PHAROS UNIVERSITY FACULTY OF ALLIED MEDICAL SCIENCE BIOCHEMISTRY 1 (MLBC-201) Dr. Dr Hewaida Fadel & Dr. Tarek El Sewedy Department of Medical Laboratory Technology Faculty of Allied Medical Sciences
Feb 24, 2016
PHAROS UNIVERSITY FACULTY OF ALLIED MEDICAL SCIENCE
BIOCHEMISTRY 1 (MLBC-201)
Dr. Dr Hewaida Fadel & Dr. Tarek El Sewedy
Department of Medical Laboratory Technology
Faculty of Allied Medical Sciences
Lecture22/12/2013
Hormones , Vitamins and mineralsStructure and function
By the end of this lecture, students will learn:
1. Recognize The structure, function and classification of hormones, Biomedical importance of hormones and pathophysiology conditions related to disturbance in the hormonal levels.
2. Learn major functions and diseases related with vitamins and minerals.
Intended Learning Outcomes
Lecture Content
• Hormone classification and types.
• Hormone structure and functions.
• Vitamins
• Minerals
• Deseases related to vitamin deficiency.
The endocrine system• The survival of multicellular organisms depends on
their ability to adapt to a constantly changing environment.
• Intercellular communication mechanisms are necessary requirements for this adaptation.
• The nervous system and the endocrine system provide this intercellular, organism-wide communication.
• The nervous system was originally viewed as providing a fixed communication system, whereas the endocrine system supplies hormones, which are mobile messages.
Hormones• The word “hormone” is derived from a Greek term that means
to arouse to activity.
• As classically defined:
o A hormone is a substance that is synthesized in one organ
and transported by the circulatory system to act on another
distant tissue (endocrine action).
• However, this original description is too restrictive because
hormones can act also on adjacent cells (paracrine action) and
on the cell in which they were synthesized (autocrine action)
without entering the systemic circulation
• There are about 200 types of differentiated cells in humans.
• Only a few produce hormones, but virtually all of the 75 trillion cells in a human are targets of one or more of the over 50 known hormones.
• The presence of a specific receptor defines the target cells for a given hormone.
• Receptors are proteins that bind specific hormones
and generate an intracellular signal.• Hormones work by binding to receptors on or within
the cell and changing the activity of that particular cell).
General features of hormone classesGroup I Group II
Types Steroids Polypeptides and
proteinsSolubility Lipophilic Hydrophilic
Transport proteins
Yes No
Plasma Half-life
Long (hours to days) Short (minutes)
Receptor Intracellular Plasma membrane
Hormones classification
• Hormones can be classified according to:
1. Chemical structure.
2. Solubility properties.
3. Location of receptors.
4. Nature of the signal used to mediate hormonal
action.
1. Structural Classifications
• Under this method of classification, there are four groups:
1. steroid hormones.
2. peptides derived.
3. amino acid derived.
4. fatty acid derived.
1. Steroid Hormones• Steroid hormones are derived from cholesterol
The sex hormones (androgens, estrogens and progesterone) and
hormones produced in the adrenal glands.
Cholesterol derived Hormones
2. Amino acid derivative hormones
• They are derived from tyrosine and tryptophan.
• There are two types of tyrosine derived hormones:
• 1. Thyroid hormones (T3 and T4): regulates the development of organs and metabolism
• 2. Catecholamines (Norepinephrine and epinephrine )
stress hormones. Both increase heart rate, dilate blood vessels and cause the release of glucose during times of stress.
Thyroxin T4 T3
Tyrosin Derived hormones
Thyroxin Pathophysiology
• Goiter (enlargement of thyroid gland iodine deficiency).
• Hyperthyroidism (Graves disease); increase apetite, rapid heart rate.
• Hypothyroidism; (hypertension, slow heart rate, sleepiness, sensitivity to cold, dry skin).
Tryptophan derived hormones• Tryptophan is a precursor to serotonin and melatonin.• 1. Serotonin is mostly found in our gastro-intestinal
tract and regulates movement in our intestines.• Serotonin is associated with mood and low levels often
result in depression.• Serotonin is also part of appetite and can make you
sleepy.• 2. Melatonin signal forms part of the system that
regulates the sleep-wake cycle by chemically causing drowsiness and lowering the body temperature
3. Peptide derived hormones
• These are hormones derived from polypeptides.
They need to be activated
1. Insulin (Hetero-dimeric polypeptide)
Decrease blood glucose level. Promote the entry of glucose and amino acids into
cells. Promote the utilization of glucose. Has anabolic effect. Stimulate protein synthesis. Stimulate the cell replication.
