Answer:
3. into ice, which is denser than liquid water.
Explanation:
Water molecules are held together by hydrogen bonds. The bonding is usually between the hydrogen atoms of one water molecules, and oxygen atom of neighboring water molecules. Structurally, both oxygen and hydrogen atoms pulls the electon towards themselves.Thus both atoms share electron by covalent bonding.
However, because oxygen has a strong positively charged nucleus it pulls the electron more to itself than oxygen. Thus oxygen is partially negative and oxygen is partially positive. This interactions take place among all the oxygen and hydrogen atoms in water molecules. . The unequal charge distributions is called dipole and the attraction between oxygen and hydrogen is called hydrogen bonding .
The orientation of hydrogen and oxygen molecules from dipole -dipole interactions of hydrogen bonding makes the oxygen and hydrogen atoms in ice to be pushed apart well spaced out in ice, making them less dense than liquid water where they were aggregated. Thus from the question option C is correct.
PH = - log [H+]
Transpose and solve for H+
3 = - log [H+]
H + =
= 0.001 M
Answer:
peptide antigens by MHC class II molecules
Explanation:
Helper T cells are activated by peptide antigens by MHC class II molecules. These antigens express on the surface of antigen-presenting cells (APCs). After activation, the T helper cells divide and secrete cytokines to assist the immune response.
