Well, exactly what you're going to need wil depend on the class, though some generalities will likely hold. I'd suggest getting a C book intended for Java programmers. It's likely to point out the major pitfalls and help you transition.
The biggest items that you're going to worry in C that you don't really worry about in Java are pointers and memory management. Java references are technically pointers, but they're seriously dumbed-down pointers, and from what I've seen, Java programmers don't really see them as the pointers that they are and often have some trouble dealing with pointers initially. Going hand in hand with that is the fact that you won't have a garbage collector, so anything that gets allocated on the heap will not only have to be manually allocated, but you'll have to manually de-allocate it when you're done with it. So, you're going to have to become familiar with
free. You also aren't going to have classes, and structs in C can't have functions in them, so you don't generally program in C in an object-oriented manner. That may or may not be a big deal for you. It does mean, however, that what you'll be learning in your systems programming course and your object-oriented design course are likely to be very different.
OOD should be more of an extension of what you know, teaching you how to better program in an object-oriented manner. Systems programming, on the other hand is much more about getting down and dirty and will be much more low-level in what it deals with. Both are really important to being a good programmer though.
Without knowing your exact skill set and experiences and without knowing the exact courses, giving more detailed advice would be difficult, but primarily, the issue is likely to be in dealing with how C doesn't doesn't manage things for you and doesn't try and keep you safe from yourself. You will have to be more careful programming in C than you would be in Java or Python. There's plenty of stuff that's perfectly legal C which would be illegal many other languages and could surprise you. The main things to be concerned about though are pointers and manual memory management.