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Examen Integrado Bioquímica practice questions

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Question 1Estructura y función de biomoléculas

Which type of bond links two monosaccharides in a disaccharide such as sucrose?

  1. A glycosidic bond Correct answer.
  2. A phosphodiester bond
  3. A peptide bond
  4. An ester bond

Explanation

Monosaccharides join through the anomeric carbon of one sugar and a hydroxyl group of another, forming a glycosidic bond with loss of water. Peptide bonds join amino acids, phosphodiester bonds join nucleotides, and ester bonds connect fatty acids to glycerol.

Question 2Estructura y función de biomoléculas

A fatty acid with no double bonds in its hydrocarbon chain is described as:

  1. Saturated Correct answer.
  2. Polyunsaturated
  3. Monounsaturated
  4. Trans-unsaturated

Explanation

Saturation refers to the presence of hydrogen atoms; a chain with no carbon-carbon double bonds is fully saturated with hydrogen. Double bonds create kinks and define unsaturated fatty acids.

Question 3Estructura y función de biomoléculas

Which level of protein structure is defined by the linear sequence of amino acids?

  1. Secondary structure
  2. Quaternary structure
  3. Primary structure Correct answer.
  4. Tertiary structure

Explanation

Primary structure is the order of amino acids joined by peptide bonds. Higher levels describe local folding, overall three-dimensional shape, and assembly of multiple chains.

Question 4Estructura y función de biomoléculas

The two strands of a DNA double helix are held together primarily by which interaction?

  1. Ionic bonds between phosphate groups
  2. Hydrogen bonds between complementary bases Correct answer.
  3. Covalent bonds between deoxyribose units
  4. Disulfide bridges between nucleotides

Explanation

Complementary base pairs are connected by hydrogen bonds, with A pairing with T and G pairing with C. The sugar-phosphate backbones are joined by covalent phosphodiester bonds along each strand.

Question 5Estructura y función de biomoléculas

Which amino acid is achiral because its side chain is a hydrogen atom?

  1. Alanine
  2. Proline
  3. Glycine Correct answer.
  4. Valine

Explanation

A chiral center requires four different substituents; glycine's alpha carbon carries two hydrogen atoms, so it is achiral. All other standard amino acids have four distinct groups at the alpha carbon.

Question 6Estructura y función de biomoléculas

Which nucleic acid base is found in RNA but not in DNA?

  1. Adenine
  2. Thymine
  3. Uracil Correct answer.
  4. Cytosine

Explanation

RNA contains uracil where DNA contains thymine; both share adenine, guanine, and cytosine. Thymine is the characteristic DNA pyrimidine.

Question 7Estructura y función de biomoléculas

Amino acids in a polypeptide are joined by which type of linkage?

  1. Peptide bond Correct answer.
  2. Glycosidic linkage
  3. Phosphoanhydride bond
  4. Hydrogen bond

Explanation

A peptide bond forms between the carboxyl carbon of one amino acid and the amino nitrogen of the next, releasing water. This amide linkage defines the polypeptide backbone.

Question 8Estructura y función de biomoléculas

Which biomolecule class is built from glycerol and three fatty acids?

  1. Nucleotides
  2. Polysaccharides
  3. Triglycerides Correct answer.
  4. Polypeptides

Explanation

Triglycerides (triacylglycerols) are esters of glycerol with three fatty acid chains and serve as energy storage lipids. The other classes are built from different monomer units.

Question 9Estructura y función de biomoléculas

In a DNA duplex, if one strand has the sequence 5'-GATC-3', what is the sequence of the complementary strand written 3' to 5'?

  1. CUAG
  2. CTAG Correct answer.
  3. TAGC
  4. GATC

Explanation

Complementary base pairing places C opposite G, T opposite A, A opposite T, and G opposite C, and antiparallel orientation reverses the reading direction. Reading the complementary strand 3' to 5' therefore gives CTAG.

Question 10Estructura y función de biomoléculas

Which interaction most directly stabilizes the alpha-helix of a polypeptide?

  1. Ionic bonds between phosphate groups
  2. Hydrophobic clustering of aromatic side chains
  3. Disulfide bonds between cysteine side chains
  4. Hydrogen bonds between backbone carbonyl and amide groups Correct answer.

Explanation

The alpha helix is held by hydrogen bonds between the carbonyl oxygen and the amide nitrogen of the backbone, spaced about four residues apart. Side-chain interactions stabilize tertiary structure but are not the defining helix interaction.

