Question

A protein consisting of more basic amino acids such as ----------exists as a cation at the physiological pH of 7.4. Such proteins are called basic proteins.

• A. Lysine and aspartic acid
• B. Methionine and arginine
• C. Lysine and arginine
• D. Proline and cysteine

Hint:

Lysine and arginine have extra basic groups that become positively charged at pH 7.4.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
Basic amino acids have an extra amino or guanidino group in the side chain. It picks up a proton at pH 7.4 and becomes positive.

Step 2: Identify them
Lysine and arginine are common basic amino acids, and histidine is the third one.

Step 3: Check the options
Aspartic acid is acidic. Methionine, proline and cysteine are neutral.

Final Answer:
The basic amino acids are lysine and arginine. \[ \boxed{\text{(C) }\text{Lysine and arginine}} \]