BIOCHM Quiz 4

chapters 9, 10 and 11 homework

What is NOT a catalytic strategy?

 

covalent catalysis

 

acid–base reactions

 

approximation of substrates

 

induced fit

 

using metal ions to facilitate catalysis

induced fit

Why does chymotrypsin cleave a peptide bond only after amino acids with aromatic or large hydrophobic side chains?

 

Its active site is preceded by a specificity hydrophobic pocket, which binds such side chains.

 

Amino acids with such side chains are in the active site of the enzyme.

 

Its active site has hydrophobic residues that lower the binding energy of such amino acids.

 

Histidine residues of the S₁ pocket are able to bind such residues due to the imidazole ring.

 

The catalytic triad of chymotrypsin is highly hydrophobic.

Its active site is preceded by a specificity hydrophobic pocket, which binds such side chains.

What catalytic strategies are used by carbonic anhydrase? Select all that apply.

 

covalent catalysis

 

general acid–base catalysis

 

catalysis by approximation

 

decreasing the binding energy

 

metal ion catalysis

general acid–base catalysis

catalysis by approximation

metal ion catalysis

Several amino acid residues of a new protease were mutated to leucine to test the contribution of individual amino acid residues to the catalytic activity. Using the plot of catalytic activities of different mutated forms, identify the class of the studied enzyme and main residues of its active site ("Uncat." = rate of the corresponding uncatalyzed reaction).

 

serine protease with catalytic triad SHD

 

cysteine protease with catalytic triad CHD

 

aspartyl protease with catalytic dyad DD

 

cysteine protease with catalytic dyad CH

 

metalloprotease with catalytic triad HDD

cysteine protease with catalytic dyad CH

What acts as a nucleophile attacking the peptide bond? Select all that apply.

 

Cys

 

Asp

 

H₂O

 

Zn²⁺

 

Ser

cys

H20

Ser

What statement about the proton shuttle is TRUE?

 

The rate of proton diffusion limits the rate of deprotonation of the zinc-bound water molecule.

 

In the presence of buffer, the rate of deprotonation of the zinc-bound water molecule is increasing.

 

The rate of protonation of the zinc-bound hydroxide ion limits the rate of proton diffusion.

 

The buffer is involved in the reaction because the rate of proton diffusion is higher than the rate of CO₂ hydration.

 

In the presence of buffer, the rate of deprotonation of the zinc-bound water molecule is decreasing.

In the presence of buffer, the rate of deprotonation of the zinc-bound water molecule is increasing.

What statement about protease inhibitors is FALSE?

 

Imitation of the oxyanion hole can prevent formation of active forms of HIV proteins.

 

Indinavir resembles the structure of the peptide that can be recognized by any aspartyl protease in the cell.

 

Imitation of the tetrahedral intermediate can prevent formation of active forms of HIV proteins.

 

Indinavir adopts a twofold symmetry of viral genes.

 

Indinavir resembles the structure of the peptide that can be recognized by specific metalloprotease in the cell.

Imitation of the tetrahedral intermediate can prevent formation of active forms of HIV proteins.

What statement about the peptide bond is TRUE?

 

Hydrolysis of the peptide bond is both thermodynamically and kinetically favorable.

 

Kinetic stability of the peptide bond is overcome by the increased nucleophilicity of the catalytic residue of the protease.

 

Formation of the acyl-enzyme intermediate distorts the resonance of the peptide bond.

 

The catalytic strategy of proteases needs to overcome the thermodynamic stability of the peptide bond by making the carbonyl carbon more reactive.

 

The catalytic strategy of proteases needs to overcome both the thermodynamic and the kinetic stability of the peptide bond.

Kinetic stability of the peptide bond is overcome by the increased nucleophilicity of the catalytic residue of the protease.

What is the order of intermediates in the deacylation stage of peptide bond hydrolysis?

 

The acyl-enzyme intermediate is prior to the second tetrahedral intermediate.

 

The second tetrahedral intermediate is prior to the acyl-enzyme intermediate.

 

The oxyanion intermediate is prior to the first tetrahedral intermediate.

 

The acyl-enzyme intermediate is prior to the pentacoordinated intermediate.

 

The tetrahedral intermediate is prior to the pentacoordinated intermediate.

The acyl-enzyme intermediate is prior to the second tetrahedral intermediate.

What statement about chymotrypsin is TRUE?

