Learn Finnish: Sinun täytyy syödä 100 grammaa proteiinia.

The current lesson teaches that exact measures act as objects. Normally, a total object in an affirmative sentence takes the genitive form. However, this sentence uses the necessity verb täytyy. In Finnish, the total object of a necessity structure is always in the nominative case, which is why we use the basic nominative sata.

If the object is a total measure, why is the word for gram in the partitive case (grammaa)?

This is because of the fundamental rule for numbers in Finnish. Any number greater than one requires the noun immediately following it to be in the partitive singular. Even though the number sata acts as the grammatical object in the nominative case, the word grammaa is forced into the partitive by the number itself.

Why is the word proteiinia also in the partitive case?

When a measurement word is followed by a mass noun or uncountable substance (like protein, coffee, or wood), that substance is put into the partitive case to express what the measurement consists of. It acts similar to the English word "of", giving us "grams of protein".

As a quick refresher, why does this sentence start with the genitive Sinun instead of the nominative Sinä?

The verb täytyy is a necessity verb indicating that someone must do something. In this specific grammatical structure, the person who has the obligation is always expressed in the genitive case. You can think of it literally as "It is of you necessary to eat".