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vitamins (b1- SMS) Flashcards

1
Q

water soluble vs fat soluble vitamins

A

water soluble: readily excreted in the urine so toxicity is rare, but can be easily deficient in these, unstable to heat & light
- precursor for many coenzymes!!

fat soluble- A,E,D,K: released, absorbed, and transported with dietary fat
- stored in liver & adipose tissue
- eliminated slower so easier for accumulation of toxic quantities
- fairly stable at normal cooking temperatures
- in contrast, only 1 vitamin (VITAMIN K) has a coenzyme function

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2
Q

what are vitamins and what are their functions?

A

“vital for life”

vitamins are group of organic nutrients that are required in small quantities in various biochemical functions, but they cannot be synthesized by the body so need to be provided by diet

  • are termed micronutrients (not like macronutrients- carbs, proteins, lipids- that are needed in high amounts)

functions: regulate metabolism, support immune function, & maintain health

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3
Q

classifications of water soluble vitamins + further division after that

A

non B complex: absorbic acid (vitamin c)

B complex: not chemically related to one another, only grouped as such because all of them function in the cells as co-enzymes
- B complex is further divided into energy releasing, hematopoietic, & other

energy releasing: help in energy production
- B1, B2, B3, B5, B7

hematopoietic: help in blood formation
- B9, B12

other: involved in various functions
- B6

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4
Q

role of vitamin B1 (thiamine) in the body

A
  • helps enzymes break down carbs into energy (active form)
  • plays key role in the Krebs cycle
  • needed for nerve signal transmission & proper functioning of nerve cells
  • helps in production of neurotransmitters like ACh
  • helps in metabolism

starter key for an engine- turns on body’s energy production & keeps nervous system running smoothly

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5
Q

what enzymes need TPP (thiamine pyrophosphate) as a coenzyme?

A

active form of thiamine

dehydrogenases need thiamine as coenzyme:
- pyruvate dehydrogenase
- α-ketoglutarate dehydrogenase (formation by transketolase)
- branched chain α-keto acid dehydrogenase
- transketolase

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6
Q

How is Thiamine Converted to TPP (Thiamine Pyrophosphate)? B1

A

thiamine + ATP → TPP + AMP

  • transfer of phosphate group to thiamine
  • done by TPP-transferease or TPK
  • in the presence of Mg2+
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7
Q

how is thiamine (vitamin B1) lost in foods?

A
  • destroyed by high temps (overcooking veggies)
  • destroyed by alkalis
  • lost by milling flour, aleurone layer (husk) is removed (polished rice/wheat - brown rice is better where the husk is still there)
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8
Q

RDA (recommended dietary allowance) of:
- thiamine

A

adults: 1.0-1.5 mg/day

children: 0.7-1.2 mg/day

pregnancy/lactation: 2 mg/day

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9
Q

4 important reactions that TPP plays a role in

A

1. Oxidative decarboxylation of pyruvate: conversion of pyruvate (from glucose) to acetyl-coA which enters Krebs cycle to make ATP (this is called the link reaction- conversion of pyruvate to acetyl coA)
- no TPP → pyruvate builds up → lactic acid accumulation (muscle pain & weakness)

2. oxidative decarboxylation of α-ketoglutarate in citric acid cycle: conversion of α-ketoglutarate to succinyl coA

  1. transketolase: in hexose monophosphate shunt (HMP- shunt), transketolase enzyme is dependent on TPP
    - this pathway is important for production of ribose (nucleotides) and NADPH
  2. α-keto acid dehydrogenase: enzyme that requires TPP
    - this enzyme does oxidative decarboxylation (breakdown) of branched chain amino acids to produce energy (protein metabolism)

is coenzyme in all these reactions, doesn’t do the reaction itself

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10
Q

5 disorders related w/ thiamine (B1) deficiency

A

wet beri beri: affects the heart, edema [swelling, filled w fluid] of legs, face, etc. (why its called wet), can lead to congestive heart failure
- heart requires ATP but when it doesnt get, pushes back and there is backlog- why fluid build up b.c of pressure

dry beri beri: affects the nerves, progressive weakness of muscles, difficulty walking, no edema

mixed beri beri: symptoms of both wet & dry

infantile beri beri: born to mother w/ thiamine deficiency (low in breast milk), sleeplessness, vomitting, cardiac dilatation, sudden death due to cardiac failure

wernicke-korsakoff syndrome: affects the brain
- primarily seen in chronic alcoholism
- “I see double (opthalmoplegia), I cannot walk (ataxia), I am confused (global confusion)”

happens in alcoholics or in places where polished rice is main source (malnourished)

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11
Q

how do lab investigations diagnose thiamine deficiency?