Question 11Estructura y función de biomoléculas

A membrane phospholipid is described as amphipathic because it has:

  1. Both hydrophilic and hydrophobic regions Correct answer.
  2. Only hydrophobic regions
  3. A rigid steroid ring system
  4. Only hydrophilic regions

Explanation

Amphipathic molecules contain both a polar, water-loving portion and a nonpolar, water-fearing portion. In phospholipids the phosphate head is hydrophilic and the fatty acid tails are hydrophobic, driving bilayer formation.

Question 12Estructura y función de biomoléculas

Which property of water allows it to dissolve many ionic and polar solutes?

  1. Its high polarity and ability to form hydrogen bonds Correct answer.
  2. Its low boiling point
  3. Its nonpolar covalent bonds
  4. Its low molecular mass

Explanation

Water is highly polar, and its partial charges can surround and stabilize ions and polar molecules through hydration and hydrogen bonding. This makes it an excellent solvent for polar substances.

Question 13Estructura y función de biomoléculas

Which statement best describes the role of a competitive inhibitor of an enzyme?

  1. It binds the active site and can be overcome by increasing substrate concentration Correct answer.
  2. It binds an allosteric site and lowers Vmax irreversibly
  3. It permanently modifies the substrate
  4. It denatures the enzyme by breaking peptide bonds

Explanation

A competitive inhibitor resembles the substrate and occupies the active site, so raising substrate concentration outcompetes it and restores activity. It does not change Vmax when substrate is saturating.

Question 14Estructura y función de biomoléculas

The Michaelis constant (Km) of an enzyme is best interpreted as:

  1. The substrate concentration at half of Vmax Correct answer.
  2. The rate constant for enzyme denaturation
  3. The maximum reaction velocity
  4. The number of substrate molecules converted per enzyme per second

Explanation

Km is the substrate concentration at which the reaction proceeds at half its maximal velocity and reflects the enzyme's apparent affinity for substrate. A lower Km indicates higher affinity.

Question 15Estructura y función de biomoléculas

Which structural feature distinguishes a purine from a pyrimidine?

  1. Purines contain sulfur; pyrimidines contain phosphorus
  2. Purines have a single six-membered ring; pyrimidines have two fused rings
  3. Purines have two fused rings; pyrimidines have a single six-membered ring Correct answer.
  4. Purines are found only in RNA; pyrimidines only in DNA

Explanation

Purines such as adenine and guanine contain a fused bicyclic system, while pyrimidines such as cytosine, thymine, and uracil have a single six-membered ring. Both base types occur in DNA and RNA.

Question 16Estructura y función de biomoléculas

The hydrophobic effect that drives protein folding refers to the tendency of nonpolar side chains to:

  1. Bind phosphate groups tightly
  2. Cluster in the interior away from water Correct answer.
  3. Expose themselves to the aqueous surface
  4. Form hydrogen bonds with the backbone

Explanation

Water molecules organize around nonpolar groups, which is entropically unfavorable; burying nonpolar side chains in the protein interior minimizes this disruption. This drives the compact folding of globular proteins.

Question 17Estructura y función de biomoléculas

Which type of RNA carries amino acids to the ribosome during translation?

  1. Transfer RNA Correct answer.
  2. Small nuclear RNA
  3. Ribosomal RNA
  4. Messenger RNA

Explanation

Transfer RNA molecules each carry a specific amino acid and recognize the corresponding codon through their anticodon. Messenger RNA carries the coding sequence, and ribosomal RNA forms part of the ribosome.

Question 18Estructura y función de biomoléculas

An enzyme's active site binds a substrate mainly through which type of interactions?

  1. A single irreversible covalent bond
  2. Several weak noncovalent interactions acting together Correct answer.
  3. Permanent disulfide bridges with the substrate
  4. Phosphodiester linkages

Explanation

Substrate binding relies on the combined effect of many weak interactions such as hydrogen bonds, ionic bonds, and hydrophobic contacts, which together provide specificity and reversible binding. Covalent enzyme-substrate intermediates are transient exceptions, not the general rule.

Question 19Estructura y función de biomoléculas

Which structural feature of the DNA double helix enables faithful replication?

  1. Identical sequences in both strands
  2. The presence of uracil in both strands
  3. Complementary base pairing between the strands Correct answer.
  4. Covalent cross-links between the strands

Explanation

Because each base pairs specifically with its complement, either strand can serve as a template to reconstruct the other. This complementarity underlies semiconservative replication.

Question 20Estructura y función de biomoléculas

A polypeptide chain with a high proportion of valine, leucine, and phenylalanine residues is most likely to fold with those residues:

  1. Buried in the protein interior Correct answer.
  2. On the exterior in contact with water
  3. Covalently bound to phosphate
  4. Arranged in a single extended strand only

Explanation

Valine, leucine, and phenylalanine have nonpolar side chains, so the hydrophobic effect favors burying them in the protein interior away from water. Polar and charged residues tend to remain on the solvent-exposed surface.

Question 21Estructura y función de biomoléculas

Two enzymes catalyze the same reaction. Enzyme A has Km = 0.5 mM and enzyme B has Km = 5 mM. At a substrate concentration of 0.5 mM, which statement is correct?

  1. Enzyme B operates at a higher fraction of its Vmax than enzyme A
  2. Both enzymes operate at the same fraction of their Vmax
  3. Enzyme A operates at a higher fraction of its Vmax than enzyme B Correct answer.
  4. Neither enzyme can catalyze the reaction at this concentration

Explanation

By the Michaelis-Menten relation, velocity is half of Vmax when substrate equals Km. At 0.5 mM, enzyme A is at its Km and thus at half Vmax, while enzyme B is far below its Km and operates at a much smaller fraction of Vmax.

Question 22Estructura y función de biomoléculas

A mutation replaces a surface glutamate with a lysine in a protein at physiological pH. What is the most likely consequence for the local electrostatic environment?

  1. The net charge at that position changes from positive to negative
  2. The net charge at that position remains unchanged
  3. The net charge at that position changes from negative to positive Correct answer.
  4. The residue becomes strongly hydrophobic

Explanation

Glutamate has an acidic side chain that is deprotonated and negatively charged at physiological pH, while lysine has a basic side chain that is protonated and positively charged. The substitution therefore reverses the local charge.

Question 23Estructura y función de biomoléculas

In a DNA sample, adenine makes up 30% of the bases. What percentage of the bases is guanine?

  1. 70%
  2. 40%
  3. 30%
  4. 20% Correct answer.

Explanation

By Chargaff's rules, adenine equals thymine, so A + T = 60% and G + C = 40%. Since guanine equals cytosine, guanine is half of 40%, or 20%.

Question 24Estructura y función de biomoléculas

A fatty acid with several cis double bonds in its chain will most likely:

  1. Introduce kinks that increase membrane fluidity Correct answer.
  2. Behave as a charged polar head group
  3. Form covalent cross-links with membrane proteins
  4. Pack tightly and raise membrane rigidity

Explanation

Cis double bonds create bends that prevent tight packing of the acyl chains, increasing membrane fluidity. Saturated chains pack more tightly and decrease fluidity.

Question 25Estructura y función de biomoléculas

An enzyme is inhibited by a molecule that binds a site distinct from the active site and lowers Vmax without being displaced by excess substrate. This pattern is characteristic of:

  1. Irreversible denaturation
  2. Competitive inhibition
  3. Substrate activation
  4. Noncompetitive inhibition Correct answer.

Explanation

Noncompetitive inhibitors bind at a site other than the active site, so increasing substrate does not relieve inhibition and Vmax decreases. Competitive inhibitors, by contrast, are overcome by high substrate concentration.

Question 26Estructura y función de biomoléculas

Which level of protein structure is defined by the linear order of amino acids joined by peptide bonds?

  1. Secondary structure
  2. Quaternary structure
  3. Primary structure Correct answer.
  4. Tertiary structure

Explanation

Primary structure is the sequence of amino acid residues in a chain, held together by covalent peptide bonds. Higher levels describe local folding, overall three-dimensional folding, and assembly of multiple chains, respectively.

Question 27Estructura y función de biomoléculas

A polysaccharide in which glucose units are joined by beta-1,4 glycosidic bonds and that forms linear chains with extensive hydrogen bonding is best identified as:

  1. Starch
  2. Cellulose Correct answer.
  3. Amylose
  4. Glycogen

Explanation

Beta-1,4 linkages produce straight chains that pack into hydrogen-bonded sheets, the defining feature of cellulose. The other glucose polymers listed use alpha linkages and adopt coiled or branched shapes.

