Gluconeogenesis involves the______. (PPSC 2021)? (a) synthesis of glycogen from glucose (b) breakdown of glycogen to form glucose (c) breakdown of glucose to produce pyruvate (d) None of the these Answer: d Explanation Gluconeogenesis is the pathway by which glucose is synthesized from non-carbohydrate metabolites. The principal gluconeogenic precursors are pyruvate and lactate, certain gluconeogenic amino acids, and glycerol, which is derived mainly from fat metabolism. Video Explanation
Which of the following disaccharides gives two same monosaccharide units on hydrolysis? (PPSC 2021)? (a) Maltose (b) Sucrose (c) Lactose (d) none of these Answer: a Explanation A dissacharide consists of two sugars joined by an O-glycosidic bond. In a dissacharide, two monosaccharides are joined together by acetal or glycoside formation. The hemiacetal OH of one monosaccharide and OH of second monosaccharide dehydrate to establish the bond called glycosidic bond. Maltose is a disaccharide which is made up of the same monosaccharide units. As you can see in the next figure Video Explanation
Which of the following tests does glucose give? (PPSC 2015)? (a) Addition product with NaHSO3 (b) 2,4-DNP test (c) Schiff’s test (d) none of these Answer: d Video Explanation
Which of the following substance produce acetaldehyde on dry distillation?? (a) (CH3COO)2Ca (b) (HCOO)2Ca (c) None of these (d) Both A and B Answer: c Video Explanation
Which of the following substances does not give iodoform test? (PPSC-2017) (a) Acetaldehyde (b) Ethyl alcohol (c) Acetone (d) Methyl alcohol Answer: d Explanation Iodoform test is used to check the presence of carbonyl compounds with the structure R-CO-CH3 or alcohols with the structure R-CH(OH)-CH3 in a given unknown substance. The reaction of iodine, a base and a methyl ketone gives a yellow precipitate along with an “antiseptic” smell. Video Explanation
Which of the following compounds will react with Tollen’s reagent? (a) CH3-CHO (b) CH3-CH-CH3 (c) CH3-COOH (d) CH3-CO-CH2-CH3 Answer: a Explanation Tollens test is generally given by compounds having aldehydic group (aldehydes,alpha-hydroxy ketones and formic acid-its -COOH behaves like a aldehydic group). It gives a white ppt of Silver (where the silver salt is reduced to silver metal and the aldehyde is oxidised to silver salt of carboxylic acid. Video Explanation
In which of the following methods are liquid samples injected into the column in gas chromatography? (PPSC 2021) (a) Gas tight syringe (b) Micro-syringe (c) Rotary sample valve (d) None of these Answer: b Explanation A microsyringe is used to inject the sample through a rubber septum into a flash vaporizer chamber at the head of the column. The sample vaporizes to form a mixture of carrier gas, vaporized solvent and vaporized analytes. Gas tight syringes are ideal for dispensing both liquids and gases. They have a precision-machined PTFE plunger tip which creates a leak-free seal. With the tight fit, the tip essentially wipes the interior of the syringe barrel free of sample. Gas and liquid sampling valves are most frequently used to sample gases or liquids in constantly flowing streams such as those in chemical reactors, chemical transfer lines, natural gas processing, and fermenters. Video Explanation
Which of the following is not the application of gel filtration? (PPSC 2021) (a) Purification (b) Relative molecular mass determination (c) Protein concentration (d) None of these Answer: (d) Video Explanation
Which solvent is usually used for SEC in our lab?(PPSC 2015) (a) tetrahydrofuran (b) toluene (c) water (d) None of these Answer: a Explanation Tetrahydrofuran (THF) is one of the most commonly used solvents for non-aqueous size-exclusion chromatography (SEC) because it is a good solvent for a wide range of polymer types THF is an aprotic solvent and cannot donate a proton for ionization. THF should be paired with a protic mobile phase (i.e. 20-50% water) when possible. The addition of 0.2% acetic acid, 0.1% formic acid or 10-20 mM NH-4OAc to the mobile phase will assist positive mode ionization. Video Explanation
Which of the following figures does not represent 1 mole of dioxygen gas at STP?? (a) 16 grams of gas (b) 22.7 litres of gas (c) 6.022 × 1023 dioxygen molecules (d) 11.2 litres of gas Answer: a & d Video Explanation
At the same temperature, the average molar kinetic energy of N2 and CO is? (a) KE1 > KE2 (b) KE1 = KE2 (c) KE1 < KE2 (d) None of these Answer: b Explanation Average kinetic energy does not depend on the nature of the gas and their weight. It only depends on temperature. These same temperature condition is given. So, kinetic energies are same. Video Explanation ?
Which law states that the volume of an ideal gas at constant pressure is directly proportional to its absolute temperature? (a) Boyle’s law (b) Joule’s Law (c) Avogadro’s law (d) Charles’s Law Answer: d Video Explanation
Which of the following atoms or ions has the electronic configuration 1s22s22p63s23p6 ? (a) Ne (b) Al3+ (c) Cl- (d) Mg2+ Answer: c Video Explanation
Which of the following contains an atom (other than hydrogen) which lacks an octet of valence electrons? (PPSC 2020)? (a) NH3 (b) H3O+ (c) NH4+ (d) BH3 Answer: d Video Explanation
An atom differs from its ion in which among the following? (a) Mass number (b) Atomic number (c) Neutrons (d) Number of protons Answer : d Explanation When an atom loses or gains electrons its forms its corresponding ion, and hence it differs in proton number. Video Explanation
Which isomerism is not exhibited in alkene? PPSC 2017? (a) geometrical (b) metamerism (c) chain isomerism (d) position isomerism Answer: b Video Explanation
Which of the following is most basic? (PPSC 2021)? (a) CH3NH2 (b) H2O (c) NH3 (d) CH3OH Answer: a Video Explanation
Among the following the maximum covalent character is shown by the compound. (PPSC 2020)? (a) MgCl2 (b) FeCl2 (c) SnCl2 (d) AlCl3 Answer: d Video Explanation
What is the value of universal gas constant in Nernst equation when the potential is given in volts? (PPSC 2015)? (a) 8.314 J mol-1K-1 (b) 0.0821 L atm mol-1K-1 (c) 8.205 m3 atm mol-1K-1 (d) 1.987 cal mol-1K-1 Answer: a Video Explanation
Which of the following is true in the case of the Zn-Cu cell? (PPSC 2020)? (a) The flow of electrons takes place from copper to zinc (b) E0 red of the copper electrode is less than that of a zinc electrode (c) Zinc acts as an anode and copper as a cathode (d) All are correct Answer: c Video Explanation
