Final answer:
Alpha and beta defensins are antimicrobial peptides secreted by neutrophils and epithelial cells, contributing to the body's defense mechanisms against pathogens by disrupting microbial cell membranes.
Step-by-step explanation:
Alpha and beta defensins are small cationic peptides known for their antimicrobial properties. They are produced in response to the presence of pathogens and are an important part of the innate immune system. These peptides are secreted by neutrophils and epithelial cells, and they contribute to the chemical barrier against microbial invasion by disrupting microbial cell membranes. Alpha defensins are mainly produced by neutrophils and some immune system cells, while beta defensins are predominantly secreted by epithelial cells lining the respiratory tract, skin, and urogenital tract where they serve as a chemical shield.Within these secretions, such as sweat, mucus, tears, saliva, and other bodily fluids, defensins perform their role by permeabilizing the membranes of invading bacteria, fungi, and enveloped viruses, leading to their eventual destruction. This is enabled by the structure of defensins, where Cys residues (cysteine amino acids) form disulfide bridges that stabilize the peptide structure and facilitate the targeting of microbial membranes.