The proximal convoluted tubule has a brush border which is due to

What is the "renal threshold"?

Glucose,$Na^+$,and amino acids are actively transported substances,because

The Loop of Henle is found in the ........

Components reabsorbed by the Proximal Convoluted Tubule $(PCT)$ - $P$
Components secreted by the Proximal Convoluted Tubule $(PCT)$ - $Q$
$I - K^{+}$,$II - \text{Ammonia}$,$III - HCO_{3}^{-}$,$IV - \text{Essential nutrients}$,$V - 70$ to $80\%$ $\text{electrolytes and water}$,$VI - H^{+}$
Select the correct option for $P$ and $Q$.
$P \quad\quad\quad Q$

Name two actively transported substances in glomerular filtrate.