Written Assignment 6

WrittenAssignment 6

A.Multiple–Choice Questions

Foreach of the following questions, give the number of the question andthe letter of the best answer. (2 points each)

  1. During the light–dependent reactions of photosynthesis,carbon dioxide is combined with ? Water molecules are split into hydrogen ions, electrons, and oxygen.

  2. In glycolysis, glucose is first broken down into fructose.

  3. The Krebs cycle takes place in the cytoplasm.produces NADH, FADH2, and ATP.

  4. The oxygen liberated by green plants during photosynthesis comes from water molecules.

  5. Which Plants that use which photosynthetic pathway are most vulnerable to photorespiration? CAM plants

  6. Which of the following has been used to “fertilize” plants? CO2

  7. How many ATP molecules are gained in the complete respiration of one molecule of glucose? 36

  8. Which of the following compounds is synthesized during the light reaction? NADPH

  9. Pigments that make it possible for photosynthesis to take place over a broader spectrum of light than is possible with chlorophyll alone include carotophylls.

  10. Respiration, which is initiated in the cytoplasm, is completed in the mitochondria.

B.True/False Questions

  1. Green light is the most extensively used wavelength for photosynthesis. False

  2. Phosphorylation of ADP produces ATP. True

  3. Respiration is a catabolic process. True

  4. Digestion nearly always involves hydrolysis. True

  5. The optimum temperatures for C4 photosynthesis are about the same as for C3 photosynthesis. False

  6. The energy released during fermentation of glucose is only a fraction of the energy released during aerobic respiration. True

  7. Pyruvic acid is produced during glycolysis. True

  8. Respiration occurs in cells only when photosynthesis is taking place. True

  9. CAM photosynthesis is most typical of succulent plants found in environments that are often stressed by limited availability of water. True

  10. A photosynthetic unit consists of a single molecule of chlorophyll a and a single molecule of chlorophyll b. False

C.Discussion Questions

  1. Devise an experiment to demonstrate that red and blue wavelengths of light are those primarily used by chloroplasts for photosynthesis. (Review experimental design study notes from Unit 1.)

Materialsrequired:Geranium leaves, prism, visible light wavelengths


Photosynthesisis the process used by plants to produce sugars, oxygen and water byusing carbon dioxide, light and water. The chlorophyll a and b foundin the chloroplasts of every leaf is responsible for absorbing thewavelengths that are used in the photosynthesis process with blue andred wavelengths being optimal. To confirm that blue and redwavelengths are the best for photosynthesis the experiment willinvolve placing red, green, blue, and black filters over fourseparate geranium leaves which are left for one week under whitelight. The comparison between the area where there was no filteredlight and the covered areas will be recorded. If there will bephotosynthesis in any of the cases, we expect the presence of starch.In each of the leaves, I2KI solution will be added to determine howmuch starch will be present. The starch will turn purple if it ispresent in the leaves under I2KI solution. The outcome of theexperiment should indicate more starch on those leaves that red andblue wavelengths were not filtered.

  1. Explain the differences between digestion and respiration. How are the processes interrelated?

Digestiontakes food from the environment and breaks it down on molecular andmacroscopic levels. During the breakdown process, the smallermolecular nutrients yielded can be absorbed by the intestine intothe bloodstream. The cells in the blood take those nutrients to buildnew molecules that furnish the body with cellular energy. InAddition, the cells can store those molecules to be used later.Respiration, on the other hand, carries the oxygen from theenvironment and takes it into the bloodstream. This process allowsthe movement of the oxygen from the lung membranes into the bloodvessels. In addition, the circulatory system supplies the oxygen toall the body cells and at the same time picks the carbon dioxidewaste returning it to the lungs to be exhaled into the atmosphere.Those two processes are interrelated because digestive depends onrespiration to carry its processes. The digestive functions in thetract depend upon the contractions of muscles to break the food as itmoves along the tract. The muscle contraction can only function inthe presence of oxygen, in fact, without oxygen the digestive tractwould cease from functioning.

