Biochemistry: Protein Structure and Function

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Questions and Answers

What is the primary function of protein phosphorylation in animal cells?

To regulate the biological activity of proteins (correct)

To modify protein degradation

To facilitate protein synthesis

To permanently deactivate proteins

Which of the following amino acids is least frequently phosphorylated in animal cells?

Threonine

Lysine

Serine

Tyrosine (correct)

What are the enzymes called that add phosphate groups to proteins?

Phosphatases

Demethylases

Methyltransferases

Kinases (correct)

Which compound serves as the activated methyl donor in protein methylation?

S-adenosylmethionine Signup and view all the answers

Which type of modification on lysine residues is associated with chromatin structure regulation?

Methylation Signup and view all the answers

How many lysine methyltransferases are expressed by humans, according to the content?

27 Signup and view all the answers

Which of the following is a key characteristic of protein methylation?

It can be reversed by demethylases Signup and view all the answers

What is the approximate ratio of phosphorylation for serine to threonine in animal cells?

900/200 Signup and view all the answers

What is the primary role of gamma-carboxyglutamate (gla) residues in proteins?

They allow the protein to chelate calcium ions. Signup and view all the answers

Which protein is involved in the initial step of ubiquitination?

E1 Signup and view all the answers

What is the process by which pre-mRNA is converted to mature mRNA?

Splicing Signup and view all the answers

What distinguishes SUMOylation from ubiquitination?

SUMOylation does not result in proteolysis. Signup and view all the answers

How does the three-dimensional structure of a protein relate to its function?

It determines its function. Signup and view all the answers

Where do N-Linked glycans typically attach to proteins?

To the nitrogen of asparagine. Signup and view all the answers

What function does the proteasome serve in the ubiquitin-proteasome pathway?

It degrades polyubiquitinated proteins. Signup and view all the answers

What does alternative splicing allow in gene expression?

Variations in protein product based on different cell types or stages. Signup and view all the answers

What is unique about O-Linked glycan assembly compared to N-Linked glycan assembly?

O-Linked glycans are assembled one sugar at a time. Signup and view all the answers

What is the primary role of proteins in organisms?

To bind a wide variety of molecules. Signup and view all the answers

Which monosaccharide is not mentioned as a component of N-Linked glycans?

Ribose Signup and view all the answers

Which part of mRNA is not kept during the maturation process?

Introns Signup and view all the answers

What signifies the evolvement of protein structure?

The sequence of amino acids. Signup and view all the answers

What is required for proteins to be correctly packaged into ER-to-Golgi transport vesicles?

They must be correctly folded. Signup and view all the answers

What is the main consequence of genetic variation due to splicing?

Diversity in protein types. Signup and view all the answers

Which molecule is primarily involved in the translation process?

mRNA Signup and view all the answers

What is the primary function of the ligand in affinity chromatography?

To bind a specific protein Signup and view all the answers

Which method can be used to elute molecules bound to immobilized antibodies in affinity chromatography?

Applying concentrated salt solutions Signup and view all the answers

How do polypeptides migrate in SDS-PAGE?

By forming complexes with negatively charged SDS Signup and view all the answers

What characteristic of polypeptides affects their speed of migration in SDS-PAGE?

The length of the polypeptide chain Signup and view all the answers

What is the purpose of staining the gel in SDS-PAGE after the separation process?

To visualize the protein bands Signup and view all the answers

What is the main objective of manufacturing a biosimilar?

To create a product with the same aa sequence as the original Signup and view all the answers

Which of the following is a key component used in the production of biosimilars?

Plasmid vectors Signup and view all the answers

What type of cell line is commonly used for producing biopharmaceuticals?

CHO cells Signup and view all the answers

Which aspect is essential for the characterization of a biosimilar?

The post-translational modifications Signup and view all the answers

What does a correct karyotype analysis provide in the context of biosimilars?

Insights into cell line stability Signup and view all the answers

What characteristic is not typically required for a biosimilar to be considered interchangeable with its reference product?

Same production method Signup and view all the answers

Which statement best describes the relationship between biosimilars and original biologics?

Biosimilars have similar but not identical characteristics to original biologics Signup and view all the answers

In the context of biosimilar manufacturing, what is the significance of 'purification'?

It removes unwanted compounds from the final product Signup and view all the answers

Study Notes

Protein Structure and Function

Proteins are versatile molecules that bind various entities, including ions, fats, sugars, nucleic acids, and other proteins.
Their efficiency and function are determined by their three-dimensional structure, which arises from the specific amino acid sequence.

Protein Synthesis

Protein synthesis, also known as translation, converts nucleic acid sequences into amino acid sequences.
This process involves two main steps: transcription of DNA to pre-mRNA and its subsequent translation into proteins.

mRNA Production and Splicing

Introns are non-coding segments in pre-mRNA that are removed through splicing, resulting in mature mRNA.
Alternative splicing allows for different exons to be included or excluded, leading to diverse protein variants from the same gene.

Protein Phosphorylation

Phosphorylation is a common modification in proteins within animal cells that regulates their activity and is typically transient.
Kinases add phosphate groups, while phosphatases remove them; serine, threonine, and tyrosine are common targets for phosphorylation.
The approximate phosphorylation ratio is 1800:200:1 for serine, threonine, and tyrosine, respectively.

Protein Methylation

Methylation occurs post-translationally on nitrogen and oxygen atoms of residues such as lysine and arginine.
S-adenosylmethionine serves as the methyl donor, crucial for histone regulation and chromatin structure.
Human cells express 27 lysine methyltransferases and 9 arginine methyltransferases.

Other Protein Modifications

Ubiquitination: Attaches ubiquitin to proteins, marking them for degradation by the proteasome.
SUMOylation: Similar to ubiquitination but does not signal for proteolysis; it can inhibit ubiquitination.
Glycosylation: Involves adding saccharides to proteins, which is accomplished in the ER and Golgi apparatus through N-Linked and O-Linked methods.

Recombinant Protein Manufacturing

Consistent amino acid sequences are critical in producing biosimilars, requiring careful selection of plasmid vectors and strains.
Affinity chromatography isolates proteins by exploiting specific ligand interactions, allowing for targeted purification.

Protein Analysis Techniques

SDS-PAGE technology separates proteins based on size, utilizing sodium dodecyl sulfate to impart a negative charge to the proteins.
The migration speed in the gel is inversely proportional to molecular weight, enabling the determination of polypeptide size and composition.
Western blotting follows SDS-PAGE as a method to detect specific proteins.

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Description

Explore the fascinating world of proteins with this quiz covering their structure, synthesis, and modifications. Understand key processes such as translation, splicing, and phosphorylation, and how these influence protein functionality. Ideal for anyone studying biochemistry or molecular biology!