Essential vs Nonessential Amino Acids Quiz
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Questions and Answers

Which of the following is a characteristic of polar amino acids?

  • They have a net negative charge at neutral pH
  • They have a net positive charge at neutral pH
  • They have a zero net charge at neutral pH (correct)
  • They have no side chain
  • What is the purpose of disulfide bonds in many extracellular proteins?

  • To increase the solubility of the protein
  • To provide flexibility to the protein structure
  • To facilitate protein folding
  • To stabilize the protein structure (correct)
  • Which of the following is a characteristic of nonpolar (hydrophobic) amino acid side chains?

  • They are attracted to water molecules
  • They have a net negative charge at neutral pH
  • They have a net positive charge at neutral pH
  • They are repelled by water molecules (correct)
  • What is the significance of the asymmetric carbon atom in amino acids?

    <p>It determines the optical activity of the amino acid</p> Signup and view all the answers

    Which of the following is the correct way to represent the formation of a peptide bond between two amino acids?

    <p>The carboxyl group of one amino acid reacts with the amino group of another amino acid</p> Signup and view all the answers

    What is the defining characteristic of alpha-amino acids?

    <p>They have an amino group attached to the alpha-carbon</p> Signup and view all the answers

    Which of the following amino acids has a nonpolar, aliphatic side chain?

    <p>Valine</p> Signup and view all the answers

    Which amino acid is classified as both nonessential and conditional?

    <p>Arginine</p> Signup and view all the answers

    What is the primary covalent bond that links amino acids together in a polypeptide chain?

    <p>Peptide bond</p> Signup and view all the answers

    Which of the following statements about the side chains of alpha amino acids is correct?

    <p>The side chain is always attached to the alpha carbon</p> Signup and view all the answers

    Which amino acid has an aromatic side chain?

    <p>Phenylalanine</p> Signup and view all the answers

    Which of the following amino acids has a sulfur-containing side chain?

    <p>Cysteine</p> Signup and view all the answers

    What is the primary determinant of an amino acid's unique biochemical properties?

    <p>The side chain (R group)</p> Signup and view all the answers

    Which of the following statements about peptide linkages is correct?

    <p>Peptide linkages are formed between the carboxyl and amino groups of adjacent amino acids.</p> Signup and view all the answers

    Which of the following is true about alpha amino acids?

    <p>They have the amino group bonded directly to the alpha carbon.</p> Signup and view all the answers

    At physiological pH (pH=7.4), what is the state of the carboxyl and amino groups in amino acids?

    <p>The carboxyl group is dissociated, forming a negatively charged carboxylate ion, and the amino group is protonated.</p> Signup and view all the answers

    Which of the following amino acids would be classified as nonpolar?

    <p>Alanine</p> Signup and view all the answers

    What is the general formula for amino acids?

    <p>NH2-CHR-COOH</p> Signup and view all the answers

    Which of the following is not a key function of amino acids in the body?

    <p>Storing genetic information</p> Signup and view all the answers

    Which type of side chain is typically found in nonpolar amino acids?

    <p>Aliphatic side chains</p> Signup and view all the answers

    Which of the following is not a common classification of amino acids?

    <p>Cationic amino acids</p> Signup and view all the answers

    What type of chemical bond links the amino acids together in a polypeptide chain?

    <p>Peptide bond</p> Signup and view all the answers

    Which of the following is not a characteristic of alpha-amino acids?

    <p>Have a linear structure with the amino and carboxyl groups at opposite ends</p> Signup and view all the answers

    What is the primary function of the side chains in amino acids?

    <p>To determine the chemical properties of the amino acid</p> Signup and view all the answers

    Which of the following statements about non-polar amino acid side chains is correct?

    <p>They are lipid-like in nature and promote hydrophobic interactions within proteins.</p> Signup and view all the answers

    What is the primary factor that determines the role an amino acid plays in a protein?

    <p>The properties of the amino acid side chain.</p> Signup and view all the answers

    Which of the following categories are amino acids typically classified into based on their side chain properties?

    <p>Polar, non-polar, basic, and acidic.</p> Signup and view all the answers

    What is the primary function of hydrophobic interactions in protein structure?