 

Serine, valine, and glycine residues of chymotrypsin are extraordinarily reactive.

 

Its reaction can be divided in two stages, and overall three intermediates are formed in the course of the reaction.

 

The catalytic triad of chymotrypsin consists of serine, histidine, aspartate, and the oxyanion hole.

 

Its reaction can be divided in two stages, and overall two intermediates are formed in the course of the reaction.

 

The tetrahedral intermediate is the transition state of the acylation reaction rather than deacylation reaction.

Its reaction can be divided in two stages, and overall three intermediates are formed in the course of the reaction.

Choose the CORRECT order of steps of covalent catalysis by serine protease.

 

Binding of the substrate serine oxygen attacks the carbonyl carbon acyl-enzyme intermediate is stabilized within the oxyanion hole acyl-enzyme collapses to yield amine and carboxylic components.

 

Binding of the substrate serine oxygen attacks the carbonyl carbon tetrahedral intermediate collapses to yield the amine component water attacks the formed acyl-enzyme release of the carboxylic component.

 

Binding of the substrate serine oxygen attacks the carbonyl carbon tetrahedral intermediate stabilized in the oxyanion hole collapses to yield an acyl-enzyme release of the amine component water attacks the acyl-enzyme intermediate tetrahedral intermediate is stabilized within the oxyanion hole release of the carboxylic component.

 

Binding of the substrate serine oxygen attacks the carbonyl carbon tetrahedral intermediate collapses to yield the amine component formed acyl-enzyme intermediate is stabilized in the oxyanion hole hydrolysis by water release of the amine component.

 

Binding of the substrate serine sulfur attacks the carbonyl carbon tetrahedral intermediate is stabilized within the oxyanion hole tetrahedral intermediate collapses to yield an acyl-enzyme release of the amine component hydrolysis by water release of the carboxylic component.

 

 

Binding of the substrate serine oxygen attacks the carbonyl carbon tetrahedral intermediate stabilized in the oxyanion hole collapses to yield an acyl-enzyme release of the amine component water attacks the acyl-enzyme intermediate tetrahedral intermediate is stabilized within the oxyanion hole release of the carboxylic component.

Choose the CORRECT order of steps of metal ion catalysis of CO₂ hydration.

 

Zn²⁺ facilitates deprotonation of bound water oxygen of the hydroxide ion attacks oxygen of bound CO₂ bicarbonate ion is exchanged for water.

 

Buffer facilitates deprotonation of water-bound Zn²⁺ positioning of CO₂ in the active site Zn²⁺ attacks the carbon of CO₂ bicarbonate ion is exchanged for water.

 

Zn²⁺ facilitates protonation of the bound hydroxide ion positioning of CO₂ in the active site oxygen of water attacks the carbon of CO₂ buffer facilitates deprotonation of Zn²⁺-bound water bicarbonate ion is exchanged for water.

 

Zn²⁺ facilitates protonation of the bound hydroxide ion oxygen of water attacks the carbon of CO₂ bicarbonate ion is exchanged for water.

 

Buffer facilitates deprotonation of Zn²⁺-bound water positioning of CO₂ in the active site oxygen of the hydroxide ion attacks the carbon of CO₂ bicarbonate ion is exchanged for water.

Buffer facilitates deprotonation of Zn²⁺-bound water positioning of CO₂ in the active site oxygen of the hydroxide ion attacks the carbon of CO₂ bicarbonate ion is exchanged for water.

What allows obtaining insight into the evolutionary history of enzymes?

 

chromogenic substrate

 

induced fit

 

synthetic analogs

 

comparison of amino acid sequences

 

covalent modification

comparison of amino acid sequences

Binding of a water molecule to the zinc ion in carbonic anhydrase induces:

 

formation of a hydronium ion.

 

a large conformational change in the binding site.

 

ionization of the His residue, which functions as a strong nucleophile.

 

lowering of pK_a for water, which leads to formation of a zinc-bound hydroxide ion.

 

altering of the K_M value.

lowering of pK_a for water, which leads to formation of a zinc-bound hydroxide ion.

If you carried out site-directed mutagenesis of subtilisin, changing serine 221 to isoleucine, what would you expect?

 

a large change in K_M

 

a small change in K_M

 

a large change in k_cat

 

a large change in K_M and a large change in k_cat

 

a small change in K_M and a large change in k_cat

a small change in K_M and a large change in k_cat

What do trypsin, subtilisin, and elastase have in common?

