TBL Proteins

Which of the following statements about protein structure is correct?

• Proteins consisting of one polypeptide chain can have quaternary structure

• The formation of a disulfide bond in a protein requires that the two participating cysteine residues be adjacent to each other in the primary sequence of the protein

• The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain

• The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure

• The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunit

β-barrel are functional membrane proteins that serve essential functions in cargo transport and signaling and are also vital for membrane biogenesis. Which hierarchy of protein structure do β-barrels belong to?

• Primary

• Secondary

• Tertiary

• Quaternary

Which quaternary protein uses the multiple subunit nature to permit a cooperative approach to binding and releasing oxygen?

• keratin

• Haemoglobin

• Myoglobin

• Insulin

• G-protein

Enzymes are usually functional tertiary proteins, which is true about enzyme denaturation?

• It leads to loss of biological activity of enzymes

• It restores the original structure of the enzyme

• It is an irreversible change to the enzyme

• Its effect can be reversed by chaperones

• It leads to protein degradation

Which class of proteins are responsible for the breakdown and degradation of misfolded proteins?

• Proteasomes

• Chaperons

• Lysosomes

• Haemoglobin

• Phagosome

An 80-year-old man presented with impairment of higher intellectual function and alterations in mood and behavior. His family reported progressive disorientation and memory loss over the last 6 months. There is no family history of dementia. The patient was tentatively diagnosed with Alzheimer's disease. Which one of the following best describes the disease?

• It is associated with β-amyloid an abnormal protein with an altered amino acid sequence

•  It results from accumulation of denatured proteins that have random conformations

• It is associated with the accumulation of amyloid precursor protein

• It is associated with the deposition of neurotoxic amyloid peptide aggregates

A student is studying a newly isolated protein and observes that it contains hydrophobic regions approximately 20 amino acids in length, which are embedded within a lipid bilayer. Additionally, the protein has a signal peptide at the N-terminal end. What type of protein is the student studying?

• Fibrous protein

• Globular protein

• Membrane protein

• Structural protein

Why are certain amino acids in a protein typically found buried in its core?

• To maintain the protein’s tertiary structure by forming disulfide bonds

• To protect hydrophilic amino acids from interacting with water

• To stabilize the protein by shielding hydrophobic amino acids from the aqueous environment

• To allow polar amino acids to interact with the surrounding environment

Which level of protein organization is stabilized by peptide bonds only?

• Primary

• Secondary

• Tertiary

• Quaternary

What is a common consequence of protein misfolding?

• Increased enzyme activity

• Lower mutation rates

• Stabilization of tertiary protein structures

• Protein aggregation disorders