17 public questions tagged with this topic.
Hydrogen bonds stabilize the alpha-helix and beta-sheet structures in the secondary structure of proteins.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Enzyme Action and Factors Affecting Enzyme Activity
The secondary structure of proteins includes both alpha-helices and beta-pleated sheets, which are stabilized by hydrogen bonds.
Ref: NCERT Class 11 Biology Chapter 9: Biomolecules Proteins and Polysaccharides - Structure and Functions
Biological macromolecules possess intrinsic chirality from L-amino acids and ordered folds, causing different interaction with left and right circularly polarized light components that constitute plane polarized light. CD spectrometer alternately shines left-handed and right-handed circularly polarized light and measures absorbance for each. Difference delta A equals A left minus A right, converted to ellipticity. Emission difference describes fluorescence anisotropy, refraction index concerns light bending, spin transitions relate to electron paramagnetic resonance. Absorption difference between left and right circularly polarized light therefore underlies CD phenomenon.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Amide chromophore exhibits two major electronic transitions relevant to protein CD. Pi to pi-star around 190 nanometers is intense, electrically allowed, occurring below 210 nanometers and sensitive to exciton coupling in helices. n to pi-star near 220 nanometers is weaker. Sigma to sigma-star requires high vacuum ultraviolet energy. Pi to n is not meaningful for amides. Both pi to pi-star and n to pi-star are optically active in chiral polypeptide arrangement, but pi to pi-star below 210 nanometers provides dominant band for secondary structure quantification.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Circular dichroism distinguishes secondary structures through differential absorption of circularly polarized light by chiral peptide bonds. Alpha helix shows exciton coupling of pi-pi* transitions producing intense positive band near 193 nm and two negative bands at 208 nm for parallel polarized component and 222 nm for n-pi* transition. Beta sheet exhibits single minimum near 218 nm. Observing double minima at 208 and 222 nm strongly indicates helical content, though NMR chemical shifts, J-couplings, and NOEs provide residue-specific confirmation. Combined CD and NMR offers robust structural validation for recombinant proteins and peptides.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.
Antiparallel β-sheet accurately describes the structural composition or molecular organization asked about in this question. In Peptide and Ramachandran plo, knowledge of molecular structure is directly linked to understanding biological function. The specific arrangement of chemical components in Antiparallel β-sheet determines its physical properties, biological activity, and interactions with other molecules. The other options (Right-handed α-helix, Left-handed α-helix, and Parallel β-sheet) describe different structural arrangements, incorrect stoichiometry, or compositions of different biological molecules.
Ref: Campbell Biology, Urry et al., 12th Ed.
They always have evenly spaced hydrogen bonds is the scientifically accurate answer to this question. Within the study of Protein Structure, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of They always have evenly spaced hydrogen bonds directly address what is being asked. Among the other options, Parallel β-sheets are more stable than antiparallel, They contain side chains pointing alternately above and below the sheet, and They are never involved in domain structures do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
Alternating β-strands and α-helices correctly identifies the characteristic feature or property described in this question. In Protein Structure, specific characteristics define and distinguish biological molecules, organisms, or processes from one another. The feature described by Alternating β-strands and α-helices is a defining property that arises from its unique molecular structure, evolutionary history, or physiological role. The other options (Only α-helices, Only β-strands, and A random coil structure) describe characteristics of different entities, represent incorrect properties, or apply to the subject under different conditions.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
It is a loop structure that reverses direction accurately defines or describes the concept asked in this question. Within Protein Structure, precise definitions and terminology are essential for clear scientific communication. The other options (It contains a helical conformation, It forms a straight structure without hydrogen bonds, and It is always composed of proline) either describe related but distinct concepts, use incorrect terminology, or confuse similar-sounding terms that have different scientific meanings. A thorough understanding of exact definitions helps distinguish between closely related biological concepts and is crucial for competitive examinations.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
β-Sheet accurately describes the structural composition or molecular organization asked about in this question. In Protein Structure, knowledge of molecular structure is directly linked to understanding biological function. The specific arrangement of chemical components in β-Sheet determines its physical properties, biological activity, and interactions with other molecules. The other options (α-Helix, Loop, and Random coil) describe different structural arrangements, incorrect stoichiometry, or compositions of different biological molecules.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
Alanine is the scientifically accurate answer to this question. Within the study of Protein Structure, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Alanine directly address what is being asked. Among the other options, Glycine, Proline, and Aspartic acid do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
1.5 Ã… is the scientifically accurate answer to this question. Within the study of Protein Structure, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of 1.5 Ã… directly address what is being asked. Among the other options, 1.18 Ã…, 1.41 Ã…, and 3.5 Ã… do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4
