Which of the following statements about amino acids is INCORRECT?

A turn or kink in a protein is more likely to be induced by a proline than by a glycine.
The more glycines that are found in a polypeptide's primary sequence, the more flexible the backbone of that polypeptide.
The bridge between cysteines, which connects parts of a protein, is a stable but noncovalent interaction.
Not every amino acid is asymmetric.
At typical cellular pH, the R groups of basic amino acids are positively charged.