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MBBCh 2- PHSL2004A > 8. Micronutrient Metabolism > Flashcards

8. Micronutrient Metabolism Flashcards

1
Q

What is Pellagra?

A

Pellagra is caused by a deficiency of vitamin B3 (niacin). Using the terms vitamin B3 or niacin
interchangeably is fine (all the vitamins have two names that can be used interchangeably).

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2
Q

What are the features of Nutrition-related Diseases? (2)

A
  • NO constants! Different individuals, different requirements.
    *Multiple nutrient deficiencies more likely
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3
Q
  • Diet:
A

Selection of foods eaten by an individual

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4
Q
  • Nutrient:
A

Substances absorbed and used to promote cellular activities + body functions e.g carbs, proteins, lipids, vitamins, mineral –> All are essential

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5
Q
  • Essential:
A

needed for cellular metabolism but cannot be synthesis by body must obtain from diet

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6
Q
  • RDA ( recommended daily allowance):
A

Amount per day needed to prevent clinical deficiency

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7
Q
  • Nutrition examines ______ + ______requirements of the diet needed to maintain good health
  • malnutrition —> Can be either ____ or ____ nutrition
A

qualitative
quantitative
under
over

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8
Q

What are vitamins? (2)

A
  • Organic compounds essential for normal metabolism + health and required in small amounts
  • found in a wide range of foods + cannot be synthesised by the body
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9
Q

How are vitamins classified?

A
  • Classified into water and fat soluble
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10
Q
  • Fat soluble vitamins —->
A

Can be stored in liver or subcutaneous tissue (with the exception of Vit. K)

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11
Q
  • Water soluble vitamins ______ in water so they can be easily excreted in urine (except for Vit. B12)
A

dissolve

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12
Q

Why are biosynthetic pathways complex? (2)

A
  • Biosynthetic pathways are complex so it’s more efficient to ingest vitamins than to synthesise enzymes required for making vitamins
  • We therefore have a dependence on other organisms to make these vitamins required for life
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13
Q

Why are biosynthetic pathways complex? (2)

A
  • Biosynthetic pathways are complex so it’s more efficient to ingest vitamins than to synthesise enzymes required for making vitamins
  • We therefore have a dependence on other organisms to make these vitamins required for life
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14
Q
  • Deficiency of a single vitamin is _____. Specific syndromes of individual vitamins exist
A

rare

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15
Q

What do the water-soluble vitamins include?

A
  • B complex vitamins, Vitamin C, folate, and biotin
  • They are easily excreted in urine Not stored in the body Need to be constantly replenished
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16
Q
  • Exception of Vit. B12 which is stored in the ____.
A

liver

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17
Q
  • All B complex vitamins act as ________.
A

coenzymes

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18
Q

How are water-soluble vitamins absorbed? (2)

A
  • Most can be absorbed by simple diffusion when taken in high doses
  • Only exception is Vit. B12 which requires intrinsic factor for its absorption from the GIT.
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19
Q

Vitamin: B1 Thiamine
Major Dietary Sources:
Major Functions:
Deficiency:

A
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20
Q

Vitamin: B2 Riboflavin
Major Dietary Sources:
Major Functions:
Deficiency:

A
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21
Q

Vitamin: B3 Niacin
Major Dietary Sources:
Major Functions:
Deficiency:

A
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22
Q

Vitamin: B5 Pantothenate
Major Dietary Sources:
Major Functions:
Deficiency:

A
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23
Q

Vitamin: B6 Pyridoxine
Major Dietary Sources:
Major Functions:
Deficiency:

A
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24
Q

Vitamin: B12 Cobalamin
Binds to intrinsic factor in the small intestine
Major Dietary Sources:
Major Functions:
Deficiency:

A
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25
Q

Dry and wet ______.

A

BeriBeri

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26
Q

What is the vitamin b12 absorption mechanism? (5)

A
  • Intestinal enteric bacteria synthesise vitamin B 12 .
  • Intrinsic Factor (IF) is a protein secreted by gastric parietal cells, which binds to the dietary vitamin B 12 .
  • The vitamin B 12 /IF complex is resistant to pancreatic proteases and is then absorbed into gastrointestinal enterocyte cells.
  • In enterocytes, vitamin B 12 binds to transcobalamin II (TCII) for delivery from the gastrointestinal tract to the liver.
  • Megaloblastic anaemia (immature red blood cells) occurs if there is decreased vitamin B 12 absorption.
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27
Q

Nucleic Acid & Myelin Derangement: Explain this process.

