60 Questions
Which method is commonly used to sequence amino acids in proteins?
Edman degradation
What can mass spectrometry measure in proteins?
Molecular mass
Which level of protein structure refers to the 3D folding of a polypeptide?
Tertiary structure
What is the primary function of protein sequencing techniques?
To determine the amino acid sequence of proteins
What is the term for homologous proteins in the same species?
Paralogs
What does bioinformatics help identify in new proteins?
Functional segments
Which amino acid residue is the most common in protein molecules?
L-isomers
Which type of amino acid R group is the most hydrophilic?
Positively charged
Which amino acid residue can form disulfide bonds?
Cysteine
Which amino acid residue has an ionizable side chain with pKa near neutrality?
Histidine
Which type of amino acid R group absorbs UV light at 270-280 nm?
Aromatic
What is the isoelectric point (pI) of an amino acid?
The pH at which the net electric charge is zero
Which of the following is true about proteins?
All of the above
What is the primary structure of a protein?
The linear sequence of amino acids in a protein.
How are amino acids joined together in proteins?
Through peptide bonds.
What is the role of enzymes in cells?
Enzymes catalyze chemical reactions in cells.
How can individual proteins be separated from other proteins in a cell?
Based on their amino acid sequences.
What is the function of antibodies in the body?
Antibodies defend against foreign invaders.
Which step in protein purification involves selectively precipitating proteins based on their lower solubility in salt?
Fractionation
Which chromatography technique separates proteins based on their size?
Size-Exclusion Chromatography
Which chromatography technique uses high-pressure pumps to improve resolution?
High-Performance Liquid Chromatography
Which chromatography technique separates proteins based on their binding affinity?
Affinity Chromatography
What does electrophoresis visualize and characterize in purified proteins?
Approximate molecular weight
What is the purpose of sodium dodecyl sulfate (SDS) in electrophoresis?
To partially unfold proteins
Which of the following is true about glycine's titration curve?
Glycine has two buffer regions
What is the isoelectric point (pI) of an amino acid?
The pH at which the net charge is zero
Which amino acid has an R group with a pKa of 6.0?
Histidine
What is the difference between a peptide and a protein?
Peptides have fewer amino acid residues than proteins
What are conjugated proteins?
Proteins that contain permanently associated chemical components
What is the most common form of amino acid residues in protein molecules?
L stereoisomers
Why is a pure protein preparation essential for studying a protein's properties?
To determine the protein's properties and activities accurately
What is the primary function of protein sequencing techniques?
To determine the order of amino acids in a protein
What is the term for modified amino acids that contribute to a protein's function?
Uncommon amino acids
What is the main factor that determines the solubility of amino acids in water?
The structure and properties of their R groups
What is the isoelectric point (pI) of an amino acid?
The pH at which the net electric charge is zero
What is the main function of histidine residues in proteins?
To serve as proton donors/acceptors in enzyme-catalyzed reactions
What is the primary structure of a protein?
The linear sequence of amino acids.
What is the isoelectric point (pI) of an amino acid?
The pH at which the amino acid has no net charge.
Which of the following is true about proteins?
Proteins are composed of a common set of 20 amino acids.
How can individual proteins be separated from other proteins in a cell?
By differences in their chemical and functional properties.
What does electrophoresis visualize and characterize in purified proteins?
The size of proteins.
Which chromatography technique uses high-pressure pumps to improve resolution?
High-performance liquid chromatography (HPLC).
Which method is commonly used to separate proteins based on their size?
Size-Exclusion Chromatography
Which level of protein structure is responsible for the 3D folding of a polypeptide?
Tertiary structure
What is the purpose of dialysis in protein purification?
To separate proteins from small solutes
What is the role of sodium dodecyl sulfate (SDS) in electrophoresis?
To give all proteins a similar charge-to-mass ratio
What is the primary function of mass spectrometry in studying proteins?
To measure molecular mass, sequence short amino acid sequences, and document the entire cellular proteome
What is the function of affinity chromatography in protein purification?
To separate proteins based on their binding affinity
What is the purpose of labeling amino-terminal α-amino group and ε-amino group of lysine residues in protein structure studies?
To track specific amino acid residues
What is the role of bioinformatics in studying proteins?
To identify functional segments in new proteins
What does electrophoresis visualize and characterize in purified proteins?
The degree of purity of proteins
What is the term for homologous proteins in different species?
Orthologs
What can be monitored during enzyme purification by assaying specific activity?
The number of enzyme units per mg of total protein
What is the term for certain protein segments that are specific to a taxonomic group?
Signature sequences
Which of the following is true about the isoelectric point (pI) of an amino acid?
The pI is the pH at which the net charge of the amino acid is zero
Which type of amino acid R group is the most hydrophilic?
Amino acids with polar R groups
What is the primary function of antibodies in the body?
To recognize and neutralize foreign substances
What is the role of enzymes in cells?
To catalyze biochemical reactions
What does electrophoresis visualize and characterize in purified proteins?
Protein size and charge
What can mass spectrometry measure in proteins?
Protein mass and sequence
Study Notes
Protein Structure and Sequencing
- Amino acid sequencing is commonly done using mass spectrometry.
- The primary function of protein sequencing techniques is to determine the order of amino acids in a protein.
- The primary structure of a protein refers to the sequence of amino acids.
Protein Properties
- The isoelectric point (pI) of an amino acid is the pH at which the amino acid has no net charge.
- The pI of an amino acid is important for understanding protein behavior and function.
- Glycine has a unique titration curve compared to other amino acids.
- Histidine residues play a crucial role in protein function, particularly in enzyme active sites.
Amino Acid Properties
- The most common amino acid residue in protein molecules is alanine.
- The most hydrophilic type of amino acid R group is the hydroxyl (-OH) group.
- Cysteine residues can form disulfide bonds, which are important for protein structure and function.
- Tyrosine residues have an ionizable side chain with a pKa near neutrality.
- The amino acid tryptophan has an R group that absorbs UV light at 270-280 nm.
Protein Purification and Separation
- Individual proteins can be separated from other proteins in a cell using techniques such as chromatography and electrophoresis.
- Electrophoresis visualizes and characterizes proteins based on their size and charge.
- The purpose of sodium dodecyl sulfate (SDS) in electrophoresis is to denature proteins and improve separation.
- Chromatography techniques include size exclusion, ion exchange, and affinity chromatography, which separate proteins based on size, charge, and binding affinity, respectively.
- High-pressure liquid chromatography (HPLC) is a type of chromatography that uses high-pressure pumps to improve resolution.
Protein Function and Bioinformatics
- Enzymes play a crucial role in cells by catalyzing biochemical reactions.
- Antibodies are proteins that help the body fight infection and disease by recognizing and binding to specific pathogens.
- Bioinformatics helps identify functional domains and motifs in new proteins.
- The primary function of mass spectrometry in studying proteins is to measure protein mass and identify post-translational modifications.
- Affinity chromatography is a technique used to purify proteins based on their binding affinity for specific molecules.
Conjugated Proteins and Post-Translational Modifications
- Conjugated proteins are proteins that have been modified by the addition of a non-protein molecule, such as a carbohydrate or lipid.
- Modified amino acids that contribute to a protein's function are referred to as post-translational modifications.
- The most common form of amino acid residues in protein molecules is the L-isomer.
- The main factor that determines the solubility of amino acids in water is the polarity of the R group.
Protein Expression and Evolution
- Homologous proteins are proteins that share a common evolutionary origin.
- Orthologous proteins are homologous proteins that are found in different species.
- Paralogous proteins are homologous proteins that are found in the same species.
- The term for certain protein segments that are specific to a taxonomic group is a protein domain.
Test your knowledge on the properties of glycine and its role as a buffer in the body. Learn about the point of inflection in its titration curve, the effect of the chemical environment on its pKa, and the acidity of its α-carboxyl group.
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