1. The term biomolecule most appropriately refers to:
ⓐ. A carbon-containing compound formed in any chemical process
ⓑ. A substance produced by or associated with living systems
ⓒ. A high-molar-mass polymer occurring only inside cells
ⓓ. An inorganic mineral ion required by living cells
Correct Answer: A substance produced by or associated with living systems
Explanation: Biomolecules are chemical substances produced by living organisms or closely associated with their structure and functioning. They include small molecules such as glucose and vitamins as well as large molecules such as proteins and nucleic acids. The presence of carbon and hydrogen alone does not make every organic compound a biomolecule. Biomolecules also need not be polymers, because many hormones and vitamins are comparatively small non-polymeric substances. Molecular size alone cannot be used to identify a biomolecule.
2. A set composed entirely of major biomolecular families or biologically important regulatory molecules is:
ⓐ. Carbohydrates, alloys, nucleic acids and ceramics
ⓑ. Proteins, hydrocarbons, minerals and vitamins
ⓒ. Nucleic acids, salts, synthetic fibres and hormones
ⓓ. Carbohydrates, proteins, nucleic acids and vitamins
Correct Answer: Carbohydrates, proteins, nucleic acids and vitamins
Explanation: Carbohydrates, proteins, nucleic acids and vitamins are all important classes of substances associated with living systems. Carbohydrates commonly supply or store energy, while proteins perform structural and catalytic functions. Nucleic acids store and transmit genetic information, and vitamins assist in the regulation of biochemical processes. Alloys, ceramics and synthetic fibres are material classes rather than major biomolecular families. These groups differ greatly in size and structure, so they should not all be assumed to be polymers.
3. The primary biological role most directly associated with glucose is:
ⓐ. Supplying readily usable chemical energy
ⓑ. Storing hereditary information
ⓒ. Forming the main structural framework of chromosomes
ⓓ. Catalysing every metabolic reaction
Correct Answer: Supplying readily usable chemical energy
Explanation: Glucose is a simple carbohydrate that can be oxidised by cells to release usable energy. It is therefore closely associated with immediate energy supply rather than long-term information storage. DNA, not glucose, carries hereditary information and forms an essential component of chromosomes. Most biological catalysts are enzymes, many of which are proteins. Glucose may also serve as a building unit for larger carbohydrates, but its direct energy role is the most immediate association here.
4. Cellulose is especially important in living systems because it:
ⓐ. carries genetic instructions from one generation to the next
ⓑ. functions as the principal catalyst in digestion
ⓒ. provides structural strength to plant cell walls
ⓓ. acts as the chief storage carbohydrate in animals
Correct Answer: provides structural strength to plant cell walls
Explanation: Cellulose is a carbohydrate polymer that forms a major structural component of plant cell walls. Its long chains associate through numerous hydrogen bonds, producing strong fibrous structures. Enzymes, rather than cellulose, carry out catalytic functions in digestion. Glycogen is the principal storage carbohydrate of animals, while DNA stores genetic information. The arrangement and interactions of polymer chains can make a carbohydrate structural rather than primarily energy-storing.
5. Many enzymes are classified chemically as:
ⓐ. carbohydrates that permanently change during reaction
ⓑ. proteins that accelerate biochemical reactions
ⓒ. nucleic acids that store all cellular energy
ⓓ. vitamins that become structural fibres
Correct Answer: proteins that accelerate biochemical reactions
Explanation: Most enzymes are globular proteins that increase the rates of specific biochemical reactions. They provide suitable active sites where reactant molecules can bind and undergo conversion more readily. A catalyst participates in the reaction pathway but is regenerated rather than permanently consumed. Carbohydrates are mainly associated with energy and structural roles, although their functions are diverse. A protein is not automatically an enzyme, because many proteins instead serve structural, transport, defence or storage functions.
