Assume a person has defective carrier molecules for a given substance. explain what effect this would have on a person's cells

The cells would have too much or too little of that substance.

The affect a defective carrier molecule would have on a person's cell is that the cell could have too much or too little water. Defects in folate metabolism, such as defective carrier molecules, could be implicated in the etiology of neural tube defects (NTDs).

Cysteinuria (cysteine in the urine) is such a disease involving defective cysteine carrier proteins in the kidney cell membranes.