HUN - Chapter 11 : The Fat-Soluble Vitamins: A, D, E, and K
what are the stages of xerophthalmia
-At first, the cornea becomes dry and hard because of inadequate mucous production = Xerosis -Then xerosis quickly progresses to keratomalacia, the softening of the cornea that leads to irreversible blindness. = Keratomalcia
Beta-carotene plays two primary roles in the body. what are they?
-First, it serves as a vitamin A precursor -Second, some beta-carotene acts as an antioxidant capable of protecting the body against disease
What are some of the major roles of Vitamin A
-Known to regulate expression of several hundred genes -Promoting vision -Participating in protein synthesis and cell differentiation, thereby maintaining the health of epithelial tissues and skin -Supporting reproduction and regulating growth
Vitamin D raises blood concentrations of bone minerals in three ways
-When the diet is sufficient, vitamin D enhances mineral absorption from the GI tract. -When the diet is insufficient, vitamin D provides the needed minerals from other sources: reabsorption by the kidneys and mobilization from the bones into the blood. -The vitamin may work alone, as it does in the GI tract, or in combination with parathyroid hormone, as it does in the bones and kidneys.
Factors that contribute to vitamin D deficiency include
-dark skin -lack of sun -breastfeeding without supplementation -not using fortified milk
Like vitamin A, vitamin D has a binding protein that carries it to the target organs—most notably, what organs?
-the intestines -the kidneys -the bones
Vitamin D in Other roles
-vitamin D protects against cognitive decline and slows the progression of Parkinson disease -Vitamin D in muscle cells encourages growth in children and preserves strength in adults. - Vitamin D signals cells of the immune system to defend against infectious diseases. -Vitamin D may also regulate the cells of the adipose tissue in ways that might influence the development of obesity. -vitamin D enhances or suppresses the activity of genes that regulate cell growth -it may be valuable in treating a number of diseases. Recent research suggests that vitamin D may protect against metabolic syndrome, type 2 diabetes, tuberculosis, inflammation, multiple sclerosis, macular degeneration, hypertension, and some cancers
These two forms of vitamin D are similar and both must be __________ before they can fully function
Acitivated
What vitamins A precursor
Beta-carotene
Vitamin D is also known as
Calciferol
what does the hydroxylation look like?
First, the liver adds an OH group, and then the kidneys add another OH group to produce the active vitamin.
^^^ Is this process reversible?
Much of the retinal is then converted back to its active cis form and combined with the opsin protein to regenerate rhodopsin
Is Beta-carotene, which is found in a wide variety of fruits and vegetables, converted efficiently enough in the body to cause vitamin A toxicity
NO
Which of the three active forms of Vitamin A support reproduction and is the major transport and storage form?
Retinol
A special transport protein picks up vitamin A from the liver and carries it in the blood. What is the name of this protein?
Retinol-binding protein (RBP)
Beta-carotene instead is stored in the fat just under the
SK=kin
Vitamin D comes in two major forms. what are they?
Vitamin D2 and Vitamin D3
What are the fat soluble vitamins?
Vitamins A, D, E, K
Can eating too much Liver cause Vitamin A toxicity? why or why not?
YES ; Liver is a rich source because vitamin A is stored in the livers of animals, just as in humans.*
What is calbindin?
a protein that binds calcium in the intestinal cells
The cells that break down bone contain what in order to dissolve the minerals and digest the matrix
acids and enzymes
Vitamin D3 derives from
animal foods & synthesis in the skin
Retinoids are compounds that are commonly found in foods derived from plants or animals?
animals
The most studied of the carotenoids with vitamin A activity is
beat-carotene
In vitamin D deficiency, production of
calibindin
who is most vulnerable to toxicity because they need less vitamin A and are more sensitive to overdoses
children
Overt signs of vitamin D deficiency are relatively rare, but vitamin D insufficiency is remarkably
commom
what is preformed vitamin a:
dietary vitamin A in its active form.
one celled glands that synthesize and secrete mucus. This is known as
globet cells
Though called a vitamin, the active form of vitamin D is actually a
hormone
—a compound manufactured by one part of the body that travels through the blood and causes another body part to respond. this is known as
hormone
Where are excess fat soluble vitamin stored
in the liver and adipose tissue
the further conversion of retinal to retinoic acid is
irreversible
Elsewhere in the body, vitamin A deficiency affects other surfaces. On the body's outer surface, the epithelial cells change shape and begin to secrete the protein
keratin
the hard, inflexible protein of hair and nails
keratin
the skin becomes dry, rough, and scaly as lumps of keratin accumulate
keratinization
the softening of the cornea that leads to irreversible blindness.
