List of top Life Science Questions

Consider four observations about the FT gene and flowering transition in the shoot apical meristem (SAM) of Arabidopsis thaliana:
(i) The FT promoter is active in leaves alone.
(ii) The ft null mutation causes delayed flowering of the SAM.
(iii) Expressing a recombinant FT protein fused to a nuclear localization signal (NLS) under the endogenous promoter does not rescue the delayed-flowering phenotype of the ft null mutant.
(iv) Downregulation of FT transcript in the SAM by RNAi in a wild-type background does not alter flowering.
Which conclusion best explains these observations?

Which one or more of the following statements is/are NOT CORRECT with respect to pollen development in angiosperm?

Regulation of phosphoenolpyruvate carboxylase (PEPCase) governs CO2 fixation in both C4 and CAM (crassulacean acid metabolism) plants. Which one or more of the following statements with respect to PEPCase activity is/are CORRECT?

Which one or more processes listed below DOES NOT produce carbon dioxide during fermentation?

Which one of the following statements on Casparian strips is correct?

Rotenone is a chemical often used to kill insect pests on crop plants and fishes in lakes. Rotenone acts by inhibiting electron transport from the NADH dehydrogenase enzyme in Complex I to ubiquinone in the mitochondrial electron transport chain. Which one of the following explains why plants can tolerate rotenone application?

Although Pseudomonas syringae infection in plants is actively inhibited by the endogenous salicylic acid (SA) of host origin, a successful infection is still established because the bacterium secretes coronatine, an effector molecule. Which one of the following best describes the mode of action of coronatine?

Four statements about lipids are given below as options. Choose the statement(s) which is/are CORRECT.

B cells produce two forms of an immunoglobulin: (i) membrane-bound form, known as B cell receptor (BCR) and (ii) soluble form, known as antibody. Which of the following statements is/are CORRECT about BCR and antibody produced by the same B cell?

A 100 ml solution of pH 10 was well-mixed with a 100 ml solution of pH 4. The pH of the resultant 200 ml solution is _______ (rounded off to two decimal places).

An organism uses only the glycerophosphate shunt pathway to transport cytosolic NADH to mitochondria. For every two electrons transported, complex I, complex III, and complex IV of the electron transport chain in this organism transport 2.5, 1.5, and 2.0 protons (H$^+$), respectively. The H$^+$ to ATP ratio of F$_0$F$_1$-ATPase of this organism is 4.0. Terminal electron acceptor is oxygen.
The number of ATP molecules synthesized by oxidizing NADH from glycolysis is _________ (rounded off to two decimal places).}

If the extracellular concentration of Na$^+$ is ten times its intracellular concentration, then the sodium equilibrium potential at $20^\circ$C in mV is __________ (rounded off to two decimal places). Assume the membrane is permeable only to Na$^+$ ions. [Use $R=1.987\ \mathrm{cal\,deg^{-1}\,mol^{-1}}$, $F=23062\ \mathrm{cal\,mol^{-1}\,V^{-1}}$]}

A lyophilized sample of 20 nanomoles of an oligonucleotide is dissolved in water and the volume of the solution is made up to 200 $\mu$L. The concentration (in $\mu$M) of the oligonucleotide in this solution is _______ (in integer).

Which one of the following amino acids has more than two acid-base groups?

Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. Assertion [a]: On a per carbon basis, palmitic acid yields more ATP than glucose.
Reason [r]: Carbons in palmitic acid are more reduced than those in glucose.

When cell components are fractionated by sedimentation, the correct order (from lower to higher gravitational force, g) in which the components get separated is .................

In a population, the probability of a susceptible individual getting infected with SARS-CoV-2 is low when a majority of individuals in the population becomes immune to this virus. This phenomenon is known as _______.

Given below are four reactions of the glycolytic pathway catalyzed by the enzymes E1, E2, E3, and E4, as indicated. Which of these enzymes is/are NOT part of the gluconeogenesis pathway?
(i) Fructose-6-phosphate \(\xrightarrow{\text{E1}}\) Fructose-1,6-bisphosphate
(ii) Fructose-1,6-bisphosphate \(\xrightarrow{\text{E2}}\) DHAP + GAP
(iii) 3-Phosphoglycerate \(\xrightarrow{\text{E3}}\) 2-Phosphoglycerate
(iv) Phosphoenolpyruvate \(\xrightarrow{\text{E4}}\) Pyruvate)

Which of the following molecules is/are second messenger(s) produced by the phosphoinositide signaling cascade?

A protein has seven cysteine residues. The maximum number of disulfide bonds of different combinations that can possibly be formed by these seven cysteine residues is ................ (in integer).

According to Hard–Soft Acid–Base (HSAB) principle, the CORRECT option(s) for the solubility trend in water is/are

The number of radial node(s) for the valence orbital of U(III) ion is _______ (in integer). (Given: Atomic number of U is 92)

The depression of freezing point of water (in K) for 0.1 molal solutions of NaCl and Na$_2$SO$_4$ are $\Delta T_1$ and $\Delta T_2$, respectively. Assuming ideal solutions, find the ratio $\Delta T_1/\Delta T_2$ (rounded off to two decimal places).

Consider two different paths in which the volume of an ideal gas doubles isothermally: (i) Reversible expansion (work done = \( w_{\text{rev}} \))
(ii) Irreversible expansion, with the external pressure equal to the final pressure of the gas (work done = \( w_{\text{irrev}} \)) Here, \[ \dfrac{w_{\text{rev}}}{w_{\text{irrev}}} = ? \]

Choose the CORRECT trend(s) of the first ionization energies among the following. (Given: Atomic numbers C: 6; N: 7; O: 8; F: 9; Si: 14; P: 15; S: 16; Cl: 17)