A pi-bond between carbons is formed when:

2p_x and 2p_y orbitals overlap laterally

Magnetic quantum number

is dependent of the Principal quantum number (n)

The difference between Group IV and Group VI elements is that;

The former are more reactive while the latter are relatively inert

The following is true about d orbitals;

an electron occupying the orbital can have a magnetic quantum number of +½

With regards to ionic compounds, the following are true EXCEPT;

None of the other choices is true

In the Periodic Table, an element with high electron affinity

is likely to have low ionization energy

is possible between a molecule with complete octet and one with incomplete octet

The following are true on Molecular geometry except;

'lone pairs' electron exerts the greatest repulsion

In the molecule H — S — D the proton (H) is;

easily lost when D is much more electronegative than S

With regards to the electronic structure of atoms the following rules applies; I: "No two electrons in an atom share all the four quantum numbers" II: "The most stable arrangement of electrons in orbital is the one with the greatest number of parallel spins"

I is Pauli's exclusion principle while II is Hund's rule

The following is true about f orbitals;

can accommodate a maximum of 14 electrons

An electron displays the following properties

Wave function and Wave function

In the periodic table;

Rare gas elements have an np⁶ configuration

Salt dissolves in well in water because water molecules

surround the ions because of their charge but do not form hydrogen bonds

Which of the following pairs would be the best buffer at pH 10.0?

H₂CO₃ and NaHCO₃ (pKaS are 3.77 and 10.4)

The normal pH of normal human urine ranges from 4.6 to 8.0, what is the hydrogen ion concentration range for normal human urine?

2.5 × 10⁻⁵ to 1 × 10⁻⁸

The following statements are true regarding the reaction between Cl₂ and C₂H₆, except

The reaction will give a single product of C₂H₅Cl.

Ether molecules are polar, but do not form hydrogen bonds among themselves because

There is no hydrogen atom bonded to the oxygen.

Membranes with unsaturated fatty acids in their structure are more flexible and fluid because:

Unsaturated fatty acids bend at the double bond preventing close packing

In aldehydes, the carbonyl group is attached to

one hydrogen and one alkyl group

The major dietary carbohydrates include

Glycogen, starch, cellulose, glucose

A physiologic buffer functions to

Minimize the increase in hydrogen ion concentration that accompanies cellular acid production.

Rank the following bonds in order of increasing bond strength.

van der Waals, hydrogen bond, ionic, covalent single bond

The solubility of alcohols in water

Is due to H- bonding between alcohol and water molecules

Members of a homologous series

may have identical physical and chemical properties.

The cis and trans or the E,Z nomenclature

E,Z nomenclature involves the use of priority groups with respect to double bond

The following statement is true regarding degree of unsaturation of organic compounds, except

each ring or multiple bond replaces 4 H's when computing the degree of unsaturation of a compound

With regards to carbocations, a tertiary carbocation,

is more stable than either a secondary or primary carbocation

Chiral, or optical, isomers have the same chemical formula but differ in their three dimensional molecular structure and their

interaction with polarized light

In a secondary amine the nitrogen atom

Is attached to a secondary carbon of the hydrocarbon

Biochemistry Makeup Exam — 2020 (Past Paper)

79 clinical MCQs in Biochemistry. HNO3 is a stronger acid when dissolved in water than in CH3COOH because;. Kenya, Africa and global revision.

