Question 1

Which of the following is considered a model for enzyme action?

Accepted Answer

Answer reason: This describes enzyme specificity by proposing that the substrate fits precisely into the enzyme’s active site, enabling catalysis. It is a foundational concept explaining how enzymes recognize substrates and form an enzyme–substrate complex. While modern understanding also includes induced-fit concepts, this option is the classic named model among the choices provided.
Category reason: This question tests a foundational concept of how enzymes bind substrates and catalyze reactions, which is core Biochemistry rather than nursing decision-making.

Question 2

Which of the following statements about enzymes is not true?

Accepted Answer

Answer reason: Catalysts speed up reactions by lowering activation energy and are not consumed in the process, so they can be reused repeatedly. Many enzymes are proteins and typically function best at an optimal pH where their active site conformation is most favorable. Although enzymes can be denatured by extremes of pH, temperature, or inhibitors, that is not the same as being destroyed as a normal consequence of catalysis.
Category reason: This question tests fundamental properties of enzymes (catalysis, protein nature, optimal conditions), which is core biochemical knowledge rather than nursing care decision-making.

Question 3

__________ is a protein which catalyse one or more specific biochemical reaction and is not consumed during the reaction?

Accepted Answer

Answer reason: Enzymes are biological catalysts (typically proteins) that speed up specific biochemical reactions by lowering activation energy. They are not permanently changed or used up in the reaction and can be reused for multiple reaction cycles. Hormones and vitamins may regulate or support metabolic processes but do not themselves function as the primary catalytic proteins in the way enzymes do. The option “proteins” is too broad because not all proteins are catalysts.
Category reason: This item tests the definition and function of enzymes as biological catalysts, which is a core concept in biochemistry rather than a nursing care or safety decision.

Question 4

What is an atom that has a positive charge called?

Accepted Answer

Answer reason: A positive charge results when an atom loses one or more electrons, leaving more protons than electrons. This positively charged ion is termed a cation. By contrast, gaining electrons produces a negatively charged ion, called an anion. Cathode and anode refer to electrodes in electrochemistry, not the charged particle itself.
Category reason: This tests foundational concepts of ions and charge (electron loss/gain), which are core chemical principles within Biochemistry rather than a patient-care decision.

Question 5

Differentiate the essential amino acid in the following:

Accepted Answer

Answer reason: Essential amino acids cannot be synthesized by the human body in adequate amounts and therefore must be obtained from dietary sources. Valine is a branched-chain amino acid and is classified as essential. Proline and glycine are nonessential because humans can synthesize them. Tyrosine is generally nonessential/conditionally essential because it can be produced from phenylalanine, becoming essential only when phenylalanine is insufficient.

Question 6

Which vitamin acts as an antioxidant?

Accepted Answer

Answer reason: Antioxidant vitamins protect cell membranes from oxidative damage by scavenging free radicals and preventing lipid peroxidation. This fat-soluble role is characteristic of vitamin E (tocopherols), which stabilizes polyunsaturated fatty acids in membrane phospholipids. Vitamin K is primarily involved in gamma-carboxylation of clotting factors, not free-radical neutralization. Vitamin D functions mainly in calcium/phosphate homeostasis, and vitamin B1 (thiamine) is a coenzyme in carbohydrate metabolism rather than a major antioxidant.

Question 7

The building blocks of protein are?

Accepted Answer

Answer reason: Proteins are polymers formed by linking monomers through peptide bonds. The monomers that polymerize to create polypeptide chains are amino acids, each contributing an amino group, carboxyl group, and variable side chain that determines protein structure and function. Glucose and fatty acids are primary building blocks for carbohydrates and lipids, respectively, rather than proteins. Minerals can act as cofactors or structural components in tissues but are not the monomeric units of protein.

Question 8

Bilirubin is formed from?

Accepted Answer

Answer reason: Heme is converted to biliverdin by heme oxygenase, then biliverdin is reduced to unconjugated bilirubin by biliverdin reductase. Globin is instead hydrolyzed into amino acids for reuse, not into bile pigments. Transferrin and ferritin are iron transport/storage proteins and are not direct precursors of bilirubin.

