21. cells of the immune system are able to respond to the presence ofinvading organisms because they recognize the(1) antigens present on the invaders2) antibodies present in invading pathogens) dna partem in the nuclei of viruses(4) antibiotics released from microbes

Animal bodies (and even plant bodies for that matter) are complex enough that life couldn't exist without enzymes. enzymes are usually large, complex biological catalysts that are expensive to make. enzymes speed up the rate of chemical reactions without being used up during the reaction (they can be reused many times). they are highly specific in the reactions they regulate. knowing what enzymes are and how they function, why does this explain why complex life forms could not exist if there were no enzymes.

Many people try to eliminate fat from their diets. which is one reason it is necessary for humans to eat fat? a. eating fat is the fastest way to get energy. b. fat eliminates triglycerides from the body. c. saturated fats clear out the blood vessels. d. fat nerves transmit signals. , this is for apex in summer school.

How does a lytic infection differ from a lysogenic infection?