BCH 313 Mineral Metabolism Flashcards
1
Q
What are minerals?
A
Inorganic compounds that are required by the body as one of its nutrients, constitute a small portion of body weight
2
Q
Functions of minerals
A
Calcification of bone
Blood coagulation
Neuromuscular irritability
Acid-base equilibrium
Fluid balance
Osmotic regulation
3
Q
Classification of minerals
A
Macrominerals:
Required in excess of 100mg/day
Ca++, P, S, Mg, Cl, Na, K
Microminerals
Required in an amount less than 100mg/day
Fe, Cu, Zn, Mo, I, Fl, Cr, CO, Mn
4
Q
Introduction to calcium
A
- Most abundant mineral found in the human body
- Makes up approx 2% of TBW
- Contains 1-1.5kg of Ca
- 99% of which is present in bone, teeth and 1% in ECF
5
Q
Sources of calcium
A
Good source: milk
calcium content is 100ml in cow’s milk
egg, fish and vegetables are medium sources of calcium
Cereal (wheat, rice) contains only a small amount of
6
Q
Biochemical functions of Ca2+
A
Growth of bone and teeth
Muscle contraction
Blood coagulation
Nerve conduction
Secretion of hormones
Calcium as an intracellular messenger
Activation of enzymes
Action on heart
7
Q
Factors decreasing calcium absorption
A
- Deficiency of vit D inhibits calcium absorption
- Phytates and oxalates form insoluble salts and interfere with absorption
- High content of dietary phosphate: results in the formation of calcium phosphate and prevents Ca uptake
- High pH is unfavorable
- High content of dietary fibre interferes with Ca absorption
8
Q
Factors increasing calcium absorption
A
20-30 % of dietary Ca is absorbed in the duodenum by active process
1. Calciferol is the active form of vitamin D. It increases the blood calcium and promotes absorption
- PTH promotes the production of calciferol and so indirectly promotes an increase in Ca
- Lactose increases the ability of intestinal cells to absorb Ca
- Low pH
- Lysin and arginine increases absorption
9
Q
What are Phytates and Oxalates
A
Oxalates in green leafy vegetables, tea, beans, nuts, beets—can bind to calcium and prevent it from being absorbed. Phytates (phytic acid) in whole grains, seeds, legumes, some nuts—can decrease the absorption of iron, zinc, magnesium, and calcium.
10
Q
Most of the blood Ca is present on_____
A
Plasma
11
Q
Normal range of plasma and urine calcium
A
Plasma calcium: 9-11mg/dl
Urine calcium: 100-250mg/dl
12
Q
Types of Calcium in the plasma
A
- Ionized or free or unbound calcium (50%)
- Bound (40%) to proteins
- Complexed (10%)
12
Q
What are Ionized or free or unbound calcium required for?
A
Maintenance of nerve function
Membrane permeability
Muscle contraction
Hormone secretion
5.5mg/dl
13
Q
What is the amount of bound calcium required?
A
4.5 mg/dl
14
Q
What is the amount of complexed calcium required?
A
1 mg/dl
10% of plasma calcium is complexed with anion which includes, bicarbonate, phosphate, lactate and citrate.
14
Q
What are the hormones that regulate plasma calcium?
A
Calcitrol
PTH
Calcitonin
15
Q
What are the organs that regulate plasma calcium?
A
Gut, bone and kidney
16
Q
Daily requirements for calcium
A
- Children (1-18) 1000mg/day
- Adults 500-800mg daily
-Pregencany 1500/Dahl my
17
Q
Disorders of calcium metabolism includes
A
Hypercalcemia
Increased intake
Increased absorption
Decreased excretion
Malignancy
Hypocalcemia:
Inadequate intake
Impaired absorption
Increased excretion
Magnesium deficiency
18
Q
Human body contains how much phosphorus
A
1kg
19
Q
Body distribution of phosphorus
A
85% of phosphorus is found in bones and teeth in combination with calcium
14% of phosphorus is present in soft tissues as a component of phospholipids, phosphoproteins, nucleic acid and nucleoproteins
1% is found in ECF as inorganic form
20
Q
Sources of phosphorus
A
Food rich in calcium is also rich in phosphorus i.e. milk, cheese, beans l, eggs, cereal, fish and meat
milk is also a good source of phosphorus
21
Q
RDA of phosphorus
A
Children 1250 mg/day
adults 800 mg/day
pregnancy and lactation 1200 mg/day
22
Q
Function of phosphorus
A
- Formation of gums and teeth
- production of high energy phosphate compounds such as ATP, CTP, GTP, creatine phosphate, etc.