Question 9

Lactose is made up of ?

Accepted Answer

Answer reason: In human nutrition, lactose specifically consists of galactose joined to glucose via a β-1,4 linkage, which is the substrate for the enzyme lactase in the small intestine. This composition explains why lactase deficiency causes symptoms after consuming dairy due to impaired breakdown of this specific disaccharide. A common distractor is sucrose, which is glucose plus fructose, not the sugar found in milk.

Question 10

Produced form of energy is ........?

Accepted Answer

Answer reason: Energy released from nutrient oxidation is conserved by phosphorylating ADP to form ATP, storing energy in high-energy phosphate bonds. ADP represents the lower-energy, spent form after ATP hydrolysis, not the main produced usable energy form. While GTP can serve as an energy source in specific pathways, ATP is the universal, dominant product for cellular energy transfer.

Question 11

Saturated Fatty Acids are all Except ?

Accepted Answer

Answer reason: Lauric (12:0), palmitic (16:0), and stearic (18:0) are classic saturated fatty acids with zero double bonds. Oleic acid is 18:1 (monounsaturated) and contains one double bond, so it is the exception among the listed choices. A common trap is assuming all common dietary fats listed are saturated, but the bond count determines saturation status.

Question 12

Hemoglobin synthesis starts with :-

Accepted Answer

Answer reason: This biochemical “first step” is classically tested as the starting substrate requirement for hemoglobin/heme production. Iron is incorporated later when protoporphyrin IX is converted to heme by ferrochelatase, so it is necessary but not the initiating substrate. Folic acid supports DNA synthesis and erythropoiesis but is not the first step in heme formation.

Question 13

Which of the following is provitamin.A?

Accepted Answer

Answer reason: Beta-carotene (a carotenoid) is the classic provitamin A compound that is enzymatically cleaved in the intestinal mucosa to form retinal and then retinol. Retinol, retinal, and retinoic acid are already preformed vitamin A forms rather than precursors. Therefore the carotenoid option is the best match for provitamin A.

Question 14

The base present in to DNA but absent into RNA is?

Accepted Answer

Answer reason: Thymine pairs with adenine in DNA, supporting stable long-term genetic storage. In RNA, uracil pairs with adenine instead, making uracil present in RNA rather than DNA. Guanine and cytosine are shared by both nucleic acids, so they cannot be the distinguishing base.

Question 15

Salivary amylase is activated by ?

Accepted Answer

Answer reason: Salivary amylase (ptyalin) is a chloride-dependent enzyme, and chloride acts as an allosteric activator required for full activity. This is distinct from many other enzymes that rely on metal ions like calcium or magnesium, which are not offered as choices here. Bicarbonate mainly provides pH buffering in saliva rather than directly activating this enzyme. Therefore, the best answer is the chloride ion.

Question 16

What are the basic structure units of proteins?

Accepted Answer

Answer reason: Each amino acid contributes an amino group, carboxyl group, hydrogen, and variable side chain that determines protein structure and function. Peptides are short chains of amino acids and therefore represent a product of assembly rather than the basic unit. Fatty acids and sucrose are building blocks of lipids and carbohydrates, respectively, not proteins.

Question 17

Green colour of bile is due to?

Accepted Answer

Answer reason: Biliverdin is produced from heme catabolism and can be converted to bilirubin; when biliverdin predominates, bile appears green. Bile salts such as taurocholate and glycocholate mainly aid fat emulsification and do not impart the green pigment color. Bilirubin is more associated with a yellow to yellow-brown coloration rather than green.

Question 18

Which provides the fastest source of energy?

Accepted Answer

Answer reason: It is quickly absorbed, enters glycolysis without needing prior breakdown, and can support anaerobic energy production when oxygen delivery is limited. In contrast, fats require slower mobilization and oxidation steps despite yielding more total energy per gram. Protein is not a primary rapid fuel because it requires deamination and is generally conserved for structural and functional roles, while minerals do not provide caloric energy.

