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Questions and Answers
What term describes the unfolding of a protein?
How many polypeptide chains are present in a haemoglobin molecule?
What is the function of the haem group in haemoglobin?
What is formed when haemoglobin combines with oxygen?
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How many molecules of oxygen can each haemoglobin carry?
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What substance begins the digestion of proteins into amino acids, dipeptides, and tripeptides in the stomach?
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Which enzymes are responsible for completing the digestion of proteins in the small intestine?
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Which type of protein structure is characterized by a regular, repeating arrangement of amino acids, such as α-helices and β-pleated sheets?
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What best describes a molecule that carries both positive and negative charges in equal numbers?
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What is the primary function of peptidases produced by the small intestine?
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What type of proteins are molecular chaperones, which assist in the correct folding of other proteins?
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What is an example of a simple protein?
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Which of the following components is derived from proteins and plays a critical role in various biological processes?
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What type of secondary structure is characterized by a pleated shape due to interchain hydrogen bonding?
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Which interaction is NOT responsible for maintaining the tertiary structure of proteins?
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What defines the quaternary structure of a protein?
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Protein folding is primarily dictated by which of the following?
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Which of the following statements about intrachain hydrogen bonding is true?
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How are the nonpolar side chains of amino acids typically arranged in a protein?
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What type of bond is formed when the –SH groups of two cysteines are oxidized?
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Which statement accurately describes the β - pleated sheet?
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What type of resin is used in the cation exchange chromatography described?
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What is the purpose of adding NaCl during the elution process?
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How do negatively charged proteins behave during the cation exchange chromatography process?
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Which ions interact with the cation resin during the elution of the protein?
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What characteristic do the proteins of interest have in the cation exchange column?
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What describes the substrate in relation to an enzyme?
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Which of the following statements is true about enzyme specificity?
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In a reaction where multiple substrates produce multiple products, which of the following represents that?
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When enzyme activity is lost due to changes in temperature or pH, it is referred to as what?
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Which feature is NOT a property of enzymes?
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Which reaction type has one substrate converting to a single product?
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What is the role of cofactors in enzymatic reactions?
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In an ordered binding reaction, which statement is correct?
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Study Notes
Protein Digestion
- Pepsinogen is activated into pepsin in the stomach.
- Pepsin breaks down proteins into amino acids, dipeptides, and tripeptides.
- Pepsin is responsible for 10-20% of protein digestion.
- Pancreatic and intestinal proteases and peptidases complete protein digestion in the small intestine.
- The small intestine also produces peptidases for complete digestion and absorbs amino acids, releasing them into the bloodstream for use by the body's cells.
Protein Structure
- Proteoses and Peptones are derived proteins.
- Albumin is a simple protein.
- Nucleoprotein is a protein containing nucleic acids.
- Primary structure of a protein refers to the sequence of amino acids.
- Alpha helix is a secondary structure formed by intrachain hydrogen bonding parallel to the peptide bond.
- Tertiary structure of a protein refers to the three-dimensional shape of a single polypeptide chain, held together by bonds between side chains.
- Disulphide bonding (disulphide bridges) is formed when two cysteine molecules combine.
- Hydrogen bonding, Ionic bonds, and Hydrophobic interactions all contribute to the tertiary structure of a protein.
- Beta pleated sheet is a secondary structure formed by interchain hydrogen bonding perpendicular to the peptide bonds.
- Silk fibroin is an example of a protein rich in beta pleated sheets.
- Heat shock proteins are molecular chaperones.
- Diaminomonocarboxylic acid is a basic amino acid.
- Asparagine is an amide group containing amino acid.
- Zwitterion is a molecule that carries both positive and negative charges in equal numbers.
- Insulin is an example of an alpha helix.
- Lipase is an example of an enzyme with tertiary structure.
Tertiary Structure
- There are four ways in which parts of the amino acid chains interact to hold the 3D tertiary shape together:
- Disulphide bonding
- Hydrogen bonding
- Ionic bonds
- Hydrophobic interactions
Quaternary Structure
- The quaternary structure of a protein is the association of several protein chains or subunits into a closely packed arrangement.
- Each subunit has its own primary, secondary, and tertiary structure.
- Subunits are held together by hydrogen bonds and van der Waals forces between nonpolar side chains.
- Haemoglobin is an example of a protein with quaternary structure.
Protein Folding
- The amino acid sequence (or primary structure) of a protein defines its native conformation.
- A protein molecule folds spontaneously during or after synthesis.
- Unfolding of a protein is called denaturation.
Haemoglobin and Myoglobin
- Haemoglobin is an iron-containing protein attached to red blood cells that transports oxygen from the lungs to the rest of the body.
- Haemoglobin is an example of both globular and quaternary structure of protein.
- Haemoglobin has 4 polypeptide chains:
- Two alpha-polypeptides, each consisting of 141 amino acids.
- Two beta-polypeptides, each consisting of 146 amino acids.
- Each polypeptide chain has a haem group, which contains iron that binds to oxygen.
- Each haemoglobin molecule can carry 4 molecules of oxygen.
- When haemoglobin combines with oxygen, it forms oxyhaemoglobin.
Ion exchange chromatography
- It is used to separate proteins based on their charge.
- Positively charged proteins bind to a cation exchanger column (CM cellulose).
- Negatively charged proteins pass through the column.
- To elute protein of interest, increasingly higher amounts of salt NaCl is added to increase the ionic strength.
- Na+ ions interact with the cation resin, and Cl- ions interact with the positively charged protein to elute it off the column.
Enzyme Properties
- All enzymes are proteins.
- Enzymes are biological catalysts.
- They lose their activity if denatured.
- They lower the activation energy of a reaction.
- Small quantities of enzymes catalyze large quantities of substances.
- Enzymes increase the rate of reaction but remain unaffected by the reaction they catalyze.
- They may contain cofactors such as metal ions or organic molecules (vitamins).
- The enzyme molecule can be reused repeatedly, as they are not consumed by the reaction.
- Enzymes are highly specific in nature, meaning a particular enzyme catalyzes a particular reaction.
Enzyme Terminology
- Substrate: The reactants that are activated by the enzyme.
- Active Site: A specific shape on an enzyme that is complementary to the substrate.
- Activation Energy: The amount of energy required for a chemical reaction to occur.
- Product: The molecules produced after the enzyme-catalyzed reaction.
Different Types of Reactions Enzymes Catalyze
- Single Substrate - Single Product: A ⇄ B
- Single Substrate - Multiple Products: A ⇄ B + C
- Multiple Substrates - Single Product: A + B ⇄ C
- Multiple Substrates - Multiple Products: A + B ⇄ C + D
Enzyme Binding
- There are two types of multi-substrate binding:
- Ordered: Substrates bind in a specific order. Ex: NADH + Pyruvate binding to Lactate Dehydrogenase.
- Random: Substrates bind in any order. Ex: Creatine + ATP binding Creatine Kinase.
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Description
Test your knowledge on protein digestion and structure with this quiz. Explore the roles of pepsin and proteases in breaking down proteins and learn about various types of proteins and their structures. Perfect for students studying biochemistry or nutrition.
