BIOC 192 Lecture 4: Amino Acids & Peptides
63 Questions
8 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

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

  • To regulate protein synthesis
  • To provide amino acids with their unique properties (correct)
  • To facilitate energy production
  • To determine the amino acid's role in metabolism

    • All amino acids have the same side chains.

    False

    What term describes the covalent bond formed between amino acids?

    peptide bond

    The twenty amino acids can be represented by a full name, a 3-letter name, and a ______ name.

    <p>1-letter</p> Signup and view all the answers

    Match the following types of bonds with their characteristics:

    <p>Peptide bond = Links amino acids together in proteins Ionic bond = Forms between charged side chains Hydrogen bond = Stabilizes secondary structure of proteins Disulfide bond = Links cysteine residues in proteins</p> Signup and view all the answers

    Which property of amino acids is primarily responsible for their function in proteins?

    <p>The variety of side chains</p> Signup and view all the answers

    Amino acids exist as zwitterions only in solid form.

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

    How many amino acids are commonly known?

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

    Which of the following modifications is essential for blood clotting?

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

    Cysteine can form a peptide bond with another cysteine.

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

    What is the term for modifications that occur to amino acids after they are added to a protein?

    <p>post-translational modification</p> Signup and view all the answers

    A covalent bond that links amino acids together is called a ______.

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

    Which amino acid is often involved in hydroxylation?

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

    Match the type of amino acid modification to its function:

    <p>Phosphorylation = Controls enzyme activity Hydroxylation = Prevents connective tissue diseases Carboxylation = Necessary for blood clotting Glycosylation = Involves sugar addition</p> Signup and view all the answers

    All amino acids start out as one of the standard 20.

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

    Who determined the structure of the peptide bond through X-ray crystallography in the 1930s-1940s?

    <p>Linus Pauling and Robert Corey</p> Signup and view all the answers

    What type of side chains do negatively charged amino acids have?

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

    All amino acids are chiral.

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

    What are the one-letter and three-letter abbreviations for Glycine?

    <p>G and Gly</p> Signup and view all the answers

    The pI, or isoelectric point, is the pH at which an amino acid has a net charge of _____ .

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

    Match each amino acid to its special characteristic:

    <p>Glycine = Non-chiral Proline = Imino acid Lysine = Positively charged Aspartate = Negatively charged</p> Signup and view all the answers

    Which amino acid is characterized by the presence of an imino group?

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

    One-letter abbreviations for amino acids are primarily used for sequence alignment.

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

    What is the pKa value in relation to an ionisable group on an amino acid?

    <p>The pH at which the group is 50% ionised.</p> Signup and view all the answers

    The mutation from glutamate to valine at position 6 is denoted as _____ .

    <p>E6V</p> Signup and view all the answers

    Which of the following amino acids is classified as basic?

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

    What is a peptide primarily made of?

    <p>Amino acids</p> Signup and view all the answers

    A peptide bond primarily exists in a cis configuration.

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

    What term is used for amino acids once they are linked in a peptide or protein?

    <p>Amino acid residues</p> Signup and view all the answers

    The peptide bond that links amino acids has a rotational barrier of approximately _______ kJ/mol.

    <p>80</p> Signup and view all the answers

    What do we mean when we say amino acids are chiral?

    <p>They have an asymmetric carbon atom.</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>pKa = The acid dissociation constant pI = The isoelectric point Post-translational modifications = Chemical changes after protein synthesis Amino acid side chains = Functional groups attached to the backbone</p> Signup and view all the answers

    What are the 4 main groups of amino acids?

    <p>Non-polar, Polar, Charged, Ionizable</p> Signup and view all the answers

    One common example of a post-translational modification is _______.

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

    Which amino acids are predominantly used in the synthesis of proteins in living organisms?

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

    All amino acids have polar side chains.

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

    What is the central atom in an amino acid to which the amino group, carboxyl group, and side chain are attached?

    <p>Alpha carbon</p> Signup and view all the answers

    Amino acids can exist in both D- and L- forms due to the presence of a point of __________.