Question 19

Macrocytic anemia case with normal methyl-malony[l] with increased level of homocysteine. Diagnosis?

Accepted Answer

Answer reason: Homocysteine rises in both folate and vitamin B12 deficiency because both are required for remethylation of homocysteine to methionine. Methylmalonic acid rises specifically in vitamin B12 deficiency (due to impaired conversion of methylmalonyl-CoA to succinyl-CoA) and is normal in folate deficiency. Therefore, the combination of elevated homocysteine with normal methylmalonic acid supports folate deficiency rather than vitamin B12 deficiency.

Question 20

Which of the following is comprised of the same type of monosaccharide or is a homopolysaccharide?

Accepted Answer

Answer reason:  A homopolysaccharide is a polymer made from repeating units of a single monosaccharide. Cellulose is composed exclusively of repeating β-D-glucose units linked primarily by β(1→4) glycosidic bonds, making it a classic homopolysaccharide. In contrast, hemicellulose is a heteropolysaccharide containing multiple different sugars, and heparin is a glycosaminoglycan with repeating disaccharide units rather than a single monosaccharide. Pectin is also a complex polysaccharide (mainly galacturonic acid with side chains) and is not purely one monosaccharide type.

Question 21

Which of the following is an example of an exothermic reaction?

Accepted Answer

Answer reason: Exothermic reactions release heat to the surroundings, producing a net output of energy. Combustion is a classic exothermic chemical reaction because forming CO2 and H2O from organic material releases substantial energy as heat and light. By contrast, phase changes like melting ice and boiling water require heat input (endothermic). Dissolving salt in water is not reliably exothermic in general chemistry contexts and is often treated as endothermic or variable depending on the solute.

Question 22

Which of the following is an example of a covalent bond?

Accepted Answer

Answer reason: In diatomic oxygen, the two oxygen atoms share pairs of electrons to complete their valence shells, creating a stable O=O double bond. By contrast, sodium chloride and calcium carbonate are primarily ionic compounds (metal cations paired with nonmetal/polyatomic anions), even though carbonate contains internal covalent bonds within the CO3 group. HCl is a polar covalent molecule, but in aqueous solution it dissociates almost completely into ions, making it less clearly the best “covalent bond” example on an exam compared with a purely covalent diatomic molecule.

Question 23

DNA is mainly found in which part of the cell?

Accepted Answer

Answer reason: The nucleus is also the site of DNA replication and transcription, which require controlled access to the genome. Ribosomes synthesize proteins from mRNA and do not store DNA, while lysosomes contain hydrolytic enzymes for intracellular digestion. Although small amounts of DNA exist in mitochondria (and chloroplasts in plants), the main cellular location is the nucleus.

Question 24

Cholesterol is synthesized in...?

Accepted Answer

Answer reason: Hepatocytes generate cholesterol for cell membranes and for packaging into lipoproteins (e.g., VLDL) and for conversion into bile acids. While some synthesis occurs in other tissues, they are not the dominant source tested in basic science MCQs. Options like kidney and stomach are not primary organs responsible for systemic cholesterol synthesis.

Question 25

DNA is?

Accepted Answer

Answer reason: Each nucleotide contains a deoxyribose sugar, a phosphate group, and a nitrogenous base, forming the characteristic double helix through base pairing. Proteins, lipids, and carbohydrates are distinct biomolecule classes with different monomers and primary biological roles. Recognizing DNA’s composition is foundational for understanding heredity, replication, and gene expression.

Question 26

After death all of following show rise in Cerebrospinal fluid (CSF) except?

Accepted Answer

Answer reason: Diffusion and breakdown of proteins also contribute to rising nitrogenous metabolites such as urea in CSF postmortem. Uric acid, however, is not a typical CSF analyte that reliably rises postmortem because it is relatively poorly represented in CSF and is more tightly linked to systemic purine metabolism and renal handling than to rapid postmortem CSF biochemical shifts. Therefore, among the listed substances, it is the best “except” choice.