- synthesis of nucleosides coenzyme such as NAD and NADP
- DNA in RNA synthesis where phosphodiester linkages form the back bone
- Formation of phosphate Estes such as glucose-6-phosphate phospholipids
6.Formation of phosphoproteins eg. Caesin
- Activation of enzymes by phosphorylation
- Phosphate buffer system in blood the ratio of NaHPO4 : NaH2PO4 in blood is 4:1 at pH if 7.4
23
90% of dietary phosphorus is absorbed in_______
Jejunum
24
Phosphorus absorption increased by
Bile salts
Acidity
PTH and Vitamin B
Calcium
25
Phosphorus absorption decreased by
High Ca:P ratio
Alkalinity
Magnesium
Aluminium
26
Regulation of plasma phosphorus (hormones)
Calcitrol
PTH
Calcitonin
27
Disorders of phosphorus metabolism
Hypophosphatemia:
Decreased intake
Decreased absorption
Increased loss
Hyperphosphatemia:
Increased intestinal absorption
Decreased renal excretion
extra cellular shift of phosphorus
Hemolysis
28
What is the abundance of Mg in the body?
Magnesium is the fourth most abundant cation in the body and
second most prevalent intracellular cation.
Human body contains - 25gm of magnesium
29
BODY DISTRIBUTION of Mg
Human body contains 25g of magnesium
About 60% of which is complexed with
calcium & phosphorous in bones
30% in soft tissues & 1% is in ECF
30
Sources of Magnesium
Cereals, beans, vegetables, potatoes, meat, milk, fruits & fish
31
RDA of magnesium
Adult man
:400 mg/day
Women
: 300 mg/day
During pregnancy & lactation : 450 mg/day
32
Magnesium is required for
Formation of bones & teeth
To maintain neuromuscular irritability
33
Mg acts as a cofactor to
Co-factor:
More than 300 enzymes requires magnesium as a cofactor
Hexokinase ,Glucokinase , Phosphofructokinase, Pyruvatecarboxylase, Peptidases,
Ribonuclease, Adenylate cyclase
34
Neuromuscular function of Mg
Necessary for neuromuscular function, low Mg+2 levels lead to neuromuscular irritability
35
Absorption of Mg
Small intestine & excreted in feces
Calcium, phosphate & alcohol decreases & PTH increases magnesium absorption.
36
Normal plasma levels of Mg
NORMAL PLASMA LEVELS:
Serum magnesium: 1.7 - 3 mg/dl
70% of magnesium exists in free state
30% is protein bound (albumin)
Small amount is complexed with anions like phosphate & citrate.
37
HYPOMAGNESAEMIA
Decrease in serum magnesium levels
<1.7 mg/dl.
CAUSES:
Decreased intake - due to malnutrition
& Decreased absorption - due to malabsorption
% Increased renal loss - due to renal tubular acidosis
SYMPTOMS:
Impaired neuromuscular function
Hypocalcemia - due to decreased PTH secretion
• Tetany, Convulsions & Muscle weakness
38
HYPERMAGNESAEMIA
> 3.5 mg/dl
Increase in serum magnesium
CAUSES:
Uncommon but is occasionally seen in renal failure - decreased excretion
Excess intake orally or parentrally
Hyperparathyroidism
SYMPTOMS:
Depression of the neuromuscular system, lethargy
Hypotension, bradycardia
39
Briefly discuss sodium and it’s body distribution
Sodium is the chief electrolyte. It is found in large concentration in ECF.