 

All contain Asp in the active site.

 

All bind hydrophobic amino acids.

 

All are synthesized in the pancreas.

 

All contain a catalytic triad at the active site.

 

All contain a hydrophilic substrate-binding pocket.

All contain a catalytic triad at the active site.

What is NOT a way in which enzymes stabilize a transition state?

 

causing the temperature of the environment to increase

 

covalent catalysis

 

using binding energy

 

general acid–base catalysis

 

catalysis by approximation

causing the temperature of the environment to increase

What metal ion is frequently found in enzyme active sites that act on phosphate-containing substrates?

 

Zn²⁺

 

Mg²⁺

 

Cu²⁺

 

Fe²⁺

 

Ni²⁺

Mg²⁺

The metal ion most commonly found at the active site of metalloproteases is:

 

zinc.

 

calcium.

 

selenium.

 

magnesium.

 

sodium.

zinc.

The mechanism of chymotrypsin involves the formation of an unstable _______-shaped intermediate that is stabilized by the oxyanion hole.

tetrahedral

What technique allows investigators to test the role of individual amino acids in the determination of enzyme structure–function relationships, even if the investigated amino acid is not present in the active site?

 

stopped-flow assay

 

use of mechanism-based inactivators

 

use of methylating agents

 

site-directed mutagenesis

 

use of acetylating agents

site-directed mutagenesis

The activity at a single functional site of an allosteric enzyme _____ the activity at others.

 

increases

 

decreases

 

doesn't affect

 

affects

 

blocks

affects

What statement about states of the allosteric enzyme is TRUE?

 

The value of K_M for the T state is lower than for the R state.

 

The value of K_M for the T state is higher than for the R state.

 

The value of K_M for the T state and the R state is the same.

 

The value of V_max for the T state is lower than for the R state.

 

The value of V_max for the T state is higher than for the R state.

The value of K_M for the T state is higher than for the R state.

Select all that apply. The protein phosphorylation rate primarily depends on:

 

relative kinase activity.

 

relative phosphatase activity.

 

kinase dedication.

 

cAMP availability.

 

ATP availability.

relative kinase activity.

 

relative phosphatase activity.

Which of the following enzymes fine-tunes metabolism?

 

lactate dehydrogenase

 

transglutaminase

 

trypsinogen

 

Hageman factor

 

α1-antiproteinase

lactate dehydrogenase

Which regulatory mechanism provides a connection between the energy status of the cell and metabolism regulation?

 

farnesylation

 

controlling at the level of transcription

 

phosphorylation

 

proteolytic cleavage

 

multiple forms of enzymes

phosphorylation

What cascade of the proteolytic enzyme's activation is CORRECT?

 

Enteropeptidase activates trypsinogen trypsin activates chymotrypsinogen, proelastase, procarboxypeptidase, and prolipase.

 

Enteropeptidase activates chymotrypsinogen chymotrypsin activates trypsinogen trypsin activates proelastase, procarboxypeptidase, and prolipase.

 

Enteropeptidase activates trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase, and prolipase.

 

Enteropeptidase activates trypsinogen trypsin activates procarboxypeptidase carboxypeptidase activates proelastase, chymotrypsinogen, and prolipase.

 

Trypsinogen activates enteropeptidase, chymotrypsinogen, procarboxypeptidase, proelastase, and prolipase.

 

Enteropeptidase activates trypsinogen trypsin activates chymotrypsinogen, proelastase, procarboxypeptidase, and prolipase.

What statements denote TRUE differences between proteolytic activation and phosphorylation? Select all that apply.

 

The proteolytic cleavage does not require ATP and can activate extracellular proteins.

 

The proteolytic cleavage requires ATP and can activate intracellular proteins.

 

The proteolytic cleavage is the reversible covalent modification of extracellular proteins.

 

The proteolytic cleavage requires ATP and can activate both intracellular and extracellular proteins.

 

The proteolytic cleavage is the irreversible covalent modification.

-The proteolytic cleavage does not require ATP and can activate extracellular proteins.

-The proteolytic cleavage is the irreversible covalent modification.

What statement about allosteric proteins is TRUE?

 

They usually display hyperbolic Michaelis–Menten kinetics.

 

Binding to the first active site displays hyperbolic Michaelis–Menten kinetics.

 

They always consist of several identical subunits.

 

The catalytic sites and the regulatory sites are always on separate polypeptide chains.

 

They respond to regulation by other molecules rather than to changes in substrate concentration.

Binding to the first active site displays hyperbolic Michaelis–Menten kinetics.

What statement about phosphorylation is FALSE?

 

Most energy provided by ATP during phosphorylation promotes conformational changes in the target protein.

 

The use of ATP provides a connection between the energy status of the cell and metabolism regulation.

 

An added phosphoryl group leads to conformational changes that alter substrate binding and catalytic activity.

 

An added phosphoryl group provides formation of the specific conformation of the target protein.

 

A single phosphate kinase is able to activate the signal transduction pathway.

Most energy provided by ATP during phosphorylation promotes conformational changes in the target protein.

What parameter is the same for the different isozymes?

 

regulatory molecules

 

K_M

 

amino acid sequence

 

substrates

 

electrophoretic mobility

substrates

An increase in the serum level of H₄ relative to H₃M is an indicator of the presence of damaged _____ cells.

 

heart-muscle

 

liver

 

skeletal muscle

 

smooth muscle

 

endothelial

heart-muscle

What statement about the M₄ and the H₄ isozymes of human lactate dehydrogenase is TRUE?

 

The M₄ isozyme functions optimally in aerobic conditions, whereas the H₄ isozyme does in anaerobic conditions.

 

The M₄ isozyme has a lower affinity to lactate. The H₄ isozyme has pyruvate as an allosteric inhibitor.

 

The concentration of the H₄ isozyme decreases in the rat heart throughout the development, whereas the concentration of the M₄ isozyme increases.

 

The M₄ and H₄ isozymes have the same affinity to lactate, whereas high levels of pyruvate allosterically inhibit the H₄ isozyme.

 

The M₄ isozyme is a tissue-specific form of lactate dehydrogenase in the heart, whereas the H₄ isozyme is located in the liver

The M₄ isozyme has a lower affinity to lactate. The H₄ isozyme has pyruvate as an allosteric inhibitor.

What effect does N-(phosphonacetyl)-L-aspartate (PALA) have on K_M for ATCase?

 

K_M stays the same.

 

K_M decreases.

 

K_M increases.

 

K_M increases to the threshold and then stays the same.

 

K_M increases to the threshold and then slowly decreases.

K_M increases.

If the allosteric coefficient for ATCase decreases from 1250 to 300, the rate of the N-carbamoylaspartate formation:

 

decreases and the curve shifts to the right.

 

stays the same and the curve shifts up.

 

increases and the curve shifts to the left.

 

decreases and the curve shifts to the left.

 

stays the same and the curve shifts to the righ

increases and the curve shifts to the left.

The binding of the substrate to the active site activates all other active sites according to the:

 

sigmoidal kinetics.

 

heterotropic effect.

 

concerted model.

 

sequential model.

 

feedback inhibition.

concerted model.

The curve of the reaction rate versus substrate concentration is sigmoidal for allosteric enzymes because:

 

regulatory subunits act cooperatively upon binding substrate molecules.

 

allosteric and catalytic subunits act together.

 

a single allosteric enzyme is able to bind multiple substrates.

 

a catalytic subunit is able to bind a phosphate.

 

catalytic subunits act cooperatively upon binding substrate molecules.

catalytic subunits act cooperatively upon binding substrate molecules.

What statement about allosteric enzymes is TRUE?

 

Different catalytic sites show the property of cooperativity.

 

Each allosteric enzyme consists of catalytic, regulatory, and allosteric subunits.

 

The allosteric enzymes display Michaelis–Menten kinetics.

 

The allosteric enzyme consists of T and R subunits.

 

Each allosteric enzyme needs a cofactor for full activity.

Different catalytic sites show the property of cooperativity.

 

The catalytic subunit of ATCase alone displays:

 

hyperbolic kinetics.

 

sigmoidal kinetics.

 

feedback inhibition.

 

allosteric kinetics.

 

allosteric inhibition.

hyperbolic kinetics.

What amino acid residues can be phosphorylated by protein kinases in target proteins? Select all that apply.

 

proline

 

serine

 

isoleucine

 

threonine

 

tyrosine

serine

threonine

tyrosine

Select all that apply. The allosteric effectors of ATCase are:

 

ATP.

 

CTP.

 

carbamoyl phosphate.

 

uridine triphosphate.

 

PALA.

ATP.

 

CTP.

Changes in ATCase conformation were detected by crystallizing the enzyme in the presence of PALA (N-(phosphonacetyl)-L-aspartate). PALA is a:

 

radioactive tag that binds to the subunits.

 

substrate analog that resembles the transition state.

 

fluorescent allosteric inhibitor analog.

 

noncompetitive inhibitor.

 

mechanism-based inhibitor.

substrate analog that resembles the transition state.

Trypsin activity is turned off by:

 

dephosphorylation.

 

binding an inhibitor protein.

 

a second cleavage.

 

phosphorylation.

 

binding cAMP.

binding an inhibitor protein.

Multifunctional kinases phosphorylate proteins by recognizing related sequences called:

 

cAMP-binding sequences.

 

calmodulin-binding sequences.

 

pseudosubstrate sequences.

 

consensus sequences.

 

palindromes.

 

consensus sequences.

Which modified amino acid is found in prothrombin that allows for Ca²⁺ binding?

 

acetyl lysine

 

phosphoserine

 

γ-carboxyglutamate

 

hydroxyproline

 

N-methyl-D-aspartic acid

γ-carboxyglutamate

What molecule is required for proper production of prothrombin?

 

factor Xa

 

factor Va

 

tissue factor

 

fibrin

 

vitamin K

vitamin K

The less active conformational form of an allosteric enzyme is called the _____ state.

 

T

 

M

 

R

 

I

 

L

T

What term describes the precursor of enzymes that are activated by proteolytic cleavage?

 

phosphatases

 

isozymes

 

kinases

 

zymogens

 

apoenzymes

zymogens

What regulatory mechanism relies on inhibition of the first step of the pathway by the final product of the pathway?

 

competitive inhibition

 

uncompetitive inhibition

 

allosteric inhibition

 

feed-forward inhibition

 

feedback inhibition

feedback inhibition

Which statement does NOT apply to carbohydrates and carbohydrate-associated proteins?

 

Carbohydrates provide cell-to-cell communication.

 

Carbohydrates, carbohydrate-containing proteins, and carbohydrate-binding proteins allow formation of tissues by cells.

 

Carbohydrates supply details and enhancements to the biological architecture of the cell.

 

Carbohydrate-containing and carbohydrate-binding proteins catalyze biochemical reactions in the organism.

 

Carbohydrates, carbohydrate-containing proteins, and carbohydrate-binding proteins define human blood groups.

Carbohydrate-containing and carbohydrate-binding proteins catalyze biochemical reactions in the organism.

What accounts for the wide range of carbohydrate functions?

 

involvement in metabolism

 

stability of molecules

 

hydrophobic property

 

hydrophilic property

 

structural diversity

structural diversity

What are constitutional isomers?

 

carbohydrates that have identical molecular formulas but differ in how the atoms are ordered

 

carbohydrates that have different molecular formulas and differ in how the atoms are ordered

 

carbohydrates that have identical molecular formulas but different spatial arrangements

 

carbohydrates that have identical molecular formulas and look like mirror images of each other

 

carbohydrates that have identical molecular formulas but a different asymmetric carbon atom in the closed ring structure

carbohydrates that have identical molecular formulas but differ in how the atoms are ordered

Calculate the number of possible stereoisomers of an aldose with two asymmetric carbon atoms.

 

2

 

3

 

4

 

5

 

6

4

What type of sugar is fructose?

 

heptose

 

hexose

 

pentose

 

tetrose

 

triose

hexose

What is the chemical basis for the cyclization of sugars in solution?

 

interaction of hydroxyl groups with each other

 

formation of peptide bonds between carbon atoms and nitrogen atoms in modified sugars

 

reaction between the aldehyde group of one sugar molecule and the aldehyde group of another sugar molecule

 

formation of hydrogen bonds between sugar and water molecules

 

reaction of the carbonyl group with an alcohol group

reaction of the carbonyl group with an alcohol group

Glucose molecules form an intramolecular hemiacetal through the interaction of the:

 

C-5 hydroxyl group and the C-1 carbon of the aldehyde group.

 

C-4 hydroxyl group and the C-1 carbon of the aldehyde group.

 

C-3 hydroxyl group and the C-1 carbon of the aldehyde group.

 

C-2 hydroxyl group and the C-5 hydroxyl group.

 

C-3 hydroxyl group and the C-6 hydroxyl group.