Question 27

Which type of molecule NEVER contains a phosphate group?

Accepted Answer

Answer reason: In contrast, phospholipids are defined by having a phosphate-containing head group. Nucleic acids have a sugar-phosphate backbone, so phosphate is an essential component. ATP is adenosine triphosphate and inherently contains three phosphate groups, making it an obvious phosphate-containing molecule.

Question 28

Which type of molecule contains the alcohol glycerol?

Accepted Answer

Answer reason: Phospholipids typically contain glycerol esterified to two fatty acids plus a phosphate-containing head group, making glycerol a defining structural alcohol in this class. Carbohydrates are polymers of sugars, DNA contains a pentose sugar (deoxyribose) rather than glycerol, and proteins are polymers of amino acids without glycerol as a core scaffold. Therefore the molecule type that contains glycerol is the phospholipid class.

Question 29

Starch, dextran, glycogen, and cellulose are polymers of?

Accepted Answer

Answer reason: Polysaccharides are carbohydrates made by linking many monosaccharide units via glycosidic bonds. Starch, glycogen, and cellulose are classic examples composed of repeating glucose monomers, differing mainly in the type of glycosidic linkage and branching. Dextran is also a glucose-based polymer produced by certain bacteria/yeasts, typically rich in α-1,6 linkages with branching. Amino acids and nucleic acids are monomers of proteins and nucleic acids respectively, and fatty acids form lipids rather than these carbohydrate polymers.

Question 30

Which type of molecule is composed of (CH2O) units?

Accepted Answer

Answer reason: This repeating unit is the biochemical basis for naming them “hydrates of carbon.” Lipids have proportionally much less oxygen, while proteins and nucleic acids contain nitrogen (and nucleic acids also contain phosphorus), so they do not fit the (CH2O) unit pattern. Therefore the molecule type built from (CH2O) units is the one consistent with sugar monomers and polysaccharide polymers.

Question 31

What is the type of bond holding hydrogen and oxygen atoms together in a single H2O molecule?

Accepted Answer

Answer reason: In water, oxygen shares electrons with each hydrogen to form two polar covalent O–H bonds, creating one H2O molecule. Ionic bonds require full electron transfer to form separate charged ions, which is not how the O–H connections in water are formed. Hydrogen bonds occur between different molecules (or different parts of large molecules) due to partial charges, explaining water-to-water attraction rather than the intramolecular bonds.

Question 32

Which type of molecule contains -NH2 (amino) groups?

Accepted Answer

Answer reason: The presence of these amino groups (and related amine-containing side chains) is a defining chemical feature of proteins. Carbohydrates and triglycerides are primarily composed of carbon, hydrogen, and oxygen without amino functional groups as a core feature. While nucleic acids contain nitrogenous bases, the classic “amino group” hallmark tested in basic chemistry/biology questions refers to amino acids and therefore proteins.

Question 33

Which are the primary molecules making up plasma membranes in cells?

Accepted Answer

Answer reason: Amphipathic phospholipids self-assemble with hydrophilic heads facing water and hydrophobic tails inward, creating a stable boundary between intracellular and extracellular environments. Proteins are essential functional components (channels, receptors, enzymes), but they are embedded within and depend on the lipid bilayer rather than forming the primary matrix. Carbohydrates are present mainly as glycolipids and glycoproteins for recognition and signaling, and nucleic acids are not structural components of membranes.

Question 34

Which molecule is composed of a chain of amino acids?

Accepted Answer

Answer reason: Carbohydrates are built from monosaccharides (sugars), not amino acids. Lipids are primarily composed of fatty acids and glycerol (or sterol backbones), so they are not amino-acid chains. Nucleic acids are polymers of nucleotides (DNA/RNA), distinguishing them from amino-acid–based macromolecules.

Question 35

Structurally, ATP is most like which type of molecule?

