C-14 has a half-life of 5,730 years. You begin with 600 grams. At the end of the first half-life, how much of the substance is still radioactive? b. After 4 half-lives, how much would remain radioactive and how much would be stable?

An enzyme lowers the energy of activation. what does that mean?

6. in the dna double helix, how are the two strands of dna held together? a. chemical bonds between base pairs hold the two strands of dna together. b. hydrogen bonds between the base pairs hold the two strands of dna together. c. hydrogen bonds between sugar groups and phosphate groups hold the two strands of dna together. d. chemical bonds between sugar groups and phosphate groups hold the two strands of dna together.

Choose the molecule that is described by each phrase. energy used during long activities: