Protein Processing

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Questions and Answers

When does protein folding occur?

Only during translation

Before and during post-translational modifications

During and after synthesis (correct)

Before translation

Where does post-translational modification mainly occur?

Endoplasmic Reticulum (ER) and Golgi (correct)

Cytoplasm and Nucleus

Cell membrane and Cytoskeleton

Mitochondria and Chloroplasts

What is the native state of a folded protein?

Its functional three-dimensional (3D) structure (correct)

Its state after post-translational modifications

Its linear chain of amino acids state

Its unfolded polypeptide or random coil state

What is the process by which a protein chain acquires its functional three-dimensional (3D) structure?

Protein folding Signup and view all the answers

Where does most of the protein targeting occur?

Golgi Signup and view all the answers

What occurs mostly at the Endoplasmic Reticulum (ER)?

Folding and post-translational modifications Signup and view all the answers

What determines the resulting 3D structure of a folded protein?

Amino acid sequence Signup and view all the answers

Which cellular compartment is mainly responsible for protein folding?

Endoplasmic Reticulum (ER) Signup and view all the answers

What is the main reason for protein folding?

Exposure of hydrophobic amino acids to water Signup and view all the answers

What is the role of chaperones in protein folding?

Aid the folding of other proteins Signup and view all the answers

Which type of glycosylation attaches the carbohydrate to Serine or Threonine residues?

O-linked glycosylation Signup and view all the answers

What is the process of adding a sulfonic acid to a tyrosine of many secreted and membrane proteins?

Sulfation Signup and view all the answers

Which process involves the addition of different fatty acids to various amino acids?

Lipidation Signup and view all the answers

What is the role of carboxylation in protein modification?

Enhances protein stability Signup and view all the answers

Which protein modification involves adding a CH3 group to a protein, influencing gene regulation?

Methylation Signup and view all the answers

Which process occurs after protein synthesis to make a protein fully stable and active?

Protein folding Signup and view all the answers

Where does glycosylation, involving the addition of oligosaccharides to some amino acids, mainly occur?

ER and Golgi Signup and view all the answers

Which type of diseases result from the accumulation of amyloid fibrils?

Neurodegenerative diseases Signup and view all the answers

What is essential for protein folding and involves many secreted and membrane proteins?

Formation of disulfide bonds Signup and view all the answers

What are some examples of prion diseases?

Creutzfeldt-Jakob disease and bovine spongiform encephalopathy (mad cow disease) Signup and view all the answers

What is the process of adding a phosphate group, serving as a major mechanism for regulation of protein function?

Phosphorylation Signup and view all the answers

What type of bond is formed between two cysteine amino acids at the ER, essential for protein folding?

Disulfide bonds Signup and view all the answers

What is the process of adding a carboxyl group to specific glutamate amino acids of some proteins?

Carboxylation Signup and view all the answers

'O-linked glycosylation' mainly occurs in which cellular compartment?

Golgi Signup and view all the answers

What is the process of hydroxyl group (OH-) added, like hydroxylation of proline and lysine amino acids of collagen chains?

Hydroxylation Signup and view all the answers

What is the process by which acetyl coenzyme A (Ac-CoA) is linked to a specific site on the protein, important for protein stability and localization?

Acetylation Signup and view all the answers

Where are molecular labels (amino acid sequences) usually located to 'address' proteins for delivery to specific locations within a eukaryotic cell?

At the N or C-terminals of the protein Signup and view all the answers

Which cellular compartment contains high concentrations of glutathione, making it unsuitable for producing proteins containing disulfide bonds?

Cytosol Signup and view all the answers

What is the main function of reducing agents in a cell?

To donate electrons in redox reactions Signup and view all the answers

Why are different proteins made on either free or bound ribosomes within a eukaryotic cell?

To allow alternative paths for proteins that cannot be synthesized and translocated through the cytosol Signup and view all the answers

What is the role of molecular labels in protein targeting within a eukaryotic cell?

They 'address' proteins for delivery to specific locations Signup and view all the answers

What is the main reason why proteins containing disulfide bonds cannot be produced within the cytosol of a eukaryotic cell?

High concentrations of glutathione in the cytosol disrupt disulfide bond formation Signup and view all the answers

What is the main reason why proteins containing disulfide bonds cannot be produced within the cytosol of a eukaryotic cell?

High concentration of reducing agents Signup and view all the answers

What is the main function of reducing agents in a eukaryotic cell?

To break di-sulfide bonds in proteins Signup and view all the answers

Where are ribosomes located that synthesize proteins containing disulfide bonds?

Bound ribosomes Signup and view all the answers

Which type of protein secretion involves proteins being stored within their transport vesicle until the appropriate time for their release from the cell?

Regulated secretion Signup and view all the answers

Where does protein synthesis for membrane and secretion proteins initiate?

