Photosynthesis Test - 7

Etiolated leaves are those which are kept in the absence of light and hence, get etiolated or their chlorophyll is lost. In the case of variegated leaves, chlorophyll is present only in certain parts in its development.

The Krebs cycle enzymes are soluble proteins located in the mitochondrial matrix space, except for succinate dehydrogenase, which is an integral membrane protein that is firmly attached to the inner surface of the inner mitochondrial membrane, where it communicates directly with components in the respiratory chain.

Many plant cells synthesize water-soluble pigments, such as anthocyanins and betanins, which are localized in the vacuole. Plants produce anthocyanins as a protective mechanism against environmental stressors, such as ultraviolet light, cold temperatures and drought. This production of anthocyanins in roots, stems and especially leaf tissues is believed to provide resistance against these environmental hazards.

Dicarboxylic acid cycle or hatch slack pathway is another process of CO₂­ fixation in C₄ plants. It occurs mostly in monocot plants and in some dicots. It is a way to avoid photo respiration.
Chlorella pyrenoidosa does not have dicarboxylic acid cycle.

Cytochromes are extrinsic proteins which function as electron transfer agents in many metabolic pathways, especially cellular respiration.

Samuel Ruben and Martin Kamen used radioactive isotopes to determine that the oxygen liberated in photosynthesis came from the water.

At carbon-3, chlorophyll has CH₃ group.

The alga used by Calvin and his co-workers in their experiments on photosynthesis was Chlorella. Calvin and his co-workers illuminated the unicellular green alga Chlorella in the presence of carbon dioxide labelled with the radioactive isotope of Carbon ¹⁴C. The algae was allowed to photosynthesise for a certain period of time after being given the labelled carbon dioxide. By identifying the intermediates formed after different periods of time and determining the time of radioactivity, the pathway through which carbon compounds are built up was established.

During photosynthesis, the electrons flow from H₂O to NADPH in Calvin cycle.

Photorespiration refers to a process in plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. C₄ plants are photosynthetically more efficient than C₃ plants because they avoid the wasteful process of photorespiration.