When you said you were going to knit1 purl1 I thought you were talking about stitches, not rows.
One thing to keep in mind is that the back of a knit stitch is a purl and vice versa. So if you knit a row, when you turn it around, you're going to see the purls that were formed. At this point--forget that they were knit on the last row and just think of them as purls. They were knits in their previous life, they are purls as they face you.
What you're doing is stockinette st--knit one row, purl one row--all the knits will be on one side and all the purls will be on the other side. So knit what you see.
BUT IT WILL CURL! In order to prevent curling, knit the first five rows--knit every row for garter stitch on those rows-- and then knit the first and last 5 stitches of each and every row. It will give you a garter stitch border and prevent curling.