You're a human being. Human beings feel naturally uncomfortable when experiencing physical and or emotional attraction to another, and you're not wrong in asking this question or feeling the way you do. Keep it professional, respect the equality you share, and respect the differences between your genders.
Long Version - Make sure to keep hydrated.
As a complimentary answer, there's something that you need to take into consideration when reading the answers here. From the looks of it, these answers are coming from a "Western" cultural perspective. You need to understand that in this cultural/world view, even the language that you use to ask this question is cause for many from this sphere to get really upset. Heck, they might even go so far as to create a new trending hashtag on twitter (oh my goodness watch out, here comes #YoureNotAllowedToBeShy).
We're bored, or something of this nature in "the west". My theory is that since we stopped striving to increase in knowledge and pursuit of discovery, and turned to pointless consumerism and 60 hour work weeks to support the consumerism machine, we have nothing better to do than find a "cause" to take up. In this case, you're kicking at the nest of those who have taken up the cause of gender equality.
Equality is great, equal wages are great, all these things are great and there was a time when this cause was a good one. In this day and age however, this cause has turned radical. Case in point is people like my wife, who are stay at home mothers, are described on popular media with a vulgar tone and being told that women like her can "go make a sandwich, b***ch" by television hosts like Ana Kasparian (Young Turks). Gender equality in the west has actually turned into the same sexism that it started out to prevent.
Anyway, it's offensive to suggest that you'd feel different or uncomfortable being a heterosexual male working closely with a female simply because of this very volatile cultural phenomenon that's taking place. So, you're going to get answers that basically tell you to treat them like a man and more than that, a man that has authority over you. I agree with Learner_101's answer, but would suggest that you don't go completely informal.
Respect your culture, where there is a clear difference between a man and a woman. Obviously women are equal in the fact that they deserve every bit of opportunity and respect that you do, but they are in fact different. Respect that part of your culture, treat them with the kind of delicacy and respect that a gentleman would. Again, because of this psychotic western issue, I have to explicitly clarify that "delicacy" does not mean treat them as if they are weak. I mean this in the sense that you honor and respect the things that are different about them, differences that they most certainly are proud to identify themselves by.
Be calm, be yourself, be professional. Definitely don't act casual as if they are "men", and let me explain. When men are casual around other men, especially in a work environment, we're usually obnoxious and rough with our verbal and body language. I'd argue that, especially in your culture, women are not this way. Again, a difference between men and women that is perfectly fine! So, consider this, conduct yourself in a way that is respectful of the differences between you, while also embracing and respecting the equality you both share.
As for the other answers and comments here that are telling you that there's basically something wrong with you or that your feelings are sexist, well now you know why I wrote this long answer. They're dead wrong, the majority of human beings are heterosexual and when these human beings are around members of the opposite sex, they're generally going to feel some degree of attraction, and feeling uncomfortable when experiencing these feelings is also as old and normal as humanity itself. That is absolutely not wrong. These people need to give being human a try, then they'll change their perspective.
Thank you for asking this question and navigating the minefield that is the western idea of morality and social justice.