvent dries 9 Allow the strip to dry for a few minutes before you return to the classroom After returning to the classroom mark the upper edge of each pigment spot with a pencil as the colors will fade over time r O Analysis of the pigments Measure the distance in millimeters from your original line with the pigment spot and each of the other pencil marks you have made on the chromatography strip You can use these measurements to calculate what is known as the Rf of each pigment the ratio of the distance each pigment ran versus the distance the solvent ran Depending on the quality of the pigment extract there should be four pigment spots on the chrom atogram Chlorophyll a 7 a bluegreen pigment Chlorophyll b 7 a yellowgreen pigment Carotenes 7 yelloworange accessory pigment Xanthophylls 7 yellow accessory pigment The last two pigments carotenes and xanthophylls may contain more than one spot Complete table 1 with your measurements and Rf calculations and identify each spot using the descriptions above in the appropriate box Table 1 Data from Chromatography mm spot Absorption Spectrum of Photosynthetic Pigments Only the light absorbed by chloroplasts can be used in photosynthesis The pigments of a green plant look green to the eye because they permit green light to pass through but absorb the red and blue light The particular wavelengths of light absorbed by a substance form a pattern called its absorption spectrum The spectrum is determined by illuminating a solution of a substance with each wavelength of light in turn and measuring the absorption in each case Using visible light we can determine the absorption spectrum of a mixture of the pigments extracted from chloroplasts Procedure 1 Fill a spectrophotometer cuvette with a dilute solution of chloroplast pigments Fill a second cuvette with 80 acetone the solvent used to extract the pigments from the chloroplasts The second tube will be your control for measuring the absorption of the pigments at each wavelength 2 Your instructor will help you obtain a spectrum using the spectrophotometer Do not attempt to use this complex piece of equipment without your instructor as it is a delicate piece of equipment and easily damaged 3 Attach a copy of the absorption spectrum in your lab report below and answer the following questions Absorption spectrum 1 How many peaks are there in this absorption spectrum 2 What wavelengths approximately doesdo the peaks occur 3 What portions of the visible spectrum based on the absorption spectrum do you think contribute the most energy to photosynthesis Photosynthesis in Elodea In an intact plant both electron transport and carbon fixation will continue as long as the plant is illuminated and it is possible to study the effect of light intensity and the concentration of C02 on the rate of photosynthesis A simple way to measure the rate of photosynthesis is to observe the rate at which oxygen bubbles are produce as a result of water splitting An actively photosynthesizing aquatic plant will produce an abundance of oxygen bubbles Procedure 1 2 Obtain a healthy green sprig of Eladea and measure back about 10cm from the tip Wipe a sharp razor blade with alcohol let it dry and make a diagonal cut across the stem of the plant as gently as you can Save the tip 9 Put the tip into a test tube upside down co that the cut end of the stem is about 3cm from the top of the test tube 4 Fill the test tube with tap water so that the cut end is completely covered 5 Obtain a lamp and place it on the bench Fill a large glass beaker with water and place it in front of the lamp to act as a heat filter Lay a meter stick along side your set up so that the zero mark is level with the face of the lamp and the meter stick extending out from the lamp 6 Place the test tube containing the Eladea sprig at a distance of 50cm from the lamp in a test tube rack Wait a few minutes for the plant to adjust to the light level If there are hardly any bubbles coming from the cut end after 15 minutes ask your instructor for help 7 Once there are two or more bubbles per minute begin counting and record the number of bubbles produced in a 5 minute interval in table 2a 8 Repeat the count for another 5 minute interval and calculate the average bubble count per minute for the light intensity at 50 cm 9 Move the tube to 25cm allow the plant to adjust Repeat your measurements and record the results 10 Now move the plant to 75cm Allow the plant to adjust and repeat the measurements Did you see a different rate of oxygen evolution when the light intensity was increased or decreased ll Replace the water in the tube with 05 NaHCO3 sodium bicarbonate which will function as a carbon source for the Eladea 2 Place the plant back at 25cm and measure the rate of bubble release for two 5 min intervals Record the results in table 2b Table 2 Oxygen Evolution by Eladea A Tap water B NaCO3 I Distance I Bubbles5 min I Average 39 I 25cm 1 25cm 2 What effect did decreasing the light increasing