Democritus contributed to our understanding of the atom in which of the following ways?
1. he determined the mass of the electron.
2. he determined the charge-to-mass ratio for the electron.
3. he hypothesized that all substances can be broken down into a smallest part called the atom.
4. he discovered the proton.

Sodium sulfate dissolves as follows: na2so4(s) → 2na+(aq) + so42- (aq). how many moles of na2so4 are required to make 1.0 l of solution in which the na concentration is 0.10 m?

Choose an equation that represents an enzyme-catalyzed reaction. (a) enzyme + substrate → enzyme-substrate complex (b) enzyme + substrate ←−→ enzyme + products (c) enzyme + substrate ←−→ enzyme-substrate complex → enzyme + products (d) enzyme + substrate ←−→ enzyme-substrate complex → enzyme-substrate complex + products

Which substance is a steroid? cholesterol fatty acid monosaccharide trans fat