6. The role that most clearly distinguishes nucleic acids from carbohydrates and proteins is:
ⓐ. genetic information storage and transmission
ⓑ. formation of lipid bilayers in every cell membrane
ⓒ. immediate energy release during cellular respiration
ⓓ. catalysis of most biochemical reactions
Correct Answer: genetic information storage and transmission
Explanation: Nucleic acids, particularly DNA and RNA, are responsible for storing, expressing and transmitting genetic information. Their nucleotide sequences contain coded instructions that influence protein formation and cellular activity. Glucose and related carbohydrates are more directly involved in energy supply and storage. Proteins perform many structural, catalytic and transport functions, but their amino-acid sequences are specified through genetic information. The information-bearing role depends on the ordered sequence of nucleotides rather than merely on the large size of the molecule.
7. A hormone differs from an enzyme mainly because a hormone generally:
ⓐ. is consumed after signalling, whereas an enzyme is regenerated after reaction
ⓑ. acts only in its source cell, whereas an enzyme acts only in blood
ⓒ. changes reaction equilibrium, whereas an enzyme changes only reaction rate
ⓓ. acts as a regulatory signal, whereas an enzyme catalyses a reaction
Correct Answer: acts as a regulatory signal, whereas an enzyme catalyses a reaction
Explanation: Hormones are signalling substances that regulate physiological or biochemical activities, often by acting on specific target cells. Enzymes primarily accelerate chemical reactions by lowering the activation barrier of a reaction pathway. A hormone may influence the production or activity of an enzyme, but the two roles are not identical. Hormones also belong to more than one chemical class; some are peptides, while others have different molecular frameworks. Functional classification should therefore be based on regulatory signalling versus catalysis, not on a claim that every hormone has the same chemical structure.
8. Glucose and starch illustrate the relationship between smaller and larger biomolecules because:
ⓐ. glucose is a disaccharide, whereas starch is a monosaccharide
ⓑ. glucose is a carbohydrate polymer, whereas starch is its monomer
ⓒ. glucose is a monomeric sugar, whereas starch is a glucose polymer
ⓓ. glucose and starch contain the same number of sugar residues
Correct Answer: glucose is a monomeric sugar, whereas starch is a glucose polymer
Explanation: Glucose is a monosaccharide and represents a relatively small carbohydrate molecule. Starch is a polysaccharide containing many glucose-derived units joined through glycosidic linkages. During polymer formation, the incorporated glucose units are described as residues because bond formation involves the loss of atoms as a small molecule. Hydrolysis reverses this construction by cleaving linkages and ultimately releasing glucose units. The monomer is the smaller building unit, so describing starch as the monomer reverses the relationship.
9. Consider the following statements.
Statement I: Glucose can act as a smaller building unit for certain larger carbohydrates.
Statement II: Starch is a naturally occurring macromolecule.
Statement III: Every vitamin is a polymer made from repeating monosaccharide units.
The acceptable statements are:
ⓐ. I only
ⓑ. I and II only
ⓒ. II and III only
ⓓ. I, II and III
Correct Answer: I and II only
Explanation: Glucose units can join to form larger carbohydrates such as starch, so Statement I is acceptable. Starch contains a large number of linked glucose residues and is therefore a biological macromolecule. Vitamins are generally small organic compounds required in limited amounts and are not all polymers. Repetition of monosaccharide units is characteristic of polysaccharides, not of vitamins as a class. The comparison shows why the terms biomolecule and polymer cannot be treated as synonyms.
10. Match each biomolecule in Column I with its principal association in Column II.
| Column I | Column II |
|---|
| P. Glucose | 1. Genetic information |
| Q. Cellulose | 2. Catalysis |
| R. Enzyme | 3. Readily usable energy |
| S. DNA | 4. Plant structural material |
ⓐ. P-4, Q-3, R-1, S-2
ⓑ. P-3, Q-2, R-4, S-1
ⓒ. P-1, Q-4, R-3, S-2
ⓓ. P-3, Q-4, R-2, S-1
Correct Answer: P-3, Q-4, R-2, S-1
Explanation: Glucose is readily used as an energy source, so P matches 3. Cellulose contributes structural strength to plant cell walls, linking Q with 4. Enzymes catalyse biochemical reactions, so R matches 2. DNA stores genetic information and therefore S matches 1. These functions are principal associations; a biomolecule may participate in additional processes without losing its central classification.