A

When cobalamin is deficient, the erythrocytes produced are abnormally large because of excessive structural proteins and excessive cytoplasmic growth. Failure to synthesise DNA causes immature nuclei to develop and the plasma membranes are weak and are easily damaged. The friction of the capillary wall exacerbates the fragility of the large and immature erythrocytes.

This loss of erythrocytes causes anaemia and mild jaundice (to be covered later on under Liver). The reticulocyte count is increased and the MCV (check your Blood notes) is increased. The other important symptom of a vitamin B12 deficiency are classed as neurologic changes that occur due to abnormal methylation of myelin protein; and incorporation of abnormal fatty acids into myelin sheaths. Be that as it may, megaloblastic anaemia is the hallmark of a vitamin B12 deficiency.

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28
Q

Vitamin: Folate (foliage = leaves)
Major Dietary Sources:
Major Functions:
Effects of Deficiency:

A
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29
Q

Vitamin: Vitamin C (Ascorbic acid)
Major Dietary Sources:
Major Functions: (3)
Effects of Deficiency:

A
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30
Q

Vitamin: Biotin (vitamin H)
Major Dietary Sources:
Major Functions:
Effects of Deficiency:

A
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31
Q

What causes Spina Bifida – a neural tube defect?

A

Folate (vitamin B-9) deficiency.

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32
Q

What are cofactors & coenzymes? (3)

A
  • Components from the diet
  • coenzymes are derived from vitamins and are organic
  • Cofactors are inorganic ions
33
Q
  • Group transfer reactions require a carrier molecule —–> Absence leads to a _______ ________.
A

nonfunctional enzyme

34
Q
  • Coenzymes & cofactors are tightly associated with…
A

the active site and are linked by non-covalent forces

35
Q
  • Enzymes are not altered after a chemical reaction but coenzymes and cofactors are _____.
A

altered

36
Q

Where does Acetyl-CoA come from?

A

The TCA Cycle

37
Q

Where does Acetyl-CoA come from?

A

The TCA Cycle

38
Q

What is the TCA cycle?

A
39
Q

What are fat-soluble Vitamins?

A
  • Vitamins A, D, E and K are the fat-soluble vitamin
40
Q

How are Fat-soluble Vitamins absorbed? (3)

A
  • Absorption occurs with fat micelles (aggregation of lipids) in the gut
  • They are only absorbed when there is normal fat absorption in the presence of bile acids and lipids
  • Diffusion occurs across brush border membrane because they dissolve in the lipid bilayer
41
Q
  • Vits. A, D, E, and K leave mainly via _____ _____ or hepatic portal vein in smaller amounts
A

lymph vessels

42
Q

How are fat-soluble vitamins stored?

A
  • Vits. A, D, and E —-> Stored in the liver some —-> protection against deficiency because there is a reservoir in liver
43
Q

Vitamin: A Retinol, Pro-A (Beta-carotene)
Dietary Sources:
Major Functions:
Deficiency or Excess:

A
44
Q

Vitamin: D Calcitriol Cholecalciferol (D3)
Dietary Sources:
Major Functions:
Deficiency or Excess:

A
45
Q

Vitamin: E Tocopherol
Dietary Sources:
Major Functions:
Deficiency or Excess:

A
46
Q

Vitamin: K
Dietary Sources:
Major Functions:
Deficiency or Excess:

A
47
Q

Vitamin K Deficiency :

A

Haemorrhages

48
Q

Why is vitamin D essential?

A
  • Essential for normal intestinal Ca2+ absorption
49
Q
  • Rate of Ca2+ absorption very low unless vit. D is present —->______ occur in deficiency
A

rickets

50
Q
  • Rate of Ca2+ absorption very low unless vit. D is present —->______ occur in deficiency
A

rickets

51
Q
  • insufficient Ca2+ in children =
A

abnormal bone growth, softer bones, more flexible —> Bow legged rickets look

52
Q

Does calcium absorption increase or decrease in the elderly?

A
  • Decreased Ca2+ absorption in elderly (especially if bedridden)
  • Diminished sunlight exposure in elderly —-> areas of low natural light, in darker skinned people and people who wear veils = Vit. D deficiencies
53
Q

Does calcium absorption increase or decrease in the elderly?