Questions, Answers & Explanations

Q1. HNO3 is a stronger acid when dissolved in water than in CH3COOH because;
- Acetic acid is a stronger conjugate base than water
- Water is a stronger conjugate base than acetic acid
- Acetic acid is a stronger conjugate base than the NO3 anion released
- The NO3 anion formed in acetic acid is weaker conjugate base than the NO3- formed in water.
- None of the above is true
Answer: Water is a stronger conjugate base than acetic acid
Q2. A pi-bond between carbons is formed when:
- 2p_x and 2p_x orbitals overlap along the same axis
- 2p_x and 2p_y orbitals overlap laterally
- 2p_x and 2p_z orbitals overlap along the same axis
- None of the above
Answer: 2p_x and 2p_y orbitals overlap laterally
Q3. Magnetic quantum number
- is dependent of the Principal quantum number (n)
- is independent of angular momentum quantum number (l)
- is dependent of electron spin quantum number (ms)
- is independent of principal quantum number
- None of the above is true
Answer: is dependent of the Principal quantum number (n)
Q4. If two electrons (i) and (ii) in an atom are described by the quantum numbers shown below; n l ml ms :--- :--- :--- :--- :--- (i) 4 1 1 +½ (ii) 4 1 1 -½ Which one is true?
- They have the same magnetic spin
- They are located in different d orbitals
- They have the same p orbitals
- They have same energy levels
- All the other choices are true
Answer: They have the same p orbitals
Q5. Repulsions between electron pairs on a central atom is
- greatest between lone pairs
- greatest between lone pair-bonding pairs
- greatest between bonding pairs
- lowest between lone pairs
- lowest between bonding and lone pairs
Answer: greatest between lone pairs
Q6. The following are noble gases except;
- Hydrogen
- Helium
- Neon
- Argon
- Radon
Answer: Hydrogen
Q7. The difference between Group IV and Group VI elements is that;
- The latter are metals, the former are non metals
- The latter are non-metals former are metals
- The former are more reactive while the latter are relatively inert
- The former are more reactive in comparison to the latter
- All the above are incorrect
Answer: The former are more reactive while the latter are relatively inert
Q8. The following is true about d orbitals;
- accommodate a maximum of 14 electrons
- have a minimum principal quantum number (n) of 2
- an electron occupying the orbital can have a magnetic quantum number of -½
- an electron occupying the orbital can have a magnetic quantum number of +½
- an electron in this orbital can have a magnetic quantum number of +½
Answer: an electron occupying the orbital can have a magnetic quantum number of +½
Q9. The strength of following acids is shown below. I II III IV V :--- :--- :--- :--- :--- :--- Ka= 10⁻⁶ Ka= 10⁻¹⁴ Ka= 10⁻³ pKa= 12 pKa= 6 Which one is true?
- I is the most acidic
- II is the least acidic
- III is less acidic than I
- IV is more acidic than II
- V is more acidic than IV
Answer: V is more acidic than IV
Q10. In the molecule CH3CHCHCCH3, the bond(s) between C4 and C5 from the left
- is a triple bond
- Has two pi bond
- Constitutes of two pi and one sigma
- Is pi only
- All the other choices are false
Answer: is a triple bond
Q11. The following is a Lewis acid(s)
- H₂O
- NH₃
- CH₂
- H₃O⁺
Answer: H₂O
Q12. With regards to ionic compounds, the following are true EXCEPT;
- Electron transfer between elements/atoms
- The union of ions that are isoelectronic to rare gas elements
- The fact that the resulting compound is lower in energy than either of the constituent ions
- NaCl is good example
- None of the other choices is true
Answer: None of the other choices is true
Q13. In the Periodic Table, an element with high electron affinity
- is likely to be in group II
- is likely to have low ionization energy
- is likely to be in group I
- readily form ionic compound with group VI elements
- Magnesium is a good example
Answer: is likely to have low ionization energy
Q14. The following elements are paramagnetic, except;
- N, 7
- O, 8
- B, 5
- Cl, 17
Answer: N, 7
Q15. Dative bond
- is possible between a molecule with complete octet and one with incomplete octet
- involves sharing a pair of electrons that was donated by the bonding atoms
- involves complete transfer of a pair of electrons between bonding atoms
