Amino Acids Quiz: Essential vs Non-Essential
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Questions and Answers

Which of the following represents essential amino acids that must be obtained from the diet?

  • Alanine
  • Glycine
  • Proline
  • Isoleucine (correct)

Which of the following amino acids contains a sulfur atom in its side chain?

  • Phenylalanine
  • Leucine
  • Methionine (correct)
  • Valine

What type of amino acid is characterized by an aliphatic side chain?

  • Sulfur-containing amino acids
  • Aromatic amino acids
  • Polar amino acids
  • Aliphatic amino acids (correct)

Which of the following amino acids is classified as apolar and also essential?

<p>Methionine (C)</p> Signup and view all the answers

What structural feature is common to apolar amino acids?

<p>Presence of aliphatic side chains (A)</p> Signup and view all the answers

Which amino acid is categorized under aromatic amino acids?

<p>Tryptophan (C)</p> Signup and view all the answers

Which of the following amino acids is non-essential and not required from the diet?

<p>Alanine (D)</p> Signup and view all the answers

Which amino acid is known for its role in protein secondary structures and contains a cyclic structure?

<p>Proline (C)</p> Signup and view all the answers

What characterizes a compound as aromatic according to Hückel's rule?

<p>The number of π electrons must equal 4n + 2 (D)</p> Signup and view all the answers

Which of the following compounds is considered aromatic?

<p>Benzene (C)</p> Signup and view all the answers

How many π electrons does cyclooctatetraene contain?

<p>8 (D)</p> Signup and view all the answers

What distinguishes amino acids from one another regarding stereochemistry?

<p>The configuration of the asymmetric carbon (D)</p> Signup and view all the answers

What is the significance of the L-stereoisomeric series in amino acids?

<p>It represents the most common form of amino acids in nature (B)</p> Signup and view all the answers

Which statement about glycine is true?

<p>It is the only achiral amino acid (A)</p> Signup and view all the answers

Which of the following compounds features a heteroaromatic ring?

<p>Imidazole (A)</p> Signup and view all the answers

What is the π electron system of indole?

<p>10 π electrons (A)</p> Signup and view all the answers

What configuration does an L-amino acid have in a Fischer projection?

<p>Amino group on the left, hydrogen on the right (A)</p> Signup and view all the answers

Which of the following correctly describes D- and L-amino acids?

<p>L-amino acids have the amino group on the left (D)</p> Signup and view all the answers

In a Fischer projection, where should the main chain be drawn?

<p>Vertically, with the group in the highest oxidation state at the top (A)</p> Signup and view all the answers

What feature distinguishes the D-series carbohydrates?

<p>Their chiral carbon is aligned with D-(+)-glyceraldehyde (B)</p> Signup and view all the answers

Which of the following accurately describes the properties of glyceraldehyde?

<p>It exists as two enantiomers (A)</p> Signup and view all the answers

How are the substituents on chiral carbons arranged in Fischer projection?

<p>Both on horizontal bonds (A)</p> Signup and view all the answers

What does the stereoscriptor 'D-' derive from?

<p>Latin word meaning 'right' (C)</p> Signup and view all the answers

Which statement is true regarding amino acids and their configurations?

<p>Amino acids can have both D- and L-configurations (D)</p> Signup and view all the answers

What can pKa values help predict regarding a compound?

<p>The percentage of ionization under specific conditions (A)</p> Signup and view all the answers

How does the ionization state of an amino acid's functional group change?

<p>It can be ionized or neutral depending on the pH of the medium. (C)</p> Signup and view all the answers

What equation is utilized to calculate the amount of ionized form of an acid or base given its pKa?

<p>Henderson-Hasselbalch Equation (D)</p> Signup and view all the answers

What is one purpose of knowing the ionization state of a compound in biological systems?

<p>It influences the compound's solubility and absorption (A)</p> Signup and view all the answers

Which factor is responsible for determining whether an amino acid is in its neutral or charged form?

<p>The pH of the medium (A)</p> Signup and view all the answers

According to the Brønsted–Lowry definition, what role does an acid play in a chemical reaction?

<p>It donates a proton. (C)</p> Signup and view all the answers

What is the typical effect of electron-withdrawing inductive effects on amino acids' carboxylic and amine groups?

<p>They increase the acidity of both groups. (A)</p> Signup and view all the answers

What is indicated by a high Ka value in terms of acid strength?

<p>The acid is strong. (C)</p> Signup and view all the answers

What does the pKa value express in relation to an acid?

<p>The strength of the acid on a logarithmic scale. (C)</p> Signup and view all the answers

How is a difference of n pKa units significant in terms of acidity?

<p>It represents a 10n-fold difference in acidity. (D)</p> Signup and view all the answers

What overall role do amino acids play in relation to their acid-base properties?

<p>They can act both as acids and bases. (D)</p> Signup and view all the answers

Which of the following amino acid properties primarily contributes to their acidic nature?

<p>Presence of carboxylic acid groups. (A)</p> Signup and view all the answers

What distinguishes strong acids from weak acids as per their pKa values?

