1Metabolism 2 Guide 3Vitamin A1. Explain the retinoids and cartoenoids.- You have two main types of Vitamin A, the retinoids and the carotenoinds. The retinoids are the active form, these are the retinal, retinol ect. The cartoenoids are the provitamins. These get cleaved in the body to retinal, which is later reduced to retinol. 2. What are the sources for both types?- The carotenoids are the form that is in the veggies, like carrots. Most colorful veggies are full of them; there are over 600. The retinoids are in animal products. The best sources are egg yolks, butter, and milk. The form in supplements is Retinyl palmitate or some have carotene. Since vitamin A is not found in low fat dairy and some breakfast items, it is supplemented at around 500 IU. Supplement pills contain 3000-25000 IU. The RDA is around 5000 IU3. How is it digested, absorbed, and transported?- In food, it is in the form as either carentoids or retinyl esters attached to a protein, so just like all the other nutrients we learned, it has to be cleaved out of the protein. First pepsin (or HCl) cleaves out the free retinols or carotenoids, and these free carentoids and the retinols then form micelles just like lipids do when they get absorbed(meaning it enters via lymph, not the blood stream, as it is a fat soluble vitamin. Retinol is 70-90% absorbed and carotenoids are 20-50%. They then go to their target, so either the retina, bone, kidney, intestine, or gonad. In order to circulate in the1plasma, they need a protein called Retinol Binding Protein, or RBP. Each mole of retinol combines with one mole of RBP to form a holo-RBP. So it is a one to one ratio. Once you have your holo-RBP, this will react with another protein called transthyretin. This complex (now a RBP-TTR) will then go to the tissues.- So you have a free retinol, it will combine with a RBP, and this will then combine with a TRR. This is the circulating form. When the retinol is deposited in whatever tissue it goes to, the RBP and the TTR will be released to bind to another free retinol.4. What is the DRI?- This is tricky. The RDA is 900 RE, and 700 RE for men and women. Or 5000 IU. Now 1 RE is considered either 1ug retinol, or 6ug beta carotene, or 12 ug of some other carotenoids. The new guidelines also call them RAE sometimes. And RAE is equal to 1ug retinol, or 12ug beta carotene, or 24 ug other some other carotenoid. o So if you notice, and RAE is double an RE if we are talking about a carotenoid. And RE can be 6ug of beta carotenoid or 12ug of another carotenoid; an RAE is 12ug beta carotenoid or 24ug of another. NOW for retinol, and RAE is equal to an RE; so no mathis involved. You will have to calculate a question of this.- Now for the IU unit. Depending on the food, it will be different. Animal products give 3.3, cheese gives 3.5, yogurt gives 4.1, and plants give 10 IU. Now these also.5. What are the functions?- Everyone knows the main function of vitamin A is for eyesight, but also for other systemic actions, such as cell differentiation/growth/reproduction/bone and immune development. How it works for vision is this: Retinal (11-cis retinal) is the form that the eyes use. The 11-cis retinal will bind with opsin (protein in the retina) to form rhodopsin. This rhodopsin helps communicate the light signal to the brain, and will break down to all-trans retinol. As this process always happens when we see light, we have to replace the11-cis retinol in our diet (that is the retinol that is in animal products)1- For the other functions, we will have to know the precursors involved in them. Retinal is oxidized to retinoic acid. Cell differentiation involves retinoic acid Growth is both retinoic acid and retinol Fertility is retinol Immunity is retinoids and carotenoids Skin integrity is retinoic acid. Then the last function is as an antioxidant. The carotenoids are the best antioxidants. 6. What is the deficiency and toxicity?- Vitamin A deficiency will lead to night blindness (as it is needed for vision is the dark), retarded growth, anorexia, lowered immunity, and keratinization of the skin. So basically if you follow the functions of it, then the deficiencies will be easy to predict. The populations that are more likely to become deficient are those with pancreatic, gallbladder, or liver disease, and those with steatorrhea.- On the other end, toxicity is very dangerous with vitamin A. This will lead to a whole list of problems, along with liver disease. This is with retinol toxicity; beta carotene toxicity just makes your skin yellow (kind of weird).7. How do you assess?- There are many tests for vitamin A assessment. One is the serum retinol test, but this a nonspecific test. The serum carotenoid test, but this is reflective of what you just consumed. The best is the relative dose response, or RDR. This test measures the storage amount in the liver. First you measure their plasma retinol, then you give them an oral dose. Measure 5 hrs later and plug the values into this formula: 5hr amount-initial/5hr multiplied answer by 100. The thing you want to know is the ranges based on this final number. This is the only thing I will copy and paste, as you just have to remember these.1Vitamin K1. What are the properties and characteristics of Vitamin K?- This is another fat soluble vitamin and is present in three forms. All fat soluble vitamins, it is mainly stored in the liver (some are in other body pools). These are Phylloquinone, Menoquinone, and menodione, also named K1, K2, and K3 respectively. K1 is found is dark green vegetables mostly. K2 is in animal products and is also made in gut from bacteria. Around 50% of our vitamin K is made in the colon. K3 is just the synthetic form. 2. What are the functions of Vitamin K?- The main function of vitamin K is with blood coagulation. Vitamin K regulates the formation of the necessary clotting proteins. It is involved with the pro-coagulant (so all make the clots) proteins: prothrombin, VII, IX, and X. It is also involved with the anti-coagulants: Protein C, S, and Z. The whole process is a cluster fuck of reactions that you will need to know. The main thing you need to know is at the end Vitamin K makes an enzyme that converts prothrombin into soluble fibrin then insoluble fibrin. This is what makes the fibrous cap that covers the wound. Based on when I took the class, Know the
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