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Biochemistry 510 > Exam 3: vitamins > Flashcards

Exam 3: vitamins Flashcards

1
Q

What is a vitamin?

A

Organic compounds essential for optimal health

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2
Q

Define mobile vs bound vs free cofactors?

A

-mobile: vitamin cofactor is a substrate for enzymes (ex. NAD)

-bound: stably bound to a protein in the body, can be covalent or non-covalent

-free: act independently of proteins

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3
Q

Define the 4 basic functions of vitamins?

A

-carriers: bind and release things unchanged (-co2, -ch3)

-catalysis: bind and change substrates (breaks/forms bonds)

-sensors: physically sense a metabolic/environmental condition

-signaling: signals a developmental or physiological state

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4
Q

What do you call a structural variation of a vitamin?

A

Vitamer (exist in different forms in our body)

-core structure that can be used equivalently to carry out vitamin function

-one of multiple usable forms of a vitamin

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5
Q

Water soluble vitamins:

A
  1. B complex vitamins
    -b1=thiamin
    -b2=riboflavin
    -b3=niacin
    -b5=pantothenate
    -b7=biotin
    -b6=pyridoxine
    -b12
    -folate
  2. Vitamin C = choline
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6
Q

Fat soluble vitamins:

A
  1. Vitamin A
  2. Vitamin D
  3. Vitamin E
  4. Vitamin K
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7
Q

What does -CoA indicate?

A

It is a b5 dependent reaction?

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8
Q

What was the first vitamin to be discovered?

A

Vitamin B-1.
-Thiamin

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9
Q

The “vitamin” hypothesis

A

…of Funk postulated the existence of a number of unidentified dietary essentials, each of which acts as a protective substance to the organism.

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10
Q

Why was the discovery of thiamin so important to the “vitamin hypothesis”?

A

sets stage that isolated compound can cure disease

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11
Q

What are the 2 conditional vitamins?

A
  1. Niacin –Tryptophan
  2. Vitamin D –sunlight
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12
Q

List 4 reactions that are dependent upon vitamin B5 (pantothenate)

-hint: 3 are dehydrogenases

A
  1. Pyruvate dehydrogenase
    –links glycolysis (pyruvate) to TCA cycle (A-coA)
    aka: oxidative decarboxylation
  2. Alpha-ketoglutarate dehydrogenase
    –4th step in TCA cycle
  3. Alpha-ketoBUTYRATE dehydrogenase
    –degradation of threonine
  4. Fatty-acid oxidation
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13
Q

Is pantothenate activated to its active enzyme cofactor form only in the liver?

A

NO! Activated in the Cytosol of cells

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14
Q

What do the enzymes involved in energy metabolism all have in common?

A

They are enzyme co-factors

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15
Q

What is the reactive site of pantothenates cofactor molecules?

A

-SH group at the end of the Beta -Mercapto-ethylamine unit

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16
Q

What is pantothenate (b5) converted to in the tissues?

A

-coA

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17
Q

What is the result of a deficiency in pantothenate?

A

RARE. caused by severe malnourishment: alcoholism, malabsorption diseases

–burning feet syndrome
-neurodegeneration

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18
Q

% sufficiency of:
-EAR:
-RDA:
-AI:
-UL:

A

-EAR: 50% sufficient
-RDA: 97.5% sufficient
-AI: estimate of intake by healthy people. Used when uncertain EAR.
-UL: Highest amount to intake to pose no adverse risk effect for 98% population

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19
Q

Pantothenate:

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-5
-Water Soluble
-Mobile as CoA. Bound in F.A.S
-Carrier

-Acetyl/Acyl groups

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20
Q

Riboflavin:

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-2
-Water Soluble
-Bound
-Carrier

-Electrons

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21
Q

Niacin:

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-3
-Water Soluble
-Mobile
-Carrier

-Electrons and ADP ribose (sirtumis)