keratomalacia
The epithelial tissues that line the inside of the body are the
mucous membranes
the linings of the mouth, stomach, and intestines; the linings of the lungs and the passages leading to them; the linings of the urinary bladder and urethra; the linings of the uterus and vagina; and the linings of the eyelids and sinus passageways is all made up of
mucous membranes
what coats and protects the epithelial cells from invasive microorganisms and other potentially damaging substances, such as gastric juices
mucus
the person loses the ability to recover promptly from the temporary blinding that follows a flash of bright light at night or to see after dark. this is known as
night blindness
what is one of the first detectable signs of vitamin A deficiency deficiency?
night blindness
Doe plants contain retinoids?
no
is vitamin D an essential nutrient?
no
Is vitamin A beneficial for acne ? what are some meds that contain in?
no; Accutane and Retin-A
Each rhodopsin molecule is composed of a protein called _______ bonded to a molecule of __________
opsin ; retinal
Vitamin D2 derives primarily from
plant foods
To make vitamin D, ultraviolet rays from the sun hit a precursor in the skin and convert it to
previtamin D3
what occurs by vitamin A in the lining of the body surface
protein synthesis and cell differentiation
previtamin D3, which is converted to vitamin D3 with the help of
the body's heat
Vitamin D's special role in bone health is to? *based on minerals
to assist in the absorption of calcium and phosphorus, thus helping to maintain blood concentrations of these minerals. . The bones grow denser and stronger as they absorb and deposit these minerals
As you might expect, diseases affecting either the liver or the kidneys can interfere with the activation of vitamin D and produce symptoms of deficiency. true or false
true
Vitamin A deficiency is responsible for death and cases of blindness. true or false
true
To activate vitamin D—whether made in the body or consumed from the die. what type of reaction (s) must occur?
two hydroxylation reactions
If a person were to stop eating vitamin A-containing foods, deficiency symptoms would not begin to appear until after stores were depleted. how long for a healthy adult? how long for a child?
—1 to 2 years for a healthy adult but much sooner for a growing child
what are the three different forms of vitamin A that are active in the body? and what are they collectively called?
- Retinol - Retinal - Retinoic acid -Collectively they are called retinoids
what are some of the several significant ways vitamins differ from water-soluble vitamins
-Being insoluble in the watery GI tract -The fat-soluble vitamins require bile for their digestion and absorption -Upon absorption, fat-soluble vitamins travel through the lymphatic system within chylomicrons before entering the bloodstreams, -In the bloodstream many of them require protein carriers for transport
why is Vitamin a considered a teratogen
-Excessive vitamin A during pregnancy leads to abnormal cell death in the spinal cord, which increases the risk of birth defects such as spina bifida and cleft palate - High intakes before the seventh week of pregnancy appear to be the most damaging.
Vitamin A status depends on
-Vitamin A status depends mostly on the adequacy of vitamin A stores, 90 percent of which are in the liver -Vitamin A status also depends on a person's protein status because retinol-binding protein serves as the vitamin's transport inside the body
Vitamin A plays two indispensable roles in the eye: what are they?
-it helps maintain a crystal-clear outer window, the cornea, -it participates in the conversion of light energy into nerve impulses at the retina
Excessive Vitamin A and Bone
-may weaken the bones and contribute to fractures and osteoporosis -Vitamin A suppresses bone- building activity, stimulates bone-dismantling activity, and interferes with vitamin D's ability to maintain normal blood calcium.
12 micrograms of dietary beta-carotene counts as how many RAE
1
One microgram of retinol counts as how many RAE
1
The richest sources of the retinoids are foods derived from
Animals-- liver, fish liver oils, milk and milk products, butter, and eggs
what color is beta-carotene
Beta-carotene is a rich, deep yellow, almost orange, compound.
Although plants don't contain any retinoids, many vegetables and some fruits contain Vitamin A precursors---
Carotenoids
Foods derived from plants provide ____________, some of which can be converted to Vitamin A
Carotenoids
The risk of toxicity is greater in water-soluble vitamins or in fat-soluble vitamins? Why?
Fat-soluble vitamins because they are not readily excreted
After absorption via the lymph system, vitamin A eventually arrives at the _________, where it is stored
Liver
Does all of the retinal covert back ?
Some retinal, however, may be oxidized to retinoic acid, a biochemical dead end for the visual process
Do to the deficiency in Vitamin A in developing countries, what did scientist do to the rice?
