The question is incomplete. Th ecomplete question is as following:
All of the following protect the skin and mucous membranes from infection EXCEPT
A) multiple layers of cells.
B) tears.
C) saliva.
D) HCl.
E) the "ciliary escalator."
Answer: D) HCl.
Explanation:
- The epidermis, the outer layer of the skin provides waterproofing and serves as a barrier to infection and other laers also sustain any type of injury.
- Tears wash out foreign bodies which enter the eye. In addition, tears contain a substance called lysozyme which has an antibacterial function and works to prevent microbial invasion and infection.
- Saliva protects against infection, especially via the innate immune system. This mechanism is an important first-line protection against bacterial and viral infection
- The mucociliar escalator is within the conducting airways and is composed of mucus and cilia that transfer the mucus up and out of the lungs where it can be removed by coughing or swallowing,
Whereas HCL helps in the digestion process.
Hence, the correct option is D.
Nuclear magnetic resonance provide information on the structure of a purified protein based on its nuclear spin properties in a magnetic field, whereas X-Ray crystallography uses diffraction pattern of protein in solid phase.
Explanation:
Nuclear magnetic resonance is a spectroscopic technique that involves change in nuclear spin energy in presence of an external magnetic field. It is based on the absorption of electromagnetic radiation in the radio-frequency region.
X-Ray crystallography is a method of determining the arrangement of atoms within a crystal.This technique is based the fact that when a beam of X-ray strikes a crystal, the beam gets diffracted. From the angle and intensities of diffraction a three-dimensional structure of electron density can be determined .
