Cell Biomolecules Functions & Detection
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Questions and Answers

What is primarily responsible for determining the primary structure of a protein?

  • The interaction of different proteins
  • The sequence of amino acids (correct)
  • The three-dimensional shape of the protein
  • Hydrogen bonds between polypeptide chains

Which of the following is NOT a function of proteins?

  • Accelerating chemical reactions
  • Transporting molecules
  • Cellular communication
  • Storing energy (correct)

Which structure is involved in the secondary structure of proteins?

  • Amino acid sequence
  • Disulfide bonds
  • Hydrophobic interactions
  • α helix and β pleated sheet (correct)

Cell-surface receptors include which of the following?

<p>Ion Channel Receptors (D)</p> Signup and view all the answers

What role do carbohydrates primarily serve in living organisms?

<p>Structural support and energy storage (B)</p> Signup and view all the answers

Which of the following types of receptors is classified as an intracellular receptor?

<p>Nuclear Hormone Receptors (A)</p> Signup and view all the answers

The secondary structure of proteins is stabilized by which type of bond?

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

What characterizes G Protein-Coupled Receptors?

<p>They undergo conformational changes upon ligand binding (C)</p> Signup and view all the answers

Which reagent is used in the Molish test to detect carbohydrates?

<p>Alpha-naphthol (B)</p> Signup and view all the answers

What type of carbohydrates does Benedict's test primarily detect?

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

Which of the following substances are detected by Barfoed's test?

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

What can be inferred if a solution turns blue in the Iodine test?

<p>Presence of starch (C)</p> Signup and view all the answers

Which carbohydrate tests involve heating the mixture for 5 minutes for a color change?

<p>Benedict’s and Barfoed’s tests (B)</p> Signup and view all the answers

Which monosaccharides are positive in the Ketose test?

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

What is the role of concentrated hydrochloric acid in the Ketose test?

<p>To hydrolyze polysaccharides (B)</p> Signup and view all the answers

What does a positive result in the Molish test indicate?

<p>Presence of all carbohydrates (B)</p> Signup and view all the answers

What is the primary interaction responsible for the tertiary structure of proteins?

<p>Interactions between R groups (C)</p> Signup and view all the answers

What type of protein structure involves the formation of a single macromolecule from multiple polypeptide chains?

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

Which test specifically detects proteins and peptides that contain at least two peptide bonds?

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

Which amino acid would give a negative result in the Ninhydrin test?

<p>Beta-alanine (B)</p> Signup and view all the answers

What color indicates a positive result in the Ninhydrin test for alpha amino acids?

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

Which type of amino acids are specifically detected by the Xanthoproteic reaction?

<p>Aromatic amino acids (D)</p> Signup and view all the answers

Which proteins are examples of quaternary structure?

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

What type of bond may reinforce the structure of certain proteins?

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

Flashcards

Biomolecules

Chemicals in living organisms that are essential for life processes like growth, reproduction, and sustenance.

Proteins

Major components of cells, often more than 50% of the dry mass, performing tasks like accelerating reactions and cell communication.

Protein functions

Enzymes accelerate chemical reactions, transport substances, and support cell communication.

Protein structure: Primary

Sequence of amino acids linked in a protein determined by genes.

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Protein structure: Secondary

Coils and folds in polypeptide chains due to hydrogen bonds.

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Cell-surface receptors

Proteins on cell surfaces that receive signals from outside the cell.

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Intracellular receptors

Proteins located within the cell which receives signaling molecules.

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Phosphorylation

Adding a phosphate group to a molecule (often a protein), changing its activity.

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Tertiary structure

The 3D shape of a single polypeptide chain, formed by interactions between its side chains (R groups).

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Quaternary structure

The arrangement of multiple polypeptide chains (subunits) in a protein, forming a complex structure.

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Disulfide bridges

Strong covalent bonds that can stabilize the tertiary and quaternary structures of proteins.

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Biuret test

A test that detects the presence of proteins by reacting with peptide bonds.

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Ninhydrin test

Used to detect α-amino acids in proteins and peptides.

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Xanthoproteic reaction

Detects the presence of aromatic amino acids, like phenylalanine, tyrosine, and tryptophan, in proteins.

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Collagen

A fibrous protein with a unique structure of three polypeptide chains intertwined like a rope.

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Hemoglobin

A globular protein responsible for transporting oxygen in red blood cells.

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Molisch Test

A general test for the presence of carbohydrates. It involves reacting the sample with Molisch reagent (alpha-naphthol in acidic medium) and concentrated sulfuric acid, which forms a purple ring at the interface if carbohydrates are present.

