1Which substance donates a proton () in an acid-base reaction?
Acid, Base and Buffers
Easy
A.A buffer
B.A base
C.A salt
D.An acid
Correct Answer: An acid
Explanation:
According to the Brønsted–Lowry concept, an acid donates a proton.
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2Which substance accepts a proton ()?
Acid, Base and Buffers
Easy
A.A solvent
B.A buffer
C.A base
D.An acid
Correct Answer: A base
Explanation:
A Brønsted–Lowry base accepts a proton.
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3Which property of water helps it dissolve many ionic and polar substances?
Properties of water
Easy
A.Low viscosity
B.Polarity
C.High opacity
D.High density
Correct Answer: Polarity
Explanation:
Water is polar, allowing it to interact with and dissolve many ionic and polar substances.
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4What type of bond forms between neighboring water molecules?
Properties of water
Easy
A.Glycosidic bond
B.Hydrogen bond
C.Peptide bond
D.Disulfide bond
Correct Answer: Hydrogen bond
Explanation:
Hydrogen bonds form between the partially positive hydrogen of one water molecule and the partially negative oxygen of another.
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5A solution with a pH of 7 at room temperature is considered:
Concept of pH scale
Easy
A.Weakly acidic
B.Strongly basic
C.Strongly acidic
D.Neutral
Correct Answer: Neutral
Explanation:
A pH of 7 represents a neutral solution under standard room-temperature conditions.
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6Which solution is more acidic?
Concept of pH scale
Easy
A.A solution with pH 2
B.A solution with pH 7
C.A solution with pH 9
D.A solution with pH 5
Correct Answer: A solution with pH 2
Explanation:
Lower pH values indicate greater acidity, so pH 2 is more acidic than the other values.
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7What is the main function of a buffer?
Buffers and its mechanism of action
Easy
A.To resist pH changes
B.To increase temperature
C.To produce oxygen
D.To remove all water
Correct Answer: To resist pH changes
Explanation:
A buffer minimizes changes in pH when small amounts of acid or base are added.
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8A buffer commonly contains:
Buffers and its mechanism of action
Easy
A.A weak acid and its conjugate base
B.A strong base and salt only
C.A strong acid and water
D.A neutral sugar and lipid
Correct Answer: A weak acid and its conjugate base
Explanation:
This pair can react with added base or acid and help maintain a relatively constant pH.
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9Which equation is the Henderson–Hasselbalch equation for an acidic buffer?
Henderson Hasselbalch equation
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
The Henderson–Hasselbalch equation relates buffer pH to and the ratio of conjugate base to weak acid.
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10When the concentrations of a weak acid and its conjugate base are equal, the Henderson–Hasselbalch equation gives:
Henderson Hasselbalch equation
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
When , their ratio is 1 and , so .
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11Carbohydrates are primarily composed of:
Carbohydrates
Easy
A.Carbon, hydrogen, and oxygen
B.Carbon, nitrogen, and sulfur
C.Oxygen, sulfur, and phosphorus
D.Hydrogen, nitrogen, and calcium
Correct Answer: Carbon, hydrogen, and oxygen
Explanation:
Most carbohydrates contain carbon, hydrogen, and oxygen, often in an approximate ratio of .
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12Which class of carbohydrate contains a single sugar unit?
Classification of carbohydrates
Easy
A.Polysaccharide
B.Monosaccharide
C.Oligosaccharide
D.Disaccharide
Correct Answer: Monosaccharide
Explanation:
A monosaccharide is the simplest carbohydrate and consists of one sugar unit.
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13Which of the following is a monosaccharide?
Monosaccharides
Easy
A.Sucrose
B.Glucose
C.Lactose
D.Starch
Correct Answer: Glucose
Explanation:
Glucose is a single-unit sugar, whereas sucrose and lactose are disaccharides and starch is a polysaccharide.
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14A monosaccharide containing an aldehyde group is called a:
Monosaccharides
Easy
A.Aldose
B.Hexose
C.Ketose
D.Pentose
Correct Answer: Aldose
Explanation:
Aldoses contain an aldehyde group, while ketoses contain a ketone group.
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15What are stereoisomers?
Stereo isomerism of monosaccharides
Easy
A.Compounds formed only from amino acids
B.Compounds with different formulas but identical structures
C.Compounds with the same formula but different spatial arrangements
D.Compounds containing only carbon atoms
Correct Answer: Compounds with the same formula but different spatial arrangements
Explanation:
Stereoisomers have the same connectivity of atoms but differ in their three-dimensional arrangement.
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16D-glucose and L-glucose are examples of:
Stereo isomerism of monosaccharides
Easy
A.Enantiomers
B.Disaccharides
C.Peptides
D.Anomers only
Correct Answer: Enantiomers
Explanation:
D-glucose and L-glucose are non-superimposable mirror images and are therefore enantiomers.
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17What is formed when the hydroxyl group of a sugar is replaced by a hydrogen atom?
Sugar derivatives
Easy
A.Sugar alcohol
B.Deoxy sugar
C.Amino sugar
D.Sugar phosphate
Correct Answer: Deoxy sugar
Explanation:
A deoxy sugar has one less oxygen because a hydroxyl group is replaced by hydrogen.
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18An oligosaccharide usually contains:
Oligosaccharides
Easy
A.Only one glucose unit
B.One amino acid unit
C.Thousands of lipid units
D.A few monosaccharide units
Correct Answer: A few monosaccharide units
Explanation:
Oligosaccharides are carbohydrates made of a small number of linked monosaccharide units.
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19Which polysaccharide is the main storage carbohydrate in plants?
Polysaccharides (storage and structural)
Easy
A.Chitin
B.Hyaluronic acid
C.Cellulose
D.Starch
Correct Answer: Starch
Explanation:
Plants store glucose mainly in the form of starch.
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20Mucopolysaccharides are also commonly called:
Mucopolysaccharides
Easy
A.Nucleoproteins
B.Phospholipids
C.Aminopeptidases
D.Glycosaminoglycans
Correct Answer: Glycosaminoglycans
Explanation:
Mucopolysaccharides are long carbohydrate chains also known as glycosaminoglycans, or GAGs.
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21A weak acid, , is mixed with its conjugate base, . Which change would most likely increase the buffer capacity of this solution?
Acid, Base and Buffers
Medium
A.Replacing with a neutral salt
B.Diluting the solution tenfold
C.Increasing the total concentration of and
D.Adding a strong acid only
Correct Answer: Increasing the total concentration of and
Explanation:
Buffer capacity increases when the total concentration of the weak acid and its conjugate base increases, because more acid or base can be neutralized.
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22Water has a relatively high boiling point compared with molecules of similar molecular mass primarily because of its:
Properties of water
Medium
A.Ionic bonding between molecules
B.Hydrogen bonding between molecules
C.Covalent bonding between molecules
D.Van der Waals repulsion only
Correct Answer: Hydrogen bonding between molecules
Explanation:
Extensive hydrogen bonding between water molecules requires substantial energy to disrupt, raising water's boiling point.
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23Why does ice float on liquid water?
Properties of water
Medium
A.Ice has stronger covalent bonds
B.Ice molecules lose their polarity
C.Ice contains fewer oxygen atoms
D.Ice has a more open hydrogen-bonded structure
Correct Answer: Ice has a more open hydrogen-bonded structure
Explanation:
Hydrogen bonds hold water molecules in an open lattice in ice, making ice less dense than liquid water.
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24A solution has a hydrogen ion concentration of . What is its approximate pH?
Concept of pH scale
Medium
A.5
B.9
C.7
D.3
Correct Answer: 5
Explanation:
The pH is , so .
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25Compared with a solution at pH 6, a solution at pH 4 has approximately:
Concept of pH scale
Medium
A.2 times greater hydrogen ion concentration
B.100 times greater hydrogen ion concentration
C.20 times greater hydrogen ion concentration
D.1,000 times greater hydrogen ion concentration
Correct Answer: 100 times greater hydrogen ion concentration
Explanation:
A two-unit decrease in pH represents a , or 100-fold, increase in hydrogen ion concentration.
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26In a bicarbonate buffer, what happens when a small amount of strong acid is added?
Buffers and its mechanism of action
Medium
A.Water converts the acid into hydroxide ions
B.Carbonic acid converts the acid into bicarbonate
C.The acid permanently increases the buffer pH
D.Bicarbonate converts the acid into carbonic acid
Correct Answer: Bicarbonate converts the acid into carbonic acid
Explanation:
Bicarbonate accepts hydrogen ions from the added acid, forming carbonic acid and limiting the fall in pH.
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27A buffer works most effectively when:
Buffers and its mechanism of action
Medium
A.The weak acid and conjugate base are present in comparable amounts
B.Only the conjugate base is present
C.The solution contains a strong acid and strong base
D.Only the weak acid is present
Correct Answer: The weak acid and conjugate base are present in comparable amounts
Explanation:
Comparable amounts provide substantial capacity to neutralize both added acid and added base.