distance have on the rate of photosynthesis What effect did increasing COZ NaHCO3 have on the rate of photosynthesis ls oxygen produced as a result of carbon fixation or of electron transport Hint compare the rate of bubble production at 25cm from the light in the presence and absence of NchOg The Uptake of Carbon Dioxide During Photosynthesis Note This procedure will be done as a demonstration by your instructor You will need to record the results in table 3 and answer the questions relating to this experiment During the second stage of photosynthesis the plant takes up carbon dioxide C02 and reduces it to carbohydrate Therefore the carbon dioxide in the solution surrounding aquatic plants should disappear as photosynthesis takes place We have already used sodium bicarbonate as a carbon source but in this procedure we will use the carbon dioxide in expired breathe as a carbon dioxide source Procedure 1 Fill two test tubes with phenol red solution Phenol red is a pH indicator it is yellow in an acid and red in a neutral solution 2 Using a straw breathe bubbles into both the test tubes until the phenol red turns from red to yellow When carbon dioxide dissolves in water it forms the acid carbonic acid H2c03 3 Place a sprig of Eladea in one test tube and place both test tubes side by side in a test tube rack in front of a lamp Protect the Eladea from the heat of the lamp with a large beaker filled with water 4 Check the color of the solutions periodically until you detect a change in color from yellow to red The time required for the color to change varies but generally takes from 2 1 hour Table 3 Carbon dioxide uptake Test tube Color before Color after light exposure light exposure Eladea Eladea Answer the following questions 1 What does the gradual change to red indicate in terms of the pH of the solution 2 What does the change in pH indicate about the carbon dioxide in the solution 3 What happened to the carbon dioxide Would you expect the pH of the water in a shallow pond with a lot of submerged plants and algae to change over a 24 hour period If so how would it change Why did we include the tube without Eladea in the experiment You may notice small bubbles in the solution with the Eladea What would you expect these bubbles to be W Introduction In 1865 an Austrian monk Gregor Mendel presented the results of painstaking experiments on the inheritance of the garden pea Those results were heard but not understood by Mendel39s audience In 1866 Mendel published his results in an obscure German journal The result of this was that Mendel39s work was ignored and forgotten Mendel died in 1884 without knowing the pivotal role his work would play in founding the modern discipline of genetics By 1899 some geneticists were beginning to realize the necessity of mathematically analyzing inheritance in order to understand how evolution might work Bateson 1899 They did not realize that Mendel had already solved this problem Then in 1900 three leading scientists of the day Hugo de Vries Carl Correns and Erik von Tscherm ak simultaneously rediscovered Mendel39s paper and realized how important it was With the rediscovery of Mendel s principles genetics as a scientific discipline exploded into activity Within two years the first human study of inheritance Gar rod 1902 describing the Mendelian inheritance of alkaptonuria was published This paper too was far ahead of its time the importance of which would only be recognized as the one geneone polypeptide principle was developed in the latter part of this century Now more than a century later Mendel s work seems elementary to modernday geneticists but its importance cannot be overstated The principles generated by Mendel39s pioneering experimentation are the foundation for genetic counseling so important today to families with health disorders having a genetic basis It39s also the framework for the modern research that is making in roads in treating diseases previously believed to be incurable In this era of genetic engineering the incorporation of foreign DNA into chromosomes of unrelated species it is easy to lose sight of the basics of the process that makes it all possible Recent advances in molecular genetics have resulted in the production of insulin and human growth hormone by genetic engineering techniques Cancer patients are being treated with cells that have been removed from their own bodies genetically altered to enhance their tumor destroying capacity and then reinserted in the hope that microscopic tumors escaping the surgeon39s scalpel may be destroyed This newfound technology has not been without controversy however Release into the environment of genetically engineered microorganisms that may make crops resistant to diseasecausing organisms or even capable of withstanding temperatures that normally would freeze plants has met with strong opposition 1n the future you may be called upon to help make decisions about issues like these To make an educated