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

    Match the following classifications of amino acids with their characteristics:

    <p>Non-polar = Have aliphatic carbon or aromatic ring side chains Polar = Contain ionizable acidic or basic groups Basic = Positively charged at physiological pH Acidic = Negatively charged at physiological pH</p> Signup and view all the answers

    Which of the following defines the importance of the peptide bond?

    <p>It links amino acids together in a stable manner</p> Signup and view all the answers

    How do amino acids generally differ from each other?

    <p>In their R-group side-chain chemical structure</p> Signup and view all the answers

    The structure of the peptide bond is rigid and allows for free rotation between adjacent amino acids.

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

    At pH 7, aspartate and glutamate primarily exist in which form?

    <p>Ionic form</p> Signup and view all the answers

    The isoelectric point (pI) is the pH at which a protein has a net charge of zero.

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

    What is the pKa range of α-amino groups in amino acids?

    <p>9-10</p> Signup and view all the answers

    Cysteine contains a __________ group that can form disulfide bonds.

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

    Match the amino acid to its classification based on charge at pH 7:

    <p>Lysine = Basic Aspartate = Negative Arginine = Basic Glutamate = Negative</p> Signup and view all the answers

    Which of the following amino acids has an ionizable side chain?

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

    All amino acids contain at least one acidic and one basic group.

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

    Name one amino acid that appears frequently in the active sites of enzymes due to its ionizable side chain.

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

    Which of the following is a type of post-translational modification?

    <p>Proteolytic cleavage</p> Signup and view all the answers

    All post-translational modifications enhance the function of proteins.

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

    What type of modification is known to facilitate the formation of disulfide bridges in proteins?

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

    One common post-translational modification that involves the addition of a sugar molecule is called _____ -glycosylation.

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

    Match the following modifications to their examples:

    <p>N-glycosylation = Addition of sugar Hydroxylation = Collagen Phosphorylation = Milk proteins C-terminal amidation = Bioactive peptides</p> Signup and view all the answers

    What does the pKa value indicate about an ionisable group in an amino acid?

    <p>The pH at which 50% of the group is ionised</p> Signup and view all the answers

    The peptide bond primarily exists in a cis configuration.

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

    What is the term for the first amino acid in a protein chain?

    <p>N-terminus</p> Signup and view all the answers

    The sequence of amino acids in a protein is known as the ______ sequence.

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

    Match the following terms with their corresponding descriptions:

    <p>Peptide bond = Covalent bond linking amino acids N-terminus = The start of an amino acid chain C-terminus = The end of an amino acid chain Trans configuration = Functional groups on opposite sides</p> Signup and view all the answers

    Which statement correctly describes the characteristics of peptide bonds?

    <p>Peptide bonds have double bond character due to electron resonance.</p> Signup and view all the answers

    Amino acids are always neutral at the isoelectric point (pI).

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

    What defines the function and structure of a mature protein?

    <p>The linear sequence of amino acids</p> Signup and view all the answers

    Study Notes

    Learning Objectives

    • Understand amino acid properties and their relevance to protein structure and function.
    • Identify types of amino acid side chains and their chemical properties.
    • Comprehend the formation of peptides and proteins from amino acids.
    • Recognize the importance and structure of the peptide bond.

    Amino Acids Overview

    • There are twenty standard amino acids, each with a common backbone but different side chains.
    • Amino acids have full names, three-letter abbreviations, and one-letter codes.
    • Amino acid side chains are responsible for the biochemical activity of proteins.

    Amino Acid Classification

    • Amino acids can be categorized based on the chemical properties of their side chains, including:
      • Nonpolar (hydrophobic)
      • Polar (hydrophilic)
      • Positively charged (basic)
      • Negatively charged (acidic)

    Amino Acid Specificities

    • Glycine (G) is non-chiral and provides flexibility; it is unique among amino acids.
    • Proline forms a rigid structure due to bonding back to its main chain.

