Biochemistry Quiz on Proteins and Enzymes
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Questions and Answers

Which of the following protein types is involved in the process of catalyzing chemical reactions, such as digestion?

  • Contractile Proteins
  • Enzymes (correct)
  • Transport Proteins
  • Nutrient and Storage Proteins

    • What is the primary function of structural proteins?

  • Defending the body against foreign invaders
  • Transporting molecules throughout the body
  • Providing support and structure to tissues (correct)
  • Regulating essential biological processes

    • Select the two major protein structures responsible for the overall three-dimensional shape of a single polypeptide chain.

  • Tertiary and Quaternary
  • Primary and Secondary
  • Secondary and Tertiary (correct)
  • Primary and Quaternary

    • Transamination is a process that involves the transfer of amino groups between amino acids and keto acids.

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

    Which of the following is a major consequence of the urea cycle?

    <p>The detoxification of ammonia into urea for excretion (B)</p> Signup and view all the answers

    What is the primary structural component of connective tissues like tendons, cartilage, and bones?

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

    Which of the following amino acids is essential for the formation of heme?

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

    The presence of high homocysteine levels in the blood has been linked to an increased risk of cardiovascular diseases.

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

    What is the primary function of the neurotransmitter GABA?

    <p>To inhibit neuronal activity and reduce the likelihood of seizures (C)</p> Signup and view all the answers

    The enzyme tyrosine hydroxylase is responsible for the initial step in the synthesis of catecholamines.

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

    Which of the following disorders is specifically caused by a deficiency of the enzyme homogentisate dioxygenase?

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

    The synthesis of serotonin in the brain plays a crucial role in regulating sleep, mood, and appetite.

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

    Melatonin is a hormone primarily produced by the pineal gland and is known to play a significant role in regulating sleep-wake cycles and circadian rhythms.

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

    Flashcards

    Contractile Proteins

    Proteins that help in movement, often found in muscles.

    Defense Proteins

    Proteins that play a role in protecting the body from threats, like invading bacteria.

    Enzymes

    Proteins that accelerate chemical reactions in the body.

    Transfer Proteins

    Proteins that carry molecules like oxygen throughout the body. Hemoglobin is an example.

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    Primary Structure

    The sequence of amino acids in a protein chain.

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    Tertiary Structure

    The overall 3D shape of a single polypeptide chain.

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    Quaternary Structure

    The arrangement of multiple polypeptide chains (subunits) into a larger protein complex.

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    Secondary Structure

    The local folding patterns, like alpha-helices and beta-pleated sheets, formed within a protein chain.

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    Oxidative Deamination

    The process of removing an amino group from an amino acid, releasing ammonia.

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    Urea Cycle

    The cycle that converts toxic ammonia into urea for safe excretion.

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    Transamination

    The transfer of an amino group between an amino acid and a keto acid.

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    Structural Proteins

    Proteins that provide structural support and are often found in tissues like tendons, ligaments, and skin.

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    Scurvy

    A deficiency of vitamin C, leading to weakened collagen and causing scurvy.

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    Phenylketonuria (PKU)

    A genetic disorder where the enzyme phenylalanine hydroxylase is deficient, leading to an inability to metabolize phenylalanine.

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    Alkaptonuria

    A genetic disorder where the enzyme homogentisate dioxygenase is deficient, leading to a build-up of homogentisic acid and dark urine.

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    Homocystinuria

    A rare genetic disorder caused by a deficiency in the enzyme cystathionine β-synthase, leading to high levels of homocysteine.

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    Collagen

    A fibrous protein that forms the basic structural unit of connective tissue, providing strength and flexibility.

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    Keratin

    The fibrous protein found in hair, nails, and skin, contributing to their strength and structure.

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    Fibroin

    The main protein found in silk, giving it its smooth and strong properties.

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    Elastin

    A fibrous protein that gives elasticity to tissues like lungs and blood vessels.

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    GABA (Gamma-Aminobutyric Acid)

    A neurotransmitter derived from the amino acid glutamate, known for its inhibitory effects on the brain.

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    Serotonin

    A neurotransmitter synthesized from tryptophan, responsible for regulating mood, sleep, and appetite.

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    Dopamine

    A neurotransmitter synthesized from tyrosine, involved in movement, motivation, and pleasure.

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    Melanin

    A pigment found in skin, hair, and eyes, responsible for protecting against UV radiation.

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    Heme

    An essential component of hemoglobin, responsible for carrying oxygen in the blood.

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    Alanine

    A non-essential amino acid that can be synthesized by the body, important for energy production and protein synthesis.

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    Glutamate

    An amino acid with a role in protein synthesis and the production of neurotransmitters.

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    Lysine

    An essential amino acid required for protein synthesis and growth, not produced by the body.

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    Valine

    An essential amino acid needed for protein synthesis, not produced by the body.

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    Methionine

    An essential amino acid required for protein synthesis, not produced by the body.

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    Study Notes

    Summary of Protein Structure and Function

    • Diagrams and pictures used in the presentation are for illustrative purposes only.
    • Proteins are large biomolecules with diverse functions within the body.
    • Proteins are constructed from amino acids.
    • The sequence of amino acids determines the unique structure and function of each protein.
    • Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
    • The primary structure is the linear sequence of amino acids.
    • Secondary structure involves local folding patterns like alpha-helices and beta-pleated sheets, stabilized by hydrogen bonds.
    • Tertiary structure is the overall three-dimensional shape of a single polypeptide chain.
    • Quaternary structure describes the arrangement of multiple polypeptide chains to form a functional protein.
    • Protein denaturation occurs when a protein loses its three-dimensional structure and function due to factors such as heat, extreme pH, or certain chemicals.
    • Proteins are crucial for a body's structure, function, and regulation.

    Protein Classification by Function

    • Enzymes accelerate chemical reactions in the body.
    • Transfer proteins transport nutrients and other molecules throughout the body.
    • Storage proteins store essential nutrients like those found in milk and eggs.
    • Contractile proteins play a critical role in movement.
    • Structural proteins provide structural support for tissues
    • Defensive proteins protect the body from pathogens via antibodies and clotting factors.
    • Regulatory proteins help to control metabolic processes.

    General Features of Proteins

    • Proteins are composed of amino acids.
    • Some proteins have chemical groups other than amino acids (conjugated proteins).
    • Conjugated proteins include lipoproteins, glycoproteins, and metalloproteins.
    • Some proteins have a prosthetic group, which is a non-protein component.
    • Protein digestion starts in the stomach and continues through the small intestine.
    • Proteins are usually not stored but are used and excreted when needed.

    Amino Acids

    • Amino acids are the building blocks of proteins.
    • The general structure of an amino acid includes a central carbon atom bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R-group (side chain).
    • Amino acids can exist as zwitterions, which are both positively and negatively charged.
    • The specific physical and chemical properties of the R-group influence the behavior and function of an amino acid within a protein.
    • Various amino acids have characteristic properties like polarity, charge, and size.

    Modified Amino Acids

    • Some proteins contain modified amino acids that have undergone post-translational modifications
    • These modifications can alter the protein's structure, such as adding a hydroxyl group to lysine, leading to a range of functions.
    • Modified amino acids are found in various proteins.

    Nomenclature of Amino Acids

    • Some amino acids have a specific naming convention that distinguishes their specific positions from the carboxyl group.

    Stereoisomerism of Amino Acids

    • Amino acids exist as L and D stereoisomers, but only L-amino acids are used in protein synthesis.

    Standard Amino Acids

    • There are 20 standard amino acids, each having specific names & structures.
    • Some are polar, some non-polar, some charged, others uncharged.

    Disulfide Bonds

    • Disulfide bonds are covalent bonds that form between certain amino acids (cysteine residues), strengthening protein structure.

    Non-Standard Amino Acid Derivatives

    • Some non-standard amino acid derivatives are found in proteins
    • This group includes ornithine and citrulline, they are intermediates in urea synthesis.

    Titration Curve of Amino Acids

    • Titration curves show the pH dependence of amino acid ionization's.
    • By measuring the pH changes different pK values can be obtained.

    Peptide Bonds

    • Peptide bonds are the covalent links between amino acids in a polypeptide chain.

    Levels of Protein Structure

    • Primary structure: The amino acid sequence of a polypeptide chain

    • Secondary structure: Local folding patterns in a polypeptide chain, stabilized by hydrogen bonds

    • Tertiary structure: Overall 3D shape of a single polypeptide chain, stabilized by various interactions among amino acids.

    • Quaternary structure: Organization of multiple polypeptide chains in a multi-subunit protein.

    Protein Secondary Structures

    • Alpha Helix: A spiral-shaped structure stabilized by hydrogen bonds along the backbone.

    • Beta-pleated sheet: A sheet-like structure stabilized by hydrogen bonds between different parts of the polypeptide chain.

    • Proteins have different secondary structures depending on its function.

    Protein Tertiary Structures

    • Tertiary structure results from further folding and interactions among amino acids.

    • The different types of interactions between amino acids (hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bonds) stabilize the polypeptide backbone, leading to the distinctive 3-D shape.

    Protein Quaternary Structures

    • Multiple polypeptide chains associate to form a functional protein complex.
    • Non-covalent interactions stabilize the quaternary structure.

    Fibrous Proteins

    • Fibrous proteins are elongated and insoluble in water
    • These proteins play structural roles in tissues (e.g., collagen, elastin).
    • These proteins have a repeating amino acid sequence.
    • They are often strong mechanically.
    • They are usually insoluble in water.
    • They typically play a structural role in the body.

    Structural Classes of Proteins

    • Fibrous proteins are extended and insoluble in water.
    • Globular proteins are compact and soluble in water.
    • Membrane proteins are embedded in cell membranes and have both hydrophobic and hydrophillic portions.

    General Features of Fibrous Proteins

    • Repeating amino acid sequence
    • Unusual amino acid composition
    • Mostly one type of secondary structure.
    • Strong mechanical.
    • Usually insoluble in water.
    • Important structural roles.

    Collagen

    • Major component of connective tissue
    • Composed of three intertwined helical chains.
    • Stabilized by hydrogen bonds.
    • Contains modified amino acid residues, like hydroxyproline and hydroxylysine.

    Elastin

    • Rubber-like elasticity
    • Found in tissues that require flexibility (e.g., lungs, blood vessels).
    • Irregular 3D structure.
    • Extensive cross-linking of lysine residues.

    Keratin

    • Structural protein in hair, nails, and skin
    • Rich in cysteine residues, forming disulfide bonds, that create toughness
    • Alpha helical secondary structures, and interactions between alpha chains lead to its strength/stability

    Silk Fibroin

    • Structural protein in silk
    • Composed of beta-pleated sheets, resulting in its strength/elasticity, durability
    • Amino acid sequence is rich in the amino acid glycine
    • Exhibits strong mechanical properties.

    Amino Acid Metabolism

    • Non-essential amino acids can be synthesized by the body.
    • Essential amino acids must be obtained from the diet.

    Urea Cycle

    • The urea cycle is a metabolic pathway that converts ammonia, a toxic byproduct of protein metabolism, into urea, making it less toxic.
    • Takes place primarily in the liver.
    • Converts toxic ammonia into urea.
    • Connects with the citric acid cycle (TCA)

    Transamination

    • Transfers an amino group from one amino acid to a keto acid, forming a new amino acid and a different keto acid.
    • Important for the synthesis and breakdown of amino acids.

    Oxidative Deamination

    • Removes an amino group from an amino acid, releasing ammonia as a byproduct.
    • Crucial for nitrogen metabolism.

    Nitrogen Containing Compounds

    • Ammonia is toxic, thus, the urea cycle is critical for its detoxification.
    • Several nitrogen-containing compounds are involved in various bodily functions.
    • These compounds include neurotransmitters, such as GABA, serotonin, and dopamine, play significant roles in the nervous system's function

    GABA (Gamma Aminobutyric Acid)

    • GABA is an inhibitory neurotransmitter in the brain.
    • It's formed from glutamate via a decarboxylation reaction.
    • It plays a crucial role in regulating neuronal excitability.

    Serotonin

    • Serotonin is a neurotransmitter involved in mood regulation, sleep, and appetite.
    • It's synthesized from tryptophan.
    • Its metabolite, 5-HIAA (5-hydroxyindoleacetic acid), is found in urine.
    • It plays roles in many bodily processes, primarily in the brain.

    Melatonin

    • A hormone produced by the pineal gland, regulating sleep-wake cycles
    • Derived from serotonin.
    • It's involved in the body's circadian rhythm.

    Tyrosine & Catecholamine Biosynthesis

    • Tyrosine is a precursor to several important molecules, including catecholamines.
    • Tyrosine is converted to DOPA, dopamine, norepinephrine, and epinephrine.
    • Involved in various body functions, including nerve signal transmission, hormone production.

    Melanin Formation

    • Melanin is a pigment produced in specialized cells (melanocytes) in the skin.
    • Tyrosine is a precursor for melanin synthesis.

    Tryptophan Metabolism

    • Tryptophan is an essential amino acid used to produce serotonin.
    • Serotonin regulates mood and sleep patterns
    • Nicotinic acid, a vitamin, is synthesized from tryptophan.

    Serotonin Metabolism

    • Serotonin is broken down into 5-HIAA, which is excreted in the urine.

    Creatine and Creatinine

    • Creatine is a compound found primarily in muscle tissue, used as an energy source.
    • Creatinine is a waste product of creatine breakdown and is excreted in urine.
    • Creatinine's blood concentration is used to assess kidney function.

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    Proteins Lecture Notes PDF

    Description

    This quiz tests your knowledge on various aspects of proteins, including their structures, functions, and roles in biochemical processes. Topics covered include catalysis, structural proteins, and the urea cycle. Prepare to dive deep into the fascinating world of biochemistry!

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