#proteasome

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

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 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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Protein

The proteolytic activity of the 26S proteasome is mainly found in:

β-subunits is the correct answer as it accurately identifies the biological location, composition, or distribution described in this question. In Protein Degradation, the spatial organization and localization of molecules are critical to their function. β-subunits is specifically associated with the structure or compartment mentioned because of its unique biochemical properties and physiological role. The other options (α-subunits, 19S regulatory particle, and 40S ribosome) are primarily associated with different cellular compartments, tissues, or structural contexts.

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

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Protein

The 26S proteasome consists of:

20S core and 19S regulatory subunits accurately describes the structural composition or molecular organization asked about in this question. In Protein Degradation, knowledge of molecular structure is directly linked to understanding biological function. The specific arrangement of chemical components in 20S core and 19S regulatory subunits determines its physical properties, biological activity, and interactions with other molecules. The other options (19S core and 20S regulatory subunits, 30S core and 10S regulatory subunits, and 40S core and 60S regulatory subunits) describe different struc

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

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