#protein degradation

DNA & RNA isolation

Which agent is used to degrade proteins during DNA extraction?

Proteinase K is a broad-spectrum serine protease widely used during DNA extraction to digest proteins, including nucleases, histones, and cellular structural proteins. It exhibits high activity in presence of SDS and EDTA and at elevated temperatures around 50-65°C, conditions that simultaneously lyse cells and denature substrates. By hydrolyzing peptide bonds, it deproteinizes DNA, inactivates DNases and RNases, and improves yield and purity. RNase specifically degrades RNA, DNase degrades DNA, and Triton X-100 is a non-ionic detergent for membrane permeabilization, not for proteolysis.

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.

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Cell Signaling ELR Pathways - I

SOCS box functions to

recruit E3 ubiquitin ligase, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Protein

In a misfolded protein, what happens if refolding attempts fail?

The protein is degraded by the proteasome correctly describes the effect or change asked about in this question. In Protein Folding, understanding cause-and-effect relationships is essential for predicting biological outcomes. The protein is degraded by the proteasome occurs because of specific molecular interactions, thermodynamic principles, or regulatory mechanisms that govern this biological process. The other options (The protein refolds by spontaneous diffusion, The protein aggregates and remains inside the cell, and The protein is stored for later refolding) describe either opposite effects, effects that occur under different conditions, or changes associated with unrelated processes.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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Protein

Which amino acid sequence is most resistant to degradation?

A sequence rich in Proline, Glutamate, Serine, and Threonine is the scientifically accurate answer to this question. Within the study of Protein Degradation, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of A sequence rich in Proline, Glutamate, Serine, and Threonine directly address what is being asked. Among the other options, A sequence rich in Arginine and Lysine, A sequence rich in Methionine and Cysteine, and A sequence rich in Phenylalanine and Tyrosine 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

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Protein

Which of the following describes the role of proteases in protein degradation?

They break peptide bonds to produce smaller peptides or amino acids is the accurate answer because it correctly identifies the biological function or role described in this question. In Protein Degradation, understanding the specific functions of molecules, enzymes, or structures is fundamental. They break peptide bonds to produce smaller peptides or amino acids fulfills this particular biological role through its specific structural properties, biochemical activity, or physiological mechanism. The other options (They synthesize proteins from amino acids, They add phosphate groups to proteins, and They bind amino acids together) serve different biological functions or are associated with other processes, pathways, or structural roles within the cell or organism.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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Protein

The major difference between 20S and 26S proteasomes is:

26S proteasome requires ATP, while 20S does not accurately describes the key difference, similarity, or comparative feature asked about in this question. In Protein Degradation, the ability to compare and contrast related concepts is essential for deeper understanding. The distinguishing feature described by 26S proteasome requires ATP, while 20S does not reflects fundamental differences in structure, function, mechanism, or origin between the compared entities. The other options (20S proteasome requires ATP, while 26S does not, 26S proteasome degrades DNA, while 20S degrades proteins, and 20S proteasome is located in the nucleus, while 26S is in the cytoplasm) either state incorrect comparisons, confuse the properties of the entities being compared, or describe features that are actually shared rather than different.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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Protein

Which of the following is NOT involved in protein degradation?

Ribosomes is the correct choice because it does not accurately describe or belong to the category addressed in this question. In the context of Protein Degradation, the other options (Lysosomes, Proteasomes, and Ubiquitin) are all valid and well-established concepts. Ribosomes is either unrelated to the topic, describes a different biological process, or represents a common misconception. Questions framed as 'which is NOT' require students to identify the exception among otherwise correct statements, demanding comprehensive knowledge of the topic rather than recognition of a single fact.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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Protein

The enzyme responsible for removing ubiquitin chains before protein degradation is:

Ubiquitin hydrolase is the accurate response regarding enzymatic activity or regulation described in this question. Enzymes are biological catalysts that accelerate reactions by lowering activation energy through specific substrate binding and transition state stabilization. In the context of Protein Degradation, Ubiquitin hydrolase plays a specific catalytic or regulatory role determined by its active site configuration and mechanism of action. The other options (Ubiquitin ligase, Protease, and Kinase) are either different enzymes with distinct substrate specificities, act through different mechanisms, or are involved in separate metabolic pathways.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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Protein

The degradation of misfolded proteins is essential to prevent:

Aggregation and amyloid formation is the scientifically accurate answer to this question. Within the study of Protein Degradation, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Aggregation and amyloid formation directly address what is being asked. Among the other options, Protein synthesis, DNA replication errors, and Membrane fusion 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

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Protein

Proteins tagged with monoubiquitination are typically targeted for:

Membrane trafficking is the scientifically accurate answer to this question. Within the study of Protein Degradation, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Membrane trafficking directly address what is being asked. Among the other options, Degradation, Signal transduction, and DNA repair 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

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Protein

The 20S proteasome primarily:

Degrades unfolded proteins is the scientifically accurate answer to this question. Within the study of Protein Degradation, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Degrades unfolded proteins directly address what is being asked. Among the other options, Synthesizes new proteins, Produces ATP, and Assembles ribosomes 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

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Protein

The minimum number of ubiquitin molecules required for a protein to be targeted for degradation by the proteasome is:

4 is obtained by applying the relevant formula or quantitative relationship to the given parameters. In Protein Degradation, numerical problem-solving requires understanding the mathematical relationships between biological variables. The calculation involves substituting the provided values into the appropriate equation and solving systematically. The other options (1, 2, and 8) result from common calculation errors such as using incorrect formulas, misidentifying variables, inverting ratios, or making arithmetic mistakes.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 4

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