p.9
Vitamin A Metabolism and Biological Roles
What transports β-carotene in the blood?
Low-density lipoprotein (LDL).
p.16
Vitamin A Metabolism and Biological Roles
What happens to retinoic acid (RA) after its uptake into cells?
It is bound by CRBP and transported into the nucleus.
p.3
Vitamin K and Blood Clotting
Why is Vitamin K epoxide reductase pharmacologically important?
It is a target for anticoagulant drugs like warfarin and coumarins.
p.29
Vitamin E Structure and Sources
Which vegetable oils are richest in tocopherols?
Corn, cotton, and wheat germ oils.
p.17
Vitamin A Deficiency and Toxicity
How many children are blinded each year by xerophthalmia?
Over 500,000 children worldwide.
p.11
Vitamin A Metabolism and Biological Roles
What is one of the biological roles of Vitamin A?
It participates in the visual process.
p.3
Vitamin K and Blood Clotting
Name some anticoagulant drugs that target Vitamin K epoxide reductase.
Warfarin, acenocoumarol, phenprocoumon, dicoumarol.
p.22
Vitamin D Synthesis and Function
What is formed after the hydroxylation of calcidiol?
1,25-Dihydroxycholecalciferol.
p.1
Vitamin A Forms and Sources
What are the lipid-soluble vitamins?
Vitamins D, E, K, and A (DEKA).
p.31
Vitamin E Clinical Indications and Toxicity
Is vitamin E recommended for the prevention of chronic diseases like CVD or cancer?
No, it is not recommended.
p.20
Vitamin D Synthesis and Function
What is the active form of vitamin D3?
1,25-dihydroxy cholecalciferol (calcitriol).
p.15
Vitamin A Metabolism and Biological Roles
How does Vitamin A support the body's defense against pathogens?
By maintaining epithelial tissues and mucus secretion.
p.23
Vitamin D Synthesis and Function
Does Vitamin D3 decrease calcium concentration in the blood?
No, it does not decrease calcium concentration.
p.16
Vitamin A Metabolism and Biological Roles
What is the role of retinoic acid in the nucleus?
It binds to specific nuclear receptors and participates in the control of gene expression.
p.6
Vitamin A Forms and Sources
What are the three biologically active forms of Vitamin A?
Retinol, retinal, and retinoic acid.
p.16
Vitamin A Metabolism and Biological Roles
What are the specific nuclear receptors for retinoic acid?
RAR (retinoic acid receptors).
p.16
Vitamin A Metabolism and Biological Roles
How do RARs function in relation to RXRs?
RARs act as heterodimers with RXRs (retinoid X receptors).
p.28
Vitamin E Structure and Sources
What are the main components of Vitamin E?
A chromanium ring and a polyisoprene side chain.
p.29
Vitamin E Structure and Sources
Are animal products rich in Vitamin E?
No, they are poor in Vitamin E.
p.21
Vitamin D Synthesis and Function
What are the two forms of Vitamin D mentioned?
Vitamin D2 (ergocalciferol from plants) and Vitamin D3 (cholecalciferol).
p.8
Vitamin A Metabolism and Biological Roles
What enzyme reduces retinal to retinol?
Retinal reductase (NADPH-dependent intestinal enzyme).
p.24
Vitamin D Synthesis and Function
What hormones regulate blood levels of calcium and phosphorus along with vitamin D3?
Parathyroid hormone (PTH) and calcitonin.
p.8
Vitamin A Metabolism and Biological Roles
How is retinol transported in the blood?
By chylomicrons after being esterified with palmitic acid.
p.24
Vitamin D Synthesis and Function
What triggers the secretion of parathyroid hormone (PTH)?
Low calcium (Ca2+) concentration in the blood.
p.24
Vitamin D Synthesis and Function
How does parathyroid hormone (PTH) affect vitamin D3?
It stimulates vitamin D3 synthesis and secretion.
p.19
Vitamin D Synthesis and Function
How is Vitamin D transported in the blood?
Bound to a specific globulin called Vitamin-D-binding protein.
p.27
Vitamin D Deficiency and Related Disorders
What characterizes rickets?
Continued formation of the collagen matrix but incomplete mineralization, resulting in soft, pliable bones.
p.30
Vitamin E Biological Role and Antioxidant Properties
What happens to tocopherol after it is oxidized?
Its active form can be restored with the participation of Vitamin C.
p.23
Vitamin D Synthesis and Function
What effect does Vitamin D3 have on calcium levels in the blood?
It increases Ca2+ concentration in the blood.
p.3
Vitamin K and Blood Clotting
What enzyme is involved in the reduction of Vitamin K to hydroquinone?
