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Vitamin D3 and Calcium

by Kevin Ahern, PhD
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    So calcium in the blood is carried in two different ways. First of all, it can be carried by proteins like albumin, that’s the most common way it’s carried. And there are other proteins that can bind and carry calcium as well. That’s not our most important consideration for calcium, however. It’s the free ion that is the unbound form of calcium in our bloodstream that your doctor measures to determine the level of calcium that you have and if that’s the proper amount. It's the uptake of calcium by cells that occurs through calcium pumps that gives us the calcium that we have. But calcium is something that cells are very, very careful with. Calcium ions are used in signalling. Calcium can cause muscular contraction and a variety of things. So cells have to be careful how much calcium they take up and when they do take it up, they tend to gobble it up and hold it inside the proteins. Another way that cells protect themselves from the effects of calcium are to sequester the calcium in an organelle known as the endoplasmic reticulum in normal cells or in the sarcoplasmic reticulum of muscle cells. Another way that calcium can be stored is by being bound to a protein called calmodulin. And calmodulin is a way of telling other proteins that, “Hey, I’ve gotten a signal that calcium is here.” And that communicates to those proteins that they need to take action. Now, the ionized calcium is regulated by vitamin D. And that’s what we’re going to focus on here. Another protein that’s very important in this process, in fact, more important than vitamin D is parathyroid hormone or PTH as I will call it here. A third protein that’s involved is calcitonin and I’m going to show...

    About the Lecture

    The lecture Vitamin D3 and Calcium by Kevin Ahern, PhD is from the course Vitamins. It contains the following chapters:

    • Vitamin D3 - Calcium Overview
    • Vitamin D and Calcium Absorption from the Diet

    Included Quiz Questions

    1. It is stored in cells in the sarcoplasmic reticulum.
    2. It readily passes through the lipid bilayer.
    3. It has its uptake from intestines stimulated by vitamin A.
    4. All of the answers are true.
    5. None of the answers are true.
    1. All of the answers are true.
    2. None of the answers are true.
    3. It is bound in the intestinal cell by calbindin.
    4. It is released from the endoplasmic reticulum into the blood.
    5. It binds to albumin in the blood.

    Author of lecture Vitamin D3 and Calcium

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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