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Digestive > Micronutrients > Flashcards

Micronutrients Flashcards

(54 cards)

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1
Q

Requirements of normal erythopoiesis

A

Iron
Folate
B12

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2
Q

Low B12 symptoms

A

Tingling in extremities
Concentrations problems
Macrocytosis

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3
Q

Reasons for low B12

A

Diet
Malabsorption
Abnormal acid, IF, pancreatic secretions and ileal absorptive function

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4
Q

Pernicious anaemia

A

Autoimmune disorder where individual develops antibodies against intrinsic factor and/or parietal cells causing decreased IF. Not enough to bind B12 so it can’t be absorbed in the terminal ileum.

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5
Q

B12 malabsorption due to small intestinal issues

A

B12 binds IF normally but abnormal terminal ileum i.e. through surgical removal or Crohns inflammation means it is not absorbed in the small intestine

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6
Q

Pernicious anaemia diagnosis

A

Antibodies to parietal cells of IF detected in blood test

Gastric biopsies can provide evidence of autoimmune gastritis, low acid output or other autoimmune diseases

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7
Q

Pernicious anaemia treatment

A

High doses of B12 required every week for 4-6 months then every 3 months
Response to treatment must be monitored to ensure B12 levels are high, haemoglobin and reticulocytes are responding and neurological symptoms have abated

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8
Q

Loss of specialised receptors on terminal ileum leads to:

A

Failure to absorb B12
Failure to reabsorb bile salts
Bile salts lost through colon causing irritation and secretory diarrhoea. Decreased bile salts means less fat emulsification and impaired fat absorption.

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9
Q

Mechanism by which partial gastrectomy can lead to low B12

A

No antrum = no G cells = no gastrin
No gastrin = less gastric acid, less B12 released from food
No pylorus = bile reflux = stomach atrophy
Atrophy = decreased parietal cells = decreased IF therefore less B12 absoprtion

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10
Q

Low B12 in celiac disease

A

Loss of small intestine villi therefore loss of endocrine cells that secrete secretin and CCK involved in pancreatic stimulation

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11
Q

Schilling test

A

Radioisotope test used to determine if patient has lack of IF
Rarely used now - time consuming, involves radioisotopes and results can be difficult to interpret

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12
Q

B12 is also known as:

A

Cobalamin

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13
Q

Steps of vitamin B12 absorption

A

1) B12 in food released during peptic digestion
2) Parietal cells secrete haptocorrin
3) Parietal cells secrete IF which binds released B12
4) B12-IF uptaken by brush border receptors in small intestine
5) B12-IF cleaved. IF taken back into enterocyte. 80% B12 binds haptocorrin, 20% B12 binds holotranscobalamin
6) B12-haptocorrin goes to liver, B12-holotranscobalamin taken up by all cells for DNA synthesis
7) Pancreatic proteases degrade B12-haptocorrin (currently stored in liver)

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14
Q

Megaloblastic anaemia

A

Slightly larger and irregularly shaped blood cells than normal

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15
Q

Water soluble vitamins

A

Vitamin C
All the Bs
Folic acid
Biotin

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16
Q

Fat soluble vitamins

A

Vitamin A
Vitamin D
Vitamin E
Vitamin K

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17
Q

Absorption of water soluble vitamins

A

Partly digested by mucosal hydrolyses
Absorbed into mucosal cell and transported to hepatic portal vein
Stored in liver

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18
Q

Absorption of fat soluble vitamins

A

Form minor components of micelles
Uptake into mucosal cells
Export into lymphatics and then plasma as chylomicrons
Stored in body lipids

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19
Q

Factors affecting bioavaliability

A 
Efficiency of digestion
Nutrient intake
Foods consumed simultaneously
Food preparation method
Synthetic or natural nutrient
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20
Q

Vitamin B1

A

Thiamin

Metabolism of energy yielding

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21
Q

Vitamin B2

A

Riboflavin

Intermediates via redox reactions

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22
Q

Vitamin B3

23
Q

Vitamin B6

Study These Flashcards
A

Pyridoxine

Transamination

24
Q

Vitamin B12

Study These Flashcards
A

Cobalamin

Transmethylation

25
Vitamin B9
Folate/folic acid
26
Vitamin B5
Pantothenic acid | Constituent of coenzyme A
27
Vitamin B7
Biotin | Carboxylation using coenzyme A
28
Sources of thiamin
Whole grain, fortified and enriched products | Pork
29
Thiamin defincieny
Wet (heart) and dry (neuro) beriberi Wernickes encephalopathy Caused by alcoholism
30
Folate deficiency
Macrocytic anaemia Poor growth and neural tube defects Caused by alcohol intake, pregnancy, some drugs
31
Sources of folate
Leafy greens | Legumes, seeds, fortified cereals
32
Sources of vitamin D
Oily fish Raw mushrooms Eggs
33
Vitamin D deficiency
Rickets | Osteomalacia
34
Vitamin D absorption
UV light from sun + precursor in liver made from cholesterol makes previtamin D3 + foods = Vitamin D3 (inactive) In liver, vitamin D3 hydroylated In kidneys, hydroxylated again to active form
35
Folate absorption
Folate occurs as polyglutamate in food. When digested, glutamate breaks off and CH3 added. Folate absorbed and delivered to cells
36
Seven major minerals
``` Calcium Phosphorous Potassium Sulfur Sodium Chloride Magnesium ```
37
Iron homeostasis
1 g stored in body 300 mg in myoglobin and respiratory enzymes 2.5 g in RBCs 2 mg taken in from diet 1 - 2 mg lost in feces 20 - 25 mg recycled daily for RBC formation
38
Iron recycling
Haemoglobin containing iron in RBCs carries oxygen Bleeding = loss Liver and spleen dismantle RBCs, package iron into transferrin and store excess iron in ferritin Sweat, skin and urine = loss Transferrin carries iron in blood Some delivered to myoglobin of muscle cells Bone marrow incorporates iron into haemoglobin of RBCs and stored excess iron in ferritin
39
Iron absoprtion
Iron in food Mucosal cells in the intestine (duodenum) store excess iron in mucosal ferritin If the body needs iron, mucosal ferritin releases iron to mucosal transferrin which hands iron to another transferrin that travels through the blood to the rest of the body If the body doesn't need iron, it's excreted in shed intestinal cells
40
Heme iron
25% absorbed Haemoglobin and myoglobin from animal products 5 - 10% dietary iron
41
Non-heme iron
Vegetable, pulses, supplements | 17% absorbed
42
Absorption of heme iron
Absorbed into mucosal cell as intact porphyrin complex | Affected by iron deficiency but not composition of meal and gastrointestinal secretions
43
Absorption of non-heme iron
Must be present in duodenum in soluble form In stomach, ionised by gastric juice and neutralised Ferric iron precipitated and is uptaken at the brush border into the cell by membrane iron binding protein Affected by meal composition
44
Vitamin C is important for iron absorption because:
It is a dietary reducing agent. DMT1 (iron membrane receptor) can only uptake Fe+2 so Fe+3 from non-animal products needs to be reduced
45
Haem oxygenase
Enzyme that cleaves haemoglobin from iron in animal products freeing up Fe+2 for storage
46
Hepcidin protein
Peptide hormone from liver that regulates iron
47
Haemochromatosis
Chronic disorder involving excess absorption and inappropriate storage of iron
48
Factors affecting heme iron absorption
Iron status of subjects | Heme iron present in meat
49
Factors affecting non-heme iron absorption
Iron status of subjects Amount of bioavailable non-heme iron Balance between dietary factors enhancing and inhibiting iron absorption
50
Factors enhancing iron absorption
Vitamin C Meat and fish (meat factor protein) Organic acids
51
Factors inhibiting iron absorption
``` Phylates Iron binding polyphenols Dietary fibre Tannins Calcium ```
52
Factors decreasing iron absorption
Intestinal motility | Steatorrhoea
53
3 stages of iron deficiency
1) Depleted storage iron - low serum ferritin 2) Iron restricted erythopoiesis - low serum transferrin saturation 3) Iron deficiency anaemia - low haemoglobin
54
Importance of iron
Myelination Neuronal growth and differentiation Neurotransmitter regulation Blood brain barrier closes off to iron at about 2 years old so intake critical in iron deficient populations before this age

Digestive (9 decks)

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