Chapter 9 Fat soluble vitamins
Terms in this set (96)
Organic compounds that are required in small amounts to maintain fundamental functions and which, generally, cannot be synthesized by the human body and must be supplied by the diet.
What vitamins can be synthesized by the body?
Niacin, Vitamin D, Biotin and Vitamin K
What is vitamin D made from?
What two vitamins are made from bacteria in the large intestines?
Biotin and vitamin K
What are the fat soluble vitamins?
A, D, E, and K
Retinol, Retinal, Retinoic acid, and pro vitamin carotenoids. Excess intake of this is a risk factor for osteoporosis. Irreversible blindness is associated with a deficiency of this.
Pro vitamins: Ergosterol, 7 hydro cholesterol, D2 & D3. A deficiency of this is a risk factor for osteoporosis.
Tocopherols and Tocotrienols
Phylloquinones, Menaquinones, and Menadione. A deficiency of this is a risk factor for osteoporosis.
This vitamin is an exception due to it is water soluble and fat soluble and can be stored in the body.
Absorption requires bile salts, transported by chylomicrons, stored in the liver and fatty tissues for long periods, eliminated slowly, and generally toxic if consumed in excess
Fat soluble vitamins because the are similar to lipids
What are the precursors to Vitamin A?
Beta carotene, Alpha carotene, and Beta cryptoxanthin
Pro vitamin A carotenoids can be converted to what in our bodies?
Formation of retinol from beta carotene requires the presence of what B vitamin?
Where is vitamin A stored in the body?
In the liver
What are good sources of vitamin A in the diet?
Primarily animal origin foods, especially liver, dairy products and fish
What are good sources of pro vitamin A carotenoids in the diet?
These are generally in color fruits and vegetables such as carrots, watermelon, papayas, tomatoes, squash, pink grapefruit, and pumpkins.
Green vegetables also contain this, but the pigment can't be seen due to chlorophyll.
Retinyl esters and carotenes in food are often complexed with protein that should be hydrolyzed by what?
Stomach and pancreatic enzymes
Released free retinols and carotenoids in small intestine are solubilized in micelles that are absorbed into what?
Beta carotene can make 2 retinals which can make retinoic acid then with the help of what is carried to the liver
Meat fat or oil helps vitamin A and carotenoid with this process in our bodies?
What can diminish carotenoid absorption?
Fiber intake (especially pectin) as well as vitamin E
Partial pro vitamin A carotenoids can convert to retinals or retinoic acid that directly enters the blood and transport to the liver via albumin. Where does this happen?
Within the enterocyte
Chylomicrons travel through our body using what system?
Retinol is stored as what in what organ of the body?
Retinyl esters in the liver
Why is looking at blood retinol levels not a good indicator that a deficiency may be occurring?
Blood retinol concentration remains fairly consistent even when hepatic retinol concentrations vary 15 fold
How does retinol get into our bodies?
It goes from the liver to blood
Dietary fat is important regarding the digestion and absorption of what?
Pre and pro vitamins A forms
Essential for vision, cellular differentiation, growth, reproduction, bone development, and immune system actions
Vitamin A functions
Within the eye, Cis-retinal is bound to Opsin and forms rhodopsin in what cells?
What is the function of rhodopsin?
Allows us to see black and white as well as see at night
As light enters, the Cis-retinal is isomerized to "trans" form and dissociated from Opsin, inducing a nervous signal to the brain. Upon completion of the cycle what is recycled and converted back to what?
Trans-retinal to Cis-retinal
Cellular retinol can be oxidized to retinal and then retinoic acid, this is an irreversible reaction. Why?
Retinoic acid as a ligand for nuclear receptors
Within the nucleus, retinoic acid can bind 2 nuclear receptors. What are they?
Retinoic acid receptors (RARs) and Retinoid X receptors (RXRs). RAR and RXR must dimerize before they can bind to DNA
Once retinoic acid binds to the receptors it leads to up or down regulation of the expression of the target genes which leads to what?
Cellular differentiation, growth and other functions
In the United States, vitamin A deficiency is rare and often associated with what?
strict dietary restrictions and excessive alcohol intake
What example was given in class concerning a genetically modified organism (GMO) that could potentially help with vitamin A deficiency?
Golden rice which is genetically engineered to biosynthesize beta carotene up to 23 times more than plain rice
Diets rich in beta carotene and vitamin A are associated with lower risk of many types of cancer. Is taking a supplement a good idea?
No, supplementation is associated with increased risk of lung cancer
This can lead to birth defects, liver abnormalities, reduced bone mineral density that may result in osteoporosis, and central nervous system disorders.
Vitamin A toxicity
Ergocalciferol is also known as what?
cholecalciferol is also known as what?
Vitamin D2 is synthesized by
Vitamin D3 is synthesized by
humans from cholesterol in the skin when it is exposed to UVB
What are good sources of vitamin D in the diet?
Fish, eggs, fortified milk, and cod liver oil
RDA of Vitamin D is actually 800IU instead of 400IU why is there this discrepancy? What % of vitamin D is actually absorbed?
Bio availability is only 50% therefore only 50% is absorbed.
What mode of transport does vitamin D3 use?
From chylomicrons or skin are bound to vitamin D binding protein (DBP) for transport
What form of vitamin D is mostly found circulating in blood? It has a 3 weeks half life.
Vitamin D needs Ca2+ to help maintain blood Ca2+, but if there is not enough circulating Ca2+ what will happen?
Vitamin D will take Ca2+ from the bones causing decreased bone density
What vitamins are involved in bone density?
Vitamin A, Vitamin D, and Vitamin K
The vitamin D receptor is a member of the super family of nuclear receptors that regulate what?