judgement you must understand the basics just as Mendel did This exercise will give you a better understanding of the basic laws that govern the inheritance of characteristics by successive generations The corncob is not the fruit of the corn plant in itself nor are the kernels the seeds Each kernel of corn is really a fruit which develops from the ovary of one of the female flowers of the plant There are a great number of inheritable characteristics in corn Zea mays In this experiment we will investigate two the color of the kernel and starchy consistency of the endosperm which gives rise to wrinkled or smooth kernels The endosperm is a nutritional reserve for the developing corn seedling that provides energy to the seedling after immediately germination This reserve is drawn on until the developing plant begins to generate its own energy by photosynthesis Three layers of cells protect the endosperm The inner most layer the aleurone layer contains purple pigments called anthocyanins The amount of anthocyanin in the aleurone layer and the amount of starch present in the endosperm are genetically determined and can be inherited according to Mendelian rules The purpose of this experiment is to demonstrate experimentally that some characteristics of ears of corn are inherited according to the Mendelian laws of inheritance By the end of this experiment you will have determined if 1 the quantities of purple and white corn kernels correspond to the Mendelian ratios of the F2 generation of a monohybrid cross and 2 the quantities of yellow and white and wrinkled and smooth kernels correspond to the Mendelian ratios of the F2 generation of a dihybrid cross The Monohybrid Cross You will be provided with an ear of corn whose kernels show two different colorsyellow and purple Place a colored pin in the end of one row of kernels and count and record the number of each type of kernel in the row Place an uncolored pin at the end of the next row and continue counting After each row is completed move the uncolored row marker pin to the next row until you return to the row marked by the colored pin All individuals in your group should individually count the kernels Record the results of the counts in table 1 below Table l When you have finished enter your totals in the class table on the board When everyone has entered their data into the class table combine the totals for each phenotype counted and record them under quotPhenotype Classquot in table 2 Record the total number of individuals counted under the quot Class Totalquot columns for table 2 Table 2 Kernel Phenotype Class Purple Yellow Class Totals Number of individuals actual counts Expected number of individuals Data Interpretation Examine the totals obtained by the class Using the kernel counts what is the dominant phenotype How do you know The corn kernels are the F2 generation resulting from a cross between a homozygous purple corn PP and a corn that is homozygous recessive white pp Fill in the following Punnett square to show how the ears were produced Parents F1 F2 PP pp 77 77 77 Purple white Determine the expected numbers for each phenotype using Mendel s law of segregation and perform a Chi square calculation to determine if the class data obeys Mendel s law of segregation Include a statement describing what the Chisquare calculation indicates about the class data Chisquare X2 Calculation The Dillybrid Cross You will be provided with an ear of corn that has not only purple or yellow kernels but are also either smooth or wrinkled The possible combinations are yellowsmooth yellowwrinkled whitesmooth and whitewrinkled Sweet corn kernels wrinkle when they dry while starchy kernels remain smooth Place a colored pin at the end of one row and count and record the phenotypes of all the kernels in that row in table 1 below Place an uncolored pin at the end of the next row and continue counting After each row is complete move the uncolored pin to the end of the next row and continue counting until you reach the row marked by the colored pin Each ear should be counted by at all people in your group When you have finished counting record your results in the class table on the board After everyone has record his or her results combine the totals for each phenotype and enter them in the quotPhenotype Classquot columns in table 3 below Table 3 When you have finished enter your totals in the class table on the board When everyone has entered their data into the class table combine the totals for each phenotype counted and record them under quotPhenotype Classquot in table 4 for kernels Record the total number of individuals counted under the quotClass Totalquot columns for table 4 Table 4 Phenotype YellowSmooth YellowWrinkled WhiteSmooth WhiteWrinkled Class Total Class Number of Individuals actual count Expected Number Data Interpretation Examine the totals obtained by the class Using the kernel counts what is the dominant phenotype How do you know The corn grains are an F2 