CVS Biochemistry > vitamins > Flashcards

vitamins Flashcards

(90 cards)

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1
Q
A
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2
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A
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3
Q

Vitamins are organic compounds that generally cannot be synthesized in adequate quantities by humans and must be supplied by the _____.

A

Diet

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4
Q

How many vitamins are currently classified as water-soluble?

A

Nine

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5
Q

Which four vitamins are classified as fat-soluble?

A

Vitamins A, D, K, and E

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6
Q

Unlike water-soluble vitamins, which fat-soluble vitamin is the only one with a known coenzyme function?

A

Vitamin K

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7
Q

What is the primary cellular function of many water-soluble vitamins?

A

They serve as precursors for coenzymes in intermediary metabolism.

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8
Q

What is the biochemical role of Tetrahydrofolate (reduced folate)?

A

It receives and transfers one-carbon fragments during synthesis of amino acids, purines, and TMP. (trimethoprim) is an antibiotic that interferes with folate synthesis.

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9
Q

Folic acid is added by federal law to which types of foods to prevent deficiency?

A

Cold cereals, flour, breads, pasta, and bakery items.

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10
Q

Pregnant women take folic acid primarily to prevent which type of birth defects?

A

Neural tube defects (such as spina bifida).

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11
Q

A primary result of folic acid deficiency is _____ anemia.

A

Megaloblastic

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12
Q

Why does folic acid deficiency lead to an inability of cells to divide?

A

Diminished synthesis of purines and TMP prevents DNA replication. TMP (thymidine monophosphate)

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13
Q

Which class of drugs competitively inhibits the synthesis of folic acid in microorganisms?

A

Sulfonamides

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14
Q

The drug Methotrexate acts as a competitive inhibitor for which enzyme in folate metabolism?

A

Dihydrofolate reductase

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15
Q

Nutritional anemia is defined by a lower than normal concentration of _____.

A

Hemoglobin

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16
Q

What is the Mean Corpuscular Volume (MCV) range for normocytic anemia?

A

$80 - 100\ fl$

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17
Q

Microcytic anemia is characterized by an MCV of less than _____.

A

$80\ fl$

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18
Q

Deficiencies in iron, copper, or pyridoxine typically cause which category of anemia?

A

Microcytic anemia

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19
Q

A deficiency in Vitamin $B_{12}$ or folate causes _____ anemia, where MCV is greater than $100\ fl$.

A

Macrocytic (or Megaloblastic)

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20
Q

What are ‘megaloblasts’ in the context of nutritional anemia?

A

Large, immature red cell precursors that accumulate in the bone marrow.

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21
Q

A hypersegmented neutrophil in a blood smear is a characteristic finding of which condition?

A

Megaloblastic anemia

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22
Q

Vitamin $B_{12}$ (Cobalamin) contains which metal ion at the center of its corrin ring?

A

Cobalt

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23
Q

Which two essential enzymatic reactions in humans require Vitamin $B_{12}$?

A

Remethylation of homocysteine to methionine and isomerization of methylmalonyl CoA.

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24
Q

Which metabolic intermediate accumulates and can be measured in the blood to diagnose $B_{12}$ deficiency?