Total body content of sodium is 4000 mEq or 1.8 gm/kg
Approximately 50% in bones
40% in ECF
10% in tissues
Sodium is found in the body mainly associated with chlorides as NaCl
40
Sources of Sodium
Table salt (NaCl), salty foods, animal foods, milk, eggs, cereals, carrot, tomato, legumes
41
RDA for sodium
5mg/day
42
Absorption and excretion of Na
From GIT --- Na+ ----K+ pump
<2% is normally sound in faeces and sweat
In diarrhoea, large quantities of sodium are lost in faeces
43
Biochemical functions of Na
1. maintenance of osmotic pressure and water balance
2. Constituents of buffer and involved in the maintenance of acid-base balance
3. it maintains muscle irritability and cell permeability
4. involved in intestinal absorption of glucose, galactose and amino acids
5. necessary for initiating and maintaining a heartbeat
44
Discuss Hyponatremia it’s causes and symptoms
HYPONATREMIA:
Decrease in serum sodium level <130 mEq/l
CAUSES:
Vomiting & Diarrhea
Addison's disease (adrenal insufficiency)
Renal tubular acidosis (reabsorption is defective)
Chronic renal failure & nephrotic syndrome
Congestive cardiac failure
Edema
SYMPTOMS OF HYPONATREMIA:
Drop in blood pressure
Lethergy, Confusion
Tremors & coma
45
Describe Hyponatremia due to water retention
Retention of water dilutes the constituents of extracellular space causing
hyponatremia, e.g. heart failure, liver diseases, nephrotic syndrome, renal failure, increased ADH secretion.
46
Discuss HYPERNATREMIA, it’s causes and symptoms
HYPERNATREMIA:
Increase in serum sodium concentration > 145 mEq/l
CAUSES:
Cushing's disease - hyper activity of adrenal cortex
In pregnancy, steroid hormones cause sodium retention in body
In dehydration, water is predominantly lost, blood volume is decreased
with increased concentration of sodium.
Symptoms include: Increase in blood volume and pressure, dry mucous membrane. fever, thirst, restlessness e.t.c
47
48
Sources of K
Sources: Vegetables, fruits, whole grains, meat, milk, legumes, coconut water.
49
RDA of K
2 to 5 gm daily
50
Discuss K
Potassium is the major intracellular cation.
About 98% of potassium is in cells, only 2% is in ECF.
Total body potassium in an adult male is about 50 mEq/kg of
body weight as most of the body's potassium is found in muscles.
51
ABSORPTION & EXCRETION of K
Potassium is readily absorbed by passive diffusion from GIT.
The amount of potassium in the body depends on the balance between potassium
intake and output.
Under the normal conditions loss of potassium through gastrointestinal tract and skin is very small
The major means of potassium excretion is by the kidney.
Potassium output occurs through three primary routes; the GIT, the skin & the
52
FUNCTIONS of K
The depolarization & contraction of heart require potassium.
During transmission of nerve impulses, there is sodium influx and potassium
efflux; with depolarization.
After the nerve transmission, these changes are reversed.
The intracellular concentration gradient is maintained by the Nat-K+
ATPase pump.
The relative concentration of intracellular to extracellular potassium determines the cellular membrane potential.
Potassium influences the muscular activity.
Certain enzymes such as pyruvate kinase require K+ as cofactor.
Involved in neuromuscular irritability and nerve conduction process.
Potassium is required for proper biosynthesis of proteins by ribosomes.
- Normal serum potassium concentration: 3.5 to 5 mEq/L
53
Hypokalemia
Low plasma K levels
< 3 mmol/L
54
Hyperkalemia
Elevelated plasma K levels
< 5 mmol/L
55
Discuss Chlorine
Chlorine is the major anion in the ECF
In the normal adult body, chloride is about 30mEq/kg of body weight.
Approximately, 88% of the chloride is found in the ECF, 12% in the ICF.
56
Sources of Cl
Table salt, leafy vegetables, eggs, milk.
57
RDA of Cl
2 to 5 gm/day.
58
FUNCTIONS of Cl
In sodium chloride, chloride is essential for water balance,
regulation of osmotic pressure and acid-base balance.
> Chloride is necessary for the formation of HCL by the gastric
mucosa and for the activation of enzyme amylase.
It is involved in the chloride shift
59
ABSORPTION AND EXCRETION of Cl
Rapidly and almost totally absorbed in the gastrointestinal tract.
Under normal conditions chloride excretion occurs in three ways;
the GIT, the skin &
urinary tract.