Accepted Answer

Answer reason: Nucleic acids (DNA/RNA) are polymers built from these same nucleotide subunits, so ATP’s chemical scaffold matches that class most closely. Carbohydrates, lipids, and proteins have distinct monomer/backbone structures (monosaccharides, fatty acids/glycerol, and amino acids, respectively) that do not resemble ATP’s base-sugar-phosphate architecture. Therefore the most structurally similar category is nucleic acid.

Question 36

Most amino acids found in cells demonstrate what type of chirality?

Accepted Answer

Answer reason: This biologic homochirality is a foundational biochemical principle and explains why naturally incorporated amino acids in human cells are almost exclusively L forms (glycine is achiral). D-amino acids are uncommon in human proteins and are more characteristic of certain bacterial cell wall components and some peptides. The remaining options are not standard stereochemical categories used for amino acids in biology.

Question 37

Which of the following compounds is NOT an enzyme?

Accepted Answer

Answer reason: Coenzymes are small organic cofactors that assist enzymes by carrying chemical groups or electrons between reactions but do not themselves provide catalytic active sites. This choice is a classic acyl-group carrier (e.g., acetyl group transfer) used by many enzymes in metabolism. The other options are established enzymes involved in oxidation-reduction or carbohydrate digestion/hydrolysis.

Question 38

An enzyme, citrate synthase, in the Krebs cycle is inhibited by ATP. This is an example of all of the following EXCEPT?

Accepted Answer

Answer reason: ATP regulating a Krebs cycle enzyme is classic end-product (feedback) control of metabolism, where a high-energy state downshifts flux through the pathway. This control typically occurs via allosteric binding at a regulatory (non-active) site, producing a noncompetitive-type effect on enzyme activity. Competitive inhibition instead requires the inhibitor to resemble and compete with the substrate for the active site, which does not describe ATP’s regulatory role on citrate synthase. Therefore, competitive inhibition is the exception among the listed mechanisms.

Question 39

Identify the following reaction: Glucose + Fructose → Sucrose + Water?

Accepted Answer

Answer reason: A glycosidic bond is created between glucose and fructose while an –OH and –H are removed to form H2O. Hydrolysis is the opposite process, where water is consumed to break a bond and split sucrose into its monosaccharides. The other choices do not describe the key biochemical mechanism of water removal during bond formation.

Question 40

Based upon the valence numbers of the elements magnesium (2) and hydrogen (1), predict how many covalent bonds would form between these atoms to achieve the full complement of electrons in their outermost energy shells?

Accepted Answer

Answer reason: Magnesium has a valence of 2, meaning it needs two electrons (or would share two electrons in covalent bonding) to complete its outer shell, while each hydrogen has a valence of 1 and can share one electron. Therefore, magnesium would need to form two single covalent bonds with two hydrogen atoms to satisfy the valence requirement. Options like one bond would leave magnesium short of its typical stable electron configuration, and higher numbers exceed the bonding capacity implied by the given valences.

Question 41

Identify the following reaction: Lactose + H2O → Glucose + Galactose?

Accepted Answer

Answer reason: Here, a disaccharide (lactose) reacts with water and is split into its monosaccharides (glucose and galactose), which is the hallmark of hydrolyzing a glycosidic linkage. Dehydration synthesis would be the opposite direction, forming lactose by removing water. This reaction is not best described as exchange or ionic, because the key mechanism is bond cleavage via water addition rather than ion formation or swapping groups between reactants.

Question 42

Two glucose molecules are combined to make a maltose molecule. What is the chemical formula for maltose?

Accepted Answer

Answer reason: Two glucose monomers would sum to C12H24O12 before bonding. Subtracting H2O for the condensation step yields C12H22O11, which matches the standard formula for maltose. Options that keep the full combined hydrogens/oxygens fail to account for the water lost during bond formation.

Question 43

Identify the following reaction: HCl + NaHCO3 → NaCl + H2CO3?

Accepted Answer

Answer reason: Hydrogen from the acid combines with bicarbonate to form carbonic acid, while sodium pairs with chloride to form sodium chloride. This pattern matches an exchange reaction rather than dehydration synthesis (which forms water as a product) or hydrolysis (which consumes water to break bonds). While it occurs via ions in solution, the defining classification here is the partner swap characteristic of double replacement.

