Do you look different at 40?

I am 29.. but, I know that 40 will be here before I know it, cause it feels like I was 19 just yesterday.. So I'm just wondering if there is a big difference between 30 and 40. I look at some famous people like Sandra Bullock and Gwen Stefani, and both look good for being in their 40s, so I'm just wondering if you start to get a lot of wrinkles at that point?