What is the term for the tiny air sacs in the lungs

What are the four basic classes of organic molecules how do they differ structurally and functionally

The carbon cycle is best defined as a process in which a. carbon changes from inorganic forms to organic forms and back b. carbon is changed into other elements such as oxygen or nitrogen c. carbon is continually created from the sun’s energy by plants d. carbon is consumed and regenerated from other elements such as oxygen and nitrogen

How would you expect the mrna codons that code for the amino acids that make up hemoglobin to compare between humans