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Nutritional Physiology > Water Soluble Vitamins > Flashcards

Water Soluble Vitamins Flashcards

1
Q

B group Vitamins involved in energy metabolism?

A
  • Thiamin (B1)
  • Riboflavin (B2)
  • Niacin (B3)
  • Pantothenic Acid
  • Biotin
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2
Q

Thiamin

Thiamin Role

A
  • Central role in generation of energy from carbohydrates
  • nerve function
  • transported by RBCs
  • excess quickly excreted in the urine
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3
Q

Thiamin

Active form of Thiamin as a coenzyme

A

Thiamin Pyrophosphate (TPP)

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4
Q

Thiamin

Coenzyme: Thiamin Pyrophospate (TPP)

A

Converts pyruvate to acetyl CoA

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5
Q

Thiamin

Deficiency of Thiamin

A

Wet Beriberi and Dry Beriberi

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6
Q

Thiamin

Wet Beriberi

A

Oedema (swelling), enlarged heart, heart failure
* Results from accumulation of pyruvate and lactate
* Generally seen in active individuals due to increased glycolysis

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7
Q

Thiamin

Dry Beriberi

A

Weakness, nerve degeneration, poor arm/leg coordination

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8
Q

Thiamin

Wernicke-Korsakoff Syndrome

A

Seen mainly in alcoholics because:
* Alcohol diminishes thiamin absorption
* Alcohol increases thiamin excretion

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9
Q

Thiamin

  1. Wernicke’s Encephalopathy (WE)
A
  • Nystagmus: involuntary eye movement; double vision
  • Ataxia: staggering, poor muscle coordination; mental confusion
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10
Q

Thiamin

  1. Korsakoff’s psychosis (KP)
A

Confusion and loss of memory

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11
Q

Thiamin

Food Sources of Thiamin

A

Bread and cereals (wholegrain or enriched), wheat germ, yeast, legumes, nuts, pork, soy milk

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12
Q

Riboflavin

Riboflavin Role

A

Involved in energy production in (notably for release of energy from nutrients in all cell bodies):
* Electron transport chain
* Citric acid cycle
* Catabolism of fatty acids

Important role in the oxidation pathways
* important in preventing damage to cells by free radicals

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13
Q

Riboflavin

Coenzymes of Riboflavin

A
  • Flavin adenine dinucleotide (FAD)
  • Flavin mononucleotide (FMN)
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14
Q

Riboflavin

Deficiency of Riboflavin - Ariboflavinosis

A

Ariboflavinosis
* Glossitis (inflamed tongue)
* Cheilosis (cracked lips)
* Stomatitis (inflammation of mucus in mouth)
* Alopecia (hair loss)
* Dermatitis

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15
Q

Riboflavin

Food sources of riboflavin

A

Dairy products such as milk and milk products (greatest
contributions)
* Wholegrains

  • Sensitive to UV radiation (sunlight) - stored in paper or
    opaque plastic containers
  • Stable to heat, so cooking does not destroy
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16
Q

Niacin

Niacin Role

A

‘Niacin’ describes two chemical structure: nicotinic acid (niacin) and nicotinamide found equally in food.

Oxidation-reduction reactions to produce energy:
* Glycolysis
* Electron transport chain
* etc.

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17
Q

Niacin

Coenzymes of Niacin

A
  • Nicotinamide adenine dinucleotide (NAD)
  • Nicotinamide adenine dinucleotide phosphate (NADP)
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18
Q

Niacin

Transportation and storage of Niacin

A

Transported from the liver to all the tissues where it is converted to the coenzymes
* Niacin can also be produced endogenously from tryptophan (essential amino acid)

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19
Q

Niacin

Deficiency of Niacin

A

The ‘4 Ds’ of Pellagra or niacin deficiency

20
Q

Niacin

Pellagra

A
  1. Dermatitis
  2. Dementia
  3. Diarrhoea
  4. Death
21
Q

Niacin

Food Sources of Niacin

A

Eggs, meat, poultry and fish – protein rich foods
* Liver
* Mushrooms
* Whole-grain and enriched breads and cereals
* Nuts and all protein-containing foods
* Heat stable; little cooking loss

22
Q

Pantothenic Acid

Pantothenic Acid Role

A

Part of coenzyme A (CoA)
* Essential for metabolism of CHO, fat, protein

23
Q

Biotin

Biotin Role and Deficiency

A
  • Metabolism of CHO, fat, and protein via carboxylase reactions (addition of CO2)
  • Deficiency rare as found in most foods (can also be produced by GI bacteria)
24
Q

