Question
Question: The alternate \[C{O_2}\] fixation mechanism was found in some tropical species of grass family by Ha...
The alternate CO2 fixation mechanism was found in some tropical species of grass family by Hatch and Slack. Where were they from?
a) England
b) USA
c) Australia
d) New Zealand
Solution
The ATP and NADPH formed in the light reaction are used in biosynthetic (dark) phase, where the CO2 fixation occurs i.e., the CO2 and H2O combines to form glucose by the expenditure of energy. It was the work of Melvin Calvin, that described that the first CO2 fixation product is a 3- Carbon compound and gave the biosynthetic pathway, named as, the Calvin cycle or C3 Cycle. Later an alternative method of CO2 fixation was discovered, which has the first stable product as 4-Carbon compound. This pathway was named as the Hatch and Slack pathway or C4 Cycle.
Complete answer:
They did not belong to England.
Option (a) is incorrect.
Neither did they belong to the USA.
Option (b) is incorrect.
Hatch and Slack were from this country, Australia.
Option (c) is correct.
They were not from New Zealand.
Option (d) is incorrect.
So the correct answer is option (c).
Additional Information:
In C3 plants the C3 cycle occurs in Mesophyll cells and has RuBP (5C) primary CO2 acceptor and forms phosphoglyceric acid (PGA−3C) as first stable product.
In C4 plants the primary CO2 acceptor is PEP (3C) and the first stable product formed is oxaloacetic acid (OAA−4C) in mesophyll cells. The decarboxylation of this C4 acid occurs in bundle sheath cells where CO2 is released which enters the C3 cycle that takes place here.
One of the main benefits of having the C4 pathway is that it neglects the process of ‘Photorespiration’ that occurs in C3 plants. This process neither does synthesis of sugar nor of ATP rather it results in release of CO2 and utilization of ATP. This is because the primary acceptor RuBisCO in C3 has both carboxylase and oxygenase activity and when the concentration of O2 increases it binds with oxygen and hence leads to decrease in CO2 fixation.
Note:
C3 Cycle occurs in all plants independent of the plant being a C3 or C4 plant but C4 cycle occurs only in C4 plants. They show a ‘Kranz anatomy’, and have large bundle sheath cells that form several layers around the vascular bundle. They are characterized by- large number of chloroplasts, thick walls, and no intercellular spaces. The plants adapted to the dry tropical region, ex. maize, sorghum, sugarcane, etc. show this pathway.