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22
Q

Thiamin

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-1
-Water Soluble
-Bound
-Catalyst

-Alpha-keto-acid

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23
Q

Biotin

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-7
-Water Soluble
-Bound
-Carrier

-CO2

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24
Q

Pyridoxine

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-6
-Water Soluble
-Bound
-Catalyst

-Amino Acids

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25
Q

Folate

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-9

-Water Soluble
-Mobile
-Carrier

-1 Carbon Units

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26
Q

Cobalamin

-Name
-Fat/Water Soluble
-Free/Mobile/Bound
-Carrier/Catalyst/Sensor/Signal
-Constituent

A

-Vitamin B-12

-Water Soluble
-Bound
-Carrier

-Methyl groups (in methyl synthesis)

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27
Q

What is a Co-enzyme?

A

A coenzyme is a nonprotein compound that is NECESSARY for the functioning of an enzyme

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28
Q

What is an enzyme?

A

Enzymes are PROTEINS that act as biological CATALYSTS by accelerating chemical reactions.

The molecules upon which enzymes may act are called SUBSTRATES,

…and the enzyme converts the substrates into different molecules known as PRODUCTS.

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29
Q

What are the Vitamins of energy metabolism? And what type of reactions do they participate in?

  • 6
A
  1. Thiamin (B-1)
    -Decarboxylation
  2. Riboflavin (B-2)
    -Redox Cofactors
  3. Niacin (B-3)
    -Redox Cofactors
  4. Pantothenate (B-5)
    -Acetyl/Acyl Transfer reactions
  5. Pyridoxine (B-6)
    -Decarbox, -trans-, de-aminations
  6. Biotin (B-7)
    -Carboxylation
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30
Q

What are the Vitamins related to blood function?
- 3

A
  1. Vitamin K
    -Carboxylations
  2. Folate (B-9)
    -One carbon transfer rxns
  3. Cobalamin (B-12)
    -One carbon transfer rxns
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31
Q

What are the Vitamins as Antioxidants?
- 2

A
  1. Vitamin C
  2. Vitamin E
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32
Q

What are the Vitamins as Signaling Molecules?
-2

A
  1. Vitamin A
  2. Vitamin D
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33
Q

What are the 4 basic functions of vitamins?

A
  1. Energy Metabolism
  2. Blood Function
  3. Antioxidants
  4. Signaling Molecules
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34
Q

Why did Vitamins become essential?

A

Over time as humans had a more constant dietary exposure to these vitamins it is possible that they lost the ability to synthesize them, as many other non-primate animals are able to. Now we MUST get them from our diet, and it is no longer optional.

35
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Pantothenate (Vitamin B-5) —> as CoA structure

A

-SH (terminal thiol) is the reactive group (part of the Beta Mercapto-ethylamine unit)

… this site forms high energy thiol ester bonds with acyl and acetyl substrates

36
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Riboflavin (Vitamin B-2)

A

N=C-C=N
Allows for resonance stabilization whether or not it is carrying electrons at the moment.

Oxidative form: FMN or FAD
^^considered Riboflavin cofactors

Reduced form: FMNH2 or FADH2

37
Q

How do the 2 Riboflavin (B-2) Co-factors differ from each other?

A

FMN = 1 Nucleotide
FAD = 2 Nucleotides

**A,T,C,G

38
Q

Who is at risk for Riboflavin deficiency? Symptoms:

A

**Deficiency uncommon
-found in many food types. Light sensitive.
-deficiency in the case of neonatal jaundice. 50% of term and 80% of pre-term babies

39
Q

What enzymes catalyze “Oxidative decarboxylation”?
…and what is the role of riboflavin in these rxns?

A
40
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Niacin (Vitamin B-3)

A

Active form of Niacin = NICOTINAMIDE
(other form is nicotinic acid)

Reactive site is the Beta Carbon of Nicotinamide in the Adenosine + Ribose + Nicotinamide structure

due to resonance capability. allows for stability when carrying electrons

41
Q

What are the 2 forms of Niacin containing cofactors in cells?

