Which is hydrophilic among the given amino acids? 

i. alanine 

ii. glutamic acid 

iii. arginine

Cell membrane proteins arbitrate the processes that are fundamental for cells. Spanning the entire membrane are called transmembrane proteins, which are involved in the transport of molecules across the membrane into the cell. The fluids inside and outside of the cell are water-based, while the interior of the cell membrane is nonpolar. Which set of amino acids below is expected to be found in the part of a transmembrane protein that lies within the cell membrane interior?

What do serine, tyrosine, cysteine, and glutamine have in common? Is it expected to find these amino acids on the interior or on the exterior of a globular protein?

Which of the following statements about the polarity of the R groups in amino acids are correct?

I) All amino acids with hydroxyl (-OH) groups in their R groups are classified as polar.

II) Amino acids with aromatic rings in their R groups are always nonpolar.

III) Amino acids with charged R groups can be classified as either polar or nonpolar.

IV) Sulfur-containing R groups in amino acids are generally nonpolar.

V) Amino acids with carboxyl (-COOH) groups in their R groups are classified as nonpolar.

Provide the structure of histidine at a physiological pH.

Which of the following statements about the polarity of the R groups, their respective acidity or basicity, and hydrophobicity or hydrophilicity are correct?

I) Amino acids with nonpolar, aliphatic R groups are generally hydrophobic and do not significantly affect the acidity or basicity of the amino acid.

II) Amino acids with polar, uncharged R groups are hydrophilic and can participate in hydrogen bonding, but they do not influence the overall charge of the amino acid.

III) Amino acids with acidic R groups are hydrophobic due to their negative charge, which repels water molecules.

IV) Amino acids with basic R groups are generally hydrophilic and positively charged, making them soluble in water.

V) Aromatic amino acids with hydrophobic rings are always neutral in terms of charge and do not participate in hydrogen bonding.

Determine the polarity of histidine (whether it is basic, acidic, or neutral) and assess if it is hydrophilic or hydrophobic.