Younis (56) and Misbah-ul-Haq (44) were at the crease at the break after Pakistan lost Shan Masood (54), Mohammad Hafeez (19) and Shoaib Malik (two) in the two sessions.
Younis and Misbah have added 93 for an unbroken fourth wicket stand after Pakistan lost Masood off the first ball of the second session.
England grabbed two wickets in the first session but then Younis batted solidly to anchor Pakistan's fightback.
He pushed spinner Moeen Ali for two to reach his half-century and was ably assisted by Misbah, who has hit five boundaries and a six.
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He hit seven boundaries and a six off 86 balls before falling after lunch, caught behind off paceman James Anderson.
England introduced spinner Ali as early as the seventh over.
Hafeez struck a boundary off the first ball of Ali's fifth over but was caught bat-pad by Jonny Bairstow at short leg off the very next delivery.
Malik, who scored a brilliant 245 in the first Test, lasted just nine balls before playing a short-pitched Ben Stokes delivery into the hands of Bairstow, who caught it on the second attempt.
England made no change from the first Test line-up.