Questions and Answers
What is the typical range of amino acids in most proteins?
What is the main focus of this lesson?
Which type of protein is linked to the membrane through a covalent bond to a lipid molecule?
Which of the following chapters are mentioned in this lesson?
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What is the registration certificate number of Eduvos (Pty) Ltd?
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What is the process by which a denatured protein returns to its native structure?
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What is the term for the non-polar, hydrophobic amino acids?
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What is the name of the Act under which Eduvos (Pty) Ltd is registered?
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What is the purpose of mentioning the page numbers of the chapters?
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Which type of protein spans the entire width of the membrane?
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What is the name of the institution that is registered with the Department of Higher Education and Training?
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What is the term for the process by which a protein loses its native structure, often due to changes in temperature, pH, or solvent composition?
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What is the average length of an alpha helix in amino acids?
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How many residues are present in each turn of an alpha helix?
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What is the direction of the helical twist in an alpha helix?
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What type of bond supports the helical twist in an alpha helix?
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Where are the hydrogen bonds that support the helical twist found in the structure of an alpha helix?
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What is the pitch of an alpha helix?
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How many intra-chain hydrogen bonds are present in an alpha helix?
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What is the direction of the Cα atoms in an alpha helix?
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What percentage of double bond character does the peptide group have?
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What is the conformation of peptide bonds where Cα atoms are on the same side?
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What is the angle between the Cα and C atoms in the polypeptide backbone?
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What is the main reason for the planar structure of peptide groups?
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What is the conformation of peptide bonds where Cα atoms are on opposite sides?
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What is the term for the rotation of the polypeptide backbone around a bond?
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What is the effect of steric interference of adjacent peptide groups?
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What is the characteristic of the peptide group that makes it planar and rigid?
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What is the effect of increased hydropathy on a protein?
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Which of the following factors can influence the denaturation of proteins?
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What is the purpose of the activity in Lesson 3?
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What is the main topic of Week 1, Lesson 3?
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What is the purpose of chaotropic agents in protein denaturation?
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What is the outcome of increased hydropathy on a protein's hydrophobicity?
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What is the purpose of protein assays in protein purification?
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What is the outcome of the activity in Lesson 3?
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Study Notes
General Properties and Structure of Proteins
- Proteins have 100-1000 amino acids.
- Amino acids are classified into hydrophobic, nucleophilic, acidic, basic, and aromatic.
- Greek alphabet and symbols are used to represent amino acids.
Levels of Protein Structure
- Peptide bonds assume a trans conformation, which is a rigid, planar structure with 40% double bond character.
- The peptide bond has Cα atoms on opposite sides in the trans conformation and on the same side in the cis conformation.
- The extended conformation of polypeptide backbone has torsion angles Phi (ϕ) and Psi (ψ) for Cα-N and Cα-C bonds respectively.
- Steric interference occurs between adjacent peptide groups.
- The α helix is a type of secondary structure with properties such as left or right handedness, amount of polypeptides, and amount of residues per turn.
- The α helix has an average length of 3.6 residues per turn and is supported by hydrogen bonds between C=O and N-H of the (N+4)th residue.
- The α helix has a pitch of 5.4 Å and is right-handed.
Hydrophobic and Hydrophilic Tendencies
- Hydrophobic and hydrophilic tendencies are measured by hydropathy, which increases with the nonpolar nature of the molecule.
- Hydrophobic and hydrophilic interactions affect protein stability.
Factors that Influence Protein Stability
- Factors that influence protein stability and denaturation include heat, pH variations, detergents, and chaotropic agents.
- Chaotropic agents denature proteins by disrupting the hydrophobic and hydrophilic interactions.
Denaturation and Renaturation of Proteins
- Proteins can be denatured and renatured, as shown in the process diagram of RNase A.
- Denaturation and renaturation involve the disruption and reformation of hydrogen bonds, ionic interactions, and disulfide bonds.
Protein Purification and Analysis
- Protein purification involves strategies to separate and purify proteins from a mixture.
- Factors to control in protein purification include protein concentration, pH, and ionic strength.
- Protein assays are used to quantify protein concentrations.
- Different protein purification techniques include salt precipitation, ion exchange chromatography, size exclusion chromatography, affinity chromatography, and electrophoresis.
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Test your knowledge on protein biochemistry and proteomics, including concepts and techniques in this field of study.