    Ionization and Charges

    • Amino acids in solution exist as zwitterions, having both positive and negative charges.
    • Some amino acids possess ionizable side chains; their charge depends on pH and is described by pKa values.
    • pI (isoelectric point) is the pH where an amino acid has no net charge.

    Amino Acid Modifications

    • Standard amino acids can undergo post-translational modifications after translation, including:
      • Phosphorylation: regulates enzyme activity.
      • Hydroxylation: critical for collagen formation and preventing scurvy.
      • Carboxylation: important for blood clotting.
      • Other modifications include glycosylation, iodination, and metal binding.

    Peptide Bonds

    • Peptide bonds link amino acids via a covalent bond formed between the carboxyl group of one amino acid and the amino group of another.
    • The peptide bond exhibits about 40% double bond character, leading to a planar and predominantly trans configuration.
    • Peptide chains vary in length and have biological functions; short chains are called peptides, while longer chains are proteins.
    • Each amino acid linked in a chain is termed an amino acid residue, denoted by its sequence position (e.g., Met 184).

    Summary of Key Terms

    • pKa: The pH at which an ionizable group is 50% ionized.
    • pI: The pH at which an amino acid or protein has a net charge of zero.
    • Amino acid modifications are crucial for protein functionality and regulation.

    Building Blocks of Proteins: Amino Acids

    • Amino acids are the fundamental units of proteins, containing both an amino group (H2N–) and a carboxyl group (–COOH), linked to a central α-carbon atom.
    • There are 20 standard amino acids in proteins, classified based on their side-chain structures (R-groups).
    • Amino acids exhibit stereochemistry with D- and L- forms; proteins in living organisms primarily utilize L-amino acids.
    • Bacteria can synthesize proteins containing D-amino acids.

    Classification of Amino Acids

    • Amino acids are categorized into non-polar (aliphatic or aromatic side chains) and polar (ionizable acidic or basic groups) types.
    • Non-polar amino acids are typically found in hydrophobic environments, while polar amino acids interact with the aqueous environment.
    • Ionizable side chains contribute to the overall charge of the amino acid, influenced by pH and pKa values.

    Peptide Bonds Formation

    • Amino acids join by peptide bonds, forming a covalent linkage between the amino (N-terminus) and carboxyl (C-terminus) ends of adjacent amino acids.
    • The peptide bond has partial double bond character, making it planar and predominantly in trans configuration.
    • The sequence of amino acids, or primary structure, is written from N-terminus to C-terminus and defines the protein's structure and function.

    Peptide Bond and Protein Structure

    • The peptide bond is stable and contributes to the protein's final three-dimensional structure through its fixed dipole.
    • The role of cis/trans configurations in peptide bonds is essential, with cis indicating similar sides and trans indicating opposite sides of the carbon chain.

    Post-Translational Modifications

    • Proteins undergo post-translational modifications, enhancing functionality after translation from the endoplasmic reticulum through the Golgi apparatus.
    • Common modifications include:
      • Proteolytic cleavage
      • N-glycosylation
      • Lipid addition
      • Disulphide bridge formation
      • Hydroxylation
      • C-terminal amidation
      • Phosphorylation
    • These modifications are crucial for achieving the correct active form of proteins.

    Protein Functionality

    • The ultimate function of proteins is determined by the amino acid sequence, structural conformation, and post-translational modifications.
    • Proteins perform various roles, including:
      • Enzymatic activity
      • Regulatory functions
      • Transport mechanisms
      • Storage solutions
      • Contractile and motility functions
      • Structural frameworks
      • Protective roles in the body

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    BIOC 192 Lecture 4 Building Blocks of Proteins PDF
    Lecture 4: Building Blocks of Proteins: Amino Acids PDF

    Description

    Dive into the building blocks of proteins with Lecture 4 of BIOC 192. This session focuses on amino acids, peptides, and the interplay of the peptide bond, providing a foundational understanding crucial for biochemistry students. Engage with the material to enhance your knowledge of protein structure and function.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser