There are twenty amino acids in living organisms. Ten of these are referred to as essential amino acids. Why are they called essential amino acids?

How does the study of genetic disorders such as pku biologists understand normal alleles?

Which action is a reflex action. a. asking for coffe in a cold climate b. blinking when light is flashed in the eyes c. drinking water when thirsty. d. swallowing food e. taking an exam

Which of the following structures is a double layer of phospholipids with proteins? a: cytoplasm b: cell membrane c: ribosome d: cell wall