7 replies to this topic

[Jonathan620]

1. The term "dark reactions" was used for many years to describe the reactions for incorporating CO₂in photosynthesis. Why was this term considered appropriate at the time and why is it considered inappropriate now?

 

2. Photorespiration is generally considered to be a wasteful process that decreases the yield of C₃plants. What experiment would you propose to minimize the role of photorespiration in plants?

 

3. What would be the consequence in each of the following if the thioredoxins in chloroplasts were reduced not by ferredoxin but by NADPH as is the case for their cytosol counterparts? Assume NADPH is constant. Explain your answer.

A. Rate of starch synthesis.

B. Hexose monophosphate pool in chloroplasts in the dark.

C. Synthesis of malate in C₄ plants.

D. Synthesis of malate in CAM plants assuming an adequate supply of phosphoenolpyruvate.

E. Activity of Rubisco.

 

4. There is current concern that the level of CO₂is increasing in the biosphere due to the burning of fossil fuels. If the level of atmospheric CO₂were to double, how would the following be affected? Explain your answer.

A. Rate of oxaloacetate synthesis in C₄ plants.

B. Rate of 3-phosphoglycerate synthesis in C₃ plants.

C. Rate of photorespiration in C₃ plants.

D. Yield of wheat in Kansas.

E. Temperature of San Francisco Bay.

 

5. It has been known for many years that the cytosolic concentration of Pi in leaves increases when plants are shifted from light to dark. What effect does this change on each of the following?

       A. The concentration of fructose-1,6-bisphosphate.

B. Synthesis of sucrose-6-phosphate from a fixed amount of fructose-6-phosphate.

C. Synthesis of sucrose from fructose-6-phosphate

D. Pool of dihydroxyacetone phosphate in chloroplasts.

 

6. Explain the adaptive advantage of chloroplast movement within mesophyll cells and solar tracking by leaves for light interception by plants.

 

 

7. Can heat absorption by leaves hinder leaf function? Explain your answer and describe ways in which leaves can dissipate absorbed heat. What is the major path for heat dissipation in leaves from irrigated cotton growing at high temperature in Arizona?

 

 

[mdfenko]

what do you think?

 

we won't just answer these for you. we may correct or direct you after we see your responses.

[Jonathan620]

1.      The term "dark reactions" was used for many years to describe the reactions for incorporating CO₂ in photosynthesis. Why this term was considered appropriate at the time and why is it considered inappropriate now?

 

 

Dark reaction also known as the light independent reaction of photosynthesis are chemical reactions that convert carbon dioxide and other compounds into glucose. These reactions occur in the stroma, the fluid area of a chloroplast outside of the thylakoid membranes. These reactions take the products of ATP and NADPH of light dependent reactions and perform further chemical process on them. At the time this term was considered appropriate because people and even scientists were naïve, they didn’t actually had the necessary resources to conduct such complex studies, so they settled with dark reaction. Probably they thought that the reaction only occurred during the night, while in reality it means that the reaction does not require light. Many students frequently think that the “dark reaction” occur only in the night. 

 

how about this answer for the first question

[Jonathan620]

now for question 3 i don't have any idea

[bob1]

Do you understand the answer you provided for Q1?... it's a direct quote from wikipedia!  Copy/paste is no way to provide answers and most schools and universities now have plagiarism detection that will easily pick this up.

[Jonathan620]

i see, well if you have a better answer, and is not plagiarized provided.

[bob1]

i see, well if you have a better answer, and is not plagiarized provided.

It's your homework... you are supposed to do it!

[Jonathan620]

yeah you are right, plagiarism inspector.