Which level of protein structure is a spatial arrangement of the secondary structure?

Which of the following was not a major animal on land during the carboniferous period? amphibians insects both a and b none of the above

Plants need carbon dioxide from their environment to produce glucose during which stage of photosynthesis?

According to the rna world hypothesis, rna acted as the genetic material and catalyzed reactions in ancient cells. what conclusion can you draw from this?               a.  this implies that dna and proteins aren't essential in cells today.    b.  this implies that rna can catalyze any chemical reaction that enzymes catalyze.    c.  this implies that if a cell has a problem with its dna, its rna can compensate for the damaged dna.    d.  this implies that dna and proteins evolved after rna.