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Benedict's Test

A test specifically for reducing sugars (like glucose, fructose, and lactose). It uses Benedict's reagent, which contains copper(II) sulfate. Reducing sugars react with the copper ions, resulting in a color change from blue to green, yellow, orange, or red depending on the concentration of the sugar.

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What causes the color change in Benedict's test?

The color change in Benedict's test is due to the reduction of copper(II) ions to copper(I) oxide, which forms the colored precipitate.

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Ketose Test

Detects the presence of ketoses (sugars with a ketone group). The sample is reacted with resorcinol and concentrated hydrochloric acid, which hydrolyzes polysaccharides and oligosaccharides to simpler sugars and then forms furfural from ketoses, resulting in a red color.

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Barfoed's Test

A test for monosaccharides (simple sugars like glucose and fructose). It uses Barfoed's reagent, which contains copper(II) acetate in acetic acid. Monosaccharides reduce the copper ions, resulting in a red precipitate.

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Iodine Test

A specific test for starch. When iodine solution is added to a solution containing starch, a distinctive blue-black complex forms due to the interaction of iodine molecules with the helical structure of starch.

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What is the function of the iodine solution in the iodine test?

The iodine solution acts as an indicator. It interacts with the helical structure of starch molecules, forming a blue-black complex that indicates the presence of starch.

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What are reducing sugars?

Reducing sugars are carbohydrates that can donate electrons to other molecules, such as copper ions in Benedict's reagent. They have a free aldehyde or ketone group that can react with another molecule.

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Study Notes

Cell Biomolecules Functions & Detection

  • Biomolecules are chemicals in living organisms.
  • Examples include carbohydrates, proteins, lipids, enzymes, and nucleic acids.
  • These biomolecules are essential for life processes like growth, reproduction, and sustenance.
  • Diversity in their shapes and structures provides diversity in their functions.
  • Cell membranes are made of a phospholipid bilayer.
  • Proteins are embedded in the membrane.
    • Some are peripheral and some are integral.
    • Globular proteins, glycolipids, glycoproteins, and cholesterol are all present.
  • Enzymes are proteins that accelerate chemical reactions.
  • DNA is a double helix structure.
  • Proteins consist of amino acid polymers linked by peptide bonds.
    • The amino acid sequence (primary structure) determines the protein's function.

Protein Structure Levels

  • Primary structure: The sequence of amino acids in a protein.
    • Determined by the genetic information.
  • Secondary structure: Coils and folds in the polypeptide chain due to hydrogen bonds.
    • Commonly a helix or pleated sheet.
  • Tertiary structure: Interactions between R groups (side chains) in a protein.
    • Hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges affect the structure.
  • Quaternary structure: Formed when two or more polypeptide chains associate.
    • Examples are collagen and hemoglobin.

Protein Detection Methods

  • Biuret test: Detects proteins and peptides with at least two peptide bonds.
    • A positive result produces a violet color.
  • Ninhydrin test: Detects amino acids.
    • Positive result: violet blue color
  • Xanthoproteic reaction: Detects aromatic amino acids.
    • Positive result: orange color.
  • Millon's reaction: Detects tyrosine amino acid.
    • Positive result: purple red spots.
  • Adamkiewicz's reaction: Detects tryptophan amino acid.
    • Positive result: violet red compound.

Sulphur Containing Amino Acids

  • A-Fohl's reaction: Detects sulfur-containing amino acids, leading to a black lead sulfide deposit.
  • B-Nitroprusside reaction: Detects sulfur-containing amino acids, producing a violet red complex.

Protein Classification

  • Simple proteins: Composed solely of amino acids.
  • Conjugated proteins: Contain a non-protein component (prosthetic group).
  • Derived proteins: Hydrolyzed or denatured proteins.

Phosphoproteins

  • Phosphoproteins have a phosphate group attached, forming an ester linkage to the OH group of amino acids like serine, threonine, or tyrosine.

Carbohydrates

  • Monosaccharides: Simple sugars.
  • Polysaccharides: Polymers of monosaccharides.
    • Examples: Starch, glycogen, cellulose
    • Function in energy storage and structural support.

Carbohydrate Detection Methods

  • Molisch test: Detects carbohydrates.
  • Benedict's test: Detects reducing sugars.
  • Seliwanoff's test: Detects ketoses.
  • Barfoed's test: Detects monosaccharides.
  • Iodine test: Detects starch.

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Description

This quiz focuses on the various types of biomolecules found in living organisms, including carbohydrates, proteins, lipids, enzymes, and nucleic acids. It explores their structures, functions, and the importance of proteins in cell membranes and enzymatic reactions. Test your knowledge on the diversity and roles of these essential biomolecules.

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