At the rough ER on free ribosomes Signup and view all the answers

What is the role of importin in protein targeting?

It helps entry to the nucleus by binding to a nuclear localization signal. Signup and view all the answers

What is required for protein targeting to peroxisomes?

A C-terminal sequence Signup and view all the answers

Which organelle's proteins require a special N-terminal sequence for targeting?

Mitochondria Signup and view all the answers

What is responsible for targeting nuclear proteins to the nucleus?

A nuclear localization signal, which binds to importin. Signup and view all the answers

What is essential for targeting cytosolic proteins?

No N-terminal signal peptide Signup and view all the answers

How do proteins travel through the cisternae in sequence at the Golgi complex?

By budding from one cisterna and fusion with the next Signup and view all the answers

Where do proteins travel through in sequence by transport vesicles that bud from one cisterna and fuse with the next?

Cis, medial, and trans regions of the Golgi complex Signup and view all the answers

Where are proteins subjected to post-translation modifications before being delivered via vesicles to the cell membrane or secreted outside?

Golgi complex Signup and view all the answers

In which region of the Golgi complex does protein modification mainly occur?

Medial region Signup and view all the answers

Which organelle is responsible for tagging lysosomal enzymes with mannose 6 phosphate?

Golgi Signup and view all the answers

What is the consequence of a defect in the tagging process of lysosomal enzymes?

Macromolecule accumulation in lysosomes Signup and view all the answers

What inheritance pattern is associated with lysosomal storage diseases?

Autosomal recessive Signup and view all the answers

Which disease is characterized by symptoms such as chronic fatigue, hepatosplenomegaly, and loss of motor skills?

Gaucher disease Signup and view all the answers

What is the result of faults in transporting specific enzymes to peroxisomes from the ER?

Small or absent peroxisomes Signup and view all the answers

What is the main consequence of lysosomal storage diseases affecting different parts of the body?

Psychomotor retardation and skeletal deformities Signup and view all the answers

What happens to the lysosomal enzymes upon reaching the lysosomes?

The tag is removed and they become functional. Signup and view all the answers

What are some symptoms commonly associated with Gaucher disease?

Abnormally enlarged liver and/or spleen, involuntary muscle spasms, mental deterioration. Signup and view all the answers

What is the tag used to mark lysosomal enzymes in the Golgi?

Mannose 6 phosphate Signup and view all the answers

Which organelle is affected in Zellweger syndrome?

Peroxisomes Signup and view all the answers

What is the inheritance pattern associated with lysosomal storage diseases?

Autosomal recessive and some X-linked recessive Signup and view all the answers

What is the most common type of lysosomal storage disease?

Gaucher disease Signup and view all the answers

What is the result of defects in the tagging process of lysosomal enzymes?

Lysosomal enzymes do not reach the lysosomes, causing macromolecule accumulation Signup and view all the answers

What is the consequence of a defect in the tagging process of lysosomal enzymes?

Accumulation of macromolecules Signup and view all the answers

What is the specific tag used to bind lysosomal enzymes to receptors inside forming vesicles in the Golgi's trans area?

Manose 6 phosphate Signup and view all the answers

What are some symptoms associated with Gaucher disease?

Chronic fatigue and hepatosplenomegaly Signup and view all the answers

Where do lysosomal enzymes dissociate from receptors and become functional after reaching their destination?

Lysosomes Signup and view all the answers

Which enzyme uses vitamin C as a cofactor in collagen biosynthesis?

Prolyl hydroxylase Signup and view all the answers

Which amino acid is found in high percentage in collagen?

Glycine Signup and view all the answers

Which type of tissues contain collagen as the main component of the extracellular matrix?

Cartilage, ligaments, tendons Signup and view all the answers

What are collagen fibers?

Bundles of collagen with great tensile strength Signup and view all the answers

What is responsible for skin strength and elasticity along with collagen?

Keratin Signup and view all the answers

What is the first step in collagen biosynthesis?

Pre-pro-collagen formation Signup and view all the answers

What process involves glucose or galactose added onto hydroxylysines' OH- in collagen biosynthesis?

Glycosylation Signup and view all the answers

What is the role of vitamin C in collagen biosynthesis?

It is a cofactor for prolyl hydroxylase and lysyl hydroxylase, which hydroxylate lysines and prolines. Signup and view all the answers

What is the primary function of collagen fibers?

To provide great tensile strength. Signup and view all the answers

Which amino acids have a high percentage in collagen?

Glycine and Proline Signup and view all the answers

What is the main function of cross-linking of alpha peptides in collagen biosynthesis?

To produce hydroxyproline and hydroxylysine. Signup and view all the answers

Which enzymes use vitamin C as a cofactor in collagen biosynthesis?

