Real secured a 3-0 advantage in the Champions League quarter-final first leg at the Estadio Santiago Bernabeu but will face a hostile crowd in Istanbul as they bid to make their 24th semi-final appearance.
Cristiano Ronaldo, Karim Benzema and Gonzalo Higuain were all on target for Jose Mourinho's side in the first leg, but while they have a solid lead ahead of the return match, Lopez believes the only way to guarantee their place in the last four is to take the attack to Gala.
"We must try to play as much as possible like in the first leg," Lopez told realmadrid.com.
"They are a team who play well on the counter-attack, and they have very fast players up front who are always looking for depth. We have to keep calm in defence, keep everything tight and go for them.
"We mustn't think about the 3-0, although it is clear that this is a knock-out match and the 3-0 is there, but I see scoring a goal or looking for goals as the key.
"Our mentality will be to go there and score, and not hide behind the 3-0 , because that would be a mistake."
Galatasaray striker Didier Drogba, who won the Champions League title last season with Chelsea, is in good form ahead of the match having scored twice in Saturday's 3-1 win over Mersin Idmanyurdu in the Turkish Super Lig.
Drogba joined Galatasaray in January after spending time at Chinese Super League side Shanghai Shenhua following his departure from Chelsea last May.
"I have a special relationship with the Champions League - it is a trophy I had to wait a long time to touch," Drogba told uefa.com.
"It is a real joy for me to be back in the Champions League, and especially to hear its anthem at the beginning of each game.
"I have found a club that is ambitious, with a great project. They at some point want to win the Champions League. It is a great choice for me.
"I wanted to rediscover the passion I experienced in Marseille. I want to be part of this adventure, part of this challenge. This is something very exciting."
Gala have seen their preparations for the match overshadowed as coach Fatih Terim is facing a lengthy touchline ban after a heated argument during the league game on Saturday.
Terim was sent to the stands with assistants Hasan Sas and Umit Davala, which could mean Duygu Erdogan might make history this weekend as the first woman to coach a Super Lig team.
Erdogan and goalkeeping coach Claudio Taffarel are the only eligible names to coach the side if Terim and his two assistants are given a ban.