Which of the following molecules need carrier proteins for transport?
Amino acid
Water
Oxygen
Carbon dioxide
Sugar, amino acid, and nucleoside diffusion are facilitated by carrier proteins. Moreover, these are the proteins that transport substances such as salts, amino acids, and glucose inside the cell. Hence option 1 is the correct answer.
Explanation for the incorrect options:
Option 2 is incorrect because oxygen is a small molecule and can enter cells passively.
Option 3 is incorrect because oxygen is a small molecule and can enter cells without the help of carrier proteins.
Option 4 is incorrect because carbon dioxide is a small molecule and can enter cells without the help of carrier proteins.