Question

the proximal convoluted tube has cells loaded with mitochondria becausethe cells use great amounts of energy to draw useful ions and other chemicals back into the blood from the filtrate draw more ions out of the blood and into the filtrate pump the filtrate into the urinary bladder. rewatch submit

Explanation:

The proximal convoluted tubule (PCT) is a part of the nephron in the kidney. One of its main functions is reabsorption. Reabsorption is the process of taking useful substances (such as ions, glucose, amino acids) from the filtrate (the fluid that has been filtered from the blood in the glomerulus) and moving them back into the bloodstream. This reabsorption often occurs against a concentration gradient, which requires energy (in the form of ATP). Mitochondria are the power - houses of the cell and produce ATP. So, the presence of a large number of mitochondria in PCT cells is related to the energy - requiring reabsorption process of taking useful ions and chemicals back into the blood from the filtrate.
The second option is incorrect because the PCT is mainly about reabsorption (taking things back into the blood) rather than secreting (putting more ions from blood into filtrate, which is more of a later part of nephron function in some cases). The third option is incorrect because the pumping of filtrate into the urinary bladder is not a function of the PCT. The PCT is involved in the initial processing of the filtrate in the nephron, not in moving the filtrate to the bladder.

Answer:

draw useful ions and other chemicals back into the blood from the filtrate