Vitamin K epoxide reductase.
p.22
Vitamin D Synthesis and Function
What occurs at position 25 during vitamin D metabolism?
Hydroxylation to form 25-OH-Cholecalciferol (calcidiol).
p.26
Vitamin D Synthesis and Function
What is the biological role of Vitamin D3?
Vitamin D3 helps regulate calcium and phosphorus levels in the body, promoting healthy bone formation.
p.2
Vitamin K and Blood Clotting
What is the main function of Vitamin K?
To participate in blood clotting.
p.26
Vitamin D Synthesis and Function
How does Vitamin D3 affect the immune system?
Vitamin D3 plays a role in modulating the immune response and may help reduce the risk of infections.
p.15
Vitamin A Metabolism and Biological Roles
What role does Vitamin A play in epithelial cell maintenance?
It is essential for normal differentiation of epithelial tissues and mucus secretion.
p.14
Vitamin A Metabolism and Biological Roles
What is the process to restore 11-cis-retinal?
It involves isomerization in light and reduction of all-trans-retinal to all-trans-retinol in the dark.
p.25
Vitamin D Synthesis and Function
What is the biological role of vitamin D3 (Calcitriol)?
It increases the blood levels of Ca2+.
p.26
Vitamin D Synthesis and Function
What are the sources of Vitamin D3?
Vitamin D3 can be obtained from sunlight exposure, certain foods, and supplements.
p.12
Vitamin A Metabolism and Biological Roles
What is formed when 11-cis-retinal binds to opsin?
The visual pigment rhodopsin.
p.10
Vitamin A Metabolism and Biological Roles
Which enzyme oxidizes retinal to retinoic acid?
Retinal aldehyde dehydrogenase (RALDHs).
p.2
Vitamin K Deficiency and Clinical Implications
Why is a deficiency of Vitamin K quickly observed?
Because it is not deposited in the body and is affected by disturbed lipid absorption.
p.28
Vitamin E Biological Role and Antioxidant Properties
How is Vitamin E absorbed in the body?
From the digestive tract with lipids.
p.30
Vitamin E Biological Role and Antioxidant Properties
How does Vitamin E protect fatty acids in membranes?
By capturing and neutralizing free radicals and oxygen species, preventing lipid peroxidation.
p.21
Vitamin D Synthesis and Function
What happens to 7-dehydrocholesterol when exposed to sunlight?
The chemical bond between C-atoms 9 and 10 is cleaved, opening ring B.
p.25
Vitamin D Synthesis and Function
How do Calcitriol and Parathyroid hormone affect calcium excretion?
They inhibit Ca2+ excretion and stimulate Ca2+ reabsorption in the kidneys.
p.10
Vitamin A Metabolism and Biological Roles
Which enzymes are involved in the synthesis of retinal from retinol?
Alcohol dehydrogenases (ADHs) or short-chain dehydrogenases/reductases (RDHs/SDRs).
p.26
Vitamin D Synthesis and Function
What is a key function of Vitamin D3 in relation to muscle health?
Vitamin D3 is important for muscle function and strength.
p.2
Vitamin K and Blood Clotting
How is Vitamin K absorbed in the body?
It is absorbed from the digestive tract with lipid products.
p.30
Vitamin E Biological Role and Antioxidant Properties
Where does Vitamin E primarily accumulate in the body?
In cell membranes, fat depots, and lipoproteins, mainly in fatty tissue.
p.28
Vitamin E Structure and Sources
What are the different forms of tocopherols?
α-, β-, and γ-tocopherols.
p.29
Vitamin E Structure and Sources
Name some vegetable sources of Vitamin E.
Green beans, green peas, salads, oats, corn germs, rye, wheat germs.
p.21
Vitamin D Synthesis and Function
What is the metabolized form of Vitamin D called?
1,25-Dihydroxycholecalciferol (calcitriol).
p.14
Vitamin A Metabolism and Biological Roles
What happens to all-trans-retinol in the regeneration of 11-cis-retinal?
It is isomerized to 11-cis-retinol and then oxidized to 11-cis-retinal.
p.25
Vitamin D Synthesis and Function
What effect do Calcitriol and Parathyroid hormone have on bones?
They stimulate bone resorption.
p.8
Vitamin A Metabolism and Biological Roles
What do all fat-soluble vitamins have in common regarding transport?
They are all carried in chylomicrons.
p.8
Vitamin A Metabolism and Biological Roles
How are carotenes ingested with food processed?
They are resorbed unchanged and transported by chylomicrons.
p.7
Vitamin A Metabolism and Biological Roles
What is retinal derived from?
The oxidation of retinol.
p.27
Vitamin D Deficiency and Related Disorders
What increases the susceptibility to fractures in osteomalacia?
Demineralization of preexisting bones.
p.15
Vitamin A Metabolism and Biological Roles
What is the role of retinoic acid in reproduction and the visual cycle?
It is inactive in maintaining reproduction and in the visual cycle.
p.24
Vitamin D Synthesis and Function
How does vitamin D3 exert its effects in the body?
Through activation of specific genes.
p.17
Vitamin A Deficiency and Toxicity
What happens to the visual threshold in vitamin A deficiency?
It increases, making it difficult to see in dim light.
p.31
Vitamin E Clinical Indications and Toxicity
What were the results of clinical trials using vitamin E supplementation?
They have been uniformly disappointing.
p.20
Vitamin D Synthesis and Function
What hormonal role does calcitriol play?
It is involved in the regulation of calcium and phosphorus homeostasis.
p.25
Vitamin D Synthesis and Function
How does Calcitriol affect intestinal absorption?
It induces the synthesis of a protein that participates in Ca2+ and PO43- absorption through intestinal cells.
p.30
Vitamin E Biological Role and Antioxidant Properties
What is the main biological role of Vitamin E?
It acts as a powerful natural antioxidant.
p.31
Vitamin E Clinical Indications and Toxicity
What was the outcome for subjects receiving high doses of vitamin E in the Alpha Tocopherol, Beta-Carotene Cancer Prevention Study?
They lacked cardiovascular benefit and had an increased incidence of stroke.
p.11
Vitamin A Metabolism and Biological Roles
What role does light play in the visual process involving Vitamin A?
It activates the visual pigment rhodopsin.
p.7
Vitamin A Forms and Sources
What is retinol?
A primary alcohol containing a β-ionone ring with an unsaturated side chain, found in animal tissues as a retinyl ester.
p.28
Vitamin E Biological Role and Antioxidant Properties
How is Vitamin E transported after absorption?
With chylomicrons to the liver.
p.1
Vitamin A Metabolism and Biological Roles
What is a key function of Vitamin A?
Vision and immune function.
p.28
Vitamin E Biological Role and Antioxidant Properties
How is Vitamin E exported from the liver?
With VLDL (Very Low-Density Lipoprotein).
p.14
Vitamin A Metabolism and Biological Roles
What role do similar reactions play in cone cells?
They are responsible for color vision.
p.20
Vitamin D Synthesis and Function
Where does the next hydroxylation of vitamin D3 occur after the liver?
In the kidneys, bones, and placenta.
p.7
Vitamin A Metabolism and Biological Roles
Can retinal and retinol be interconverted?
Yes, they can readily be interconverted.
p.5
Vitamin K Deficiency and Clinical Implications
What can lead to hypoprothrombinemia?
A decrease in the bacterial population in the gut, such as from antibiotics.
p.7
Vitamin A Metabolism and Biological Roles
What is retinoic acid derived from?
The oxidation of retinal.
p.5
Vitamin K Deficiency and Clinical Implications
How can vitamin K deficiency affect bone health?
It can negatively impact bone health.
p.13
Vitamin A Metabolism and Biological Roles
What is rhodopsin?
The visual pigment of the rod cells in the retina.
p.9
Vitamin A Metabolism and Biological Roles
Where is retinol stored in the body?
In the liver, specifically in Kupffer cells, as a lipid ester.
p.18
Vitamin A Deficiency and Toxicity
Why should pregnant women avoid excessive vitamin A intake?
Due to its potential for teratogenesis, causing congenital malformations.
p.27
Vitamin D Deficiency and Related Disorders
Why is vitamin D synthesis reduced in northern latitudes?
Due to reduced exposure to ultraviolet light.
p.13
Vitamin A Metabolism and Biological Roles
What two components make up rhodopsin?
11-cis retinal and the protein opsin.
p.7
Vitamin A Forms and Sources
What is β-carotene?
A provitamin A found in plant foods that can be cleaved to yield retinal.
p.24
Vitamin D Synthesis and Function
What effect does calcitonin have on blood calcium levels?
It decreases blood levels of calcium (Ca2+).
p.21
Vitamin D Synthesis and Function
Where does the synthesis of calcitriol begin?
In the endoplasmic reticulum of the liver cell.
p.17
Vitamin A Deficiency and Toxicity
What is one of the earliest signs of vitamin A deficiency?
Night blindness (nyctalopia).
p.31
Vitamin E Clinical Indications and Toxicity
What is the observed toxicity level for vitamin E at doses of 300 mg/day?
No toxicity has been observed.
p.18
Vitamin A Deficiency and Toxicity
What liver condition can result from chronic hypervitaminosis A?