A

NADP+
-levels highest in mitochondria
-involved in catabolic reactions

NADPH
-levels highest in cytosol
-involved in antioxidant and biosynthetic reactions
-source of electrons for redox reactions

42
Q

What are sirtuins?

A

enzymes that catalyze DEACYTYLATION and ADP RIBOSYLATION reactions

Deacetylase Reaction:
protein acetyl+ NAD+—>protein (no acetyl group) + 2 acetyl ADP ribose +niacin

ADP ribosylatoin rxns:
protein + NAD+. ——>. protein ADP ribose + niacin

basically carries the adp ribose

43
Q

What are the roles of niacin in alcohol metabolism?
Why does heavy alcohol consumption disrupt metabolism?
How does this disrupt fatty liver

A

NADH ratio and how accumulation of NADH disrupts metabolism

inhibit breakdown of fatty acids and stimulate synthesis leads to cirrhosis, stimulates elongation of acyl groups which FA can be loaded on to form tg

44
Q

What is a redox reaction?

A

Adds or removes protons/electrons

–any reactions using NADP+, NADH, NADP+, NADPH

45
Q

Symptoms of Niacin defficiency?

A

-Pellgra & the 4 D’s:

  1. Dermatitis
  2. Diarrhea
  3. Dementia
  4. Death
46
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Thiamin (Vitamin B-1)

A

The carbon between the S & N

Electronegativity draws Hydrogen’s to it.

47
Q

What is the result of Thiamin deficiency?

A
  1. Beri-Beri: Weakness, thermoregulation problems, cardiovascular failure
  2. Wernicke’s Encephalopathy: Dementia, memory problems, neuropathy (common in alcoholics), leucine toxicity?
  3. Marginal Deficiency: About 60 million people in US get <70% of RDA
47
Q

What is the active coenzyme form of Thiamin?
Where does this transformation occur?

A

TDP = Thiamin Diphosphate

T–> TDP conversion happens ONLY in liver

48
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Biotin (Vitamin B-7)

A

NH of the ring structure
–Nitrogen is loaded with CO2 and can react with phosphate

(vs attachment site = COOH)

**ATP dependent: hydrolysis of ATP so we can attach a phosphate group onto the COOH

49
Q

What symptoms indicate Biotin deficiency?

A

**RARE

-Lethargy
-Seizures
-Ataxia
-Nausea
-Hair loss
-Dermatitis

50
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Pyridoxine (Vitamin B-6)

A

CHO group of Pyridoxal ring

The Schiff base allows the structure to form intermediates with substrates

51
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Folate (Vitamin B-9)

A

N-C-C-N bond
–can carry different carbon groups (CH2) while holding onto one of the N’s (forming an N-N bond) …. can attach to one or the other or both at the same time

THF, THF, or DHF
(Tetrahydrofolate, or Dihydrofolate)

52
Q

What is the reactive site of the following vitamin’s co-factor and how does this site allow the vitamin to carry out it’s function (of carrier/catalyst):

Cobalamin (Vitamin B-12)

A
53
Q

True or False:
The vitamins involved in energy metabolism ALL serve as enzyme cofactors?

A

TRUE!

54
Q

What role does pantothenate play in fatty acid synthesis? How does this role compare and contrast with the role it plays in fatty acid Beta oxidation?

A

Pantothenate’s role is to activate acetyl, malonyl, and intermediate chain fatty acyl groups during their anabolism by the biotin-dependent fatty acid synthase complex.

55
Q

What symptoms indicate Pantothenate (Vitamin B-5) malnourishment?

A

**deficiency is RARE (abundant in most plant and animal derived foods)

-Burning feet syndrome
-neurodegeneration

56
Q

What active transporter does pantothenate share with?