C-5 hydroxyl group and the C-1 carbon of the aldehyde group.

Which pair of carbohydrates is epimeric at C-2?

 

 

 

 

 

e

In the figure, which numbered bonds define the glycosidic bond? Select all that apply.

 

1

 

2

 

3

 

4

 

5

3 and 4

What carbohydrate is an essential energy source for virtually all forms of life?

 

fructose

 

cellulose

 

glucose

 

galactose

 

starch

glucose

Why is corn syrup with a high concentration of fructose in the β-D-pyranose form used as a sweetener in cold, but not hot, drinks?

 

Heating leads to decyclization and eventually degrades the molecule.

 

Heating makes corn syrup bitter without causing any conformational changes.

 

Heating converts sweet β-glucopyranose to the tasteless α-glucopyranose form.

 

Heating converts sweet β-fructopyranose into the bitter β-glucopyranose form.

 

Heating converts sweet β-fructopyranose into the less sweet β-fructofuranose form.

Heating converts sweet β-fructopyranose into the less sweet β-fructofuranose form.

Which structure depicts β-D-ribofuranose?

 

 

 

 

 

b

What distinguishes D and L isomers?

 

configuration of the carbonyl group

 

configuration of the second carbon atom from the aldehyde or keto group

 

configuration of the asymmetric carbon atom farthest from the aldehyde or keto group

 

configuration of all the hydroxyl groups

 

charge of the molecule

configuration of the asymmetric carbon atom farthest from the aldehyde or keto group

What are the consequences of sugar phosphorylation? Select all that apply.

 

Sugars gain a negative charge.

 

Sugars gain a positive charge.

 

The gained charge prevents spontaneous interaction of modified sugars with transporters of the unmodified sugar.

 

Phosphorylation creates intermediates that are less available for metabolic reactions.

 

The gained charge causes sugars to leave the cell by crossing the lipid bilayer membrane.

Sugars gain a negative charge.

The gained charge prevents spontaneous interaction of modified sugars with transporters of the unmodified sugar.

Maltose is a disaccharide composed of:

 

α-D-glucopyranose and β-D-fructofuranose.

 

α-D-galactopyranose and α-D-glucopyranose.

 

α-D-glucopyranose and α-D-glucopyranose.

 

β-D-fructofuranose and α-D-galactopyranose.

 

β-D-glucopyranose and β-D-fructofuranose.

α-D-glucopyranose and α-D-glucopyranose.

What property of reducing sugars is used to assess the effectiveness of treatments for diabetes mellitus?

 

ability to dissolve in polar solvents

 

ability to react with and form a covalent bond with a free amino group of hemoglobin

 

ability to avoid reactions with amino acids of hemoglobin by forming a ring

 

ability to prevent a rise in the blood glucose level by binding with specific diabetes factors

 

ability to induce the proliferation of red blood cell

ability to react with and form a covalent bond with a free amino group of hemoglobin

Where in the cell are glycoproteins and glycolipids commonly located?

 

external surface of the plasma membrane

 

Golgi complex

 

lumen of the ER

 

inner surface of the plasma membrane

 

ER membrane

external surface of the plasma membrane

What monosaccharide lacks an asymmetric carbon atom?

 

fructose

 

mannose

 

altrose

 

galactose

 

dihydroxyacetone

dihydroxyacetone

Why is it more advantageous to store glucose in the form of glycogen rather than in its free form?

 

Glycogen is more water soluble than glucose.

 

Glycogen strengthens the cell wall.

 

Glycogen is more reactive than glucose.

 

Glucose is osmotically active.

 

Glucose is less calorie-dense than glycogen.

Glucose is osmotically active.

Which statements about the components of cartilage are TRUE? Select all that apply.

 

Aggrecan cushions compressive forces.

 

Collagen has three globular domains with an extended region for glycosaminoglycan attachment.

 

Dermatan sulfate filaments form a network by linking together.

 

Water does not bind to glycosaminoglycans due to a lack of negative charges.

 

Osteoarthritis is characterized by the loss of water from proteoglycan with aging.

Aggrecan cushions compressive forces.

Osteoarthritis is characterized by the loss of water from proteoglycan with aging.

Which polysaccharides are hydrolyzed by α-amylase? Select all that apply.

 

mucin

 

glycogen

 

amylopectin

 

cellulose

 

amylose

glycogen

 amylopectin

amylose

Where does protein glycosylation take place in the cell? Select all that apply.

