In animal cell culture, a CO$_2$ enriched atmosphere in the incubator chamber is used to maintain the culture pH between $6.9$ and $7.4$. Which one of the following statements is CORRECT?

1. Higher the bicarbonate concentration in the medium, higher should be the requirement of gaseous CO$_2$
2. Lower the bicarbonate concentration in the medium, higher should be the requirement of gaseous CO$_2$
3. Higher the bicarbonate concentration in the medium, lower should be the requirement of gaseous CO$_2$
4. CO$_2$ requirement is independent of bicarbonate concentration in the medium