Bio360K Test 1 Key - Bio360K Test 1 Key Name 1) What is the...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Bio360K Test 1 Key Name 1) What is the source of anti-microbial peptides in skin epidermis? (2) Keratinocytes Bacterial infection increases the level of anti-microbial peptides in the skin. Why? (3) Bacterial infection induces the production of inflammatory cytokines from macrophages and mast cells in the skin. The inflammatory cytokines increase the expression of anti-microbial peptides from keratinocytes. In addition, keratinocytes also express a subset of TLRs and NLRs, and the engagement of these receptors with PAMPs from the infectious agents can also stimulate the production of anti-microbial peptides. 2) Many anti-microbial peptides are enriched for lysine and arginine residues, and the peptides tend to adopt amphipathic conformations. How do these properties contribute to their function? (4) The positively charged lysine and arginine residues of anti-microbial peptides enable the anti-microbial peptides to interact with the negatively charged bacterial membranes. The hydrophobic region of the anti-microbial peptides associates with the hydrophobic core of the bacterial membrane, while the hydrophilic region of the anti-microbial peptides allows the passage of water and solutes through the membrane, thus disrupting membrane integrity. 3) Anti-microbial peptides damage bacteria, but not human cells. Why? (3) The plasma membrane of human cells displays asymmetric distribution of phospholipids: the outer leaflet is enriched for zwitterionic phospholipids, which are neutral in overall charge. By comparison, the bacterial plasma membrane contains more negatively charged phospholipids in the outer leaflet. For this reason, the positively charged anti-microbial peptides interact more strongly with the bacterial membrane relative to human cell membrane. In addition, human, but not bacterial, plasma membranes contain cholesterol, which strengthens the hydrophobic core of the phospholipids bilayer. 4) What is the source of complements in blood? (2) The hepatocyte of liver is the principal source of complements in blood. Blood complement levels increase during severe bacterial infections. Why? (3) Severe bacterial infections can elicit the acute phase response. Under this condition, large amount of inflammatory cytokines are produced by macrophages and mast cells. These cytokines are distributed throughout the body via blood circulation, and can affect the function of many organs. In particular, IL-1 β , IL-6, and TNF- α , can increase the production of complement factors by hepatocytes in the liver.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 5) Blood contains abundant antibodies. In the absence of infectious agents, these antibodies normally do not activate complements. Why? (3) The classical pathway of complement activation is initiated by the interaction of C1 with the Fc region of antibodies. The C1 binding site on the Fc region is only revealed when antibodies are bound to antigens in an immune complex formed in response to infections. In the absence of infection, immune complexes
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/25/2010 for the course BIO 51285 taught by Professor Tianming during the Spring '10 term at University of Texas at Austin.

Page1 / 5

Bio360K Test 1 Key - Bio360K Test 1 Key Name 1) What is the...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online