  1. Smokey the Bear is slowing down carbon cycling. Explain.

Smokeythe bear commercials dictate that it`s only the individuals who canprevent the forest fires. Throughout the 20th century, the Americanshave adopted the message of protecting their forests. There isformation of aggressive policies to fight the forest fires which haveproved to be successful. Indeed, this interference with the naturalfire cycle have slowed down the carbon cycle and have seen manywestern forests overgrow and become thick which is an unhealthycondition. Therefore, the net outcome is that, when there is a firein the forest today, the blazes are unstoppable and consumes theforests, destroying virtually every animal and plant. In fact, alarge proportion of forest is destroyed, and the likelihood ofgrowing back is minimal. Eventually, the carbon cycle is affectedbecause there is no vegetation to support slowing the process down.

  1. Explain why flooding often kills trees.

Floodingkills tree because it affects the fundamental aspects that supportthe life of the tree. Firstly, flooding yields poor aeration of thesoil because the supply of oxygen to the flooded soil is inhibitedinjuring the plant in the flooded area. Secondly, when flood takes place it either raises the pH of acidic soils or lowers the pH ofalkaline soils. Thirdly, the rate of decomposition in the floodedsoil of the organic matter slows down, and this inhibits the releaseof the end products such as humic materials, methane and carbondioxide which support tree to grow. Similarly, the flooded soilsproduce hydrogen sulfide and ethanol, which damages the tree’s rootsystem. Lastly, the flooding water carries the sand that seals thetree roots, hence, exposing the roots, making the tree vulnerable towindthrow.

  1. Explain why the concentration of alcohol in alcoholic beverages doesn`t exceed 12 percent unless they are distilled.

Alcoholis generated through a natural process called fermentation. Thisprocess requires the right conditions to take place. There must bemoisture, air and moderate temperatures. When grape juice isfermented into an alcoholic drink, those right conditions must takeplace to yield the best beverage with the required alcohol content.During the fermentation, complex molecules are broken down intosimpler molecules through the assistance of microorganism such as theyeast. The yeast is present naturally in the grape’s skin, makingthe fermentation easier. However, modern fermentation uses commercialyeast for a controlled fermentation process. Commercially, it is donein the absence of oxygen to yield ethanol and carbon dioxide. Theprocess of fermentation continues until the concentration of ethanolis between 10 to 12 percent and the process stops because the highconcentration of ethanol inhibits the growth of yeast. Therefore,through fermentation the alcohol in an alcoholic beverage cannot gobehold 12%. During the distillation, high percentages of alcohol canbe achieved through a purification process where the substance isvaporised, and collected through condensation. Distillation,therefore, will achieve high alcohol content since it separatesalcohol from other substances through fractional distillation wherethe concept different boiling point is utilized.

  1. Discuss three reasons why increased concentrations of carbon dioxide and other greenhouse gases in the atmosphere might limit worldwide food production.

Increasedlevels of Carbon dioxide may compensate for the deficiencies found inthe environment. However, high level of CO2 does not compensate theloss of other essential minerals such as potassium and phosphorous,which accompany carbon dioxide for the growth of the plants.Therefore, increased carbon dioxide increases the moisture in theatmosphere that causes high temperature and low rainfall. In the longrun, those high temperature limits photosynthesis, which will reducecrop production. Secondly, the concentration of greenhouse gases andcarbon dioxide raises the temperature, which favors themultiplication and prosperity of insects. High temperatures increasethe reproductive rate by lengthening the breeding season. Therefore,the number of pests attacking the crops will increase, and this willdecrease the crop production. Thirdly, presence of greenhouse gasesand carbon dioxide depletes the ozone layer that protects the plantsfrom ultraviolet radiations. Hence, the crops will be susceptible todiseases in the presence of ultraviolet radiation. Eventually, thecrop production will reduce because of this exposure.