A

Biotin

57
Q

What are the 5 measures of assessing vitamin levels in a person?

A

-Direct measurement of nutrient (blood, hair, fingernails)

-Direct assessment of its homeostasis (urine excretion, bolus input test)

-Direct measure of biochem actions
(Enzymatic rxn, gene expression levels)

-Indirect measure of physiological action (Excretion of pathway metabolites, blood clotting)

-Epidemiological relationships (diet recalls, intake vs disease)

58
Q

What is the most common way to assess a person’s PANTOTHENATE status?

A

direct measurement and urinary status

59
Q

What is the most common way to assess a person’s RIBOFLAVIN (B-2) status?

A

direct measure of biochemical actions via:

glutathione reudctase activity in erythrocytes
**if added FAD increases activity >40% that indicates deficiency

59
Q

What is the most common way to assess a person’s Thiamin (B-1) status?

A
  1. Direct assessment via urine excretion
  2. Direct measure of biochemical actions via transketolase activity in RBC’s (If activity increases <15% then adequate, but if activity increases >25% than deficient)
60
Q

What type of reactions is Thiamin (B-1) necessary for?

Give 4 examples

A

Oxidative Decarboxyllations

  1. Pyruvate dehydrogenase
    -Links Gly to TCA (pyruv. to A-CoA)
  2. Alpha-Ketoglutarate dehydrogenase
    -4th step in TCA
  3. Alpha-Ketobutyrate dehydrogenase
    -degrades threonine to succinylcholine coA
  4. Branched chain Alpha keto acid dehydrogenase
61
Q

What does TDP stand for?

A

Thiamin Di-Phosphate

–the structure that Thiamin Is utilized throughout the body

62
Q

What types of reactions is Riboflavin (B-2) necessary for?

Give 6 examples

A

Dehydrogenase’s (redox co-factor)
–All except ETC are FMN form

  1. Succinate dehydrogenase
    –6th step TCA
  2. Acyl CoA dehydrogenase
    –FA Beta Oxidation
  3. Pyruvate dehydrogenase
    –Glycolysis to TCA (Pyruv. to AcoA)
  4. Alpha-Ketoglutyrate dehydrogenase
    –4th step TCA
  5. Alpha-Ketobutyrate dehydrogenase
    –Threonine to succinylcoA
  6. Electron Transport Chain –FMN!!
    -Complex 1
63
Q

What does FMN stand for?

What does FAD stand for?

A

FMN= Flavin-Mono-Nucleotide
–only used in ETC complex 1

FAD= Flavin Adenine Di-nucleotide
–more complex structure. More present in body!

64
Q

What types of reactions is Niacin (B-3) necessary for?

Give 6 examples

A

Redox reactions (generally dehydrogenases)

HARVESTS/CARRIES ELECTRONS

  1. Pyruvate dehydrogenase
    –Glycolysis to TCA (pyruvate to AcoA)
  2. Alpha-ketoglutarate dehydrogenase
    –4th step in TCA cycle
  3. Alpha-ketobutyrate dehydrogenase
    –Threonine to succinyl coA
  4. Beta-hydroxylacyl CoA dehydrogenase
    –F.A. beta oxidation
  5. Alcohol/ aldehyde dehydrogenase
    –Alcohol metabolism
  6. Microsomal ethanol oxidizing system
    –Alcohol metabolism
65
Q

What form is niacin found in the body?

A

NAD: Nicotinamide adenine dinucleotide

(or NADP… Nicotinamide adenine dinucleotide phosphate)

66
Q

What do dehydrogenase enzymes do?

A

Dehydrogenase enzymes transfer electrons from the substrate to an electron carrier.

67
Q

What is the second major role of Niacin in addition to carrying electrons in dehydrogenase reactions?

A

Substrate to sirtuins.

  1. Ribosyllation
  2. De-acytyllation
68
Q

What types of reactions is Pantothenate (B-5) necessary for?

