Sucrose-phosphate synthase (SPS) and sucrose-phosphate phosphatase (SPP) are two key enzymes involved in the biosynthesis of sucrose. Following are certain statements regarding these two enzymes: A. Fructose-6-phosphate is one of the substrates of SPS enzyme. B. Fructose-6-phosphate and UDP-glucose are the substrates of SPP enzyme. C. Sucrose is the final product of SPP enzyme. D. UDP is one of the products of SPS enzyme while Pi is one of the products of SPP enzyme. Which one of the following options represents the combination of all correct statements?
A, C and D
Sucrose Biosynthesis Enzymes: SPS and SPP
Sucrose biosynthesis in plants involves several steps, with Sucrose-phosphate synthase (SPS) and Sucrose-phosphate phosphatase (SPP) being two crucial enzymes in the pathway. Let's analyze each statement regarding these enzymes to determine which ones are correct.
The main reactions catalyzed by these enzymes are:
- Sucrose-phosphate synthase (SPS): Catalyzes the reaction between UDP-glucose and Fructose-6-phosphate to form Sucrose-6-phosphate and UDP.
- Sucrose-phosphate phosphatase (SPP): Catalyzes the hydrolysis of Sucrose-6-phosphate to form Sucrose and inorganic phosphate (Pi).
Analyzing Statements about Sucrose Biosynthesis Enzymes
Let's examine each statement provided:
Statement A: Fructose-6-phosphate is one of the substrates of SPS enzyme.
- The reaction catalyzed by SPS is: \( \text{UDP-glucose} + \text{Fructose-6-phosphate} \rightarrow \text{Sucrose-6-phosphate} + \text{UDP} \)
- As seen from the reaction, Fructose-6-phosphate is indeed one of the reactants that SPS acts upon.
- Therefore, statement A is correct.
Statement B: Fructose-6-phosphate and UDP-glucose are the substrates of SPP enzyme.
- The reaction catalyzed by SPP is: \( \text{Sucrose-6-phosphate} + \text{H}_2\text{O} \rightarrow \text{Sucrose} + \text{Pi} \)
- The substrate for SPP is Sucrose-6-phosphate. Fructose-6-phosphate and UDP-glucose are substrates for SPS.
- Therefore, statement B is incorrect.
Statement C: Sucrose is the final product of SPP enzyme.
- The reaction catalyzed by SPP is: \( \text{Sucrose-6-phosphate} + \text{H}_2\text{O} \rightarrow \text{Sucrose} + \text{Pi} \)
- The products of this reaction are Sucrose and Pi. Sucrose is the dephosphorylated product and the desired end product of this specific enzymatic step.
- Therefore, statement C is correct.
Statement D: UDP is one of the products of SPS enzyme while Pi is one of the products of SPP enzyme.
- From the SPS reaction: \( \text{UDP-glucose} + \text{Fructose-6-phosphate} \rightarrow \text{Sucrose-6-phosphate} + \text{UDP} \). UDP is a product of SPS.
- From the SPP reaction: \( \text{Sucrose-6-phosphate} + \text{H}_2\text{O} \rightarrow \text{Sucrose} + \text{Pi} \). Pi (inorganic phosphate) is a product of SPP.
- Therefore, statement D is correct.
Summary of Correct Statements
Based on the analysis:
- Statement A is correct.
- Statement B is incorrect.
- Statement C is correct.
- Statement D is correct.
The combination of all correct statements is A, C, and D.
| Statement | Enzyme | Analysis | Correct/Incorrect |
|---|---|---|---|
| A | SPS | Fructose-6-phosphate is a substrate. | Correct |
| B | SPP | Fructose-6-phosphate & UDP-glucose are not SPP substrates. | Incorrect |
| C | SPP | Sucrose is a product. | Correct |
| D | SPS & SPP | UDP is SPS product, Pi is SPP product. | Correct |
Thus, the correct statements are A, C, and D.
Important Questions from Photosynthesis
Kranz anatomy is found in _____ plant.
Which plant pigment is present in tomatoes?
Which one of the following reactions takes place during the reduction phase of the Calvin - Benson cycle?
The following statements were made with the assumption that the concentration of 3- phosphoglycerate is high inside chloroplasts of an actively photosynthesizing leaf.
A. There will be high concentration of triose phosphate in the chloroplast.
B. The activity of ADP-glucose pyrophosphorylase will be inhibited.
C. The carbon flow will be diverted from sucrose to starch.
D. Starch synthesis will be inhibited and carbon flow will be more towards sucrose synthesis.
Which one of the following combinations of above statements is correct?
The table below shows photosynthetic type, temperature and sunlight intensity levels.
Photosynthetic Type Temperature Sunlight Intensity A. C3 Plant i High P. High B. C4 plant ii Moderate Q. Moderate iii Low R Low Which of the following correctly matches the plant photosynthetic type with the temperature and sunlight conditions in which photosynthetic rate per unit leaf area is maximum for that plant?
