The "scientific" body of knowledge is just like any other active body of knowledge. They are all growing, and nobody can possibly claim to know everything there is to know about any one of them. You can't read every piece of literature written in any one language and know everything there is to know about it, you can't study every musical composition, you can't study every prehistoric fossil ever collected, and you can't learn every organic reaction.
What you can do is learn some general principles that will allow you to understand the basics underlying the field of study, practice some techniques that are repetitive and generally useful in applications of that field, and if you are so inclined, learn the basics of research which will eventually allow you to contribute to the growth and development of the field. Then you get out of college and begin applying what you have learned, and focus on either getting very good at applying a very small slice of the field, or in pushing the boundaries of knowledge in the field in very specific directions.