Biotin

Toxicity of Biotin

A
  • No toxicity level reported
  • Avidin (found in egg whites ) inhibits absorption
  • More than a dozen raw eggs a day to cause this effect
25
Vitamin B6 (Pyridoxal, Pyridoxine, Pyridoxamine)
Vitamin B6 is involved in the transamination and deamination process. * Synthesis of haemoglobin * Niacin synthesis (from tryptophan) * Synthesis of neurotransmitters (serotonin, dopamine, histamine and GABA)
26
Coenzyme form of Vitamin B6
**Pyridoxal Phosphate (PLP)** - active in amino acid metabolism
27
Deficiency of Vitamin B6
* depression, confusion * Anaemia * Dermatitis (related to niacin deficiency) * Reduced immune response * Peripheral nerve damage
27
Food Sources of Vitamin B6
* Meat, fish, poultry * Whole grains * Bananas * Spinach * Avocados * Potatoes * Heat and alkaline sensitive* - foods lose vitamin B6 when heated
28
Alternative names for Folate
Folic Acid or Folacin
29
Coenzyme form of Folate
**Tetrahydrofolate (THF)** – helps synthesis of DNA for rapidly growing cells
30
In what form do foods moslty deliver folate in?
Foods mostly deliver folate in the **‘bound’ form** – known as **polyglutamate**
31
How is folate absorbed?
Small intestine prefers to absorb ‘free’ folate form instead of ‘bound’ form (i.e., free contains only one glutamate attached) * Enzymes on the intestinal cells breaks glutamates off and adds a methyl group. Folate in this form (with methyl, NH3) can be absorbed and delivered to cells * However, in the cells, methyl groups must be removed in order to function * Therefore, to activate this, vitamin B12 removes the methyl group
32
Difference between Folate and Folic Acid
1. Folate is the form found in food and represents the various biochemical forms of pteroyl glutamic acid (folicin; vitamin M; vitamin B9) 2. Folic acid is the synthetic form of folate and used extensively in dietary supplements and food fortification (does not occur naturally in significant amounts)
33
Deficiency of Folate
* seen in late pregnancy, malabsorption syndromes and alcoholics Results in: * **Megaloblastic anaemia** (immature RBCs lose ability to divide from impaired DNA synthesis) * Absorption problems (from immature intestinal cells)- GI tract deterioration * Neural tube defects (NTDs)
34
Food Sources of Folate
Bread (~140 µg/serve) * Fortified breakfast cereals * Grains, legumes (lentils, pinto beans) * Green, leafy vegetables Susceptible to heat, oxidation, ultraviolet light
35
Vitamin B12 Role
Closely related to folate: each depends on the other for activation * Removal of methyl group to active the folate coenzyme * Involved in the metabolism of folate
36
Deficiency of Vitamin b12
**Pernicious anaemia** Clinically looks like folate deficiency (megaloblastic) * Nerve degeneration, weakness * Tingling/numbness in the extremities (parasthesia) * Paralysis and death
37
Food Sources of Vitamin b12
Synthesised by bacteria * Animal products * Organ meat * Seafood * Eggs, Milk * Fortified soy * Easily destroyed by microwave cooking*
38
B-group food sources: summary
* Grains provides thiamin, riboflavin, niacin and folate * Fruits and vegetables provide folate * Meat group provides thiamin, niacin, vitamin B6 and vitamin B12 * Milk group provides riboflavin and vitamin B12
39
Vitamin C
Ascorbic acid (reduced form), dehydroascorbic acid (oxidised form) * Synthesised by most animals (not by humans) * Passive transport if intake is high * Excess excreted
40
Functions of Vitamin C
* Reducing agent (antioxidant) * Immune functions * Increase Iron absorption * Converts Fe3+ to Fe2+ (more absorbable) * Collagen synthesis – form fibrous structural protein of tissues
41
Deficiency of Vitamin C
Scurcy and Rebound Scurvy
42
Scurvy
* Fatigue, pinpoint haemorrhages * Bleeding gums and joints
43
Rebound Scurvy
Seen rarely with immediate halting of megadose vitamin C supplements
44
Food Sources of Vitamin C
* Citrus fruits * Green and red capsicums * Cauliflower/Broccoli * Strawberries * Spinach * Kiwi fruit - easily lost through cooking - sensitive to heat - sensitive to iron, copper and oxygen
45
Vitamin C toxicity
*Toxicity Symptoms:* * Nausea, abdominal cramps, diarrhoea, headache, fatigue and insomnia * Hot flashes and rashes * Aggravation of gout symptoms, urinary tract infections and kidney stones * In those with iron overload diseases (**haemochromatosis**)

Nutritional Physiology (5 decks)

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