Question

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. 2. describe a technique for measuring photosynthetic rate. 3. many deciduous trees have leaves which turn yellow in the fall. what do you suppose is happening in the leaves at the cellular and molecular level? 4. chloroplasts and mitochondria are both are unusual in that they have double membranes and contain their own set of dna. can you think of any explanations for this observation?

Answer 1

The pigments have a similar structure of 40 carbon atoms covalently bonded in a chain. Carotenoids contain oxygen atoms in their chemical structure (retinyl functional group) while xanthophyll does not. This makes carotenoids more non-polar compared to xanthophylls, hence move farthest in chromatography paper using a nonpolar mobile phase. Chlorophyll pigment, on the other hand, has chlorin rings (which are larger) as functional units hence move slowly in chromatography.

Photosynthetic rates can be measured by either the amount of oxygen they consume per particular time period or the amount of carbon dioxide produced per particular time period. This is conducted while immersed in water so as to measure bubble rate formation in case of oxygen production or the change in water pH in the case of carbon dioxide consumption.

When autumn approaches, the amount sunlight received by the plant is reduced due to longer night than days. Deciduous trees have adapted by losing chlorophyll a and b pigments (most important in photosynthesis) during this time. This leaves a higher amount of the other red and yellow pigments hence making the leaves change from green to yellow-red.

It is believed that this is the result of an ancient endosymbiotic relationship between a protist and a eukaryotic cell. The protist generates energy that the eukaryotic can utilize in its growth and reproduction while the protist is sheltered. This relationship became obligatory symbiosis over time.