Hey! The basic eligibility criterion for pursuing B.Sc. (Biochemistry) degree is qualifying 10+2 or equivalent examination in Science stream with a minimum of 50% marks secured from a recognized board of the country. But some colleges conduct their entrance exam separately. Hope this may help you. 

Cutoff shall depend on college you are applying.

For Bsc Biochemistry cutoff varies from 80 to 95% range as per Institute reputation and its demand for course.

However on safe side aggregate of 88% above in 12th is considered safe for Bsc Courses.