The Argentine forward sidefooted the spot kick into the top corner after stand-in defender Lucas Digne was judged to have handled the ball after it hit the post, the first time Barca have given away a spot kick in the league for over two years.
The Catalans had little fortune with refereeing decisions and their players and coach Ernesto Valverde were furious when Las Palmas goalkeeper Leandro Chichizola was not punished for appearing to handle the ball outside of the area.
Barca have 66 points and lead the table from Atletico, who visit the Nou Camp on Sunday having won their last eight games in all competitions. Barca have drawn four of their last eight. Third-placed Real Madrid have 51 points with Valencia on 50.
Valverde told reporters he still did not know if the penalty had been given for Digne's handball or a foul and the usually pragmatic coach could not hide his despair at the decision.
"The penalty came as a shock to us because of how it was awarded. We felt that they equalised with an 'invisible' penalty, they grew stronger after that and we played in too much of a hurry," the agitated Valverde said.
"We really wanted to leave here with three points. In the first half we felt we were always creating danger and their players kept on picking up yellow cards. We went ahead in the first half but it was not a big enough margin."
Las Palmas coach Paco Jemez snapped a miserable run of eight consecutive defeats to Barca from when he was in charge of Rayo Vallecano and said his team were slowly but surely finding their feet in their fight against the drop.
"Right now we sure are playing like a team, we're able to help each other out and keep fighting until the last minute," he said. "We're still not creating as many chances as we are capable of but I'm seeing signs of progress.
"Taking a point against Barca gives us more belief than if it was any old point," he added.
(Reporting by Richard Martin in Barcelona; Editing by Ken Ferris)
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