A
  • blood thiamine level (obv)
  • raised blood lactate, pyruvate levels (pyruvate is building up b/c not metabolizing it)
  • urinary tests (low urinary thiamine)
  • how much transketolase activity improves after adding extra thiamine in test tube- if activity increases by 15%+, confirms thiamine deficiency
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12
Q

if conversion of pyruvate to acetyl-coA is impaired, what vitamin is deficient?

A

thiamine

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13
Q

vitamin B6 is a collective term for what 3 compounds? and what form is it excreted in urine in?

A

pyridoxine: primarily in plants

pyridoxal: food from animals
- aldehyde form

pyridoxamine: food from animals
- amine form

these are all derivatives of pyridine and only differ in **nature of functional group* attached to ring

but all 3 of these can synthesize the active form pyridoxal phosphate (PLP)

B6 excreted in urine as 4-pyridoxic acid

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14
Q

what is the role of PLP (pyridoxal phosphate) in the body?

A

active form of vitamin B6 (pyridoxine)

  • important in transamination reactions like ALT, AST
  • amino acid metabolism (ex. transsulfuration of Hcy to cysteine)
  • synthesis of specialized products like serotonin and histamine (biogenic amines)
  • making sphingomyelin of your nerves (which makes myelin) → lack causes nerve issues
  • makes heme → makes hemoglobin
  • decrease in homocysteine levels
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15
Q

recommended daily allowance for vitamin B6 (pyridoxine)

A

adults: 2.0-2.2 mg/day

pregnancy/lactation: 2.5 mg/day

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16
Q

6 reactions that PLP (pyridoxal phosphate) participates in (imp)

A

1. Transamination: converts amino acids to keto acids that enter the citric acid cycle & make new amino acids
- ex. alanine → pyruvate (keto acid) → becomes new amino acid
- ex. aspartate → oxaloacetate

2. Decarboxylation: uses enzyme decarboxylates to make corresponding amines
- another card has all the examples

  1. Deamination: PLP removes amino groups when breaking down amino acids for energy
    - serine → pyruvate + NH3
  2. Trans-sulfuration: homocysteine (bad for body) changed into harmless amino acid in presence of PLP
  3. Heme Synthesis (Condensation): glycine + succinyl CoA → δ-Aminolevulinic acid → makes heme
  4. production of Niacin: converts tryptophan to niacin (which is needed for synthesis of NAD+ and NADP)
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17
Q

4 examples of PLP participating in decarboxylation reactions (should know the examples)

A
  1. tryptophan → serotonin in presence of PLP
  2. histidine → histamine in presence of histidase (which uses PLP)
  3. catecholamines: group of neurotransmitters/hormones made from amino acid tyrosine
    - dopamine, norepinephrine, epinephrine (adrenaline)
    tyrosine → L-DOPA by tyrosine hydroxylase → dopamine by dopa decarboxylase that uses PLP → norepinepherine → epinephrine
  4. glutamate → GABA in the presence of PLP

but the imp examples are serotonin & histamine

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18
Q

vitamin B6 (pyridoxine) symptoms

A
  • effect on neurotransmitters: depression, nervousness, irritability, mental confusion, convulsions (GABA)
  • decreased hemoglobin synthesis
  • hypochromic microcytic anemia: small, pale, oxygen-deficient red blood cells
  • xanthurenic acid excretion in urine *without B6, no breakdown of tryptophan into NAD = increased production of xanthurenic acid
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19
Q

when you prescribe Isoniazid, what do you also need to prescribe with it?