- is not a covalent bond
- All the other choices are true
Answer: is possible between a molecule with complete octet and one with incomplete octet
Q16. The following are true on Molecular geometry except;
- is dictated by the number of electron pairs on the central atom
- 'lone pairs' electron exerts the greatest repulsion
- is the arrangement in space of atoms bonded to a central atom
- is dictated by the VSEPR-model
Answer: 'lone pairs' electron exerts the greatest repulsion
Q17. In the Periodic Table the atomic size of elements;
- increases across the Group
- increases down the Period
- Decreases down the Period
- Remains constant across the Group
- None of the other choices is true
Answer: increases across the Group
Q18. In the molecule H — S — D the proton (H) is;
- easily lost when D is much more electronegative than S
- easily lost when D is a Methyl group
- Remains unchanged when D is replaced by a more electronegative element
- easily lost when S and D are equal in electronegativity
- None of the other choices is true
Answer: easily lost when D is much more electronegative than S
Q19. With regards to the electronic structure of atoms the following rules applies; I: "No two electrons in an atom share all the four quantum numbers" II: "The most stable arrangement of electrons in orbital is the one with the greatest number of parallel spins"
- I is Hund's rule
- II is Pauli's exclusion principle
- I is Pauli's exclusion principle while II is Hund's rule
- I and II are never applicable at the same time
- None of the other choices is true
Answer: I is Pauli's exclusion principle while II is Hund's rule
Q20. The following is true about f orbitals;
- can accommodate a maximum of 14 electrons
- can have a principal quantum number (n) of 2
- an electron occupying the orbital can have a magnetic quantum number of -½
- can have a principal quantum number (n) of 3
- an electron in this orbital can have a magnetic quantum number of +½
Answer: can accommodate a maximum of 14 electrons
Q21. An electron displays the following properties
- Wave function
- Magnetism and Wave function
- Wave function and Wave function
- Mass and Magnetism
- All the other choices are true
Answer: Wave function and Wave function
Q22. In the periodic table;
- Elements are arranged into six blocks
- Transitional elements are in the s-block
- Electrons are added to s-atomic orbital in p-block elements
- Rare gas elements have an np⁶ configuration
- Electronegativity increases down the Group
Answer: Rare gas elements have an np⁶ configuration
Q23. The f orbital has
- n = 3
- nine orbitals
- sixteen orbitals
- none of the other choices is true
Answer: n = 3
Q24. Expansion of octet
- account for SF₆
- account for PCl₅
- is quite common in Period 2 elements
- accounts for the existence of Boron trifluoride (BF₃)
- None of the other choices is true
Answer: account for SF₆
Q25. If chemical analysis of a sample of DNA shows that 20% of the bases present are Guanine, what percentage would be Thymine?
- 10%
- 20%
- 30%
- 40%
- 80%
Answer: 30%
Q26. Salt dissolves in well in water because water molecules
- make nonpolar covalent bonds with the positively charged ions only
- share electrons with the ions to make polar covalent bonds
- surround the ions because of their charge but do not form hydrogen bonds
- are larger than the salt molecules
- form hydrogen bonds with the positively and negatively charged ions
Answer: surround the ions because of their charge but do not form hydrogen bonds
Q27. Which of the following pairs would be the best buffer at pH 10.0?
- NaH₂PO₄ and Na₂HPO₄ (pKaS are 2.1, 7.2, 12.4)
- Acetic acid and sodium acetate (pKa = 4.76)
- H₂CO₃ and NaHCO₃ (pKaS are 3.77 and 10.4)
- Sodium succinate and succinic acid (pKa = 4.21)
- Lactic acid and sodium lactate (pKa = 3.86)
Answer: H₂CO₃ and NaHCO₃ (pKaS are 3.77 and 10.4)
Q28. The normal pH of normal human urine ranges from 4.6 to 8.0, what is the hydrogen ion concentration range for normal human urine?
- 2.5 × 10⁻² to 1 × 10⁻⁸
- 2.5 × 10⁻³ to 1 × 10⁻⁷
- 2.5 × 10⁻⁴ to 1 × 10⁻⁸
- 2.5 × 10⁻⁵ to 1 × 10⁻⁸
- 2.5 × 10⁻⁶ to 1 × 10⁻⁹
Answer: 2.5 × 10⁻⁵ to 1 × 10⁻⁸
Q29. The following statements are true regarding the reaction between Cl₂ and C₂H₆, except
- It is a substitution reaction.
- The reaction will give a single product of C₂H₅Cl.
- The reaction mechanism involves free radicals.
- The reaction can be initiated with either sunlight or heat.
- The first step in the mechanism is the cleavage of the Cl-Cl bond to give chlorine atoms.
Answer: The reaction will give a single product of C₂H₅Cl.
Q30. The name of the alkane isomer of cis-3-hexene is:
- 2-methylpentane
- 3-methylpentane
- n-hexane
- 2,3-dimethylbutane
- Cyclohexane
Answer: Cyclohexane
Q31. Glucocorticoid drugs such as betamethasone acts by inhibiting one of the following enzymatic reactions in prostaglandin synthesis
- Cytochrome P450
- Cyclooxygenase
- Diacylglycerol lipase
- Phospholipase A2
- Diacylglycerol kinase
Answer: Phospholipase A2
Q32. Ether molecules are polar, but do not form hydrogen bonds among themselves because
- There are too many hydrogen atoms on the molecules to bond with just one oxygen atom.
- There is no hydrogen atom bonded to the oxygen.
- Only binary compounds form hydrogen bonds.
- Ether molecules are so reactive such that they cannot form hydrogen bonds.
- Ether molecules are generally too large.
Answer: There is no hydrogen atom bonded to the oxygen.
Q33. Membranes with unsaturated fatty acids in their structure are more flexible and fluid because:
- Saturated fatty acids have a "kink" that produces more fluid aggregates.
- Unsaturated fatty acids have cis double bond that makes it more "sticky".
- Unsaturated fatty acids bend at the double bond preventing close packing
- Unsaturated fatty acids pack closely together to form ordered arrays.
- Saturated fatty acids are naturally flexible
Answer: Unsaturated fatty acids bend at the double bond preventing close packing
Q34. In aldehydes, the carbonyl group is attached to
- one hydrogen and one oxygen
- one hydrogen and one alkyl group
- two alkyl groups
- one oxygen and one alkyl group
- One carbon and one hydroxyl group
Answer: one hydrogen and one alkyl group
Q35. The major dietary carbohydrates include
- Glucose, fructose, galactose and ribose.
- Glucose, fructose, mannose and deoxyribose.
- Sucrose, lactose, starch and cellulose.
- Sucrose, lactose, galactose and glycogen.
- Glycogen, starch, cellulose, glucose
Answer: Glycogen, starch, cellulose, glucose
Q36. A physiologic buffer functions to
- To alter the rate of reactions
- Regulate the partial pressure of venous carbon-dioxide.
- Transport carbon dioxide from the site of its production to the site of its elimination.
- Minimize the increase in hydrogen ion concentration that accompanies cellular acid production.
- Maximize the decrease in hydrogen ion concentration that accompanies alkali formation
Answer: Minimize the increase in hydrogen ion concentration that accompanies cellular acid production.
Q37. Hydrocarbons are not soluble in water because
- The C-H bond is nonpolar.
- They are lighter than water.
- They are hydrophilic.
- The C-H bond is polar.
- They are large molecules.
Answer: The C-H bond is nonpolar.
Q38. Rank the following bonds in order of increasing bond strength.
- ionic, hydrogen bond, van der Waals, covalent single bond
- van der Waals, hydrogen bond, ionic, covalent single bond
- van der Waals, ionic, hydrogen bond, covalent single bond
- covalent single bond, van der Waals, ionic, hydrogen bond
- Ionic, covalent single bond, van-der Waals, hydrogen bond
Answer: van der Waals, hydrogen bond, ionic, covalent single bond
Q39. The solubility of alcohols in water
- Increases as the carbon chain length increases.
- Decreases as the number of –OH groups present increases.
- Increases with increasing molecular mass.
- Is due to H- bonding between alcohol and water molecules
- Increases there alcohol proof
Answer: Is due to H- bonding between alcohol and water molecules
Q40. Members of a homologous series
- are all constitutional isomers.
- are always hydrocarbons.
- may have identical physical and chemical properties.
- each differ from its nearest neighbors by 14 amu.
- may also be classified as tautomers
Answer: may have identical physical and chemical properties.
Q41. The cis and trans or the E,Z nomenclature
- cis and trans require end groups to differ in pairs
- Cis, trans nomenclature only works for di-substituted double bonds