Chloride is excreted, mostly as sodium chloride & chiefly by way of
the kidney.
About 2% is eliminated through the faeces.
60
What much Plasma chloride is the in the body?
95 to 105 mEq/L
61
HYPOCHLOREMIA
It is caused by gastrointestinal & renal loss chloride.
Gastrointestinal loss occurs by vomiting because of loss of bicarbonate.
Renal loss occurs in Addison's disease and salt losing nephropathy.
62
HYPERCHLOREMIA
An increase in serum chloride level may be due to
Dehydration,
Cushing's syndrome,
Hyperaldosteronism,
Severe diarrhoea (loss of bicarbonate)
Respiratory acidosis
63
Sources of Zinc
Meat, liver, dairy products, legumes, pulses, nuts, beans, spinach
64
RDA of Zn
Adults- 15mg daily
65
Discuss Zinc
Zinc is a micro mineral.
Total body content of zinc: 2 gm.
- Prostate gland is very rich in Zn.
n is mainly an intracellular element.
60% of zine is present in skeletal muscle and 30% in bones.
It is also present in liver, brain & skin.
66
ABSORPTION of Zn
From duodenum.
- It requires a transport protein - matallo-thionein.
Phytates, Cat, copper & iron decreases zinc absorption.
Small peptides & amino acids promotes zinc absorption
67
Metalloenzymes of Zn
Zine is component of many metalloenzymes.
Carbonic anhydrase
Alkaline phosphatase
Alcohol dehydrogenase
Lactate dehydrogenase
Carboxy-peptidase
Superoxidase dismutase (cytosol) - anti-oxidant
DNA and RNA polymerases
68
BIOCHEMICAL FUNCTIONS of Zn
Zn is necessary for
Storage & secretion of insulin
To maintain normal levels of vitamin A.
Synthesis of RBP.
Proper reproduction, growth & division of cells
Important element in wound healing.
Stabilizes protein, nucleic acids & membrane structure.
Gusten, a zinc containing protein of the saliva, is important for
taste sensation
69
Normal plasma level of Zn
100 mg/dl
70
Causes and symptoms of Zn deficiency
Causes:
1. Dietary deficiency
2. Malabsorption
3. Chronic alcoholism
Symptoms:
1. Impaired spermatogenesis
2. Growth failure
3. Loss of taste sensation
4. Impaired wound healing
5. Skin lesions such as dermatitis
71
Discuss Zn toxicity
Zinc toxicity is rare.
Seen in welders due to inhalation of zinc oxide fumes
Clinical features:
1. Nausea
2. Gastric ulcer
3. Pancreatitis
4. Diarrhea
5. Anemia
6. Excessive salivation
72
Sourcs of iron
green leafy veg
pulses
legumes
liver and meat
cereals
Egg
73
RDA of Fe
Adults- 10 to 20mg per day
Pregnancy- 40mg per day
74
Describe the site, forms and efficiency of Fe absorption
Site: small intestine
Form: Haem and non-haem
Efficiency: 10% of Fe is absorbed by the small intestine
75
Factors affecting Fe absorption
Increasing
Ferrous from
Ascorbic acid
Cysteine
HCl
Decreasing
Phytates and phosphates
Antacid, achlorhydria
GI diseases
76
Functions of Fe Heme compounds
Haem compounds
Haemoglobin
Myoglobin
Cytochrome
Calactase
77
Functions of Non-haem compounds
Non-haem compounds
Succinate dehydrogenase
Xanthine oxidase
Iron sulfur proteins
78
Causes of iron deficiency
Decreased intake of iron - Malnutrition
Decreased absorption of iron - Achlorhydria and chronic diarrhea
Increased loss of Iron - Bleeding,
hookworm infestation
Increased iron requirement- Pregnancy,
infancy
79
Lab findings of Fe deficiency
**Hematological findings**
Decreased hemoglobin
Microcytic hypochromic anemia
**Biochemical findings**
Decreased serum iron
Increased serum total iron binding capacity
Decreased plasma ferritin
80
Discuss Fe overload
Haemosiderosis
- Increase in Fe stores as haemosiderin
- Without associated tissue injury
Haemochromatosis
- excessive deposition of Fe in the tissue
- Associated with tissue injury
