If I get my number 19 tooth extracted. Would this cause problems with biting down on food?

Losing a first molar may be a big deal as this tooth serves an important function in the jaw.  I would fight tooth and nail to try and save the tooth.  Implants are a great replacement option but it sounds like you are just considering extracting the tooth without weighing the benefits of saving it if possible.Best,

Yes, you will find your ability to chew significantly reduced by losing a lower molar. Consider a dental implant to replace it. Also, you may experience upper teeth over erupting in the space below and adjacent teeth shifting and drifting into the space. Not a good idea to just leave the space there in my experience 

#19 is your first molar and an important tooth in chewing and keeping your bite aligned and balanced. For may people, they find it difficult to chew once it has been extracted. Additionally, over time, the adjacent teeth may become overloaded causing dental or periodontal problems. The best option is to replace in order to maintain your chewing and comfort and keep your bite and teeth stable and strong.