Ls4203_midsem_2016 please answer only question no.5. (1.5+2+1.5=5 marks) Open wi

Question

Ls4203_midsem_2016

please answer only question no.5. (1.5+2+1.5=5 marks)

Open with 3. What is the function of Pyruvate Dehydrogenase complex (PDH)? Describe the role of each cofactors involved in the reaction catalyzed by the pyruvate dehydrogenase complex. What are the regulations of activity of pyruvate dehydrogenase complex? 1+2+2=5 4. Why animal could not survive with only on acetate as sole carbon source? How plant and microbes can survive with acetate as sole carbon source? In adult animal if the food is only lipid: what will be the consequences? What is role of Peroxisome in fatty acid oxidation? 1+2+1+1=5 5. Explain why referring to the Calvin cycle as the "dark reactions" of photosynthesis is misteading and incorrect. Compare the photosynihesis in C3 plant s C4 Plam. What is CAM pathway of Pholosynthesis? 1.5+2+1.5-5 6. What is fimetion of protein Glycogenin and Thermogenin? Whiat is brown fa Why it is called brown fat? What is the actios or uhenim cin? 1-1 + 1 + 1 +1-5

Explanation / Answer

PART 1-

The process of photosynthesis depends on the interactions between two sets of reactions: the light reactions and the Calvin cycle. Chlorophyll and the other molecules which are responsible for the light reactions are built into the thylakoid membranes. The enzymes which helps catalyze the Calvin cycle are located in the stroma. Beginning with the absorption of light by chlorophyll, the light reactions converts the light energy into chemical energy in the form of ATP and NADPH. The ATP provides the energy, and the NADPH helps supply the electrons for the Calvin cycle, which converts carbon dioxide into sugar. The ADP and NADP+ that result from the Calvin cycle shuttle back to the light reactions, which regenerate ATP and NADPH.

PART 2-  

C3

C3 plants are numerous in number and they use the pathway known as the C3 pathway. In C3 plants, the chloroplast is of one type, that is monomorphic and they do not have peripheral reticulum. The bundle sheath of C3 plants do not have much chloroplast. Light reactions which occurs in the C3 plants occur in mesophyll cells where carbon fixation occurs with the help of ribulose bisphosphate carboxylase oxygenase. The incoming carbon dioxide reacts with G3P and goes through a series of reduction. These biochemical processes are almost similar in all plants.

C4

C4 plants mostly dwell in warm water and in moist climate. In the mesophyll cells of the C4 plants, the oxygen is in more concentration than the carbon dioxide. Oxygen concentration is high in these cells due to photolysis. C4 cycle is the alternate pathway of calvin cycle which takes place during the dark phase of photosynthesis. Oxaloacetic acid is the first formed compound of the C4 cycle and the leaves of these plants have a special type of anatomy called krans anatomy.

PART 3-

CAM stands “Crassulacean Acid Metabolism” – is a method by which carbon fixation evolved by some plants in dry circumstances.

In most plants, the stomata – which are like tiny mouths that consume oxygen all along the surfaces of their leaves – open during the day to take in CO2 and release O2.

Plants must take in CO2 in order to use it as a source for carbon atoms to build sugars, proteins, nucleotides, and the other building blocks of life. They must also release waste O2, which is kindof biproduct that is left over after the carbon atom from has CO2 been incorporated into a sugar.

Most plants have their stomata during the daytime because that is when energy is received from the Sun. The energy from the Sun is harvested by the chloroplasts and used to make ATP and NADPH. These short-term energy storage molecules are then used to power the fixation of carbon into sugar.

In plants living in very dry environments, however, large amounts of water can be lost if the stomata are open during the hot, dry days. During the night, which tends to be much cooler in dry environments, far less water is lost by opening the stomata.

In order to meet the needs to combine the Sun’s energy with CO2 from the air, CAM plants take in CO2 at night and store it in the form of a four-carbon acid called “malate.” Then the malate is released during the day, where it can be combined with the ATP and NADPH created by the Sun’s energy.

In this way, the plant is allowed to conserve their water by closing their stomata during the hot daytimes.

The name “Crassulacean Acid Metabolism” comes from the Crassula plant, which was the first place that CAM metabolism was discovered and studied.

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