Calcitriol acts with what hormone to affect intestine, bone, and kidney
This has several functions via either activating signal transduction pathways to enhance calcium uptake into osteoblasts and skeletal muscle cells or binding nuclear receptor to regulate calcium homeostasis. It is the active form of vitamin D
Promotes calcium absorption in the gut, enhances mobilization of calcium and phosphorus from bone, maintains adequate blood calcium and phosphate concentrations, and involved in bone mineralization with calcitonin hormone (from thyroid)
Vitamin D functions: Calcium homeostasis
Modulation of neuro muscular and immune function and reduction of inflammation and regulate cell proliferation, differentiation, and apoptosis are modulated
Other functions or vitamin D
Vitamin D and calcium supplements have been proven effective against what in children and adults
Rickets in children and osteoporosis in adults
Adequate Intake levels are based on what assumption for the general public
The vitamin is not synthesized by exposure to sunlight
This is rare, but can occur when usual intake is low, exposure to sunlight is limited, kidney cannot convert vitamin D to its active form, or absorption of vitamin D from digestive tract is inadequate
Vitamin D deficiency
This can cause non specific symptoms such as nausea, vomiting, poor appetite, constipation, weakness, and weight loss. In more serious cases can cause Ca2+ to rise, increasing deposits of Ca2+ in soft tissues and causing mental status changes such as confusion and heart abnormalities and a risk of kidney stones.
Vitamin D toxicity
The two types of Vitamin E
Tocopherol and Tocotrienol
What is the most active form in humans and in the US food supply
What is usually contained in a vitamin E supplement?
What are good sources of vitamin E in the diet?
Found in both plants and animal sources. Canola, olives, sunflower, cottonseed, soybean, corn oil, wheat, barley, rice,oats, wheat germ, green leafy vegetables, nuts, and the fatty tissues of the animal
Where do we store vitamin E?
What is the principle transport vehicle for vitamin E in the blood?
What form of vitamin E is usually readily absorbed?
Tocopherols (due to isomerism, there are 4 of these)
What system does vitamin D and E use to get through our bodies?
The lymphatic system
Tocopherols are free in foods, but what is esterfied and must be hydrolyzed by pancreatic esterase before absorption?
Tocotrienols (due to isomerism, there are 4 of these)
The path that vitamin E takes, and what transfer protein does it need?
From the liver via alpha tocopherol transfer protein to blood and other tissue via VLDL. Alpha tocopherol transfer protein is a specific liver protein.
Vitamin E deficiency is rare, but can be caused by what?
Gene defect of alpha tocopherol transfer protein
During periods of low vitamin E in our blood can we access the concentration in adipose tissue?
No, we must continue to get it from our diet
Functions of vitamin E
Non specific and data is inconclusive. There are ideas proposed about the potential functions, such as treatment for health conditions or as antioxidant, but nothing has been proven
Two positive effects of vitamin E supplementation
Reduced incidence of bladder cancer and lens clarity in cataracts in better
Which mechanism has been proposed but not proven as Vit E's principle function against chronic disease prevention?
Increased risk of bleeding in high doses, especially when taken with a medication like warfarin. This can happen from supplementation, but cannot happen if we get this from diet only. A tolerable upper limit has been set for this reason.
Vitamin E toxicity
Works as a co-enzyme, is required for some systems functions, making this an essential vitamin. Required for coagulation and has been used to prevent and treat osteoporosis due to bone calcium loss
Found in dark green plants, contains 4 isoprenoid residues, one of which is unsaturated and is the chemical name for vitamin K in green plants.
From bacteria, have 6-13 unsaturated isoprenoid residues designated as MK-n. Animal source. Also made in the body by normal beneficial gastrointestinal bacteria.
Good sources of Phylloquinone
Dark green leafy vegetables such as spinach and kale, cabbage, cauliflower, broccoli, avocado, and kiwi
Good sources of menaquionone
Meat, eggs, and dairy products
Where is vitamin K stored in the body?
seceral tissues, but generally high in the liver
As co-enzyme, vitamin K is "required" in the carboxylation of Gla proteins by converting what?
Glutamate residues to gama-carboxyglutamate residues
Warfarin is an anticoagulant. Where did "Warf" in this name come from?
Wisconsin Alumni Research Foundation
Osteocalcin, and matrix Gla protien (MGP). Prevents calcium deposits in bone
14 proteins with Gla domains have been discovered in the regulation of what 3 physiological processes?
Blood coagulation, bone metabolism, and vascular biology
A series of reactions generates this inactive clotting factor
Inactive clotting factor X then uses vitamin K and calcium to activate to form what
Xa which is the active form of factor X
Active Xa convert prothrombin to what
Thrombin which is active
Active thrombin catalyzes soluble fibrinogen to what
Fibrin aggregates to for a polymer which help to stop what
The venom of a number of Australian snakes acts by Gla containing enzymes that bind to the endothelium of human blood vessels and activate the conversion of what kind of factors leading to unwanted and potentially deadly clotting.
Pro-coagulant clotting factors
What are the 2 Gla proteins found in bone, cartilage, and dentin?
Osteocalcin or bone Gla protein and Matrix Gla protein
With vitamin K dependent carboxylation, both BGP and MGP can bind what which suggests that BGP is involved in remodeling or calcium mobilization, but MGP may function to prevent calcium precipitation
What specific population is at risk for osteoporosis due to decrease in estrogen?
Post menopausal women
A deficiency of vitamin K is most often seen in what specific population?
Although allergic reaction is possible, there is no known toxicity associated with high doses of phylloquinone and menaquinone so no upper intake level has been established, but this synthetic form can cause liver damage when ingested in relatively large amounts.
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