Pathophysiology
Diabetes mellitus
Biological importance
• Single polypeptide chain
It opposes the insulin action
Pathophysiology
Diabetes mellitus
Biological importance
2.Glucagon
4. Fatty Acid derived hormones• Hormones that are arrived from fatty acids are
called eicosanoids.• hey are synthesized from a 20-carbon amino acid
called arachidonic acid.• they are produced and secreted by nearly every cell in
the body instead of just one gland. • Eicosanoids have various important roles in the body
including inflammation, blood pressure and blood clotting.
• Prostaglandins are classified as eicosanoids.
2. Classification according to solubility
Lipid Soluble vs Water Soluble Hormones
• Lipid soluble hormones are able to pass right through the target
cell’s membrane.
• They work by binding to receptors inside the cell. This binding
activates certain proteins, which then binds to a portion of DNA
inside the cell’s nucleus causing genes to turn enzyme activity on
or off, which alters the activity of the target cell.
• Steroid derived hormones are lipid soluble.
• Water soluble hormones, act indirectly on target cells. Since the
cell membrane has a lipid bi-layer, it is hydrophobic, or water
fearing. This simply means that anything that is water soluble is
not getting through. Unlike lipid soluble hormones,
• water soluble hormones have to bind to receptors on the surface
of the target cell.
• Once the hormone is bound to the receptor, enzyme activity
inside the cell is altered. Depending on the hormone, enzyme
activity is increased or decreased.
• Water soluble hormones include those that are derived from
amino acids and polypeptide hormones.
2. Classification according to solubilityLipid Soluble vs Water Soluble Hormones
Vitamins & Minerals
BIOMEDICAL IMPORTANCE OF VITAMINSA. Lipid Soluble vitamins
• Vitamins are defined as a group of organic nutrients required in small
quantities for a variety of biochemical functions and which, generally, cannot
be synthesized by the body and must therefore be supplied in the diet.
• However, vitamin D, which can be made in the skin after exposure to sunlight,
and niacin, which can be formed from the essential amino acid tryptophan, do
not strictly conform to this definition.
• The lipid-soluble vitamins are apolar hydrophobic compounds that can only be
absorbed efficiently when there is normal fat absorption. They are transported
in the blood, like any other apolar lipid, in lipoproteins or attached to specific
binding proteins.
• Lipid-soluble Vitamins have diverse functions:
• vitamin A, vision;
• vitamin D, calcium and phosphate metabolism;
• vitamin E, antioxidant;
• vitamin K, blood clotting.
Biological importance of lipid-soluble
vitamins
• dietary inadequacy or conditions affecting the digestion and
absorption of the lipid-soluble vitamins can all lead to
deficiency syndromes, including:
• Night blindness and xerophthalmia (vitamin A);
• Rickets in young children and osteomalacia in adults
(vitamin D);
• Neurologic disorders and anemia of the newborn (vitamin E);
• Hemorrhage of the newborn (vitamin K).
• Vitamin A as well as vitamin E, are antioxidants and have
possible roles in atherosclerosis and cancer prevention.
• Toxicity can result from excessive intake of vitamins A and D.
B. Water-Soluble vitamins• Water-soluble vitamins comprise the B complex and vitamin C and function
as enzyme cofactors.
• Folic acid acts as a carrier of one-carbon units.
• Deficiency of a single vitamin of the B complex is rare, since poor diets are
most often associated with multiple deficiency states. Nevertheless,
specific syndromes are characteristic of deficiencies of individual vitamins:
1. Beriberi (thiamin);
2. Glossitis (riboflavin);
3. Pellagra (niacin);
4. Peripheral neuritis (pyridoxine);
5. Megaloblastic anemia and pernicious anemia (vitamin B12);
6. Megaloblastic anemia (folic acid).
7. Vitamin C deficiency leads to scurvy
Night Blindness and
Xerophthalmia (Retinol Vit A)
Rickets (Vit D)
Beriberi (Thiamin ,
B1)
Pellagra (Niacin)
Anemia (Vit B, Folic acid and B12)
Dermatitis (Biotin Vit H)
Scurvy (Ascorbic Acid, Vit C)
Inorganic Minerals• Inorganic minerals must be provided in the diet. When the intake
is insufficient, deficiency symptoms may arise, eg, anemia (iron), goiter (iodine).
• If present in excess as with selenium, toxicity symptoms may occur.
• For any nutrient, particularly minerals and vitamins, there is a range of intakes between that which is clearly inadequate, leading to clinical deficiency disease, and that which is so much in excess of the body’s metabolic capacity that there may be signs of toxicity.
• Between these two extremes is a level of intake that is adequate for normal health and the maintenance of metabolic integrity.
Assignments
• Any student who did not deliver an assignment should deliver an assignment on the “Physiological importance of vitamins” before 24 /12/2013 or will not be accepted anymore.
*Study Question*Write the actions of insulin and glucagon.
*Mention the difference between Water soluble and insoluble hormones.
Principles of Biochemistry, Donald J. Voet, Judith G. Voet, Charlotte W. pratt; Willey, 3rd ed.
* Suggested readings: