Is it possible to designate my only child from my first marriage to get everything that I own upon my death?

In California you can leave your property (but not your spouse's property!) to whomever you like, even to your cat. You accomplish that by adopting a Will or a Trust, or by other arrangements with the institution holding the asset you want to go to your child; e.g., by beneficiary designation on life insurance or an IRA, or by designating the child as "pay on death" to an account.

You need to get a trust in place.

Yes, you can easily prepare a Will that leaves everything to your child, but if you live in a state that has community property laws you spouse get half of the community property. If your assets are greater than his,you should prepare a pre-nup. and be careful to keep your assets separate from his or they can be converted into community property. ?Be sure to tell him what your intentions are, otherwise you will have a bitter living spouse when you die. Remember also that women normally live longer then men and if you segregate your private assets from him, he will likely do the same to you.

You definitely need a will (or, if you own real estate, a trust). You should see a lawyer with experience in the estate planning field.