Explain the relationship of the following to renal secretion and excretion of hydrogen ions: a. plasma carbon dioxide levels, b. phosphate, and c. sodium bicarbonate reabsorption.

Video transcript

Hi, everyone. Our next question says which of the following to the kidneys is excrete in the urine to maintain the Ph of the blood A HCO three minus bh plus CN A plus or DC L minus. When we think about Ph, we often think about uh H plus or oh minus. In this case, we're thinking about those hydrogen ions and the kidneys do excrete choice BH plus or the hydrogen ions. And this makes sense because increased excretion of hydrogen ions leads to a decreased H plus concentration. And then that would lead to an increased Ph less H plus means lower ph excuse me, higher ph. So let's look at our other answer choices. And all of them are actually molecules that are involved in this process, but they're not specifically what's being excreted to maintain the ph. So HCO three minus or bicarbonate has actually two roles in this uh for every molecule of H plus that is excreted. One molecule of bicarbonate enters the capillary blood and the sodium and chloride ions to C and D are part of the transport process. So part of the HCO three minus transport process as it's being moved into these capillaries. As we know, every time we are transporting ionic particles, we have to have some sort of uh active transport happening and often other ions are used to counterbalance this. So that's why choice of C and D aren't correct. And then what's the second role of the HCO three minus? Which is that in the filtrate, the hydrogen ions combine with the bicarbonate ions to form carbonic acid. So, hth two co three and that ends up breaking down into carbon dioxide and water releasing both of those. So this HCO three minus or bicarbonate is involved in this process in uh being balanced with the hydrogen as it's excreted. And then also combining with the H plus ions in the filtrate to form carbon dioxide and water. But it's not what's actually being excreted to maintain the Ph that would be choice bh Plus. See you in the next video.