Practice free Botany NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Consider the following two statements:
I. Except for plants in shade or in dense forests, light is rarely a limiting factor in nature for photosynthesis.
II. Light saturation occurs at 50% of the full sunlight.
Page 222, XI NCERT
For assimilation of one CO2 molecule via photosynthesis, the energy required in form of ATP and NADPH2 are:
In Clavin cycle, CO2 acceptor molecule is RuBP or RuDP. The enzyme catalyzing this reaction is RuBP carboxylase/oxygenase (Rubisco). As Clavin cycle takes in only one carbon (as CO2) at a time, so it takes six turns of the cycle to produce a net gain of six carbons )i.e., hexose or glucose). In this cycle, for formation of one mole of hexose sugar (Glucose), 18 ATP and 12 NADPH2 are used. For 6 molecules of CO2 it needs 18 ATP and 12 NADPH2 , molecules so for one molecule of CO2 it needs 3 ATP and 2 NADPH2 molecules.
Phosphoenol pyruvate (PEP) is the primary CO2 acceptor in
Phosphoenol Pyruvate (PEP) is found in the mesophyll cell, which accepts the atmospheric CO2 in C4 -plants and converts it to oxaloacetate — a C4 compound. It is the first stable compound of C4 -plants.
Concept Enhancer C4 -plants possess special adaptation anatomy in their leaves to cope up the photorespiratory losses. There are dimorphic chloroplast present in them—agranal in bundle sheath cells and granal in mesophyll cells.
With reference to factors affecting the rate of photosynthesis, which of the following statements is not correct?
In C4 -plants, the initial fixation of CO2 occurs in mesophyll cells. The primary acceptor of CO2 is Phosphoenol Pyruvate (PEP). It combines with CO2 in the presence of enzyme PEP carboxylase to form the first stable product, i.e., oxaloacetic Acid (OAA). C3 plants lack PEPcaboxylase enzyme. They posses RuBisCO enzyme. This enzyme can work as both carboxylase (fixation of CO2) and oxygenase (fixation of O2). RuBisCO has much greater affinity for CO2 than for O2 and the binding is competitive. At higher temperature, its ffinity for CO2 decrease and it works as oxygenase.
Therefore, at higher temperature photosynthesis decrease in C3 -plants, while in C4 -plants increases.
The process which makes major difference between C3 and C4 Plants is
Photorespiration is the process which makes a different between the C3 and C4 plants. In this process, there is a continuous loss of carbon fixed in the form of CO2. It occurs due to the high O2 content, high temperature conditions in which RuBP carboxylase starts working as RuBP oxygenate and normal photosynthesis does not occur.
Water vapour comes out from the plant leaf through the stomatal opening. Through the same stomatal opening carbon dioxide diffuses into the plant during photosynthesis. Reason out the above statements using the following options.
Diffusion of water vapour and CO2 are independent process. Their diffusion depends on the difference in their partial pressure in the atmosphere as well as inside the leaves.
Emerson's enhancement effect and red drop have been instrumental in the discovery of
Emerson performed photosynthetic experiment on Chlorella. He provided monochromatic light of more than 680 nm and observed decrease in rate of photosynthesis known as red drop.
Later he provided synchronised light of 680 nm and 700 nm and observed increase in rate of photosynthesis, known as enhancement effect. This experiment led to discovery of two photosystems PS-I and PS-II operating in photosynthesis.
In a chloroplast the highest number of protons are found in
Proton concentration is higher in the lumen of thylakoid due to photolysis of water. H+ pumping and NADP reductase activity which occurs in stroma of the chloroplast.
The oxygen evolved during photosynthesis comes from water molecules. Which one of the following pairs of elements involved in this reaction?
Photolysis of water during photosynthesis evolve nascent oxygen in the presence of manganese, calcium and chloride ions.
The structures that are formed by stacking of organised flattened membranous sacs in the chloroplasts are
In chloroplasts, the stacked membranous structures formed by the flattened thylakoid discs are called grana. These grana are connected by unstacked thylakoid membranes called stroma lamellae, which are present in the stroma region of the chloroplast.
Ready to ace NEET?
Free access · No credit card required
Yes. You can attempt every Botany question on this page for free without logging in, and check the correct answer with a detailed explanation instantly.
No account is required to attempt questions and view answers. A free account adds bookmarks, personal notes, and progress tracking.
The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.