- E,Z nomenclature involves the use of priority groups with respect to double bond
- Cis- trans should only be used when there are two H's and two non-hydrogen groups attached to each carbon.
- Both nomenclature are examples of structural isomerism
Answer: E,Z nomenclature involves the use of priority groups with respect to double bond
Q42. The following statement is true regarding degree of unsaturation of organic compounds, except
- relates molecular formula to possible structures
- is the number of multiple bonds or rings in a compound
- each ring or multiple bond replaces 4 H's when computing the degree of unsaturation of a compound
- the compounds C4H6Br2 and C4H8 have each one degree of unsaturation
- when connected by single bonds oxygen atoms do not affect the degree of unsaturation
Answer: each ring or multiple bond replaces 4 H's when computing the degree of unsaturation of a compound
Q43. The following are pairs of functional group isomers?
- CH3CH2OCH3 and CH3CH2CHO
- CH3CH2CHO and CH3CH2CH2OH
- CH3COCH2CH3 and CH3CH2COCH3
- CH3CH2CH2CHO and CH3COCH2CH3
- CH3CH2CH2CH2OH and CH3CH2COCH3
Answer: CH3CH2CH2CHO and CH3COCH2CH3
Q44. Constitutional isomers with a molecular formula of C4H9Cl have the following IUPAC names, except
- 1-chloro-2-methylpropane
- 3-chlorobutane
- 2-chloro-2-methylbutane
- 1-chloro-3-methylpropane
- 3-methyl-4-chloro-butane
Answer: 3-methyl-4-chloro-butane
Q45. With regards to carbocations, a tertiary carbocation,
- is more stable than either a secondary or primary carbocation
- carries three positive charges
- has a pyramidal configuration
- has a trigonal planar configuration
- possesses three electron-donating substituent groups
Answer: is more stable than either a secondary or primary carbocation
Q46. Chiral, or optical, isomers have the same chemical formula but differ in their three dimensional molecular structure and their
- interaction with a catalyst
- interaction with polarized light
- interaction with carbon
- number of carbon bonds
- configuration around carbon-carbon double bond
Answer: interaction with polarized light
Q47. Halothene is
- An ether
- An alcohol
- An amine
- Alkylhalide
- Aromatic
Answer: Alkylhalide
Q48. In a secondary amine the nitrogen atom
- Is attached to hydrogen
- Is attached to two hydrogens
- Has no hydrogen attached to it
- Is attached to a secondary carbon of the hydrocarbon
- Is attached to a carbonyl group
Answer: Is attached to a secondary carbon of the hydrocarbon
Q49. The following statements are true regarding alkanes, except, alkanes CAT 2 Make up Aug 2020
- are non-polar molecules
- are soluble in water
- experience dispersion forces
- have low boiling points
- undergo halogenation reactions
Answer: are soluble in water
Q50. Which of the following indicates the pKa of an acid is numerically equal to the pH of the solution when the molar concentration of the acid and its conjugate base are equal.
- Michaelis-Menten equation
- Haldanes equation
- Henderson Hasselbalch equation
- Hardy Windberg law
- Law of mass action
Answer: Henderson Hasselbalch equation
Q51. Polar molecules can readily dissolve in water because
- Polar molecules can form hydrogen bonds with water
- Polar molecules can replace water-water interactions with the mere energetically favorable water solute interactions
- Polar charged water can interact with the charge of polar molecules
- All polar molecules are amphipathic in nature
- All the other statements are true
Answer: All the other statements are true
Q52. The following lipids are found in animal membranes, except
- Phosphoglycerides
- Cholesterol
- Triacylglycerols
- Glycolipids
- Sphingolipids
Answer: Triacylglycerols
Q53. The structure of a nucleoside consists of.
- A pyrophosphate group
- A 1' base linked to a pentose sugar
- A 5'-phosphate group linked to a pentose sugar
- A 3'-phosphate group linked to a pentose sugar
- A terminal triphosphate
Answer: A 1' base linked to a pentose sugar
Q54. The oxygen carrier of muscle is the globular protein myoglobin. One of the following amino acids is highly likely to be localized within the interior of the myoglobin molecule
- Arginine
- Aspartic acid
- Glutamic acid
- Valine
- Lysine
Answer: Valine
Q55. One of the following statements is true regarding the properties of aqueous solutions
