L20 Photosynthesis PDF

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Energy and Photosynthesis PRE-LAB QUESTIONS 1. Describe how the functional units for beta carotene, xanthophyll, chlorophyll A, and chlorophyll B are different. Be sure to identify the subunits that adhere to paper during chromatography. Beta carotene does not have any form of hydrogen bond, therefore travels fur up the paper. Xanthophyll contains oxygen group which forms hydrogen bond with the paper thus will not travel up the paper as far as beta carotene. Chlorophyll A contains both oxygen and nitrogen which binds more stronger to the paper and therefore travels less than xanthophyll.

2. Describe a technique for measuring photosynthetic rate. Measure the number of bubbles produced by a water plant in a fixed length of time

3. Many deciduous trees have leaves that turn yellow in the fall. What do you suppose is happening in the leaves at the cellular and molecular level? Since trees have life cycles in which occur all year round depending on the seasons (spring, summer, fall, winter), trees prepare for each change differently. What I suppose is happening to the leaves at the cellular and molecular levels of the deciduous trees in which are turning yellow in the fall is due to the nights being longer and the days shorter. In fall it gets dark much earlier than the seasons of spring and summer. The chloroplasts contained in their cells because of all this are breaking down thus, not able to retain its pigment. If the leaves are not able to retain pigment, this is going to prevent the plant from performing photosynthesis. It also is going to make the tree want to go into hibernation during the cold of winter months. When leaves become dry, the connection between the leave and the stem become loose and fall off creating that fall like appearance you see outside your window during this time of year.

4. Chloroplasts and mitochondria are both unusual in that they have double membranes and contain their own set of DNA. Can you think of any explanations for this observation? Both chloroplasts and mitochondria are subjected to phagocytosis, but they cannot be digested, or the plant would die, so they need double membranes to protect themselves.Their DNA suggest that they were once free-living prokaryotes. This agree with the endosymbiosis theory which states that eukaryotic cell organelles developed from prokaryotic cells.

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Energy and Photosynthesis EXPERIMENT 1: PAPER CHROMATOGRAPHY Result Tables Table 1: Chromatography Data Solvent Water

Distance from Original Line to Solvent Front 8.6cm

Number of Bands

0.92

2

8.5cm

Acetic Acid

0.66

1

6.0cm

Mineral Oil

0.39

0

7.1cm

Acetone

Rf Factor

0

1

Table 2: Photosynthesis Data Test Tube

Are chloroplasts present?

Initial Color

Final Color

Time Required to Change Color (Hours)

1

yes

green

yellow

0.5 hours

2

yes

yellow

blue

12 hours

3

yes

blue

Dark blue

24 hours

Post-Lab Questions 1. What did the different colored bands signify in each solvent for Part 1? What pigments can you associate them with? The dark green and yellow green signified the chlorophyll, the yellow signified the xanthophyll, and the orange was carotenes.

5. What is the osmolarity fluid used in Part 2? Why is this important? Why is it essential to keep it cool? Osmolarity fluid is used in part 2 because the acids/other organic solvent can change the osmolarity of the leaf due to which can change the result of chromatogram paper observed.

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Energy and Photosynthesis 6. How could you modify this experiment to show the effects of different wavelengths of light on the photosynthetic rate? use different color lights or have test tubes sit different distances from the light.

7. Some plants (grasses) tend to contain a greater concentration of chlorophyll than others (pines). Can you develop a hypothesis to explain this? Would it be testable? Some plants like grass have more chlorophyll than others like pines. The concentration of chlorophyll in any plant depends on many factors. Grasses tend to concentrate carbon dioxide and have more chlorophyll concentration. This helps in the adaptation process of grasses as they can make their own food in adverse conditions also. Pines are evergreen trees that do not fall their leaves in winter. These produce their food by photosynthesis. The hypothesis can be- the greater the tendency of plants to concentrate the carbon dioxide, the greater will be the concentration of chlorophyll in the leaves. Yes, this hypothesis can be easily tested by measuring the amount of concentrated carbon dioxide and amount of chlorophyll in grasses and in pines. The difference in the amount of chlorophyll can be compared between the two plants and result can be noted.

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