 

endoplasmic reticulum

 

mitochondria

 

cytosol

 

Golgi complex

 

nucleus

endoplasmic reticulum

Golgi complex

What is the role of the variable number of tandem repeats (VNTR) region in mucin?

 

It facilitates extensive glycosylation.

 

It facilitates polymerization of molecules.

 

It forms a region for bacterial cells adhesion.

 

It is responsible for the formation of long fibers.

 

It provides for the high activity of the molecule.

 It facilitates extensive glycosylation.

What carbohydrate is the most abundant organic compound in the biosphere?

 

glucose

 

starch

 

maltose

 

cellulose

 

amylopectin

cellulose

Most glycogen monomers are connected by what type of linkage?

 

α-1,6

 

α-1,4

 

α-1,4 and β-1,6

 

α-1,6 and β-1,4

 

β-1,4

α-1,4

What property causes cellulose molecules to form long, straight chains and a proper supportive structure?

 

osmotic activity

 

heteropolymeric structure

 

molecular weight

 

glucose residues

 

β linkages

β linkages

Why are animals unable to digest wood?

 

Animals lack cellulase.

 

Animals lack amylase.

 

Cellulose molecules have a β configuration.

 

Cellulose is an unbranched polymer.

 

Cellulose fibers are not an important dietary component.

Animals lack cellulase.

Which statement about glycosylation is FALSE?

 

Glycosyltransferases catalyze the formation of glycosidic bonds.

 

Dolichol phosphate is a lipid molecule located in the membrane of the endoplasmic reticulum.

 

Glycosylation of hemoglobin influences oxygen binding.

 

O-linked glycosylation takes place in the Golgi complex.

 

N-linked glycosylation begins in the endoplasmic reticulum and continues in the Golgi complex.

Glycosylation of hemoglobin influences oxygen binding.

How does zanamivir help treat influenza infection?

 

It blocks viral RNA synthesis.

 

It makes glycoproteins and glycolipids on the cell surface invisible to the virus.

 

It makes the virus weaker but still active.

 

It destroys the capsid right after virus ingestion.

 

It inhibits viral neuraminidase.

It inhibits viral neuraminidase.

Which term describes a class of compounds with the molecular formula (CH₂O)_n?

 

proteoglycans

 

glycogen

 

mucoproteins

 

polysaccharides

 

monosaccharides

monosaccharides

Why is sucrose NOT a reducing sugar?

 

Both anomeric carbons are involved in the glycosidic bond.

 

Only the anomeric carbon of glucose can be oxidized, and it is involved in the glycosidic bond.

 

Only the anomeric carbon of fructose can be oxidized, and it is involved in the glycosidic bond.

 

Neither anomeric carbon is involved in the glycosidic bond.

 

None of the answers is correct because sucrose is a reducing sugar.

Both anomeric carbons are involved in the glycosidic bond.

Select the monosaccharide that is correctly paired with its description.

 

D-glucose – ketohexose

 

D-galactose – aldopentose

 

D-fructose – ketohexose

 

D-ribulose – ketotetrose

 

D-ribose – ketopentose

D-fructose – ketohexose

The enzyme that digests amylopectin is:

 

α-amylase.

 

α-glucosidase.

 

cellulase.

 

invertase.

 

None of the answers is correct.

α-amylase.

The simplest carbohydrates are the three-carbon molecules:

 

glycerate and glycerol.

 

dihydroxyacetone and D- and L-glyceraldehyde.

 

dihydroxyacetone and glycerate.

 

dihydroxyacetone and glycerol.

 

glycerol and D- and L-glyceraldehyde.

dihydroxyacetone and D- and L-glyceraldehyde.

What proteins facilitate cell-to-cell recognition by binding to specific carbohydrate structures?

 

mucoproteins

 

glycosaminoglycans

 

glycoproteins

 

lectins

 

proteoglycans

lectins

Sugars are commonly linked to which amino acid residues in glycoproteins?

 

tyrosine and asparagine

 

serine, threonine, and asparagine

 

serine, tyrosine, and asparagine

 

serine and glutamine

 

threonine and glutamine

serine, threonine, and asparagine

Two monosaccharides that differ in stereochemistry at only a single asymmetric carbon are called:

 

aldoses.

 

epimers.

 

anomers.

 

pentoses.

 

enantiomers.

epimers.