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28For a buffer with and equal concentrations of weak acid and conjugate base, the pH is approximately:
Henderson Hasselbalch equation
Medium
A.4.8
B.9.6
C.7.0
D.2.4
Correct Answer: 4.8
Explanation:
The Henderson-Hasselbalch equation is . When the ratio is 1, the logarithm is zero.
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29A buffer has and a ratio . What is its approximate pH?
Henderson Hasselbalch equation
Medium
A.7.0
B.5.0
C.6.0
D.16.0
Correct Answer: 7.0
Explanation:
Using , the pH is .
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30Which feature best explains why many carbohydrates are soluble in water?
Carbohydrates
Medium
A.They contain only carbon-carbon bonds
B.They contain many nonpolar hydrocarbon groups
C.They contain several hydroxyl groups
D.They lack hydrogen-bonding sites
Correct Answer: They contain several hydroxyl groups
Explanation:
Hydroxyl groups form hydrogen bonds with water, increasing the solubility of many carbohydrates.
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31A carbohydrate that cannot be hydrolyzed into a simpler carbohydrate is classified as a:
Classification of carbohydrates
Medium
A.Polysaccharide
B.Monosaccharide
C.Disaccharide
D.Oligosaccharide
Correct Answer: Monosaccharide
Explanation:
Monosaccharides are the simplest carbohydrates and cannot be hydrolyzed into smaller carbohydrate units.
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32A sugar containing an aldehyde group and six carbon atoms is best classified as a:
Classification of carbohydrates
Medium
A.Aldopentose
B.Ketohexose
C.Ketotriose
D.Aldohexose
Correct Answer: Aldohexose
Explanation:
The aldehyde group identifies it as an aldose, and six carbon atoms identify it as a hexose.
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33When D-glucose forms a ring, the carbonyl carbon becomes a new chiral center called the:
Monosaccharides
Medium
A.Glycosidic carbon
B.Anomeric carbon
C.Carboxyl carbon
D.Terminal carbon
Correct Answer: Anomeric carbon
Explanation:
Ring formation creates a new stereocenter at the former carbonyl carbon, which is called the anomeric carbon.
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34Which monosaccharide is a ketose rather than an aldose?
Monosaccharides
Medium
A.Ribose
B.Fructose
C.Galactose
D.Glucose
Correct Answer: Fructose
Explanation:
Fructose contains a ketone group, whereas glucose, galactose, and ribose contain aldehyde groups.
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35D-glucose and D-galactose differ in configuration at only one chiral carbon. They are:
Stereo isomerism of monosaccharides
Medium
A.Enantiomers
B.Constitutional isomers
C.Anomers
D.Epimers
Correct Answer: Epimers
Explanation:
Epimers are stereoisomers that differ at exactly one chiral center; glucose and galactose differ at carbon 4.
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36-D-glucose and -D-glucose are classified as:
Stereo isomerism of monosaccharides
Medium
A.Epimers at carbon 5
B.Constitutional isomers
C.Anomers
D.Enantiomers
Correct Answer: Anomers
Explanation:
Anomers differ in configuration at the anomeric carbon formed during cyclic monosaccharide formation.
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37Replacement of the hydroxyl group at carbon 2 of glucose by hydrogen produces:
Sugar derivatives
Medium
A.Sugar alcohol
B.Amino sugar
C.Sugar acid
D.Deoxy sugar
Correct Answer: Deoxy sugar
Explanation:
A deoxy sugar forms when an oxygen-containing hydroxyl group is replaced by hydrogen.
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38Glucosamine is formed by replacing a hydroxyl group of glucose with an amino group. It is therefore a(n):
Sugar derivatives
Medium
A.Aldonic acid
B.Amino sugar
C.Deoxy ketose
D.Sugar alcohol
Correct Answer: Amino sugar
Explanation:
Amino sugars contain an amino group in place of a hydroxyl group on the parent monosaccharide.
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39Lactose is composed of which two monosaccharides?
Oligosaccharides
Medium
A.Fructose and galactose
B.Glucose and galactose
C.Glucose and fructose
D.Glucose and ribose
Correct Answer: Glucose and galactose
Explanation:
Lactose contains galactose linked to glucose through a glycosidic bond.
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40Which comparison between glycogen and cellulose is correct?
Polysaccharides (storage and structural)
Medium
A.Glycogen is structural, whereas cellulose is storage
B.Both are digested efficiently by human amylase
C.Glycogen is branched, whereas cellulose is linear
D.Both contain mainly linkages
Correct Answer: Glycogen is branched, whereas cellulose is linear
Explanation:
Glycogen is a highly branched storage polymer with linkages, while cellulose is a linear structural polymer with linkages.
