The Gunners looked down and out as Zlatan Ibrahimovic opened up a two-goal lead as the reigning champions put on a sumptuous display.
However, his efforts were cancelled out by substitute Theo Walcott and a late penalty from Cesc Fabregas as Carles Puyol was dismissed for tangling with the Gunners skipper.
An absorbing first-half somehow yielded no goals as the Gunners somehow managed to keep Josep Guardiola's magnificent outfit at bay.
Barcelona started like a house on fire and Sergio Busquets was unlucky not to open the scoring inside two minutes.
His low drive was turned away for a corner by Manuel Almunia before Ibrahimovic missed a number of chances as Barca turned the screw.
Lionel Messi threatened from distance on occasions as the all-conquering outfit dominated the early exchanges.
Arsene Wenger's decision to rush William Gallas back into the team proved a bad one as he left on a stretcher to be replaced by Denilson.
This was after Andrey Arshavin had limped out of the action midway through the half, with Emmanuel Eboue coming on for the Russian.
Fabregas passed a late fitness test, but was cautioned with the interval looming. The booking, his third of the competition, rules him out of the second leg at Camp Nou, a bitter blow for the Barcelona-born star.
Arsenal's first-half resistance counted for nothing as Ibrahimovic opened the scoring within 30 seconds of the re-start.
Gerard Pique's ball forward was chased down by the Swede and, as first-half hero Almunia rushed off his line, Ibrahimovic lofted the ball into the far corner of the net for a deserved lead.
He doubled the advantage, slamming into the top corner after being played through on goal on the hour.
His goal sparked a blistering Arsenal fightback and Wenger made one final change, bringing on Theo Walcott for defender Bacary Sagna.
His bold move proved to inspire the hosts and it was Walcott who halved the deficit. He collected a telling pass on the right-hand side of the penalty area and slotted through Victor Valdes to renew hope.
With both sides looking weary, it was the hosts that grabbed the initiative.
As Nicklas Bendtner's header fell into the Barca penalty area, Fabregas fell to the ground under Puyol's challenge and referee Massimo Busacca awarded a penalty.
He sent the defender off, allowing Fabregas to level with five minutes remaining.
Arsenal huffed and puffed, but Barca's ten-men held firm and now Arsenal must score in Spain to stand any chance of progressing.