A

Isoniazid = treats tuberculosis but induces vitamin B6 (pyridoxine) deficiency

so need to supplement with B6 otherwise patient can develop peripheral neuropathy

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20
Q

4 pyridoxine antagonists

A
  1. Isoniazid (INH) → used for tuberculosis (TB)
    - causes B6 deficiency
  2. penicillamine → used to chelate (remove) copper in wilson disease
    - causes B6 deficiency
  3. L-Dopa (Levodopa) → used for Parkinson’s Disease
    - B6 reduces effectiveness of Parkinson’s treatment making symptoms worse
  4. cycloserine → used for multi-drug resistant TB (MDR-TB)
    - induces B6 deficiency
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21
Q

which best explains biochemical basis of why B6 deficiency causes irritability, depression, and cognitive impairment?

A

reduced synthesis of serotonin and dopamine due to impaired decarboxylation of amino acids

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22
Q

Which best describes biochemical mechanism linking Vitamin B6 deficiency to microcytic anemia and elevated homocysteine levels?

A

Impaired heme synthesis due to reduced aminolevulinic acid (ALA) production

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23
Q

which type of patients have vitamin B6 deficiency?

A

rare occurrence but this deficiency has been observed in:
- women taking oral contraceptives (birth control)
- newborn infants fed formulas low in B6
- alcoholics

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24
Q

RDA for riboflavin (vitamin B2)