A

Methylmalonic acid

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25
The degradation of which substances produces the methylmalonyl CoA that requires $B_{12}$ for isomerization?
Odd-number fatty acids and certain amino acids (valine, isoleucine, threonine, methionine).
26
What is the dietary source of Vitamin $B_{12}$ for humans?
Animal-derived foods (meat, dairy, eggs) or bacterial flora.
27
Which glycoprotein, produced by parietal cells, is essential for the absorption of Vitamin $B_{12}$ in the ileum?
Intrinsic Factor (IF)
28
Pernicious anemia is most commonly caused by an autoimmune destruction of which cells?
Parietal cells of the stomach.
29
How does Vitamin $B_{12}$ deficiency lead to neurological manifestations?
Unusual fatty acids accumulate and become incorporated into the membranes of the nervous system.
30
Why is Vitamin $B_{12}$ typically administered via injection to patients with pernicious anemia?
To bypass the need for Intrinsic Factor in the gut for absorption.
31
The active form of Vitamin C is known as _____.
Ascorbic acid
32
What is the primary biochemical function of Vitamin C?
It acts as a reducing agent (antioxidant) in various reactions.
33
Vitamin C maintains the iron of hydroxylases in the _____ state.
Ferrous ($Fe^{2+}$)
34
Vitamin C is required for the hydroxylation of which protein essential for connective tissue maintenance?
Collagen
35
A deficiency in Ascorbic Acid results in which disease?
Scurvy
36
What symptom of Scurvy is caused by defective collagen synthesis?
Spongy gums, loose teeth, or fragile blood vessels.
37
Vitamin C facilitates the absorption of which dietary mineral from the intestine?
Iron
38
Vitamin C is known to regenerate the functional, reduced form of which other vitamin?
Vitamin E
39
Vitamin $B_{6}$ is a collective term for which three pyridine derivatives?
Pyridoxine, pyridoxal, and pyridoxamine.
40
What is the biologically active coenzyme form of Vitamin $B_{6}$?
Pyridoxal phosphate (PLP)
41
Pyridoxal phosphate (PLP) is a coenzyme primarily for enzymes catalyzing reactions involving _____.
Amino acids
42
Which drug used to treat tuberculosis can induce a Vitamin $B_{6}$ deficiency?
Isoniazid
43
Sideroblastic anemia is a microcytic anemia caused by reduced activity of which PLP-dependent enzyme?
Aminolevulinic acid (ALA) synthase
44
What are 'sideroblasts'?
Iron-loaded erythroblasts in the bone marrow.
45
What is the only water-soluble vitamin that shows significant toxicity at high doses?
Vitamin $B_{6}$ (Pyridoxine)
46
Ingestion of more than $200\ mg/day$ of Pyridoxine can cause which toxic symptom?
Sensory neuropathy
47
The biologically active form of Vitamin $B_{1}$ is _____.
Thiamine pyrophosphate (TPP)
48
Severe thiamine deficiency found in populations relying on polished rice is known as _____.
Beriberi
49
Which syndrome, characterized by encephalopathy and memory problems, is seen in chronic alcoholics with thiamine deficiency?
Wernicke-Korsakoff syndrome
50
Vitamin $B_{3}$ (Niacin) is also known as _____ acid.
Nicotinic
51
What are the two active coenzyme forms of Vitamin $B_{3}$?
$NAD^{+}$ and $NADP^{+}$
52
Which amino acid can be used by the body to synthesize Niacin?
Tryptophan
53
A deficiency of Niacin causes which disease?
Pellagra
54
What are the 'Three Ds' that characterize the progression of Pellagra?
Dermatitis, diarrhea, and dementia.
55
High doses of Niacin are used therapeutically to treat which condition?
Type II hyperlipoproteinemia (elevated VLDL and LDL).
56
Niacin reduces plasma cholesterol by inhibiting the synthesis of _____ in the liver.
Triacylglycerol (TAG)
57
What are the two active forms of Vitamin $B_{2}$ (Riboflavin)?
Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD).
58
Symptoms of Riboflavin deficiency include cheilosis, which is defined as _____.
Fissuring at the corners of the mouth.
59
Biotin serves as a coenzyme in which type of chemical reaction?
Carboxylation reactions (carrier of activated $CO_{2}$).
60
Which food product contains the protein avidin, which prevents biotin absorption?
Raw egg whites
61
A large percentage of the human requirement for Biotin is supplied by _____.
Intestinal bacteria
62
Vitamin $B_{5}$ (Pantothenic acid) is a vital component of which coenzyme?
Coenzyme A (CoA)
63
What functional group in Coenzyme A carries acyl compounds as activated thiol esters?
The thiol ($-SH$) group.
64
The term 'retinoids' refers to several related molecules with the activity of Vitamin _____.
A
65
Dietary Vitamin A is transported from the intestine to the lymphatic system in which form?
Chylomicrons (as retinyl esters).
66
Where is the majority of Vitamin A stored in the body?
The liver (as retinyl esters).
67
Which plasma protein is responsible for transporting retinol from the liver to extrahepatic tissues?
Retinol-binding Protein (RBP)
68
Which specific isomer of retinal is a component of the visual pigment rhodopsin?
11-cis retinal
69
Vitamin A is essential for the normal differentiation of which type of tissues?
Epithelial tissues
70
What is one of the earliest signs of Vitamin A deficiency regarding vision?
Night blindness
71
All-trans retinoic acid (tretinoin) is used pharmacologically to treat which conditions?
Psoriasis and promyelocytic leukemia.
72
Isotretinoin (13-cis retinoic acid) is a common treatment for which skin condition?
Severe acne
73
The Vitamin D vitamins are a group of sterols that function similarly to which class of molecules?
Hormones
74
What is the active molecule of Vitamin D?
$1,25-dihydroxycholecalciferol$ (Calcitriol)
75
The active form of Vitamin D interacts with receptors in the cell _____ to stimulate gene expression.
Nucleus
76
What are the two primary minerals regulated by Vitamin D?
Calcium and Phosphorus
77
Which molecule in the skin is converted to cholecalciferol ($D_{3}$) upon exposure to UV light?
7-Dehydrocholesterol
78
In Vitamin D metabolism, the first hydroxylation step occurs in the liver to form _____.
25-hydroxycholecalciferol (Calcidiol)
79
The second hydroxylation of Vitamin D, forming calcitriol, occurs in which organ?
The kidney
80
Vitamin D maintains plasma calcium levels by increasing uptake in the intestine and stimulating _____ in the bone.
Resorption
81
Nutritional rickets is a Vitamin D deficiency disease occurring in _____.
Children
82
What is the adult form of Vitamin D deficiency, characterized by demineralization of bone?
Osteomalacia
83
The principal role of Vitamin K is the posttranslational modification of various _____.
Blood clotting factors
84
Vitamin K serves as a coenzyme for the carboxylation of which amino acid residues?
Glutamic acid (forming $\gamma$-carboxyglutamate or Gla)
85
Which four blood clotting factors require Vitamin K for their hepatic synthesis?
Factors II (prothrombin), VII, IX, and X.
86
Warfarin acts as a synthetic analog and inhibitor of which vitamin?
Vitamin K
87
Why are newborn infants often given a single intramuscular dose of Vitamin K?
They have sterile intestines and lack the bacteria that synthesize it.
88
What is the primary function of Vitamin E?
It acts as an antioxidant to prevent nonenzymic oxidation of cell components (like polyunsaturated fatty acids).
89
Vitamin E deficiency is almost entirely restricted to which population group?
Premature infants
90
What is a clinical sign of Vitamin E deficiency in humans?
Sensitivity of erythrocytes to peroxide (hemolysis) and abnormal cell membranes.
CVS Biochemistry
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