- A pH change from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration ([OH-]) of 20%.
- A pH change from 8.0 to 6.0 reflects a decrease in the proton concentration ([H+]) by a factor of 100.
- Charged molecules are generally insoluble in water.
- Hydrogen bonds form readily in aqueous solutions.
- The pH can be calculated by adding 7 to the value of the pOH.
Answer: Hydrogen bonds form readily in aqueous solutions.
Q56. Blood is drawn from a child with severe anemia and the hemoglobin protein is degraded for peptide and amino acid analysis. Of the results below, which change in hemoglobin primary structure is most likely to correlate with the clinical phenotype of anemia?
- ile-leu-val to ile-ile-val
- leu-glu-ile to leu-val-ile
- gly-ile-gly to gly-val-gly
- gly-asp-gly to gty-glu-gty
- val-val-val to val-leu-val
Answer: leu-glu-ile to leu-val-ile
Q57. In the relationship between the concentrations of substrate and the rate of an enzyme catalyzed reaction, the existence of a limited value (Vmax) of the reaction rate is primarily due to the
- Exhaustion of the substrate supply.
- Saturation of the enzyme with substrate.
- Inhibition of the enzyme by the reaction products.
- Denaturation of the enzyme at higher substrate concentrations.
- Balance between the increase in reaction rate with increasing substrate concentrations
Answer: Saturation of the enzyme with substrate.
Q58. If the presence of a specific compound, C, increases the Km for an enzyme-substrate reaction, which of the following would be true about that enzyme?
- C would be a competitive inhibitor of the enzyme.
- C would be a noncompetitive inhibitor of the enzyme.
- The velocity vs. [S] plot for the enzyme would be the same with or without C.
- With C present, the enzyme would convert substrate to product faster.
- With C present, it would take less substrate to drive the reaction
Answer: C would be a competitive inhibitor of the enzyme.
Q59. The following features contributes to the water-binding properties of proteoglycans
- The carboxyl groups acting as buffers
- Central hyaluronate (a helix) trapping water within
- The space between the core proteins and the hyaluronate being highly charged.
- Large number of alcohol groups on the polysaccharide chaining H-bond to water.
- Large number of serine & threonine residues in the core protein offering H-bonding sites.
Answer: Large number of alcohol groups on the polysaccharide chaining H-bond to water.
Q60. Prostaglandins are synthesized within cells
- On an RNA template.
- On rough endoplasmic reticulum.
- From methionine.
- From progesterone.
- From polyunsaturated fatty acids.
Answer: From polyunsaturated fatty acids.
Q61. The buffer system most important in maintaining the physiological pH of plasma is
- Protein/proteinate
- Acetic acid/acetate
- Carbonic acid/bicarbonate
- Phosphoric acid/phosphate
- Hydroxybutyric acid/hydroxybutyrate
Answer: Carbonic acid/bicarbonate
Q62. The bicarbonate buffer system of the blood is very efficient because
- bicarbonate is rapidly excreted by the kidneys.
- bicarbonate is able to be stored in the tissue.
- carbon dioxide is able to combine with hemoglobin
- carbon dioxide forms a stable combination with base.
- carbon dioxide is rapidly eliminated through the lungs.
Answer: carbon dioxide is rapidly eliminated through the lungs.
Q63. Certain amino acids are not part of the primary structure of proteins but are modified after translation. In scurvy, which amino acid that is normally part of collagen is not synthesized?
- Hydroxytyptophan
- Hydroxytyrosine
- Hydroxyhistidine
- Hydroxyalanine
- Hydroxyproline
Answer: Hydroxyproline
Q64. Before prescribing protein-containing parenteral feeding to a patient, a doctor sent the patient's blood to a laboratory to determine the electrophoretic spectrum of proteins. What physicochemical properties of proteins is this method based on?
- Viscosity
- Presence of charge
- Inability to denaturation
- Solubility and capacity for swelling
- Optical activity.
Answer: Presence of charge
Q65. Choose from these carbohydrates the disaccharide:
- Glycogen
- Cellulose
- Starch
- Glucose
- Sucrose.
Answer: Sucrose.