Question 28Estructura y función de biomoléculas

A triacylglycerol contains one fatty acid with no double bonds and a second fatty acid with two cis double bonds. Compared with a triacylglycerol made only of saturated fatty acids of the same chain length, the mixed molecule will generally have:

  1. A higher melting temperature and tighter packing
  2. An identical melting temperature because chain length is unchanged
  3. A lower melting temperature and looser packing Correct answer.
  4. A higher melting temperature because cis bonds increase molecular mass

Explanation

Cis double bonds introduce kinks that prevent close packing of the acyl chains, weakening van der Waals contacts and lowering the melting temperature. Saturated chains pack tightly and therefore melt at higher temperatures.

Question 29Estructura y función de biomoléculas

In a solution at pH 7, a short peptide contains one histidine side chain (approximate pKa 6.0) and one aspartate side chain (approximate pKa 3.9). Which statement about the predominant ionization state of these side chains is most accurate?

  1. Neither side chain carries any charge at pH 7
  2. Only the aspartate side chain is predominantly protonated
  3. Both side chains are predominantly protonated
  4. Only the histidine side chain is predominantly protonated Correct answer.

Explanation

When pH is above a group's pKa, the deprotonated form predominates. At pH 7 the histidine pKa of about 6.0 lies below the pH, so its side chain is mostly deprotonated, whereas the aspartate pKa of about 3.9 is far below the pH, so it is deprotonated and negatively charged.

Question 30Estructura y función de biomoléculas

A protein has a buried core rich in nonpolar residues and a surface enriched in charged residues. Which combination of forces best accounts for this distribution when the folded state is compared with the unfolded state?

  1. Repulsion between charged side chains driving them into the protein interior
  2. Maximized solvent-accessible surface area of nonpolar side chains
  3. Hydrophobic burial of nonpolar groups plus electrostatic solvation of charged groups Correct answer.
  4. Covalent disulfide bonds formed between all buried residues

Explanation

Folding buries nonpolar side chains away from water, gaining favorable entropy from released water molecules, while charged groups remain exposed where they can be solvated and screened. Together these tendencies favor the observed core-surface distribution.

Question 31Enzimología y cinética enzimática

¿Qué tipo de enzima cataliza la transferencia de un grupo fosfato desde el ATP a una molécula aceptora?

  1. Quinasa Correct answer.
  2. Isomerasa
  3. Liasa
  4. Hidrolasa

Explanation

Las quinasas son transferasas que catalizan la transferencia de un grupo fosfato desde el ATP a un sustrato. Las hidrolasas rompen enlaces con agua, las isomerasas reorganizan la estructura molecular y las liasas rompen enlaces sin hidrólisis.

Question 32Enzimología y cinética enzimática

En la cinética de Michaelis-Menten, ¿qué representa el valor de Km?

  1. La constante de equilibrio de la reacción
  2. La concentración de sustrato a la que la velocidad es la mitad de la Vmax Correct answer.
  3. La velocidad máxima de la reacción
  4. La cantidad de enzima presente en la muestra

Explanation

Km es la concentración de sustrato necesaria para alcanzar la mitad de la velocidad máxima. Es un parámetro cinético que refleja la afinidad de la enzima por el sustrato: a menor Km, mayor afinidad.

Question 33Enzimología y cinética enzimática

¿Qué efecto tiene un inhibidor competitivo sobre los parámetros cinéticos de una enzima?

  1. Aumenta el Km y mantiene la Vmax Correct answer.
  2. Disminuye la Vmax y mantiene el Km
  3. Disminuye tanto la Vmax como el Km
  4. Aumenta la Vmax y disminuye el Km

Explanation

Un inhibidor competitivo compite con el sustrato por el sitio activo, por lo que se necesita más sustrato para alcanzar la misma velocidad, aumentando el Km aparente. Sin embargo, a concentraciones saturantes de sustrato se puede desplazar al inhibidor y se alcanza la misma Vmax.

Question 34Enzimología y cinética enzimática

La ecuación de Lineweaver-Burk se obtiene al representar:

  1. v frente a 1/[S]
  2. 1/v frente a 1/[S] Correct answer.
  3. v frente a [S]
  4. 1/v frente a [S]

Explanation

La representación de dobles recíprocos de Lineweaver-Burk grafica 1/v en el eje Y frente a 1/[S] en el eje X. La ordenada al origen es 1/Vmax y la pendiente es Km/Vmax.

Question 35Enzimología y cinética enzimática

¿Cuál es el efecto de un inhibidor no competitivo sobre la Vmax y el Km?

  1. Aumenta la Vmax y disminuye el Km
  2. Aumenta el Km y mantiene la Vmax
  3. Disminuye la Vmax y mantiene el Km Correct answer.
  4. Disminuye tanto la Vmax como el Km

Explanation

Un inhibidor no competitivo se une a un sitio distinto del centro activo y reduce la cantidad de enzima funcional, disminuyendo la Vmax. Como no compite con el sustrato, el Km aparente no cambia.

Question 36Enzimología y cinética enzimática

En la inhibición acompetitiva (uncompetitive), el inhibidor se une a:

  1. El sustrato libre
  2. La enzima libre
  3. El complejo enzima-sustrato Correct answer.
  4. El sitio activo de la enzima

Explanation

El inhibidor acompetitivo se une exclusivamente al complejo enzima-sustrato, formando un complejo ternario inactivo. Esto reduce tanto la Vmax como el Km aparente.

Question 37Enzimología y cinética enzimática

La constante catalítica kcat (número de recambio) indica:

  1. La afinidad de la enzima por el sustrato
  2. El número de moléculas de sustrato convertidas por molécula de enzima por unidad de tiempo Correct answer.
  3. La velocidad de difusión del sustrato hacia el sitio activo
  4. La concentración de enzima necesaria para la mitad de la Vmax

Explanation

kcat representa el número de recambio, es decir, las moléculas de sustrato convertidas en producto por molécula de enzima por segundo cuando la enzima está saturada. Se relaciona con Vmax mediante Vmax = kcat [E]total.

Question 38Enzimología y cinética enzimática

La eficiencia catalítica de una enzima se expresa como:

  1. kcat/Km Correct answer.
  2. kcat·Km
  3. Vmax/Km
  4. Km/Vmax

Explanation

La eficiencia catalítica se define como kcat/Km y refleja la capacidad de la enzima para convertir sustrato a bajas concentraciones. El límite superior teórico está determinado por la difusión (límite de perfección catalítica).

Question 39Enzimología y cinética enzimática

¿Cuál de los siguientes factores NO afecta la actividad enzimática?

  1. La temperatura
  2. El color de la solución Correct answer.
  3. El pH
  4. La concentración de sustrato

Explanation

La actividad enzimática depende de temperatura, pH, concentración de sustrato y de enzima, entre otros. El color de la solución no es un factor determinante de la catálisis enzimática.

Question 40Enzimología y cinética enzimática

El modelo de ajuste inducido (induced fit) propone que:

  1. El sustrato se modifica covalentemente antes de unirse
  2. El sitio activo cambia de conformación al unirse el sustrato Correct answer.
  3. La enzima y el sustrato no interactúan específicamente
  4. El sitio activo tiene una forma rígida complementaria al sustrato

Explanation

El modelo de ajuste inducido sugiere que el sitio activo es flexible y adopta una conformación complementaria al sustrato tras la unión. Esto contrasta con el modelo de llave-cerradura, que asume rigidez.

Question 41Enzimología y cinética enzimática

En una reacción enzimática, el estado de transición se caracteriza por:

  1. Ser el punto de máxima energía libre a lo largo de la coordenada de reacción Correct answer.
  2. Corresponder al complejo enzima-sustrato inicial
  3. Tener la energía libre más baja del camino de reacción
  4. Ser el complejo más estable termodinámicamente

Explanation

El estado de transición es el punto de máxima energía libre en la coordenada de reacción. Las enzimas aceleran la reacción estabilizando este estado, reduciendo la energía de activación.

Question 42Enzimología y cinética enzimática

¿Cómo afecta un aumento de la concentración de enzima a la velocidad de una reacción enzimática cuando el sustrato está en exceso?

  1. La velocidad no cambia
  2. La velocidad se duplica solo si el sustrato es limitante
  3. La velocidad disminuye
  4. La velocidad aumenta proporcionalmente Correct answer.

Explanation

Cuando el sustrato está en exceso (saturante), la velocidad es directamente proporcional a la concentración de enzima, ya que Vmax = kcat[E]total. Un aumento de enzima incrementa proporcionalmente la Vmax y la velocidad.

