Biochemistry: Peptides and Amino Acids Quiz
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Questions and Answers

What is the maximum number of amino acids that can be present in a peptide?

  • 100 amino acids
  • Less than 50 amino acids (correct)
  • 10 amino acids
  • 50 amino acids

Which term refers to a peptide composed specifically of three amino acids?

  • Polypeptide
  • Oligopeptide
  • Dipeptide
  • Tripeptide (correct)

What type of bond joins the amino acids in a peptide?

  • Hydrogen bond
  • Ionic bond
  • Peptide bond (correct)
  • Disulfide bond

Which of the following is TRUE concerning polypeptides?

<p>Polypeptides are chains of more than 50 amino acids. (D)</p> Signup and view all the answers

What is the sequence of amino acids in a peptide primarily responsible for?

<p>Defining the peptide's biological function (A)</p> Signup and view all the answers

How many amino acids are present in a tetrapeptide?

<p>4 (B)</p> Signup and view all the answers

What is an oligopeptide?

<p>A peptide consisting of a few amino acids (B)</p> Signup and view all the answers

What is one of the mechanisms through which lactoferricins exert their antibacterial action?

<p>Disruption of normal membrane permeability (C)</p> Signup and view all the answers

Which amino acid addition can enhance the antioxidant activity of peptides derived from milk proteins?

<p>Leucine or proline at the N-terminus (A)</p> Signup and view all the answers

Which of the following statements about bioactive peptides is true?

<p>Some peptides can exhibit multiple beneficial effects. (C)</p> Signup and view all the answers

What role do microbial fermentation processes play in the production of bioactive peptides?

<p>Fermentation helps release peptides from host proteins in dairy. (A)</p> Signup and view all the answers

Why have peptides gained importance in molecular biology recently?

<p>They allow for the development of peptide antibodies without protein purification. (A)</p> Signup and view all the answers

What is the minimum number of amino acids required to form a polypeptide?

<p>50 (A)</p> Signup and view all the answers

Which of the following peptide types contains the largest number of amino acids?

<p>Decapeptide (B)</p> Signup and view all the answers

What type of bond is formed between amino acids to create peptides?

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

Which peptide is an example of a nonapeptide?

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

What is the role of Substance P in the body?

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

The formation of a peptide bond includes the release of which molecule?

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

Which peptide is directly associated with childbirth?

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

What type of compounds are polymyxin B and bacitracin classified as?

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

Which compound primarily serves as a toxin derived from mushrooms?

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

What specifically can break peptide bonds in proteins?

<p>Prolonged exposure to strong acid or base (A)</p> Signup and view all the answers

Which of the following is NOT a characteristic of peptide bonds?

<p>Flexible and allows free rotation (D)</p> Signup and view all the answers

What is a key function of glutathione in the body?

<p>Regenerates itself and reduces free radicals (B)</p> Signup and view all the answers

Which of the following peptides is modified to form a different compound?

<p>Thyrotropin releasing hormone (TRH) (A)</p> Signup and view all the answers

What effect does increasing glutathione levels have on physical performance?

<p>Decreases muscle damage (B)</p> Signup and view all the answers

Which of the following peptides is known to cause hypertension?

<p>Angiotensin I (B)</p> Signup and view all the answers

Which amino acid is mentioned as the master antioxidant's component?

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

What stabilizes the structure of proteins through peptide bonds?

<p>Hydrogen bonds in different peptide parts (C)</p> Signup and view all the answers

Which peptide is classified as a nanopeptide?

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

Which amino acid forms part of the structure of glutathione?

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

What is the primary action of nisin against microorganisms?

<p>Acts on the cytoplasmic membrane (C)</p> Signup and view all the answers

Which characteristic allows nisin to function effectively in food preservation?

<p>Presence of multiple thioether bridges (B)</p> Signup and view all the answers

What types of microorganisms is nisin particularly effective against?

<p>Gram-positive microorganisms (C)</p> Signup and view all the answers

Which health benefits are associated with food-derived peptides?

<p>Cholesterol-lowering ability (A)</p> Signup and view all the answers

Which unusual amino acid is NOT part of nisin's structure?

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

What effect do food-derived peptides have on mineral absorption?

<p>They enhance mineral absorption (C)</p> Signup and view all the answers

Which of the following statements regarding nisin's use is true?

<p>It is permitted as a preservative in several countries. (C)</p> Signup and view all the answers

Which peptides contain a β-amino acid bound to histidine?

<p>Carnosine, anserine, and balenine (C)</p> Signup and view all the answers

How do peptides derived from food affect blood pressure?

<p>They can lower blood pressure. (A)</p> Signup and view all the answers

What is a notable application of nisin in food processing?

<p>Suppressing anaerobes in cheese products (C)</p> Signup and view all the answers

Flashcards

Peptides

Short chains of amino acids (less than 50).

Polypeptides

Longer chains of amino acids (more than 50).

Peptide bond

Covalent bond connecting amino acids in peptides and polypeptides.

Dipeptide

Peptide chain with two amino acids.

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Tripeptide

Peptide chain with three amino acids.

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Oligopeptide

A few amino acids joined together.

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Biochemical Function (Peptides/Polypeptides)

Structure and function depend on amino acid type, sequence, and spatial relationships.

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Peptide length naming

Peptides of different lengths (e.g monopeptide, dipeptide, tripeptide etc.)

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Function of peptides

Peptides have diverse functions, including hormones, neuropeptides, antibiotics, and toxins.

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Example of peptide

A peptide with a specific function, such as insulin (regulates blood sugar).

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Peptide bond formation

Peptide bonds are formed by a condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a water molecule.

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Peptide bond angle

Peptide bond angle is approximately 120 degrees.

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Peptide bond strength

Peptide bonds are strong and resistant to typical denaturing agents, requiring strong acids/bases at high temperatures or specific enzymes for breakage.

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Peptide bond characteristics

Peptide bonds are rigid, planar, uncharged, and polar, allowing hydrogen bonding.

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Peptide roles

Peptides fulfill diverse biological functions, including hormones, toxins, and antibiotics.

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TRH

A tripeptide (Glu-His-Pro), important for regulating the release of hormones.

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Oxytocin/Vasopressin

Nanopeptides (9 amino acids) secreted by the posterior pituitary, influencing physiological processes.

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Angiotensin I/II

Peptides (10 and 8 amino acids, respectively) that regulate blood pressure.

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Glutathione

A peptide (L-glutamyl-L-cysteinyl-glycine) crucial for antioxidant function, immune response, and metabolic processes.

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Glutathione function

Plays a role in protecting the body against disease and illness and in building muscle.

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Lysine Peptides

Peptides containing lysine, potentially beneficial for human growth.

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Peptide Diversity

A variety of peptides exist in nature, each with its specific role in living organisms.

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Antimicrobial Peptides

Short chains of amino acids that can kill or inhibit the growth of bacteria, fungi, and viruses.

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Lactoferricins

Antimicrobial peptides derived from lactoferrin, a protein found in milk.

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Antioxidant Peptides

Peptides that protect cells from damage caused by free radicals.

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Food Applications of Bioactive Peptides

Bioactive peptides can be found naturally in foods, and their activity can be enhanced by food processing techniques like fermentation.

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Peptides in Molecular Biology

Peptides are used to create antibodies against specific proteins, which can be used for research and diagnostics.

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Nisin's function

Nisin is a peptide that inhibits Gram-positive microorganisms, especially effective against spores.

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Nisin's use in food

Nisin is used as a preservative in certain foods, allowing for milder sterilization conditions.

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Nisin's target

Nisin targets the cytoplasmic membrane of microorganisms, especially when the microorganism is in the spore stage.

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Carnosine structure

Carnosine, anserine, and balenine are peptides containing a specific amino acid linked to an histidine or a modified histidine.

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Bioactive Food Peptides

Peptides derived from food sources that have health benefits beyond basic nutrition.

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Food-derived Peptide Benefits

Food peptides can offer various health impacts including antimicrobial, blood pressure and cholesterol regulation, antioxidant effects, and mineral absorption improvement.

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Peptides from Animal and Plant Proteins

Many bioactive peptides are produced during protein digestion (within the body or in the lab), offering different possible health-promoting effects beyond basic nutrition.

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Unusual amino acids in nisin

Nisin contains unique amino acids like dehydroalanine, dehydro-ß-methyl-alanine, lanthionine, and ß-methyl-lanthionine, and thioether bridges.

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ß-amino acid

A beta-amino acid is an amino acid in which the amino group is attached to the second carbon atom in the carbon chain.

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Health-promoting peptide function

Biologically active fragments of protein within food with health-promoting functions beyond basic nutrition.

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Study Notes

Peptides, Polypeptides & Biochemical Importance

  • Peptides are formed when fewer than 50 amino acids join via a peptide bond.
  • Alternatively, peptides are short polymers of amino acids; usually monomers linked by peptide bonds. These covalent chemical bonds form between two molecules when the carboxyl group of one molecule reacts with the amino group of another molecule.
  • Polypeptides are peptides with more than 10 amino acid residues.
  • Peptides' structure and function depend upon the nature of amino acids present, their sequence, and spatial relationship.
  • Many peptides stem from the breakdown of proteins. Peptides are relatively small polymers (2-10 amino acids). If 2 amino acids are involved, it's a dipeptide; 3 is a tripeptide, and 10 is a decapeptide. Oligopeptides contain a few amino acids. Polypeptides are larger peptides; containing more than 50 amino acids.

Types of Peptides

  • The shortest peptide is a dipeptide, made of two amino acids joined by a peptide bond, to form a dipeptide molecule.
  • Tripeptides
  • Tetrapeptides and so on...

Proteins

  • Proteins are chains of amino acids.
  • Short chains of amino acids are called peptides.
  • Peptides of more than 10 amino acid residues are called polypeptides.

Peptide/Polypeptides

  • Peptides are polymers of amino acids.
  • Their structure and functions depend upon the nature of amino acids, sequence and spatial relationship among them.

Peptide Bond Formation

  • Amino acids attach covalently via a carboxyl group on one side and an amino group on the other side.
  • This forms an amide bond (called a peptide bond).
  • Peptide bond formation is a condensation reaction. A water molecule is removed when two amino acids link.

Characteristics of Peptide Bonds

  • Peptide bonds are strong, possessing partial double bond character.
  • They are typically not broken by common denaturing agents (e.g., heat or high salt concentrations).
  • Strong acids or bases at elevated temperatures or specific enzymes (such as digestive enzymes) can break them.
  • Peptide bonds are rigid and planar, resisting free rotation. This rigidity stabilizes protein structure.
  • Peptide bonds are uncharged but polar. Polar hydrogen atoms of amino groups and polar oxygen atoms of carboxyl groups contribute to this polarity.
  • This polarity allows hydrogen bonds to form between peptide bonds in different parts of the chain.

Individual Peptides

  • Peptides are widespread in nature.
  • They are often involved in specific biological activities such as peptide hormones, peptide toxins, and peptide antibiotics.
  • Examples include:
    • Thyrotropin-releasing hormone (TRH): a tripeptide.
    • Glu-His-Pro is its sequence; Glu is modified to form pyroglutamic acid.
    • Oxytocin and Vasopressin (ADH): nanopeptides (9 amino acids). Secretion from posterior pituitary.
    • Angiotensin I (10 amino acids) and Angiotensin II (8 amino acids) cause hypertension.
    • Glutathione (L-glutamyl-L-cysteinyl-glycine). Widespread in animals, plants, and microorganisms
    • Cysteine, glycine, and glutamine: Produced naturally in the body. Master antioxidant. Itself regenerates in the liver. Crucial for muscle damage recovery, strength/endurance, shifts from fat metabolism to muscle development and immune system health.
    • 2-Lysine Peptides: As effective as lysine in rat growth and feeding trials.
    • 3-Nisin: Formed by several strains of Streptococcus lactis to combat gram-positive microorganisms (lactic acid bacteria, Streptococci, Bacilli, Clostridia).
    • 4- Carnosine, Anserine, and Balenine: Peptides containing a β-amino acid (β-alanine) bound to L-histidine or a derivative. Found in meat extract.

Types of Bio-Active Peptides

  • Antimicrobial peptides
  • Antioxidant peptides

Food Applications of Bioactive Peptides

  • Many peptides occur naturally in foods.
  • Some are released during food fermentation (e.g., cheese ripening).
  • Enzymes in the gut can create peptides from proteins in food.

Peptides in Molecular Biology

  • Peptides have become essential in molecular biology.
  • They permit the creation of peptide antibodies in animals without purifying the protein of interest.
  • Peptides are also used in mass spectrometry to identify proteins based on mass and sequence.

C-Peptide

  • Patients with diabetes may have their C-peptide levels measured to distinguish type 1 from type 2 diabetes.
  • C-peptide levels may also assist in diagnosing hypoglycemia.
  • C-peptide levels can be checked in PCOS patients to assess insulin resistance.
  • C-peptide can also be used to identify gastrinomas associated with multiple endocrine neoplasm syndromes.

Peptide/Chemical Applications

  • Antimicrobial peptides have been used as therapeutic agents. (e.g., Bacitracin, Boceprevir, Dalbavancin, Daptomycin, Enfuvirtide, Oritavancin, Teicoplanin, Telaprevir, Telavancin, Vancomycin, and Guavanin).
  • Benefits of collagen peptides (therapeutic). Includes improving joint/bone health and aiding aging/skin beauty/connective tissue health.
  • Brain Peptides: Receptors that bind opiates like morphine; called endorphins (endogenous morphine). Dynorphin is a significant peptide (13 amino acids) due to its potency (superopioate).
  • The term peptide can refer to secretogue peptides or peptide hormones in sports doping.
  • This class includes substances that cause other substances to release.
  • Proteins can be classified functionally; including enzyme/protease which breaks down proteins; defence functions such as antibodies fighting viruses; contracts, transportation, regulation, and support functions.

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Peptides, Polypeptides & Biochemical Importance PDF

Description

Test your knowledge on the structure, function, and characteristics of peptides and amino acids. This quiz covers key concepts such as the types of peptides, amino acid bonding, and the biological significance of peptides. Perfect for students studying biochemistry or molecular biology.

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