Subject: Do carbonhydrates turn to fat?

For some months now, I've had several arguments with some of my friends 
regarding sugar and how it's connected to fat increasment or decreasment 
in the human body. What I have learned and claim to be right, is that 
carbonhydrates is basically chains of sugar molecules, and that sugar is 
needed to burn fat (turn it into protein) during exercise. My friends 
claim that sugar, when digested turns more or less completely to fat, and 
that sugar doesn't have any positive effect on the body at all. What is 
right and what is wrong?

Re: Do carbonhydrates turn to fat?