A

women: 1.1 mg/day

men: 1.3 mg/day

average intake is above RDA
- toxicity not documented

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25
flavoproteins & metalloflavoproteins
*riboflavin does not exist freely in the body but rather exists in tissues bound w/ enzymes (is attached to enzymes in the form of FMN or FAD)* **flavoproteins**: FMN and FAD are bound tightly to them - ex. *NADH dehydrogenase [FMN] and succinate dehydrogenase [FAD]* (these examples are from the book) **metalloflavoproteins**: more complex b/c contain metal ions like *molybdenum and iron* along with FAD or FMN *imp for electron transfers and redox reactions*
26
list the functions of riboflavin (vitamin B6) in the body
- oxidation-reduction reactions - electron transport chain - citric acid cycle (Krebs cycle) - catabolism of fatty acids (**β-oxidation**) - purine metabolism (**xanthine oxidase to uric acid** which is then excreted in urine) - growth, repair, development of body tissues- healthy skin, eyes, tongue - **principal growth promoting factor in the vitamin B complex**
27
impairment of which biochemical process can be directly associated with **riboflavin deficiency**?
Electron transfer in the mitochondrial respiratory chain
28
how are FAD & FMN formed
*both are active forms of B2 - riboflavin* **riboflavin → FMN** through phosphorylation - *byproduct*: ADP (ATP initially and 1 P removed) **FMN → FAD** by transfer of AMP to FMN - *byproduct*: PPi which was initially ATP
29
example of reaction that requires FMN
**L- amino acid + FMN → α-keto acid + NH3 + FMNH2** *enzyme: L-amino acid oxidase* FMN accepts electrons from the amino acid during its conversion to an α-keto acid - "ammonia is released & FMN is reduced to FMNH2"
30
2 reactions involving FAD
1. **Pyruvate + CoA + NAD+→ Acetyl-CoA + CO2 + NADH + H+** (pyruvate dehydrogenase complex) - FAD takes electrons to oxidize lipoamide and then donates e- to NAD+ to produce NADH for energy production 2. **Succinate + FAD → Fumarate + FADH2** (citric acid cycle) - FAD is oxidizing agent, removes 2 H atoms from succinate - converts succinate into fumarate & reduces FAD to FADH2 - happens in **complex II of ETC** (know this!!)
31
riboflavin (vitamin B6) deficiency causes + symptoms
- usually accompanied in other vitamin deficiencies but not really associated w/ major human disease - can be caused by **low milk intake or intake of pasteurized milk** (pasteurization = loss of riboflavin) - also in alcoholics **ariboflavinosis (deficiency) symptoms**: *dermatitis* (dandruff + skin gets rough), *cheilosis* (fissuring at corners of the mouth), *glossitis* (tongue appearing smooth and dark), *corneal vascularization* (eye disorder)
32
most important sources of pantothenic acid (vitamin B5)
- liver - egg - meat - milk but pantothenic is found everywhere - why deficiency is so rare
33
how is CoA (coenzyme A) formed in the body
1. **Phosphorylation of Pantothenic Acid** - add a phosphate group with the removal of P from ATP 2. **Addition of Cysteine** - sulfur containing amino acid cysteine is added 3. **Decarboxylation of cysteine** - carboxyl group (-COOH) is removed from cysteine 4. **Addition of AMP (adenosine monophosphate)** 5. **Final phosphorylation** - final phosphate group added = active CoA produced **CoA = active form of pantothenic acid (B5)**
34
4 biochemical functions of CoA in body with examples
1. Fatty acid activation (β-Oxidation) **Fatty Acid → Fatty acyl CoA** - uses *thiokinase and CoA* 2. Formation of acetyl CoA from pyruvate **Pyruvate → acetyl CoA** - *uses pyruvate dehydrogenase, CoA, TPP, Lipoid Acid, NAD, FAD (above arrow, enzyme complex)* 3. Metabolism of branched chain amino acids **corresponding keto acids of valine, leucine, & isoleucine → corresponding CoA derivates** - *uses same enzyme complex as above example and branched chain keto acid dehydrogenase on bottom of arrow* 4. Formation of acetylcholine (*imp neurotransmitter!!*) **Acetyl CoA + Choline → Acetylcholine + CoA**
35
3 additional biochemical functions of CoA in body (w/o examples)
1. Acetylation of drugs - *acetyl group added to detoxify drugs* - also like histone acetylation to regulate gene expression 2. Cholesterol synthesis 3. Heme synthesis
36
RDA for pantothenic acid (B5)
**adults**: 5-10 mg
37
4'-Phosphopantetheine is a Prosthetic Group of...
**1. Acyl Carrier Protein (ACP** - plays role in fatty acid synthesis - helps carry fatty acid chains during their elongation 2. **Coeznzyme A (CoA)** - helps in transferring acyl groups (like acetyl or fatty acid groups) in metabolic reactions **prosthetic group**: non-protein molecule thats tightly bound to protein & helps it function *idk this was just on the slides*
38
why does CoA have an adenine nucleotide?
allows it to interact w/ enzymes that recognize nucleotides = important role in metabolism
39
what does CoA carry/transfer?
