Are block ciphers used in public key crypto? I was reading about block ciphers and most articles state they are being used in symmetric key cryptography. Are they also being used in public key cryptography? if not, what alternative pkc use?

Thanks,
Yes, block ciphers are used in public key cryptography, though typically as auxiliary building blocks rather than as the heart of the public key scheme by themselves.

One example is in digital signatures: many use a hash such as SHA-1, to digest the message being signed into a short cryptogram, and/or as part of a Mask Generating Function (loosely speaking: used as a randomizer before applying a public-key primitive). And in turn many hashes, including SHA-1, use a compression function built from a block cipher. Sometime, the function of a Mask Generating Functions is directly performed by a block cipher, as in this proposal.

Also, as rightly pointed in this other answer, block ciphers are often used in combination with public key cryptography, to form a hybrid cryptosystem.