Basics of proteins Dr Analhaq Shaikh
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Transcript of Basics of proteins Dr Analhaq Shaikh
GOOD MORNING
Dr. SHAIKH ANALHAQ A.1ST YEAR
POSTGRADUATEDEPT. OF
ORTHODONTICS
BASICS OF PROTEINS
Proteins are polymers of L-α-amino acids, which are bonded by peptide bonds.
Proteins are made of 20 amino acids linked by peptide bonds
Polypeptide backbone is the repeating sequence of the N-C-C-N-C-C… in the peptide bond
The side chain or R group is not part of the backbone or the peptide bond
Amino acid: Basic unit of protein
COO-NH3+ C
R
HAmino group
Carboxylic acid group
An amino acid
20 Amino acidsGlycine
(G)Nonpolar,hydrophobic
Polar, uncharged
Polar, charged
Proteins play key roles in a living system Three examples of
protein functions Catalysis:
Almost all chemical reactions in a living cell are catalyzed by protein enzymes.
Transport:Some proteins transports various substances, such as oxygen, ions, and so on.
Information transfer:For example, hormones.
Alcohol dehydrogenase oxidizes alcohols to aldehydes or ketones
Alcohol dehydrogenase oxidizes alcohols to aldehydes or ketones
Haemoglobin carries oxygen
Insulin controls the amount of sugar in the blood
General properties of proteinTaste- Tasteless. Hydrolytic or derived
products are bitter.Odor- odorless. On heat drying –burning
odor.
Viscosity- It depends upon the pH, concentration, size and shape of the molecule.
Shape- There is a wide variation In the protein shape. It may be globular, oval, fibrous or elongated .
Elemental composition of protein
5 major elements Carbon- 50-55%
Hydrogen- 6-7.3%
Oxygen- 19-24%
Nitrogen- 13-19%
Sulfur- 0-4%
Classification of proteinsBased on chemical composition:Simple proteins: Contain amino
acids(E.g: Serum albumin, serum globulins, keratin etc)
Conjugated proteins or compound proteins: Conjugated groups + amino acids (E.g.: Egg albumin, hemoglobin, immunoglobulins etc.)
Derived proteins: Partial hydrolysis of simple or compound proteins.(E.g: Gelatin, proteoses & peptones etc.)
Based on shape:Globular proteins: Spherical or
oval E.g.: Hemoglobin, Albumin, and
Enzymes.Fibrous proteins: Elongated and
fiber-like structures. E.g.: Keratin, Collagen etc.
Based on biological function: Catalytic proteins E.g.: Hexokinase, Amylase etc. Defence proteins E.g.: Immunoglobulins as
antibodies Structural proteins E.g.: Keratin, Collagen
Hormonal proteins E.g.: Growth hormone, Insulin etc. Contractile proteins E.g.: Actin, Myosin and
Tropomyosin . Transport proteins E.g.: Serum albumin Storage proteins E.g.: Ferritin Visual proteins E.g.: Rhodopsin & Iodopsin
Membrane proteins E.g.: Sodium potassium pump Hemostatic proteins E.g.: Fibrinogen, Prothrombin. Buffer proteins E.g.: Plasma proteins, Hemoglobin Respiratory proteins E.g.: Hemoglobin, Myoglobin Receptor proteins E.g.: Insulin receptors, Glucagon
receptors, Steroid hormone receptors etc.
Protein structure: Made up of one or more polypeptide
chains.
Proteins with a single polypeptide chain- monomeric proteins.
Proteins with more than one – oligomeric proteins.
Each polypeptide chain in an oligomeric protein is called subunit or monomer.
Examples for oligomeric proteins are hemoglobin, lactate dehydrogenase.
Structural organisation of proteins
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Quaternary structure
Hierarchical nature of protein structure
Primary structure (Amino acid sequence) ↓Secondary structure (α-helix, β-sheet) ↓Tertiary structure (Three-dimensional
structure formed by assembly of secondary structures)
↓Quaternary structure (Structure
formed by more than one polypeptide chains)
Primary Structure
It is the amino acid sequence (1940) that “exclusively” determines the 3D structure of a protein
20 amino acids – modifications do occur post translationally
Secondary structure
Regular patterns of hydrogen bonding in proteins result in two patterns that emerge in nearly every protein structure known: the -helix and the-sheet.
The location of direction of these periodic, repeating structures is known as the secondary structure of the protein.
α-helix β-sheet
Secondary structures, α-helix and β-sheet, have regular hydrogen-bonding patterns.
α- helix is the most common secondary structure found in proteins.
Most commonly seen in globular protein.
β- pleated sheet is an extended structure.