    <p>To promote the folding of proteins into their three-dimensional shapes.</p> Signup and view all the answers

    Which of the following statements about hydrophobes is correct?

    <p>They are non-polar molecules with long carbon chains that do not interact with water.</p> Signup and view all the answers

    Which of the following is a characteristic of amino acids with polar side chains?

    <p>They have an uneven distribution of electrons and can form hydrogen bonds.</p> Signup and view all the answers

    Which of the following statements about amino acid side chains (R groups) is correct?

    <p>The chemical nature of the side chain determines the unique properties and function of each amino acid.</p> Signup and view all the answers

    Which of the following best describes nonpolar, hydrophobic side chains?

    <p>They are repelled by water molecules and tend to cluster together within a protein.</p> Signup and view all the answers

    What is the primary factor that determines whether an amino acid is classified as essential or nonessential?

    <p>The ability of the human body to synthesize it.</p> Signup and view all the answers

    Which of the following statements accurately describes the peptide linkage between amino acids in a polypeptide chain?

    <p>It is a covalent bond formed by the removal of a water molecule between the amino and carboxyl groups.</p> Signup and view all the answers

    Which of the following statements about alpha-amino acids is true?

    <p>They have both an amino and a carboxyl group attached to the same carbon atom.</p> Signup and view all the answers

    What is the primary structural difference between a peptide and a polypeptide?

    <p>A peptide is a short chain of amino acids, while a polypeptide is a longer chain.</p> Signup and view all the answers

    Which of the following statements about conditional amino acids is correct?

    <p>They are only required in certain medical conditions or stages of life.</p> Signup and view all the answers

    What is the primary role of peptide bonds in the structure of proteins?

    <p>They link the individual amino acids together in a linear chain.</p> Signup and view all the answers

    Which of the following statements about stereoisomers or optical isomers is true?

    <p>They have different arrangements of atoms in the molecule and different properties.</p> Signup and view all the answers

    Study Notes

    Amino Acids

    • Amino acids are organic compounds that contain amine (-NH2) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid.
    • At physiologic pH (pH=7.4), the carboxyl group is dissociated, forming a negatively charged carboxylate ion, and the amino group is protonated.
    • The carbon atom next to the carboxyl group (which is therefore numbered 2 in the carbon chain starting from that functional group) is called the α–carbon.

    Classification of Amino Acids

    • Amino acids are classified into four categories based on the properties of their side chains: non-polar, polar, acidic, and basic.
    • Non-polar amino acids have an even distribution of electrons and do not gain or lose protons or participate in hydrogen or ionic bonds.
    • Polar amino acids have an uneven distribution of electrons, such as acids and bases.
    • Acidic amino acids have acidic side chains.
    • Basic amino acids have basic side chains.

    Essential and Non-Essential Amino Acids

    • Essential amino acids cannot be made by the body and must come from food.
    • There are 9 essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
    • Non-essential amino acids are produced by the body and include: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
    • Conditional amino acids are usually not essential, except in times of illness and stress, and include: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine.

    Protein Structure

    • A polypeptide chain is a series of amino acids joined together in a specific sequence.
    • Each amino acid unit in a polypeptide is called a residue.
    • Proteins are long chains of amino acids held together by peptide bonds.
    • A peptide is two or more amino acids joined together by peptide bonds.

    Hydrophobic Interactions

    • Hydrophobic interactions describe the relations between water and hydrophobes (low water-soluble molecules).
    • Hydrophobes are nonpolar molecules and usually have a long chain of carbons that do not interact with water molecules.
    • Non-polar side chains fill up the interior of the folded protein and help give it its three-dimensional shape.

    Optical Properties of Amino Acids

    • Amino acids that have an asymmetric center at the α–carbon can exist in two forms, designated D and L.
    • The two forms in each pair are termed stereoisomers, optical isomers, or enantiomers.

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    Amino Acids PDF

    Description

    Test your knowledge on essential and nonessential amino acids with this quiz. Learn about the 9 essential amino acids that must be obtained from food and the nonessential amino acids that our bodies can produce. Identify the differences between essential and nonessential amino acids.

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