Q66. A small molecule that decreases the activity of an enzyme by binding to a site other than the catalytic site is termed a(n):
- allosteric inhibitor.
- alternative inhibitor.
- competitive inhibitor.
- stereospecific agent.
- transition-state analog.
Answer: allosteric inhibitor.
Q67. Sulfanilamide drugs are used for treatment of infectious diseases. What is the mechanism of bacteria growth inhibition of the drugs?
- Inhibition of the intracellular protein synthesis
- Inhibition of the SH-enzyme groups of the microorganisms
- Inhibition of cell wall synthesis of the microorganism
- Allosteric inhibition of bacterial enzymes
- They are structural analogs of para-aminobenzoic acid required for the synthesis of folic acid
Answer: They are structural analogs of para-aminobenzoic acid required for the synthesis of folic acid
Q68. What type of inhibitors does the pesticides belong to?
- Arsenic acid
- cyanides
- Sulfa drugs
- organophosphate compounds
- Malonic acid.
Answer: organophosphate compounds
Q69. Hydrolysis of sucrose by the enzyme sucrase yields
- Two molecules of glucose.
- Glucose and maltose.
- Glucose and fructose.
- Glucose and galactose.
- Fructose and maltose.
Answer: Glucose and fructose.
Q70. As DNA is denatured, each of the following events take place EXCEPT,
- Total G-C content of total DNA increasing
- UV light absorption increasing
- Complementary strands becoming random coils
- Base stacking becoming disrupted
- Hydrogen bond breaking
Answer: Total G-C content of total DNA increasing
Q71. One of the following describes the Henderson Hasselbalch equation where HA is the acid?
- pH = pK + log [A ]/[HA]
- pH = pK log [A ]/[HA]
- pH = pK + log [HA]/[A ]
- pK = pH + log [A ]/[HA]
- pH = PI + log [A ]/[HA]
Answer: pH = pK + log [A ]/[HA]
Q72. In the link that occurs between two consecutive nucleotides in RNA molecule is referred to as a
- Disulfide linkage
- Phosphodiester linkage
- Peptide linkage
- Ester linkage
- N-glycosidic linkage
Answer: Phosphodiester linkage
Q73. Blocking of enzyme action by blocking its active sites is:
- Allosteric inhibition
- Feedback inhibition
- Competitive inhibition
- Non-competitive inhibition
- Uncompetitive inhibition
Answer: Competitive inhibition
Q74. HNO₃ is a stronger acid when dissolved in water than in CH₃COOH because;
- Acetic acid is a stronger conjugate base than water
- Water is a stronger conjugate base than acetic acid
- Acetic acid is a stronger conjugate base than the NO₃ anion released
- The NO₃ anion formed in acetic acid is weaker conjugate base than the NO₃⁻ formed in water.
- None of the above is true
Answer: Water is a stronger conjugate base than acetic acid
Q75. A π-bond between carbons is formed when;
- 2pₓ and 2pᵧ orbitals overlap along the same axis
- 2pₓ and 2pₓ orbitals overlap laterally
- 2pₓ and 2pᵧ orbitals overlap along the same axis
- 2pₓ and 2pᵧ orbitals overlap along the same axis
- None of the above
Answer: 2pₓ and 2pₓ orbitals overlap laterally
Q76. If two electrons (i) and (ii) in an atom are described by the quantum numbers shown below; n l mᵢ mₛ :--- :--- :--- :--- :--- (i) 4 1 1 +½ (ii) 3 1 1 -½
- They have the same magnetic spin
- They are located in different *p* orbitals
- They have same energy levels
- All the above are true
Answer: They are located in different *p* orbitals
Q77. The following is true about d -orbitals;
- accommodate a maximum of 14 electrons
- have a minimum principal quantum number (n) of 2
- an electron occupying the orbital can have a magnetic quantum number of -½
- can have a principal quantum number (n) of 3
- an electron in this orbital can have a magnetic quantum number of +½
Answer: can have a principal quantum number (n) of 3
Q78. The strength of following acids is shown below. I II III IV V :--- :--- :--- :--- :--- :--- kₐ = 10⁻⁶ kₐ = 10⁻¹² kₐ = 10⁻³ pkₐ = 12 pkₐ = 6 Which one is true?
- I is the most acidic
- II is the least acidic
- III is less acidic than I
- IV is more acidic than II
- V is more acidic than IV
Answer: V is more acidic than IV
Q79. In the molecule CH₃CHCCHCH₃ the bond(s) between C4 and C5 from the left
- is a sigma bond only
- Has two π bond
- Constitutes of two π and one sigma
- is π only
- All the other choices are false
Answer: is a sigma bond only

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