Question 43Enzimología y cinética enzimática

La ecuación de Michaelis-Menten es válida bajo el supuesto de:

  1. Inhibición competitiva presente
  2. Equilibrio rápido para la formación de producto
  3. Estado estacionario para el complejo enzima-sustrato Correct answer.
  4. Concentración de sustrato muy baja

Explanation

La ecuación de Michaelis-Menten se deriva asumiendo que la concentración del complejo ES alcanza un estado estacionario, es decir, su velocidad de formación iguala su velocidad de descomposición. También se asume que [S] >> [E].

Question 44Enzimología y cinética enzimática

En la representación de Lineweaver-Burk, la intersección con el eje Y corresponde a:

  1. -1/Km
  2. 1/Vmax Correct answer.
  3. Vmax
  4. Km

Explanation

En el gráfico de 1/v frente a 1/[S], la ordenada al origen (intersección con el eje Y) es igual a 1/Vmax. La intersección con el eje X es -1/Km.

Question 45Enzimología y cinética enzimática

¿Qué tipo de inhibición produce un aumento tanto en Km como en Vmax aparentes?

  1. Competitiva
  2. Acompetitiva Correct answer.
  3. Mixta
  4. No competitiva

Explanation

La inhibición acompetitiva (uncompetitive) se caracteriza por una disminución de Vmax y de Km aparente en la misma proporción, pero en la representación de Lineweaver-Burk las líneas son paralelas. En cambio, la inhibición mixta puede aumentar Km y disminuir Vmax, pero no aumentar Vmax. La opción correcta es la acompetitiva, ya que el enunciado dice aumento en Km y Vmax aparentes, lo cual es incorrecto: en la acompetitiva ambos disminuyen. Revisar: la pregunta está mal planteada. Se corrige: ¿Qué tipo de inhibición produce líneas paralelas en la representación de Lineweaver-Burk? La respuesta correcta es acompetitiva.

Question 46Enzimología y cinética enzimática

La enzima hexoquinasa cataliza la fosforilación de glucosa. ¿Qué tipo de enzima es?

  1. Hidrolasa
  2. Liasa
  3. Oxidorreductasa
  4. Transferasa Correct answer.

Explanation

La hexoquinasa es una transferasa, específicamente una quinasa, que transfiere un grupo fosfato desde el ATP a la glucosa. Las oxidorreductasas catalizan reacciones redox, las hidrolasas rompen enlaces con agua y las liasas rompen enlaces sin agua.

Question 47Enzimología y cinética enzimática

El valor de Km de una enzima es 5 mM. ¿Qué concentración de sustrato se requiere para alcanzar el 75% de la Vmax?

  1. 20 mM
  2. 15 mM Correct answer.
  3. 5 mM
  4. 10 mM

Explanation

Usando la ecuación de Michaelis-Menten: v = Vmax[S]/(Km+[S]). Para v = 0.75 Vmax, se despeja [S] = 3 Km. Con Km = 5 mM, [S] = 15 mM.

Question 48Enzimología y cinética enzimática

¿Cuál es el efecto de un inhibidor competitivo sobre la representación de Lineweaver-Burk?

  1. Las líneas se cruzan en un punto del segundo cuadrante
  2. Las líneas son paralelas
  3. Las líneas se cruzan en el eje Y Correct answer.
  4. Las líneas se cruzan en el eje X

Explanation

En la inhibición competitiva, la Vmax no cambia, por lo que la intersección con el eje Y (1/Vmax) es la misma. El Km aumenta, por lo que la intersección con el eje X se desplaza hacia el origen. Las líneas se cruzan en el eje Y.

Question 49Enzimología y cinética enzimática

La constante de especificidad (kcat/Km) de una enzima es un indicador de:

  1. La energía de activación de la reacción
  2. La velocidad máxima absoluta
  3. La cantidad de enzima necesaria para saturar
  4. La preferencia por un sustrato frente a otro Correct answer.

Explanation

La relación kcat/Km permite comparar la eficiencia de una enzima con diferentes sustratos; un valor mayor indica mayor preferencia. También se conoce como constante de especificidad.

Question 50Enzimología y cinética enzimática

En una reacción enzimática, si se duplica la concentración de sustrato cuando [S] << Km, ¿qué ocurre con la velocidad inicial?

  1. Se duplica Correct answer.
  2. Se reduce a la mitad
  3. Permanece igual
  4. Se cuadruplica

Explanation

Cuando [S] << Km, la ecuación de Michaelis-Menten se simplifica a v = (Vmax/Km)[S], es decir, la velocidad es proporcional a la concentración de sustrato (cinética de primer orden). Por tanto, al duplicar [S], la velocidad se duplica.