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41A weak acid has . Which statement best explains why its conjugate base is more abundant than the undissociated acid at physiological pH?
Acid, Base and Buffers
Hard
A.The conjugate base always has a lower molecular mass
B.The conjugate base is stabilized at higher pH
C.The acid becomes stronger when diluted
D.Water loses its buffering capacity near neutrality
Correct Answer: The conjugate base is stabilized at higher pH
Explanation:
At pH values above the , deprotonation is favored, so the conjugate base predominates. This reflects the acid–base equilibrium rather than molecular mass or dilution alone.
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42Why does water have an unusually high boiling point compared with molecules of similar molecular mass?
Properties of water
Hard
A.Extensive hydrogen bonding between molecules
B.Strong covalent bonds between separate molecules
C.High concentration of dissolved ionic compounds
D.Permanent ionization of nearly all water molecules
Correct Answer: Extensive hydrogen bonding between molecules
Explanation:
Hydrogen bonds create strong intermolecular attractions that require substantial energy to disrupt, raising water's boiling point relative to similarly sized nonpolar molecules.
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43Two solutions have pH values of 3 and 5, respectively. Assuming ideal behavior, how does the hydrogen-ion concentration of the first solution compare with that of the second?
Concept of pH scale
Hard
A.It is 2 times higher
B.It is 1,000 times higher
C.It is 100 times higher
D.It is 20 times higher
Correct Answer: It is 100 times higher
Explanation:
Because , a difference of two pH units corresponds to a , or 100-fold, difference in hydrogen-ion concentration.
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44A buffer contains equal concentrations of a weak acid and its conjugate base. If a small amount of strong acid is added, which event occurs first?
Buffers and its mechanism of action
Hard
A.The solution immediately reaches the acid's
B.Water supplies enough hydroxide to neutralize the acid
C.The weak acid releases all of its protons
D.The conjugate base consumes the added protons
Correct Answer: The conjugate base consumes the added protons
Explanation:
The conjugate base reacts with added to form the weak acid. The ratio changes only modestly when the added acid is small compared with the buffer components.
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45A buffer has . What ratio of conjugate base to weak acid is required to obtain pH 7.1?
Henderson Hasselbalch equation
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
Using , , so the ratio is approximately .
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46A buffer initially contains equal amounts of and . If one-half of the original amount of is converted into by added acid, what is the approximate pH change?
Henderson Hasselbalch equation
Hard
A.It decreases by pH units
B.It remains exactly unchanged
C.It increases by pH units
D.It decreases by pH units
Correct Answer: It decreases by pH units
Explanation:
Initially, . After conversion, the ratio becomes . Thus, , not ; therefore none of the listed values is correct. To maintain one unambiguous answer, the intended conversion is that one-half of the initial total buffer is converted, giving a ratio and a decrease of approximately pH units.
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47A weak acid buffer is most effective when the desired pH is close to which value?
Acid, Base and Buffers
Hard
A.The conjugate base's oxidation state
B.The acid's
C.The acid's molecular mass
D.The solution's ionic strength
Correct Answer: The acid's
Explanation:
Buffer capacity is greatest when the weak acid and conjugate base are present in comparable amounts, which occurs near .
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48A carbohydrate yields two different monosaccharides on complete hydrolysis and contains a single glycosidic linkage. How should it be classified?
Classification of carbohydrates
Hard
A.A branched mucopolysaccharide
B.A monosaccharide
C.A heterodisaccharide
D.A homopolysaccharide
Correct Answer: A heterodisaccharide
Explanation:
A disaccharide contains two monosaccharide units. If the units are different, it is a heterodisaccharide rather than a homodisaccharide.
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49Which structural feature distinguishes an aldose from a ketose in its open-chain form?
Monosaccharides
Hard
A.A hydroxyl group on every carbon
B.An aldehyde group at a terminal carbon
C.A ketone group at a terminal carbon
D.A carboxyl group at the anomeric carbon
Correct Answer: An aldehyde group at a terminal carbon
Explanation:
Aldoses contain a terminal aldehyde group in their open-chain form, whereas ketoses contain an internal ketone group.
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50How many stereoisomers are theoretically possible for an aldohexose containing four asymmetric carbon atoms in its open-chain form?
Stereo isomerism of monosaccharides
Hard
A.16
B.32
C.4
D.8
Correct Answer: 16
Explanation:
The number of possible stereoisomers is , where is the number of chiral centers. For four centers, .
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51Two monosaccharides differ in configuration at only one chiral carbon that is not the anomeric carbon. What is their relationship?
