Regarding the reabsorption of bicarbonate ions in the proximal convoluted tubule, the correct statement is:
1. The cuboidal brush bordered epithelium directly reabsorb bicarbonate ions.
2. The cells secrete H⁺ ions to reabsorb all of the filtered bicarbonate.
3. Carbonic anhydrase is not found in the PCT.
4. More bicarbonate is reabsorbed and less bicarbonate is excreted in alkalosis.