Which statement accurately describes an enzyme? An enzyme is used only once and increases the rate of a chemical reaction by raising the activation energy.
O An enzyme is used only once and increases the rate of a chemical reaction by lowering the activation energy.
An enzyme is reusable and increases the rate of a chemical reaction by raising the activation energy.
An enzyme is reusable and increases the rate of a chemical reaction by lowering the activation energy.

The health, management and conservation of biodiversity, is a challenge facing ecosystems worldwide. the major factors that affect the health and function of the great barrier reef are climate change and pollution. which question investigates the effects of a biotic factor on the reef ecosystem?

Which is an advantage of having memory cells when a pathogen is encountered for a second time. a) the memory cells are what proliferate into clones of cells in response to the binding of an antigen. b) memory cells are vital to the primary immune response in that they immediately recognize pathogens even at the first encounter. c) memory cells are essentially effector cells that are short lived and attack antigens even without having a receptor specific to that antigen. d) it ensures that more lymphocytes with a receptor specific to a particular antigen will be present than in a host that had never encountered that pathogen.

The first amino acid of a new polypeptide chain is