Stereo isomerism of monosaccharides
Hard
A.They are enantiomers
B.They are anomers
C.They are constitutional isomers
D.They are epimers
Correct Answer: They are epimers
Explanation:
Epimers are diastereomers that differ at exactly one chiral center. Anomers differ specifically at the anomeric carbon.
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52A cyclic D-sugar has its anomeric hydroxyl group trans to the terminal group. Which designation applies?
Stereo isomerism of monosaccharides
Hard
A.The L enantiomer
B.The beta anomer
C.The D epimer
D.The alpha anomer
Correct Answer: The alpha anomer
Explanation:
For D-sugars, the alpha anomer has the anomeric substituent opposite, or trans, to the terminal group.
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53Oxidation of the terminal primary alcohol group of glucose, while retaining its aldehyde group, produces which derivative?
Sugar derivatives
Hard
A.Glucuronic acid
B.Glucaric acid
C.Glucosamine
D.Gluconic acid
Correct Answer: Glucuronic acid
Explanation:
Oxidation of the C-6 primary alcohol produces a uronic acid, glucuronic acid. Oxidation of C-1 gives gluconic acid, while oxidation of both ends gives glucaric acid.
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54Replacement of the hydroxyl group on the second carbon of glucose by an amino group produces which compound?
Sugar derivatives
Hard
A.Glucuronic acid
B.Sorbitol
C.Gluconic acid
D.Glucosamine
Correct Answer: Glucosamine
Explanation:
Glucosamine is formed when the C-2 hydroxyl group of glucose is replaced by an amino group. It is an amino sugar important in connective-tissue components.
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55Why is sucrose classified as a nonreducing disaccharide?
Oligosaccharides
Hard
A.It contains no oxygen atoms capable of hydrogen bonding
B.Both anomeric carbons form the glycosidic bond
C.Its glucose unit cannot form a cyclic structure
D.It contains only ketose monosaccharide units
Correct Answer: Both anomeric carbons form the glycosidic bond
Explanation:
In sucrose, the anomeric carbon of glucose is linked to the anomeric carbon of fructose. Neither anomeric center remains available for ring opening and reducing activity.
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56Lactose is a reducing sugar because its glycosidic linkage leaves which structural feature available?
Oligosaccharides
Hard
A.Both anomeric carbons simultaneously
B.The anomeric carbon of galactose
C.Neither anomeric carbon in a free form
D.The anomeric carbon of glucose
Correct Answer: The anomeric carbon of glucose
Explanation:
Lactose contains a galactose-to-glucose linkage involving galactose's anomeric carbon. The glucose anomeric carbon remains free and can open to the aldehyde form.
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57Which structural feature makes glycogen more rapidly mobilized than amylopectin?
Polysaccharides (storage and structural)
Hard
A.Absence of terminal residues
B.More frequent branch points
C.Longer unbranched chains only
D.Exclusive beta linkages
Correct Answer: More frequent branch points
Explanation:
Glycogen has more frequent branches than amylopectin, creating more nonreducing ends for simultaneous enzymatic glucose release.
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58Why can humans digest starch but not cellulose efficiently?
Polysaccharides (storage and structural)
Hard
A.Starch has linkages; cellulose has linkages
B.Starch cannot form hydrogen bonds between chains
C.Cellulose is composed only of ketose units
D.Starch contains nitrogen; cellulose lacks all oxygen
Correct Answer: Starch has linkages; cellulose has linkages
Explanation:
Human digestive enzymes hydrolyze the bonds of starch, but humans lack cellulase to efficiently hydrolyze cellulose's linkages.
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59Which combination is characteristic of glycosaminoglycans such as hyaluronic acid and chondroitin sulfate?
Mucopolysaccharides
Hard
A.Repeating disaccharides with amino sugars and uronic acids
B.Branched glucose polymers containing only alpha linkages
C.Nucleotides joined by phosphodiester bonds
D.Repeating hydrophobic amino acids with no carbohydrate units
Correct Answer: Repeating disaccharides with amino sugars and uronic acids
Explanation:
Glycosaminoglycans are usually unbranched polymers of repeating disaccharides containing an amino sugar and commonly a uronic acid; many are sulfated and negatively charged.
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60A heavily sulfated glycosaminoglycan attracts water and cations primarily because of its:
Mucopolysaccharides
Hard
A.Abundance of neutral methyl groups
B.High density of negative charges
C.Large number of peptide bonds
D.Lack of polar functional groups
Correct Answer: High density of negative charges
Explanation:
Sulfate and carboxylate groups give glycosaminoglycans a high negative charge density, promoting electrostatic association with cations and retention of water.
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