Give 5 examples

A

Acetyl/Acyl transfer reactions
–it is a component of Co-A
**office hours image

  1. Pyruvate dehydrogenase
    –Glycolysis to TCA (pyruv to AcoA)
  2. Alphaketoglutarate dehydrogenase
    –4th step of the TCA cycle
  3. Alpha ketobutyrate dehydrogenase
    –Deg. of threonine to succinyl coA
  4. Fatty Acid beta oxidation
    -Break down of Fatty Acids
  5. Fatty acid synthesis
    -Acetyl CoA is building block
69
Q

What form is Pantothenate (B-5) present in the body?

A

Co-A

70
Q

What types of reactions is Biotin (B-7) necessary for?

Give 4 examples

A

Carboxyllations

  1. Pyruvate Carboxyllase
    –replenishes O.A.A. in TCA cycle
  2. Propionyl coA carboxylase
    –odd chain fatty acid Beta oxidation
    –Amino acid degradation (threonine to Succinyl coA)
  3. Beta methyl crotonyl CoA carboxylase
    –leucine degradation
  4. Acetyl coA carboxylase
    –Fatty acid synthesis
71
Q

What happens during a carboxylation reaction?

A

A carboxylic acid is produced by treating a substrate with carbon dioxide

72
Q

What types of reactions is Pyridoxine (B-6) necessary for?

Give examples

**DO I NEED SPECIFICS

A

Involved in Hundreds of reactions:

-Decarboxylations
-Transaminations
-Deaminations

-Synthesize neurotransmitters

**pyridoxine binds to the alpha carbon of Amino acids and can cleave the co2 group, R group OR amine group
(A.A. metabolism, heme synthesis, cleavage reactions, etc.)

73
Q

Why does a deficiency in B6 result in Nitrogen imbalances?

A

-Failure to efficiently recycle or excrete Nitrogen via deamination and transamination
-Reduced synthesis of nonessential Amino Acids

74
Q

What occurs as a result of Pyridoxine (B-6) deficiency?

A

RARE but can occur with other B vitamins
(alcoholics, pregnancy, malabsorption due to IBD adn bariatric surgery)

  1. Nitrogen imbalances
  2. Mental disorders (loss of neurotransmitters)
  3. Anemia (failure to make heme… hypochromic microcytic anemia)
75
Q

How do you define Anemia:

A

A deficiency in the number of mature red blood cells or the quantity of hemoglobin in those cells

76
Q

What types of reactions is Folate (B-9) necessary for?

Give 6 examples

A
  1. Dihydrofolate reductase
    –Reduction of dietary folate and DHF reaction product
  2. Methionine synthetase
    –Removal of homocysteine
  3. Thymidylate synthetase
    –Pyrimidine synthesis
  4. Reactions of purine synthesis (adenine, guanine)
    –10-formyl THF donates 2C to these rings
  5. Serine hydroxymethyltransferase
    –loading carbon onto THF
  6. Formiminotransferase
77
Q

What is the folate trap?

A

If a person has a deficit of Vitamin B12 (cobalamin) it could be because Folate is trapped as 5-methyl THF

**masking effect

78
Q

why does red blood red cell production require so much DNA synthesis relative to most other tissues in the body? Which tissues would have a similarly high demand for DNA synthesis?

A

because there are 250 billion cells

-developing fetus needs lots of DNA replication
-gut lining
-immune synthesis
-chemotherapy

79
Q

How do we measure folate deficiency?

A

Indirect measure of physiological action via
FIGLU levels

80
Q

Active site of Cobalamin (B-12)

A

Cobalt
–handles methyl group

81
Q

What reactions are dependent upon Cobalamin (B-12)

A

1) Methylmalonyl coA mutase
-odd chain FA b oxidation
-amino acid degradatoin

2) Methionine synthetase

82
Q
A

Biochemistry 510 (2 decks)

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