<p>Strong acids have a lower pKa value. (A)</p> Signup and view all the answers

What is the main difference between peptides and proteins?

<p>Peptides are formed from fewer than 50 amino acids, while proteins contain more than 50. (C)</p> Signup and view all the answers

What is the correct definition of oligopeptides?

<p>Chains of 2 to 7 amino acids. (A)</p> Signup and view all the answers

What does the N-terminus of a polypeptide represent?

<p>The amino acid with the free α-amine group. (C)</p> Signup and view all the answers

Which is a correct representation of a peptide sequence?

<p>Ser-Phe-Ala indicates the N-terminus as Ser. (D)</p> Signup and view all the answers

How can the sequence of Met-enkephalin be concisely written?

<p>Tyr-Gly-Gly-Phe-Met (C)</p> Signup and view all the answers

Why might arrows be used in peptide sequences?

<p>To show the specific order of peptide bonds. (C)</p> Signup and view all the answers

Which of the following correctly identifies a characteristic of proteins?

<p>They can be made up of sequences exceeding 50 amino acids. (C)</p> Signup and view all the answers

What is the smallest protein referenced in the context?

<p>Insulin, composed of 51 amino acids. (D)</p> Signup and view all the answers

Flashcards

Apolar amino acids

Amino acids with non-polar side chains, insoluble in water.

Essential amino acids

Amino acids the body cannot produce, must be consumed through diet.

Aliphatic amino acids

A type of apolar amino acid with a side chain of aliphatic hydrocarbons.

Glycine

Simplest amino acid with a hydrogen atom as a side chain (H).

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Leucine

Essential amino acid; key role in protein structure and function.

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Phenylalanine

Essential amino acid with an aromatic side chain.

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Methionine

An essential sulfur-containing amino acid.

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Polar amino acids

Amino acids with polar side chains; soluble in water.

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Aromaticity

A special stability in planar cyclic conjugated systems with a specific number of pi electrons.

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Hückel's Rule

A rule that determines aromaticity; a planar cyclic conjugated system is aromatic if it has 4n + 2 π electrons (where n is an integer).

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Aromatic Compound

A planar cyclic conjugated system with 4n + 2 pi electrons, exhibiting enhanced stability.

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Heteroaromatic Compound

Aromatic compounds containing atoms other than carbon (e.g., nitrogen, oxygen, sulfur).

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Chiral Carbon

A carbon atom bonded to four different groups, creating a molecule with non-superimposable mirror images (enantiomers).

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Enantiomers

Non-superimposable mirror-image isomers

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α-amino acid

Amino acid with the amino group and carboxyl group attached to the same carbon (the alpha carbon).

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L-stereoisomer

A specific type of chiral amino acid found in nature.

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α-amino acid stereochemistry

Describes the spatial arrangement of atoms in amino acids, utilizing the D/L system.

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Fischer projection

A way to represent a three-dimensional molecule on a two-dimensional plane.

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Stereoscriptors

Symbols (like D and L) used to describe the spatial arrangement of molecules.

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Glyceraldehyde

A simple molecule with one chiral carbon, used as a reference for defining D/L configurations in carbohydrates and amino acids.

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pKa

The pH value at which half of the molecules of an acid are ionized. It indicates the strength of an acid.

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Henderson-Hasselbalch Equation

This equation relates pH, pKa, and the concentrations of an acid and its conjugate base to calculate the degree of ionization at a given pH.

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Ionization of Amino Acids

The functional groups of an amino acid, like carboxyl and amino groups, can exist in either neutral or ionized forms depending on the pH of the environment.

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pKa and Nucleophilicity

Lower pKa values indicate stronger acids, which also tend to be better leaving groups and more nucleophilic.

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pKa and Solubility

pKa influences the ionization state, which in turn impacts the solubility of a molecule in different environments.

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Brønsted-Lowry Acid

A substance that donates a proton (H+) in a chemical reaction.

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Brønsted-Lowry Base

A substance that accepts a proton (H+) in a chemical reaction.

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Why are amino acids considered both acids and bases?

Amino acids contain both a carboxylic acid group (donates H+) and an amine group (accepts H+), making them able to act as both acids and bases.

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Inductive Effect

The electron-withdrawing or electron-donating effect of a substituent on the electron density of a molecule, affecting acidity.

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How does the inductive effect affect amino acid acidity?

The carboxylic acid and amine groups in amino acids exert an electron-withdrawing inductive effect on each other, making them more acidic than if they were alone in the molecule.

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Acidity Constant (Ka)

A measure of the strength of an acid, indicating the extent to which an acid ionizes in a solution.

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What does a difference of n pKa units indicate?

A difference of n pKa units signifies a 10^n-fold difference in acidity between two acids.

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Peptide

A shorter chain of amino acids, typically consisting of 2 to 50 amino acids.

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Polypeptide

A chain of amino acids longer than a peptide, containing 8 to 49 amino acids.

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Protein

A long chain of amino acids, containing more than 50 amino acids.

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N-terminus

The end of a polypeptide or protein chain where the amino group (NH2) is free.

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C-terminus

The end of a polypeptide or protein chain where the carboxyl group (COOH) is free.

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Peptide Bond

A covalent bond that links amino acids together in a polypeptide or protein chain.

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Met-enkephalin

A natural pentapeptide (5 amino acids) that regulates pain signals in the body.

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Three-letter & one-letter abbreviations

Shortened representations of amino acids used in polypeptide sequences. Three-letter abbreviations use three letters (e.g., Tyr) and one-letter abbreviations use a single letter (e.g., Y).

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Study Notes

Drug Discovery & Biotechnological Drugs

  • This is a Master's degree in Medical and Pharmaceutical Biotechnology
  • The course material covers drug discovery and biotechnological drugs.

Outline

  • Amino acids:
    • Nomenclature, structure, stereochemistry, and acid-base properties of amino acids.
    • Peptides and proteins (primary, secondary, tertiary, and quaternary structure)
    • Protein binding sites and weak interactions
  • Carbohydrates:
    • Monosaccharides (structures, Fischer projections, cyclic hemiacetals)
    • Glycosides
    • Oligosaccharides and polysaccharides
    • Aminosugars
  • Peptide and peptidomimetic drugs:
  • Chemical protein modifications

Amino acids: definition and structure

  • Amino acids are organic compounds containing an amino group (-NH2) and a carboxylic acid group (-COOH).
  • Natural a-amino acids are the building blocks of proteins, joined by amide bonds (peptide bonds).
  • Important examples include L-alanine, γ-aminobutyric acid (GABA), tyrosine, and p-aminobenzoic acid (PABA).

Functional groups

  • A table detailing different functional groups (hydrocarbons, oxygen-containing, nitrogen-based, sulfur-based, and aromatic groups) with their nomenclature and examples.

  • A diagram illustrating functional groups (different diagrams on different pages of the document) such as alkane, alkene, alkyne, alcohol, ether, epoxide, haloalkane, aldehyde, ketone, carboxylic acid, amine, nitrile, imine, isocyanate, ester, amide, acid anhydride, acyl halide, thiol, sulfides, disulfides, sulfoxide, sulfone, phosphine, etc).

Additional Functional Groups - Page 5

  • Detailed presentation of different functional groups.
  • Separate categories (hydrocarbons, halogen-containing, oxygen-containing, sulfur-containing, nitrogen-containing, and phosphorus-containing groups) with examples and structural diagrams.

Functional Groups of Drugs (verapamil, fenofibrate, etc.)

  • Examples of drugs (e.g., verapamil, fenofibrate) and identification of their functional groups (e.g., ether, aromatic ring, ketone, ester, aryl halide).

Amino acids: definition and structure - additional specifics

  • Different classifications of amino acids based on the nature of the side chain (e.g., polar, non-polar, acidic, basic)
  • Examples of specific amino acids grouped based on their side chain features. (Essential/non-essential, aromatic,heterocyclic, etc.)
  • Information on the zwitterion form of amino acids
  • The general structure shared by the 20 amino acids (α-amino acids)

Amino acids:stereochemistry

  • The α carbon is asymmetric in all amino acids except glycine; therefore they can exist as enantiomers.
  • Most amino acids in nature are L-stereoisomers based on Fischer projection.
  • Explanation of chiral carbon and R/S notation.
  • Detailed explanation of the D/L system, Fischer projection, and the absolute configuration.

Aromatic compounds

  • Overview of aromatic compounds (defined as cyclic unsaturated molecules with conjugated double bonds).
  • Features like conjugation, stability and different chemical reactivity highlighted.
  • Introduction to general aromatic structures (e.g. benzene).
  • Explanation of Hückel's rule and its application for determining aromaticity.

Aromatic heterocycles:

  • Description of unsaturated cyclic compounds containing elements beyond carbon.
  • Examples highlighted, including pyrimidine, pyrrole, and quinoline).

Chirality

  • Indication of chiral centers.
  • The function groups are identified with a star.
  • Examples of compounds used for chirality are nelfinavir, and ezetimibe

Amino acids: acid-base properties

  • Amino acids have both acidic (carboxylic acid) and basic (amine) groups.
  • Discussion on pKa values and their relation to ionization and acidity.
  • Henderson-Hasselbalch equation for calculating the relative amounts of deprotonated and protonated species of amino acids under different pH conditions
  • Isoelectric point discussed.

Peptides

  • Peptide bond formation between amino acids.
  • Different types of peptides (oligopeptides, polypeptides, proteins).
  • Biological Functions of peptides (e.g., insulin).
  • Peptides hydrolysis by acid/base catalyzed reactions.
  • Hydrolysis by enzymes (proteases)
  • Special focus on Glutathione, including its unusual amide bond.
  • Structural features of peptide bonds.

Resonance

  • Explanation of resonance structures and their relation to stability
  • Rules for resonance structures.

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Drug Discovery & Biotechnological Drugs PDF

Description

Test your knowledge of amino acids with this quiz covering essential and non-essential types, their structures, and characteristics. Delve into their significance in protein synthesis and stereochemistry. Perfect for students studying biochemistry or nutrition.

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