I'm using Campbell's Biology textbook, and it states that certain carrier proteins transport glucose across the cell membrane much faster than would occur normally. It states that the "glucose transporter" is an extremely selective protein, which doesn't accept even fructose, which is an isomer of glucose. However, another hexose, galactose, appears to me to be even more similar to glucose- it's just that one of the H-OH pairs is flipped. In comparison, though fructose is indeed an isomer, it's a ketose, but glucose and galactose are both aldoses. Given this, I'm pretty sure galactose is more similar to fructose.
My question is: is the carrier protein specific enough to carry only glucose and not even galactose? If it isn't and it's able to carry galactose, what would happen if galactose was transported into the cell in greater quantities?
Note: I'm a bio beginner, so please have some patience if my questions are nonsensical or my facts are incorrect, any corrections would be welcome.