Enlargement and potential cirrhosis.
p.15
Vitamin A Metabolism and Biological Roles
What does retinoic acid promote?
Growth and differentiation of epithelial cells.
p.24
Vitamin D Synthesis and Function
What role does vitamin D3 play in the immune system?
It is involved in the differentiation and proliferation of immune system cells.
p.17
Vitamin A Deficiency and Toxicity
What can prolonged vitamin A deficiency lead to?
An irreversible loss in the number of visual cells.
p.18
Vitamin A Deficiency and Toxicity
How can hypervitaminosis A affect the CNS?
It may cause a rise in intracranial pressure, mimicking brain tumor symptoms.
p.5
Vitamin K Deficiency and Clinical Implications
Why do newborns initially lack vitamin K?
Because they have sterile intestines and lack the bacteria that synthesize vitamin K.
p.7
Vitamin A Metabolism and Biological Roles
Can retinoic acid be reduced in the body?
No, it cannot be reduced and cannot give rise to either retinal or retinol.
p.17
Vitamin A Deficiency and Toxicity
What severe condition can result from vitamin A deficiency?
Xerophthalmia, a pathologic dryness of the conjunctiva and cornea.
p.9
Vitamin A Metabolism and Biological Roles
What protein is involved in the transport of retinol from the liver to extrahepatic organs?
Serum retinol binding protein (RBP, α1-globulin).
p.5
Vitamin K Deficiency and Clinical Implications
What is recommended for newborns to prevent hemorrhagic disease?
A single intramuscular dose of vitamin K.
p.17
Vitamin A Deficiency and Toxicity
What causes xerophthalmia?
Increased keratin synthesis due to vitamin A deficiency.
p.13
Vitamin A Metabolism and Biological Roles
What happens to rhodopsin when it is exposed to light?
A series of photochemical isomerizations occurs, resulting in bleaching and the release of all-trans retinal and opsin.
p.9
Vitamin A Metabolism and Biological Roles
What does retinol bind to in extrahepatic cells?
Cellular retinol binding protein (CRBP).
p.5
Vitamin K Deficiency and Clinical Implications
What can prolonged administration of large doses of menadione cause in infants?
Hemolytic anemia and jaundice due to toxic effects on the RBC membrane.
p.18
Vitamin A Deficiency and Toxicity
What effect does excessive vitamin A have on bone health?
Decreased bone mineral density and increased risk of fractures.
p.7
Vitamin A Metabolism and Biological Roles
How efficient is the conversion of β-carotene to vitamin A in humans?
The conversion is inefficient, with vitamin A activity being about 1/12 that of retinol.
p.17
Vitamin A Deficiency and Toxicity
What can untreated xerophthalmia lead to?
Corneal ulceration and ultimately blindness.
p.5
Vitamin K Deficiency and Clinical Implications
Why is menadione no longer used to treat vitamin K deficiency?
Because it can produce hemolytic anemia and jaundice in infants.
p.17
Vitamin A Deficiency and Toxicity
In which population is xerophthalmia most commonly seen?
Children in developing tropical countries.
p.13
Vitamin A Metabolism and Biological Roles
What triggers the nerve impulse transmitted to the brain?
The activation of transducin by rhodopsin bleaching.
p.5
Vitamin K Deficiency and Clinical Implications
Why is true vitamin K deficiency unusual?
Because adequate amounts are generally obtained from the diet and produced by intestinal bacteria.
p.17
Vitamin A Deficiency and Toxicity
What is the primary cause of xerophthalmia?
Insufficient vitamin A in the diet.
p.4
Vitamin K and Blood Clotting
Where are the proteins involved in blood clotting synthesized?
In the liver as inactive precursor proteins.
p.4
Vitamin K and Blood Clotting
What are the substrates required for the carboxylation reaction of Vitamin K?
O2, CO2, and the hydroquinone form of vitamin K.
p.4
Vitamin K and Blood Clotting
What effect does warfarin have on Vitamin K?
It inhibits vitamin K epoxide reductase (VKOR), preventing regeneration of the functional hydroquinone form of vitamin K.
p.4
Vitamin K and Blood Clotting
What is the main biological role of Vitamin K?
Maintaining the normal level of proteins involved in blood clotting.
p.4
Vitamin K and Blood Clotting
Which proteins are involved in blood clotting that require Vitamin K?
Factor II, VII, IX, X, protein C, and protein S.
p.4
Vitamin K and Blood Clotting
What happens when Ca2+ is released by prothrombin?
It interacts with membrane phospholipids and is proteolytically degraded to thrombin.
p.4
Vitamin K and Blood Clotting
What is required for the conversion of inactive clotting factors to active forms?
Post-translational modification of specific glutamate residues.
