Question

3.Explain the term semiautonomous and the developmental relationships between the various plastid types – “how they are formed, what stimulates their formation”.

4.Compare and contrast between the general products and substrates of photosynthesis and respiration.

Answer 1

4) Photosynthesis and respiration share some similarity that both generate ATP via an chemiosmosis, ATP synthase, and electron transport chain.

In photosynthesis,  in the light reactions, ATP is produced by photophosphorylation through an electron transport chain, chemiosmosis and ATP synthase in chloroplasts.

In respiration, anaerobic production of ATP takes place outside the mitochondria during glycolysis by substrate-level phosphorylation, and inside the mitochondria,ATP is aerobically produced by substrate-level phosphorylation in the citric acid cycle, and by oxidative phosphorylation through an electron transport chain, chemiosmosis and ATP synthase.

Photosynthesis is the process involved in green plants by which they can produce their own food by using carbon dioxide, water and sunlight, to produce glucose.

Formula:

During respiration, oxidisidation of glucose takes place and energy is released in the form of ATP. The break down of glucose into C02and water.

Formula:

glucose + oxygen ———-> carbon dioxide + water + energy(ATP)

Similar products - CO2, water, oxygen and glucose is used by both reaction. Respiration is almost the opposite of Photosynthesis , however the later requires sunlight energy, whereas the former doesn’t.

3) Semiautonomus means acting somehow as an independent. Chloroplast has its own 70s ribosomes, circular DNA and set of RNAs so it can replicate its own. So chloroplast are not completely dependent on the cell for its functions. So they are semi autonomous.

Evolution of plastid from a endosymbiont cyanobacteria, and plastid division and segregation maintain their continuity that is regulated by the eukaryotic host cell. Inner- and outer- membranes of plastid constricts and then divide. Small vesicular, colorless and undeveloped structures present in meristematic cells are called proplastids. Maturation of cells depends upon the organs and presence or absence of light, proplastids either develop into colorless leucoplasts or colored chromoplasts also green chloroplasts.

Proplastids redivide into meristematic cells, then they are delivered to cell derivatives on light exposure, depending upon the structures also depending upon the intra cellular factors that they either develop into colorless plastids or colored plastids.On exposure to light leucoplasts into green plastids. Similarly chloroplasts may converted into leucoplasts; but colored plastids present in petals are mostly terminally differentiated.