Hi Shaista,
For the MCAT you should know the structure of glucose. Other sugars should be provided.
It is helpful to remember glucose in its chair, haworth and open chain forms if convenient (or know how to convert quickly)
An easy way to remember glucose is to see that all the OHs on glucose in chair form are equatorial.
Another good way to remember glucose is that in the haworth projection, the CH2OH is up and then groups alternate up and down until you get to the anomeric carbon.
For the fischer, some say that glucose looks like a hand with the middle finger, there is only one OH on the left side and in the middle, the rest are on the right. I find the fischer hardest to remember so usually I convert from the haworth/chair forms.
I hope this helps!