**acyl groups** (such as acetyl groups) in the form of **thiol esters** (-S- bond) - the -SH (thiol) group at the end of CoA forms a **high energy bond** with acyl groups - *ex. succinyl CoA, fatty acyl CoA, acetyl CoA*
40
acyl vs acetyl
**acyl** - may or may not contain methyl group **acetyl** - def contains methyl (-CH3) group
41
pantothenic acid (B5) deficiency
- uncommon - has been linked to **burning feet syndrome**: 1. pain & numbness in toes 2. sleeplessness 3. fatigue
42
why is biotin (B7) deficiency rare?
bc it can be synthesized by the body (specifically **intestinal bacteria**) - but its also present in a lot of food
43
RDA for biotin (B7)
**adults**: 100-300 mg/day
44
biotin (B7) deficiency
not common, in order to get this, need to eat a lot of **raw egg whites** (egg yolk has biotin but the whites have **avidin**) ~ **20 raw eggs/day** **avidin**: tightly binds biotin preventing absorption from intestine **symptoms**: dermatitis, hair loss, loss of appetite, nausea
45
laboratory findings of biotin (B7) deficiency
elevated lactate, pyruvate, & organic acids in urine (due to defective carboxylase activity)
46
what is the role of biotin (B7) in the body?
- is **prosthetic group** (covalently bound to e-amino group of lysine) in carboxylase - serves as **carrier of CO2 in carboxylation reactions** - coenzyme form is *biocytin*
47
4 biochemical pathways that biotin is part of
*all carboxylation reactions* 1. Pyruvate Carboxylase **Pyruvate → Oxaloacetate** - essential for **gluconeogenesis** (product of glucose from non glucose- imp step in it that requires biotin) and **citric acid cycle** 2. Acetyl CoA Carboxylase **Acetyl CoA → Malonyl CoA** w/ enzyme *acetyl CoA carboxylase* - 1st step in synthesis of fatty acids is carboxylation reaction 3. Propionyl CoA Carboxylase - biotin is an intermediate in metabolism of certain amino acids (valine, isoleucine, threonine, etc) & degradation of odd chain fatty acids **Propionyl CoA → methylmalonyl CoA** w/ enzyme *propionyl CoA carboxylase* 4. Required in metabolism of **leucine**
48
2 forms that ascorbic acid (vitamin C) exists as
**L-ascorbic acid**: reduced form **L-dehydroascorbic acid**: oxidized form *both are active forms but ratio is 15:1 in body* (ascorbic acid is much more) most of the properties of vitamin c are b/c of its ability to undergo redox reactions (switch back & forth b/w oxidized & reduced forms)
49
which enzyme is missing that makes vitamin c not synthesize able in humans?
gulonolactone oxidase *imp to know the name of this enzyme*
50
how is ascorbic acid (vitamin c) secreted out of the body?
in the presence of water, oxidized form (dehydroascorbic acid) is converted into the **inactive form** (diketo L-gulonic acid) which is then turned to **oxalic acid** that is excreted through urine *is not stored in the body*, sent out *high levels of oxalic acid in urine causes stones to form*
51
RDA of vitamin c (ascorbic acid)
**adults**: 60-75 mg/day **infants**: 30 mg/day **pregnant/smokers**: 100 mg/day (*need more b/c oxidative stress on body due to smoking so need more antioxidant*) more than 100 mg/day by nonsmoker → too saturated so body excretes rest through urine
52
4 metabolic roles of vitamin c (ascorbic acid) in the body
- increases **absorption of iron** by keeping it in Fe2+ form instead of Fe3+ (body can't absorb Fe3+ well) - **anti-oxidant** along with vitamin E (vitamin C regenerates vitamin E) - main biological role is as a **reducing agent** in several imp. **hydroxylation reactions** of the body - helps in **wound healing** & **collagen synthesis** (IMP)
53
5 examples of hydroxylation reactions vitamin c partakes in
1. **proline → hydroxy proline** w/ enzyme pollen hydroxylate 2. **lysine → hydroxy lysine** w/ enzyme lysine hydroxylase 3. **Norepinephrine → Epinephrine** w/ enzyme dopamine β hydroxylase 4. hydroxylation of **tryptophan** → serotonin 5. synthesis of **carnitine** (through hydroxylation reactions) both lysine & proline residues are hydroxylated in the presence of ascorbic acid for collagen synthesis
54
4 other roles of vitamin c
- enhances utilization of **folic acid** - involved in control of **histamine levels** - **bone formation** (organic bone has collagen) - preventative action on **chronic disease** (cancer, cataract, coronary disease)
55
4 people at higher risk of vitamin c deficiency
1. increased physical stress (infection, fever, burns, trauma, diabetes, etc.) 2. chronic use of drugs/smokers (aspirin, oral contraceptives) 3. older people (aging = oxidative stress) 4. periods of rapid growth (childhood, pregnancy, adolescence)
56
vitamin c deficiency (effect & symptoms)
causes **SCURVY** **effect**: - impaired synthesis of collagen - impaired antioxidant activity - impaired iron absorption **symptoms**: - sore & spongy gums - loose teeth - fragile blood vessels - hemorrhage - swollen joints (due to bleeding into joints) - impaired wound healing - "sandpaper skin" - fatigue *was common in pirates & sailors who were on ships for months w/o eating fresh fruit & vegetables* **microcytic anemia**: also seen due to decreased iron absorption
