Biochemistry : Toll-Like Receptors

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #1 : Toll Like Receptors

A bacterium is often recognized and attacked by the immune cells. What is true regarding this process?

Possible Answers:

Toll-like receptors (TLRs) on the bacteria signal and recruit immune cells and peptidoglycan is a molecule recognized by immune cells

None of these

Toll-like receptors (TLRs) on the bacteria signal and recruit immune cells

Peptidoglycan is a molecule recognized by immune cells

Correct answer:

Peptidoglycan is a molecule recognized by immune cells

Explanation:

Toll-like receptors are special molecules that recognize specific portions of pathogens called PAMPs (pathogen associated molecular patterns). The toll-like receptors on the immune cells recognize PAMPs on the pathogen. One of the most common PAMPs recognized by toll-like receptors is peptidoglycan on the cell walls of the bacteria.

Example Question #2 : Toll Like Receptors

Which of the following is true regarding toll-like receptors?

I. They are found on pathogens

II. They are involved in both acute and chronic inflammation

III. They are not found on complements

Possible Answers:

I and III

II and III

III only

I only

Correct answer:

II and III

Explanation:

Toll-like receptors found on immune cells recognize pathogens and recruit other immune cells to clear the pathogen. These toll-like receptors are found in both innate immune system (macrophages and neutrophils) and in adaptive immune system (lymphocytes). Recall that acute inflammation is mediated by neutrophils and macrophages whereas chronic inflammation is mediated by lymphocytes; therefore, toll-like receptors can activate both acute and chronic inflammation. Complements are part of the innate immune system and serve as markers (opsonins) for pathogen recognition. Complements bind to an infected cell or to an antibody-antigen complex and signal immune cells to eliminate the pathogen. They do not utilize toll-like receptors.

Example Question #3 : Toll Like Receptors

Which of the following processes will be ultimately modulated by activation of toll-like receptors?

Possible Answers:

Transcription

DNA replication

Translation

Protein phosphorylation

Correct answer:

Transcription

Explanation:

Upon activation, toll-like receptors activate a transcription factor called nuclear factor kappa-light-chain-enhancer of activated B cells (NF-KB). This transcription factor ultimately activates genes in the genome that are involved in immune response. Upon activation of NF-KB, genes undergo transcription and produce mRNA which can eventually be converted to proteins that facilitate the immune response; therefore, activation of toll-like receptors (TLR's) activates transcription.

Example Question #4 : Toll Like Receptors

What are some characteristics of toll-like receptors?

I. Toll-like receptors are transmembrane proteins characterized by an extracellular domain and a cytoplasmic tail containing the toll receptor domain.

II. Toll-like receptors can be activated by viral double-stranded RNA.

III. Toll-like receptors alert immune cells to the presence of bacterial infections.

IV. Toll-like receptors are expressed in antigen presenting immune cells (dendritic cells).

Possible Answers:

I, II, III, and IV

I, II, and III

II and III

II, III, and IV

I and II

Correct answer:

I, II, III, and IV

Explanation:

Toll-like receptors can be activated by bacterial components such as lipopolysaccharide, peptidoglycan, flagellin, and bacterial DNA. Toll-like receptors activate transcription factors and immune regulatory factors.Activation triggers the production of pro-inflammatory cytokines such as interleukins.

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