A
  • Decreased Ca2+ absorption in elderly (especially if bedridden)
  • Diminished sunlight exposure in elderly —-> areas of low natural light, in darker skinned people and people who wear veils = Vit. D deficiencies
54
Q
  • Certain anti acid drugs _____ Ca2+ absorption from gut
A

decrease

55
Q

What is the process of vitamin D biosynthesis?

A

Don’t worry about remembering the structures shown in this slide. What is important to note is that vitamin D is derived from cholesterol. 7-dehydrocholesterol is made in the liver, and the first activation step occurs in the skin, when the skin is exposed to sunlight. This is why vitamin D technically is not a vitamin, as the body can make it. The figure also shows that vitamin D3 can be obtained from the diet, and so in this case it is a vitamin. Vitamin D3 is then hydroxylated first in the liver and then in the kidney. Therefore severe hepatic and kidney disease will prevent vitamin D activation, prevent calcium absorption and cause bone demineralisation. This slide will be covered again when you do Endocrinology towards the end of the year.

56
Q

What are Reactive Oxygen Species (ROS)?

A
  • Are powerful oxidation agents that damage cellular structures and functional molecules
57
Q

What are the Reactive Oxygen Species (ROS) formula?

A
58
Q
  • ROS can be catalysed by _____ ions
  • Antioxidants are ______ agents that react easily with oxidative substances + protect cells e.g B-carotene and Vit. E
A

iron
reducing

59
Q

What are minerals? (2)

A
  • Inorganic ions needed for normal cellular activity.
  • Many are cofactors in biological reactions.
60
Q
  • Macrominerals. Humans need > ____ mg per day.
  • Microminerals (trace elements). We need < ____ mg per day (Does NOT mean low importance!
A

100

61
Q
  • Deficiencies may occur when foods come from one region where the ____ in which the food is grown may be deficient in some minerals.
A

soil

62
Q

What are macrominerals used for? (3)

A
  • Nutrients/electrolytes used for signalling
  • Na+, K+, and Cl- Body fluids + action potentials
  • required for fluid balance and nerve and muscle function
63
Q
  • Na+ & Cl- are ______ in food, so deficiency is impossible
  • Food processing Na+ content in food
  • K+ major _______ ion —> Spinach, fruits —> Loss in diarrhoea
A

common
intracellular

64
Q

Mineral: Calcium
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
65
Q

Mineral: Magnesium
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
66
Q

Mineral: Phosphorous
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
67
Q

Mineral: Sulphur
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
68
Q

Osteoporosis In Spinal Vertebra:

A
69
Q

What are Microminerals? (3)

A
  • are cofactors for enzymes (inorganic ions)
  • Many are present
  • others include copper, fluorine, chromium
70
Q

Iron
* Storage sites =

A
  • Storage sites = liver and haemoglobin
71
Q

How is iron absorbed? (2)

A
  • Absorption is limited as iron tends to form insoluble salts with hydroxides, phosphates, bicarbonate and other anions in the gut
  • Vit. C enhances absorption by forming soluble complexes
72
Q
  • Vit. C = antioxidant so ____ (ferric) is converted to _____ (ferrous)
A

Fe3+ (ferric)
Fe2+ (ferrous)

73
Q
  • Fe2+ is more _______ —-> When iron supplements are prescribed, Vit. C should be taken
  • Iron required for _____ ______ & redox reactions
A

soluble
electron transport

74
Q
  • Fe2+ is more _______ —-> When iron supplements are prescribed, Vit. C should be taken
  • Iron required for _____ ______ & redox reactions
A

soluble
electron transport

75
Q

Mineral: Iodine
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
76
Q

Mineral: Iron (poor intestinal absorption)
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
77
Q

Mineral: Selenium
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
78
Q

Mineral: Zinc
Major Dietary Sources:
Major Functions:
Effects of deficiency:

A
79
Q

Summary
* Vitamins are _______ nutrients with essential metabolic functions.
* Water- & fat-soluble have different functions varying from coenzymes to ________.
* Sources encompass a wide range of foods.
* Vitamins and minerals are associated with _____ signs in deficiency.
* Multiple nutrient are more likely than _______ nutrient deficiencies.

A

organic
antioxidants
clinical
single

MBBCh 2- PHSL2004A (19 decks)

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