57
patient presents with **bleeding gums, fatigue, and poor wound healing**. His dietary history reveals a lack of fresh fruits and vegetables. which enzymatic reaction is most likely impaired in this patient?
Conversion of proline to hydroxyproline
58
which vitamin is required for the post-translation modification of lysine & proline?
vitamin C
59
the **dehydrogenases** (pyruvate dehydrogenase, a-ketoglutarate dehydrogenase, & branced chain a-keto acid dehydrogenase) require which 5 coenzymes?
"my **T**i**FL**aw**N** **Co**mpany" T = thiamine F = FAD N = NAD L= Lipoic Acid C = CoASH (pantothenic acid)
60
active form of niacin (vitamin B3)
niacin & nicotinic acid are synonyms **niacinamide** (nicotinamide) is the active form but only as precursor- present in tissues - its *nutritionally equivalent to nicotinic acid- they're more or less the same* the ultimate active forms are **NAD** (nicotinamide adenine dinucleotide) and **NADP** (nicotinamide adenine dinucleotide phosphate) **NMN** (nicotinamide mono nucleotide) is step closer to NAD but not the final active form itself (but also considered an active form)
60
sources of niacin (vitamin B3)
- found in unrefined and enriched grains and cereal, milk, and lean meats (esp liver) - can also be **synthesized in the body from tryptophan** (amino acid) - 60 mg = 1 mg of niacin
61
formation of NAD+ from the **body**
nicotinamide (*w/ deamidase*) → nicotinate → nicotinate mono nucleotide (NMN) → NAD+
62
formation of NAD+ from **diet**
diet → tryptophan → quinolinate (*by enzyme pyridoxal phosphate [PLP]*)→ nicotinate mono nucleotide (NMN) (*by enzyme QPRT [quinolinate phosphoribosyl transferase*)
63
what types of enzymes does niacin (vitamin B3) serve as coenzymes in + mechanism of action
**1. Oxidoreductases**: enzymes that transfer e- from 1 molecule to another - **NAD+ & NADP+ act as their coenzymes** **2. Dehydrogenases (oxidative)**: specific type of oxidoreductase enzyme that remove H from molecules - *need NAD+ or NADP+ to accept/carry H+ away* **mechanism of action**: reversible addition of electron to pyridine ring + generation of a free H+ ion
64
2 examples of niacin (in active form) use in citric acid cycle (Krebs cycle)
1. **isocitrate → α-ketoglutarate** - NAD+ is added in and comes out NADH2 2. **Malate → Oxaloacetate** - NAD+ is added in and comes out NADH2
65
2 examples of niacin (in active form) use in glycolysis
1. **Pyruvic acid → Lactic Acid** - NADH2 is put in & comes out NAD+ 2. **3-Phosphoglycerade → 1,3-biphosphoglycerate** - NAD+ is put in & comes out NADH2
66
example of niacin in fatty acid synthesis
8-acetyl CoA + 7ATP + **14 NADPH + H+** → Palmitic Acid + 7(ADP+Pi) + **14 NADP**
67
example of niacin use in the pentose phosphate pathway (HMP-Shunt)
the enzyme used (**6 phosphate dehydrogenase**) requires NADP
68
therapeutic use of niacin
**treatment of hyperlipidemia (high cholesterol)**: decreases formation of cholesterol bearing lipoproteins (VLDL, IDL, LDL) aka **dyslipidemia** - basically lowers bad cholesterol (LDL) & triglycerides while increasing good cholestrol (HDL)
69
niacin deficiency
causes **pellagra** → NAD+ & NADP+ levels are low = - impaired energy production - ineffective DNA repair & cell maintenance (causes defects in regeneration skin & GIT issues) **3 D's**: Dermatitis Diarrhea Dementia 4th D → death is too severe case **hartnup's disease**: defective absorption of tryptophan, similar symptoms to pellagra
70
6 causes of niacin deficiency (pellagra)
1. dietary deficiency of both niacin & tryptophan 2. dependence on corn-based diets (sorghum)- *has high amounts of leucine that inhibit key enzyme in formation of niacin from tryptophan* 3. Vitamin B6 deficiency 4. Drugs like isoniazid (*used to treat TB*) 5. Diseases like carcinoid syndrome (*tryptophan is diverted*) and Hartnup's disease (*impared tryptophan absorption*)
71
how is niacin deficiency diagnosed?
niacin is excreted through urine so niacin deficiency is determined by testing these metabolite levels. the metabolites are: 1. **N-methyl nicotinamide (NMN)** - should be more than 0.8 mg/day (less than that indicates niacin deficiency) 2. **2-pyridone** - another niacin metabolite excreted in urine, reduced level suggest niacin deficiency
72
Which of the following biochemical pathways is most directly influenced by Vitamin B3 (Niacin) in the human body?
TCA (krebs) cycle *heavily depends on NAD+ as coenzyme for dehydrogenase enzymes to drive oxidative reactions*
73
Which of the following coenzyme is involved in the formation of hydroxy-proline during collagen synthesis?
ascorbic acid (vitamin C)

1st year- biochem (8 decks)

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