11. The functional group that occurs repeatedly in many carbohydrates and strongly promotes hydrogen bonding with water is:
ⓐ. hydroxyl group
ⓑ. phosphate group
ⓒ. amino group
ⓓ. amide group
Correct Answer: hydroxyl group
Explanation: A hydroxyl group contains the unit \(\mathrm{-OH}\) and is present several times in molecules such as glucose. Its polar oxygen-hydrogen bond allows the molecule to form hydrogen bonds with water. Multiple hydroxyl groups therefore contribute significantly to the water solubility of many small carbohydrates. Phosphate groups are prominent in nucleotides, while amino and amide groups are especially important in amino acids and proteins. Water solubility also depends on molecular size and structure, so the presence of hydroxyl groups does not guarantee that every large carbohydrate is highly soluble.
12. An aldehyde and a ketone are both carbonyl compounds, but they differ because:
ⓐ. an aldehydic carbonyl is internal, whereas a ketonic carbonyl is terminal
ⓑ. an aldehydic carbonyl bonds to two carbon groups, whereas a ketonic carbonyl bonds to hydrogen
ⓒ. an aldehydic carbonyl is terminal, whereas a ketonic carbonyl lies within the chain
ⓓ. both carbonyls are terminal, but only the ketonic carbonyl determines chain position
Correct Answer: an aldehydic carbonyl is terminal, whereas a ketonic carbonyl lies within the chain
Explanation: Both aldehydes and ketones contain the carbonyl group \(\mathrm{C=O}\). In an aldehyde, the carbonyl carbon is bonded to at least one hydrogen and normally appears at the end of an open carbon chain. In a ketone, the carbonyl carbon is bonded to two carbon groups and is located within the chain. This distinction later separates aldoses such as glucose from ketoses such as fructose. The classification depends on the bonding environment of the carbonyl carbon, not simply on the presence of oxygen.
13. An \(\alpha\)-amino acid is recognised by the presence of:
ⓐ. amino and carboxyl groups bonded to adjacent carbon atoms
ⓑ. two amino groups bonded to the same carbon atom
ⓒ. hydroxyl and amide groups bonded to the same carbon atom
ⓓ. amino and carboxyl groups on the same carbon atom
Correct Answer: amino and carboxyl groups on the same carbon atom
Explanation: A typical \(\alpha\)-amino acid has the general structure \(\mathrm{H_2N-CH(R)-COOH}\). The amino group and carboxyl group are both connected to the carbon adjacent to the carboxyl carbon, called the \(\alpha\)-carbon. The side chain \(\mathrm{R}\) varies and gives each amino acid many of its distinctive properties. The amino and carboxyl groups also allow amino acids to display acid-base behaviour. An amide linkage appears after amino acids join in a peptide; it is not the pair of free functional groups defining an individual amino acid.
14. Assertion: Condensation between suitable biomolecular units commonly eliminates a small molecule such as water.
Reason: Hydrolysis cleaves a linkage by consuming water.
ⓐ. Both statements are true; the Reason explains why the Assertion holds
ⓑ. Both statements are true; the Reason does not explain why the Assertion holds
ⓒ. The Assertion is true; the Reason is false and cannot explain the Assertion
ⓓ. The Assertion is false; the Reason is true but cannot explain the Assertion
Correct Answer: Both statements are true; the Reason does not explain why the Assertion holds
Explanation: Condensation forms a new covalent linkage between molecular units and commonly releases \(\mathrm{H_2O}\). Hydrolysis is the reverse type of process in which water is used to cleave a susceptible bond. Both statements are true and describe complementary reactions. The Reason does not explain why water is eliminated during condensation; instead, it describes the opposing bond-cleavage process. Tracking whether water appears as a product or a reactant separates the two processes.
15. A short carbohydrate chain contains four monosaccharide units joined by condensation. The whole chain and each incorporated monosaccharide unit are best described, respectively, as:
ⓐ. an oligomer and a residue
ⓑ. a monomer and a polymer
ⓒ. a residue and an oligomer
ⓓ. a polymer and a free monomer
Correct Answer: an oligomer and a residue
Explanation: An oligomer is a molecule containing a relatively small number of linked monomer-derived units. Each monosaccharide after incorporation into the chain is called a residue because linkage formation changes it from the completely free monomeric form. A polymer usually contains a much larger number of repeating or related units. The entire four-unit chain is not a single monomer, and an incorporated unit is not described as a free monomer. The terms identify different levels of organisation: residue for an individual incorporated unit and oligomer for the short chain.
