Which group of integral proteins assists the facilitated diffusion of glucose into heterotrophic cells?

1. Glucose enters heterotrophic cells by two routes. 2. One is secondary active transport, which works against the glucose concentration gradient. 3. The other uses integral proteins called GLUT proteins, also known as glucose transporter proteins. 4. These transporters assist the facilitated diffusion of glucose. 5. Cytochrome proteins carry electrons in the transport chain and have nothing to do with importing sugar. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.2 Glycolysis_