An employer must make a "reasonable accommodation" to an employee's disaability, but an reasonable accommodation is a  change in the job, or the provision of some assistive device, which is not too costly or disruptive to the employer and which allows the employee to do the core functions of his or her job.So if the things you can't do are not core or key to your job--the job can readily, without disrupting or more than moderately (at most) inconveniencing the employer, be done despite these limitations, the employer  must accommodate you and allow you to not do these things. In this case, if the employer will not accommodate you, you could contact the federal EEOC or your state's equal/civil rights agency to file a complaint.But if you can't do core or major parts of your job due to these limitations, the employer does not need to accommodate you--the law requires that you be able to do the core of your job. In this case, they can continue to require you to do these things, and if you cannot or will not, terminate you.