This is the 4325th most frequent Russian word.
белков
"Белков" is the genitive plural form of "белок," meaning "proteins."
In this sentence, "белков" translates to "proteins" in English and is used to indicate biological compounds necessary for muscle growth. This is the genitive plural form of the word "белок".
Для роста мышц необходимо употреблять достаточно белков.
To grow muscles, it is necessary to consume enough proteins.
Here, "белков" again stands for "proteins." It is in the genitive plural form to signify the abundance of these substances in eggs.
В яйцах содержится много белков и других питательных веществ.
Eggs contain a lot of proteins and other nutrients.
In this context, "белковой" (genitive feminine singular form of the adjective "белковый") describes the protein-like structure of the molecule.