generation resulting from a cross between a homozygous yellowsmooth YY 55 and a corn that is homozygous whitewrinkled yy ss To better understand how these ears are produced fill in the following placing the symbol for an allele in each blank Y gene for yellow color y gene for white color S gene for smooth s gene for wrinkled X Parents 77 X 77 F1 X F1 cross F2 Generation Calculate the expected number of individuals of each phenotype using Mendel s law of independent assortment and perform a Chisquare calculation to determine if the class data fits Mendel s law of independent assortment Include a statement that describing what the Chisquare calculation indicates about the class data Chisquare X2 Calculation The Chi square Test When scientists set out to solve a problem they formulate a hypothesis that suggests a possible solution to the problem They then carry out experiments and collect data to test if the hypothesis is correct an therefore a solution to the problem As part of the development of the hypothesis the scientists should be able to make some predictions about the data that they will collect An oftenoccurring problem when analyzing data is that it does not always fit into the predictions from the hypothesis The question then is do the data still fit the predictions or does it differ from the predictions This is where statistical analysis is used There are a large number of statistical tests each with its own specific use One important consideration is which statistical test is the most appropriate for the data This usually depends on the type of data and how it was collected For most of our experiments the most appropriate test is the chisquare X2 test The formula for the chisquare test is x2 2OE2E where O are the observed or experimental results and E is the expected or hypothetical results To illustrate how to use the formula let39s look at an example using a coin A coin has two sides a head and a tail According to the laws of probability the chance of ipping a coin and having it land head up is 2 05 and the same for a tail Based on this law if we tossed a coin 100 times half the time it should be a head and half the time it should be a tail Our hypothesis is that there is an equal probability of tossing a head or a tail and our expected results for 100 repetitions would be 50 heads and 50 tails Now we take a coin and toss it 100 times and get 52 heads and 48 tails These results differ from what we expected but do they still fit with our hypothesis To test the validity ofour results we carry out a chisquare test as follows xZ 52 50Z50 4850Z50 2250 2Z50 450 450 850 or 016 Notice that you have to set up the OEZE term for each data set that is the head data set and the tail data set and that the result of each of these is added together to give the X2 value Now that we have a value for X2 what does it tell us about our data The main consideration here is to remember what we are testing with the chisquare test Many people think that it is testing the original hypothesis which is incorrect What we are testing is a statistical hypothesis called the NULL hypothesis Simply put this hypothesis says that any deviation of the observed experimental results from the expected hypothetical results is due to random chance alone The X2 value is used to determine the probability of this hypothesis being true or false Statisticians and biologists have set an arbitrary value of 5 as the probability level at which the NULL hypothesis is false that is if the probability of the deviation being due to chance alone is 5 or less then the NULL hypothesis is false To determine the probability level we use a X2 table which tabulates probabilities XZ values and another property of data called the degrees of freedom The degrees of freedom is equal to the number of data sets minus one or the number of OEZ E terms minus one For instance in our example there are two data sets so the degree of freedom is one Now let s look at the X2 table and nd our probability value First we nd the degrees of freedom for our data in the DF column then we move across that row until we nd our XZ value We then read off the probability value as a decimal from the top of that column The table in the lab manual only shows values for probabilities from 01 or less as 005 or 5 is the key value The rule of thumb here is that any X2 value that gives a probability value greater than 005 says that the NULL hypothesis is correct39 a probability value less than 005 means the NULL hypothesis is false For our example the X2 value was 016 with a degree of freedom of one From the table the probability is much greater than 005 or in terms of the NULL hypothesis the probability is very high that the deviation in the observed data is due to random chance alone This in turn means that our experimental data t with the predicted results based on our original hypothesis and support this hypothesis Chisquare Table


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