PHAROS UNIVERSITY FACULTY OF ALLIED MEDICAL SCIENCE

BIOCHEMISTRY 1 (MGBC-101)

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: