21 Questions
What percentage of the body weight are proteins?
50%
What is the relationship between the 3D structure of a protein and its function?
The 3D structure is related to its function
Where is the genetic information for the amino acid sequence of a protein encoded?
DNA
Which type of proteins are in contact with water and considered hydrophilic?
Globular proteins
How many common amino acids are coded in DNA?
20
What type of isomers do amino acids have?
L and D
In proteins, what type of stereoisomers are all amino acid residues?
L
What do peptide bonds form when two amino acid molecules are joined?
Flat, planar structure
What do nonpolar and polar amino acids lead to in a peptide chain?
Insoluble and water-soluble protein, respectively
What does the primary structure of a protein describe?
Amino acid sequence in a polypeptide chain
What is the main feature of α-helices in proteins?
Right-handed, helical conformations
Which type of bond stabilizes proteins through interactions between side chain functional groups?
Covalent disulfide bonds
What denaturing agents can lead to protein precipitation and aggregation?
pH and heat
What is the smallest unit of a quaternary structure protein called?
Monomer or subunit
What is the process called when an unfolded (denatured) protein is refolded to restore its native structure and function?
Renaturation
Which type of interaction is NOT involved in stabilizing proteins?
Metallic bonds
What is the three-dimensional structure of a multisubunit protein known as?
Quaternary structure
What leads to the partial or complete unfolding of the specific native conformation of a protein?
Denaturation
What do denaturing agents such as urea lead to?
Protein aggregates
What are two or more separate polypeptide chains, or subunits, in a multisubunit protein called?
Oligomeric proteins
What is the biologically active conformation of a protein known as?
Native conformation
Study Notes
- Amino acids have a general structure with an α-carbon bonded to a carboxyl group, an amino group, an R group (except for glycine), and a hydrogen atom. The α-carbon is a chiral center, leading to the existence of two stereoisomers: L and D.
- All amino acid residues in proteins are L stereoisomers, and cells can specifically synthesize L isomers through stereospecific reactions.
- Amino acids are amphoteric molecules, capable of donating and accepting protons and functioning as acids or bases.
- Peptide bonds form when two amino acid molecules are covalently joined, forming a flat, planar structure that is stable and can participate in hydrogen bonding.
- Amino acid composition in a peptide chain significantly affects its physical and chemical properties, with nonpolar and polar amino acids leading to insoluble and water-soluble protein, respectively.
- Proteins have a complex structure, consisting of primary, secondary, tertiary, and quaternary levels.
- Primary structure describes the amino acid sequence in a polypeptide chain, which is essential for the unique function of each protein.
- Secondary structure refers to the local spatial arrangement of the mainchain atoms, which can form various structures like α-helices and β-pleated sheets.
- α-helices are right-handed, helical conformations of a polypeptide chain, stabilized by hydrogen bonding between peptide linkages.
- β-pleated sheets are extended conformations of polypeptide chains, stabilized by hydrogen bonding between the carbonyl and amino groups of the polypeptide chain.
- β turns are important in globular proteins, connecting the ends of two adjacent segments of an antiparallel β sheet through a 180° turn involving glycine and proline.
- Tertiary structure describes the overall three-dimensional arrangement of all atoms in a protein, reflecting its biologically active conformation and overall shape.
Test your knowledge of the characteristics, structure, and classification of amino acids and proteins. This quiz covers topics such as peptide bonds, structural protein levels, and the relationship between 3D protein structure and function.
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