16. The linkage \(\mathrm{-CO-NH-}\) joining amino-acid residues in a peptide is chemically an ______ linkage.
ⓐ. ether
ⓑ. ester
ⓒ. amide
ⓓ. phosphate diester
Correct Answer: amide
Explanation: The group \(\mathrm{-CO-NH-}\) contains a carbonyl carbon directly bonded to nitrogen and is therefore an amide linkage. In proteins and peptides, this particular amide linkage is called a peptide bond. It forms by condensation between the carboxyl group of one amino acid and the amino group of another. An ester has a carbonyl carbon bonded to oxygen rather than directly to nitrogen. Recognising the \(\mathrm{-CO-NH-}\) pattern connects peptide structure with ordinary functional-group chemistry.
17. Phosphate groups are especially important in nucleic acids because they:
ⓐ. build the repeating sugar-phosphate backbone
ⓑ. link each nitrogenous base directly to an amino-acid residue
ⓒ. replace pentose sugars in the polynucleotide backbone
ⓓ. form peptide bonds between adjacent nucleotide units
Correct Answer: build the repeating sugar-phosphate backbone
Explanation: A nucleotide contains a pentose sugar, a nitrogenous base and a phosphate group. In a nucleic-acid chain, phosphate groups form linkages between sugar units and help create the repeating sugar-phosphate backbone. The bases project from this backbone and carry sequence information. Phosphate does not convert a nucleotide into an amino acid, nor does it replace the nitrogenous base. Its negative charge also contributes to the strongly polar character of nucleic acids.
18. A molecule contains one tetrahedral carbon bonded to four different substituents and has no internal symmetry that removes chirality. Pure mirror-image forms of this molecule are expected to:
ⓐ. have different molecular formulas and identical optical rotations
ⓑ. contain different functional groups and identical molecular formulas
ⓒ. form superimposable mirror images with the same optical rotation
ⓓ. form non-superimposable enantiomers with opposite optical rotations
Correct Answer: form non-superimposable enantiomers with opposite optical rotations
Explanation: A tetrahedral carbon attached to four different groups is a stereogenic or chiral centre. Such a molecule can exist as two non-superimposable mirror-image forms called enantiomers. The enantiomers have the same molecular formula and the same types of functional groups. In an achiral environment, many of their physical properties are identical, but pure enantiomers rotate plane-polarised light by equal magnitudes in opposite directions. A mixture containing equal amounts of both enantiomers can show no net rotation even though the individual molecules remain chiral.
19. The most useful distinction between micromolecules and macromolecules is that:
ⓐ. micromolecules are always inorganic, whereas macromolecules are always organic
ⓑ. micromolecules occur only outside cells, whereas macromolecules occur only inside cells
ⓒ. micromolecules are small, whereas macromolecules are very large and often contain many smaller units
ⓓ. micromolecules contain no functional groups, whereas macromolecules contain several functional groups
Correct Answer: micromolecules are small, whereas macromolecules are very large and often contain many smaller units
Explanation: Micromolecules are relatively small biomolecules such as glucose, amino acids and many vitamins. Macromolecules have much larger molecular masses and commonly contain numerous smaller building units joined together. Proteins and nucleic acids are major examples of biological macromolecules. Both groups may be organic and may occur within living cells. Functional groups are present in small as well as large biomolecules, so their presence does not determine the micromolecule–macromolecule distinction.
20. A sample contains glucose, vitamin C, glycine and starch. The macromolecule in this set is:
ⓐ. starch
ⓑ. glucose
ⓒ. vitamin C
ⓓ. glycine
Correct Answer: starch
Explanation: Starch is a polysaccharide composed of a large number of glucose residues and is therefore a biological macromolecule. Glucose is a monosaccharide and represents a comparatively small carbohydrate molecule. Glycine is the simplest amino acid and acts as a building unit of proteins. Vitamin C is also a small non-polymeric biomolecule. A substance can be biologically important without having a very high molecular mass.