Through biotechnology, scientists have been able to genetically modify rice to be a significant source of beta-carotene. Commonly called golden rice because of its yellowish tinge
Visual activity leads to repeated small losses of retinal, necessitating its constant replenishment either directly from foods or indirectly from retinol stores. True or false
True
Without vitamin A, the goblet cells in the GI tract diminish in number and activity, limiting the secretion of mucus. With less mucus, normal digestion and absorption of nutrients falter, and this, in turn, worsens malnutrition by limiting the absorption of whatever nutrients the diet may deliver. Similar changes in the cells of other epithelial tissues weaken defenses, making infections of the respiratory tract, the GI tract, the urinary tract, the vagina, and inner ear likely. True or False
True
retinoic acid can stimulate cell growth in the skin and inhibit cell growth in tumors. Cells use vitamin A have special protein receptors for it, and its action within each cell may differ depending on the receptor. This is because True or Flase
True
remodeling. To convert a small bone into a large bone, some bone cells must "undo" parts of the bone before other cells can build new bone. What vitamin places a role in this dismantling?
Vitamin A
what helps protect the skin against damage from sunlight?
Vitamin A and beta-carotene
Vatimin A (right amount in the body) supports immune function and inhibits replication of measles virus. what else does it do>
Vitamin A supplements also protect against blindness and the complications of other lifethreatening infections, including malaria, lung diseases, and HIV (human immunodeficiency virus, the virus that causes AIDS).
Only a few carotenoids have vitamin A activity; the carotenoid with the greatest vitamin A activity is
beta-carotenoid
what would happen to Animals raised on retinoic acid as their only source of vitamin A
can grow normally, but they become blind because retinoic acid cannot be converted to retinal
a process by which each type of cell develops to perform a specific function. is
cell differentiation
The beta-carotene in dark green, leafy vegetables is abundant, but masked by large amounts of the green pigment
chorophyll
All body surfaces, both inside and out, are covered by layers of cells known as
epithelial cells
Vitamin A promotes differentiation of what two types of cells?
epithelial cells and goblet cells
Night blindness is caused by a lack of vitamin A at the back of the eye, the retina; total blindness is caused by a lack of vitamin A at the
front of the eye, the cornea.
Children lacking vitamin A fail to grow; given vitamin A supplements, these children
gain weight and grow taller.
Bright color is not always a sign of vitamin A activity, however. Beets and corn, for example, derive their colors from the red and yellow xanthophylls. does it have vitamin A activity ?
no xanthophylls doesn't
Is vitamin A deficiency common in the U.S? If not, where is it common?
no; in many developing countries
As mentioned, vitamin A also supports reproduction and regulates growth. in women, vitamin A supports
normal fetal development during pregnancy.
The growth of bones illustrates that growth is a complex phenomenon of
remolding
Which of the three active forms of Vitamin A is active in vision and is also an intermediate in the conversion of retinol to retinoic acid
retinal
Because the body can derive vitamin A from both retinoids and carotenoids, its content in foods and its recommendations are expressed as
retinol activity equivalents (RAE).
a measure of vitamin A activity; the amount of retinol that the body will derive from a food containing preformed retinol or its precursor, betacarotene. This is known as
retinol activity equivalents (rae):
Which of the 2 can be converted to other active forms of vitamin A by the cells as needed
retinol and retinal
beta-carotene can be split to form
retinol in the intestine and liver
Which of the three active forms of Vitamin A acts like a a hormone, regulating cell differentiation, growth , and embryonic development
retionoic acid
The conversion of retinol to retinal is
reversible
When light passes through the cornea of the eye and strikes the retina, what responds?
rhodopsin
Some of the photosensitive cells of the retina contain pigment molecules called
rhodospin
The epithelial tissue on the outside of the body is, of course, the
skin
As mentioned, vitamin A also supports reproduction and regulates growth. In men, retinol participates in
sperm development
a substance that causes abnormal fetal development and birth defects
teratogen
^^ As it does, opsin is released and retinal shifts from a cis to
trans configuration
After completing their work, the bone-dismantling cells die, leaving their excavation site to be rebuilt by the bone-building cells. true or false
true
Several proteins participate in the digestion and absorption of vitamin A. True or False
true
With the help of vitamin A, these bone-dismantling cells destroy selected sites in the bone, removing the parts that are not needed. true or false
true
which vitamin was the first fat-soluble vitamin to be recognized
vitamin A
what begins when ll the binding proteins are loaded, and vitamin A is free to damage cells.
vitamin A toxicity
Blindness due to vitamin A deficiency, is known as what?
xerophthalmia
the cornea becomes dry and hard because of inadequate mucous production—a condition known as
xerosis
Although overconsumption of beta- carotene from foods may turn the skin _________, this is not harmful
yellow
can the body synthesize vitamin D? if so, How?
yes; with the help of sunlight, from a precursor that the body makes from cholesterol.
Toxicity is a real possibility when concentrated amounts of preformed vitamin A in foods derived from
•Preformed vitamin A from animal sources •Fortified foods •Supplements
