Clumsiness of Rubisco

Q.

Is photorespiration present at low light intensities in C3 and C4 plants?

Q.

RuBisCo is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RuBisCo carries out more carboxylation in $C_4$ plants?

Q.

Question 59
Why is RuBisCo enzyme the most abundant enzyme in the world?

Q. The enzyme RuBisCO has

1. more affinity for $C{O}_2$ than for $O_2$
2. more affinity for $O_2$ than for $CO$
3. equal affinity for both
4. more affinity for sugars than for $C{O}_2$

Q.

What is wrong with photorespiration?

Q. Phosphoglyceric acid (PGA) is formed when carbon dioxide is fixed onto the 5C compound:

1. nicotinamide adenine dinucleotide phosphate
2. ribulose bisphosphate
3. adenosine monophosphate
4. adenosine triphosphate

Q.

Question 35
What conditions enable RuBisCO to function as an oxygenase? Explain the ensuring process.

Q.

How do plants avoid photorespiration?

Q.

The number of 'ends' in a glycogen molecule would be

(a) Equal to the number of branches plus one

(b) Equal to the number of branch points

(c) One

(d) Two, one on the left side and another on the right side

Q. Which among the following is the initial acceptor of carbon dioxide during photosynthesis?

1. Ribulose - 1, 5 - bisphosphate
2. Ribose - 5 - phosphate
3. Ribulose - 5 - Phosphate
4. Phosphoglyceric acid.

Q. The following question consist of two statements, printed as assertion and reason. While answering the question, you are required to choose any one of the following five responses.

Assertion: Photosynthetically $C_4$ plants are less efficient than $C_3$ plants.

Reason: The operation of $C_4$ pathway requires the involvement of only bundle sheath cells.

Q. RuBisCO is an enzyme that acts both as a carboxylase and oxygenase. Why do you think RuBisCO carries out more carboxylation in C4 plants?

Q.

How does photorespiration lower the efficiency of photosynthesis?

Q. Rubisco has active sites for both $C{O}_2$ and $O_2$, but binding to brings down its efficiency.

1. $C{O}_2$
2. $H_2$
3. $O_2$
4. $H_{2}O$

Q.

Question 56
Why is the RuBisCo enzyme more appropriately called RUBP carboxylase-oxygenase and what important role does it play in photosynthesis?

Q. First product formed from Ribulose – 1, 5 – biphosphate in C3 cycle is

1. 3 – Phosphoglycerate
2. 1, 3 – biphosphoglyceric acid
3. 4 – Phosphoglycerate
4. dihydroxyacetone – 3 – phosphate

Q. The number of carbon atoms present in ribulose biphosphate is

1. 5
2. 4
3. 6
4. 3

Q.

Can dinoflagellates kill fish?

Q. Read the assertion and reason carefully to mark the correct option in the question.

Assertion: $C_4$ plants show tolerance to higher temperatures.

Reason: $C_4$ plants have both $RuB$is$CO$ and $PEP$case enzymes.

Q. $6C{O}_2+12H_{2}O\stackrel{Light}{\to }{C}_6{H}_{12}{O}_6+6H_{2}O+6O_2$.
where $C_6{H}_{12}{O}_6$ represents glucose. The $O_2$ released is from water; this was proved using radio isotope techniques. Note that this is not a single reaction but description of a multistep process called photosynthesis. Can you explain why twelve molecules of water as substrate are used in the equation given?

Q. Write about various types of restriction enzymes.

Q. Enzymes PEP carboxylase and RuBP carboxylase are located in chloroplasts of

1. CAM plants
2. $C_3$ plants
3. Both B and C
4. $C_4$ plants

Q. The enzyme used in $C{O}_2$ fixation in mesophyll cells of C4 plants:

1. Malate dehydrogenase
2. Pyruvate kinase
3. PEP carboxylase
4. RuBisCO

Q. $FAD{H}_2$ is produced in Krebs cycle during the conversion of

1. isocitrate
2. $\alpha$ - ketoglutarate
3. succinate
4. malate

Q. The first stable product of Calvin cycle and Hatch and Slack cycle are

1. 4- C and 3- C compounds
2. 4- C and 6- C compounds
3. 3- C and 4- C compounds
4. 5- C and 4- C compounds

Q.

1. Respiration, anabolic
2. Photosynthesis, catabolic
3. Respiration, catabolic
4. Photosynthesis, anabolic

Q. During dark reaction for fixation of carbon, three carbon atoms of each molecule of 3-PGA are derived from

Q. Ribulose bi phosphate carboxylase enzyme catalyses the reaction between

1. Ribulose biphosphate and PGA
2. Dihydroxyacetone phosphate and PGA
3. Carbon dioxide and ribulose 1, 5 biphosphate
4. Oxalacetic acid and Acetyl– COA

Q. Rubisco has active sites for both $C{O}_2$ and $O_2$, but binding to brings down its efficiency.

1. $C{O}_2$
2. $H_2$
3. $O_2$
4. $H_{2}O$

Q. In plants, the water molecules split into hydrogen and oxygen with the help of ............ energy.

1. Light
2. Chemical
3. Electrical
4. Mechanical