Question 44

Which of the following pairs is mismatched?

Accepted Answer

Answer reason: Potassium dihydrogen phosphate dissociates primarily into K+ and H2PO4−, which is an amphiprotic conjugate base/acid species; the dissociation step shown is characteristic of an ionic salt, not an acid dissociation releasing H+. In contrast, HF and H2SO4 are acids because their dissociation produces hydrogen ions, while NaOH produces hydroxide and MgSO4 is a typical salt. The mismatch is therefore the classification of KH2PO4 as an acid based on the dissociation equation provided.

Question 45

Identify the following reaction: NH4OH ⇌ NH3 + H2O?

Accepted Answer

Answer reason: Here, ammonium hydroxide can dissociate to ammonia and water, and ammonia can also combine with water to re-form ammonium hydroxide under appropriate conditions. This is not dehydration synthesis because no larger molecule is being formed by removing water, and it is not hydrolysis because water is not being used to cleave a bond into two new products. While weak bases can partially ionize in water, the defining feature being tested is the equilibrium notation, making reversibility the best classification.

Question 46

Which one of the following would you predict is an allosteric inhibitor of the Krebs cycle enzyme, α-ketoglutarate dehydrogenase?

Accepted Answer

Answer reason: α-ketoglutarate dehydrogenase is inhibited by its products and high-energy signals, including NADH (and succinyl-CoA), to prevent excessive flux through the TCA cycle. NAD+ is a required oxidized cofactor and would support, not suppress, catalytic turnover. ADP generally indicates low energy demand and tends to activate TCA/respiratory pathways rather than inhibit this step.

Question 47

Which biochemical process is NOT used during glycolysis?

Accepted Answer

Answer reason: It is therefore a form of carbohydrate catabolism carried out through a sequence of enzyme-catalyzed reactions. Beta oxidation, in contrast, is the mitochondrial (or peroxisomal) pathway for fatty acid degradation into acetyl-CoA, not a step or mechanism used in glycolysis. A common confusion is that both pathways produce reducing equivalents, but they act on different substrates and occur in distinct metabolic routes.

Question 48

Fatty acids are oxidized in?

Accepted Answer

Answer reason: Fatty acids are primarily broken down by beta-oxidation to generate acetyl-CoA, NADH, and FADH2. The acetyl-CoA produced is then oxidized in the citric acid (Krebs) cycle, where its carbons are converted to CO2 and additional reduced cofactors are generated. The electron transport chain does not oxidize fatty acids directly; it uses NADH and FADH2 (including those produced from beta-oxidation and the Krebs cycle) to drive oxidative phosphorylation. Glycolysis, the pentose phosphate pathway, and the Entner-Doudoroff pathway are carbohydrate-focused pathways rather than the central route for fatty-acid carbon oxidation.

Question 49

Which of the following statements regarding metabolism is FALSE?

Accepted Answer

Answer reason: Anabolism refers to biosynthetic pathways that build larger, more complex molecules from smaller precursors and generally require an input of energy. Degradative pathways are catabolic, where complex molecules are broken down and energy is harvested, commonly capturing it in ATP and releasing some as heat. Therefore calling anabolic reactions “degradative” reverses the core definitions of anabolism versus catabolism, making this statement false. A common distractor is confusing energy use with heat release; even energy-requiring reactions can still dissipate some energy as heat depending on coupling and inefficiency.

Question 50

Antacids neutralize acid by the following reaction. Identify the salt in the following equation: Mg(OH)2 + 2HCl → MgCl2 + H2O?

Accepted Answer

Answer reason: Here, Mg(OH)2 provides Mg2+ and HCl provides Cl−; combining these yields the ionic product magnesium chloride. Water is the other product formed when H+ reacts with OH− to make H2O. The reactants Mg(OH)2 and HCl are base and acid, respectively, not the salt product.

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