Prolyl hydroxylase and lysyl hydroxylase Signup and view all the answers

Where are collagen fibers primarily found?

Cartilage, ligaments, tendons, bone, skin, eye cornea and lens tissues Signup and view all the answers

What are the two non-standard amino acids found in collagen?

Hydroxyproline and Hydroxylysine Signup and view all the answers

Which amino acids have a high percentage in Collagen?

Glycine and Proline Signup and view all the answers

What are the two non-standard amino acids found in Collagen?

Hydroxyproline and Hydroxylysine Signup and view all the answers

Where are Collagen fibers primarily found?

Connective tissue Signup and view all the answers

What occurs after modifications of the pre-pro-peptide in collagen biosynthesis?

Cross-linking of the alpha peptides by hydroxylation of lysines and prolines Signup and view all the answers

Study Notes

Proteins carry out various functions in cells and are synthesized in one compartment of Eukaryotes.
Proteins undergo several processes after synthesis to become functional: folding, post-translational modifications, and protein targeting.
Protein folding is the process of a protein chain acquiring its 3D structure. It occurs during and after synthesis, with the help of chaperones. Hydrophobic amino acids play a role in the protein folding process.
Non-folded proteins may aggregate and form amyloid fibrils, leading to various diseases such as prion diseases and neurodegenerative disorders.
Post-translational modifications (PTMs) are processes that occur after protein synthesis, making the protein fully stable and active. Some PTMs are part of the folding process, targeting process, or gene regulation. PTMs mainly occur at the ER and Golgi.
Major types of PTMs include: formation of disulfide bonds, phosphorylation, glycosylation, sulfation, lipidation, hydroxylation, acetylation, cleaving, carboxylation, and methylation.
Protein targeting involves labeling proteins with specific tags to direct them to their final destination in the cell or to the extracellular space. This process occurs at the ER and Golgi and uses different types of ribosomes for labeling.
Proteins contain various functional domains, and some parts may remain unfolded. Some functional proteins may also remain partially unfolded.
Hydrophobic amino acids play a crucial role in the protein folding process. They tend to hide from water, leading to the formation of a protein fold.
Proteins are essential for cell–cell communication and the secretion of various molecules, including hormones and digestive enzymes, which undergo PTMs to become active.
Some PTMs, such as phosphorylation, serve as critical signaling molecules that regulate various cellular processes.
Misfolded proteins can form aggregates, which are associated with several neurodegenerative diseases and allergies.
The unfolded protein response (UPR) is a mechanism that cells use to respond to the accumulation of unfolded proteins in the ER.
The endoplasmic reticulum (ER) is a key organelle in protein synthesis, folding, and modification. It also serves as the site for the processing and packaging of proteins for their targeting to specific cellular locations.
The Golgi apparatus is a membrane-bound organelle responsible for post-translational modifications and the modification, processing, and packaging of proteins and lipids for their targeting to specific cellular locations.
Chaperones are proteins that aid in the folding of other proteins and prevent their aggregation. They are essential for the proper functioning of the cell.
The process of protein folding is important for protein stability and the maintenance of cellular homeostasis.
Proteins can undergo various modifications, such as cleaving, carboxylation, and methylation, to become functional.
The ER and Golgi are the main sites for protein synthesis, folding, modification, and targeting in eukaryotic cells.
PTMs are critical for various cellular processes, including cellular signaling, cell growth, differentiation, and the regulation of cellular metabolism.
PTMs are involved in the regulation of various cellular processes, such as cell adhesion and cell–cell communication.
The proper functioning of the ER and Golgi is essential for the maintenance of cellular homeostasis and the health of the cell.
PTMs, such as phosphorylation, can act as key signaling molecules, regulating various cellular processes, including cell growth, differentiation, and metabolism.
Proteins play a crucial role in the maintenance of cellular homeostasis and the proper functioning of the cell.
The proper functioning of the ER and Golgi is vital for the health and well-being of the cell.
PTMs are essential for the proper functioning of various proteins, including enzymes, hormones, and structural proteins.
The process of protein folding is critical for the stability and function of proteins in the cell.
The ER and Golgi are key organelles responsible for the synthesis, folding, modification, and targeting of proteins in eukaryotic cells.
The unfolded protein response is a cellular mechanism that responds to the accumulation of unfolded proteins in the ER.
Chaperones are essential proteins that aid in the folding of other proteins and prevent their aggregation, ensuring proper protein function in the cell.
PTMs are involved in various cellular processes, including cell growth, differentiation, and cell signaling.
The proper functioning of the ER and Golgi is crucial for the proper functioning of the cell and the maintenance of cellular homeostasis.

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Test your knowledge of the steps involved in protein synthesis and distribution within eukaryotic cells, including folding, post-translational modifications, and distribution to different cellular compartments.