Why does the fructose monomer in sucrose appear different from isolated fructose?
Ah, a (fairly) common conundrum that assails us Chemistry students when we start Biochem. ;-)

At first glance, the fructose molecule in your first picture, and that in the second picture appear to have different conformations:


  
  


Believe me, they're the same. "How?" you ask? Stay with me here (it requires a little imagination):

Draw a vertical line/axis on your first diagram along the plane of the furanose ring, connecting the oxygen atom at the apex, right down to the middle of the C3-C4 bond. Then rotate the molecule 180 degrees counter-clockwise. 

Now compare this with the fructose residue in sucrose.

(I lack the necessary Org. Chem. sketching tools to depict this... apologies) 



If you weren't able to wrap your head around "rotation" bit, then, let's assign locant numbers to the carbon atoms in the two diagrams and then compare them:


  
  
  
   I've drawn them tiny, my bad 


Must've clicked by now ;)