β- pleated structure is stsbilized by hydrogen bonding.
Tertiary structure Tertiary structure of protein refer to
the further folding of secondary structure of polypeptide chain giving the compact three dimensional conformation.
Tertiary structure results in the orientation of hydrophobic side chain towards the water free interior and the hydrophilic polar groups towards the surface of the protein.
Quaternary structureProtein having more than one
polypeptide chain show more level of higher structure called the quaternary structure.
Quaternary structure refer to the spatial arrangement of the subunits of an oligomeric protein.
Denaturation of proteins The process of disorganization of
native protein structure is called Denaturation.
Denaturation involves the loss of secondary , tertiary and quaternary structures without breaking the primary structure.
Denaturation involves a changes in physical, chemical and biological properties of protein .
Decreases the solubility, increase the precipitiability and increase the viscosity of proteins.
Protein Energy Malnutrition (PEM)
Deficiency disease caused in the infants due to ‘Food Gap’ between the intake and requirement.
It affects children under 5 mostly belonging to the poor underprivileged communities.
PEM is particularly serious during the post-weaning stage and is often associated with infection.
TypesMarasmus
Kwashiorkor
Marasmus Kwashiorkor
MarasmusIt is an overall deficit of food
intake which results from near starvation from with deficiency of protein and non-protein nutrients.
Clinical FeaturesAge – 1 and 3 years
Weight loss
Wasting of subcutaneous fat and muscle
Head of the child seems larger than the body
Very little hair
Ribs of the child are visible
Adomen of the child appears extended and protruding
Child suffers and is more prone to infections
Skin has some pigmentation
KwashiorkorKwashiorkor is another form of
PEM, is it uncommon in the children under one year of age.
It is associated with primary dietary protein deficiency.
Clinical Feature Three essential features of
kwashiorkor are Growth failure
Oedema
Mental changes
Oral ManifestationTongue- Bright reddening, loss of papillae. In kwashiorkor – odema of tongue and
may develop scalloping around lateral margins.
Xerostomia- Mouth becomes dry.
Jaws- Decreased overall growth of jaws.
Teeth- Delayed eruption
Periodontal membrane – Gingiva and periodontal ligament membrane exhibit varying degree of degenration.
Maxillofacial gangrene- Severe infection, spread in mouth from necrotizing gingivitis.
Extra oral- Bilateral angular cheilosis, fissuring of lips.
AmylodosisIt is also called as amyloid
disease.
It is deposition of amyloid in the tissue.
Type A amyloid is a fibrillar protein of unknown origin.
Clinical FeatureCommonly affected kidney,
heart, G.I tract, liver, respiratory tract, skin, eyes, nerves and spleen.
Fatigue, weakness, ankle edema, weight loss.
Purpuric spot
Oral ManifestationThere are difficulty in• Chewing • Swallowing• Speech
Tongue – Enlarged • Mobility of tongue decreased • Presence of yellowish nodules• Impression from the teeth also visible
Gingiva-• Infiltrated• Bluish color• Spongy• Hypertrophied
Salivary gland-Xerostomia may result from
salivary gland involvement.
Bone morphogenic proteinBone morphogenetic proteins form a unique group
of proteins within the transforming growth factor superfamily of genes and have a vital role in the regulation in the bone induction and maintenance.
The activity of bone morphogenetic proteins was first identified in the 1960s, but the proteins responsible for bone induction were unknown until the purification and cloning of human bone morphogenetic proteins in the 1980s, because of their osteoinductive potential.
Bonemorphogenetic proteins have gained a lot of interest as therapeutic agents for treating periodontal defects.
From the times of Hippocrates it has been known that bone has considerable potential for regeneration and repair.
Several decades ago Urist reported the discovery that BMPs induce cartilage, bone formation when implanted intramuscularly in a rodent model.
Bone morphogenetic proteins play essential role in regulation of bone formation and repair.
BMPs are frequently referred to as growth factors, they are now regarded as differentiation factors, because BMPs are involved in morphogenesis and organogenesis.
Periodontal tissue regeneration entails the induction of periodontal ligament, cementum, and alveolar bone.
several studies have shown significant regeneration of the periodontal tissues with the use of BMP.
References Nutrition Science by B Srilakshmi Nutrition and Child Care : A practical
guide by Shanti Ghosh Textbook of Human Nutrition by
Mahtab S. Bamji, N Pralhad Rao and Vinodini Reddy.
Textbook of Biochemistry by Prasad R.M. 2nd edition.
Textbook of Biochemistry by Satyanarayana.
Textbook of Medical Biochemistry by S.S Randhawa.
Textbook of Oral Medicine by Anil Ghoms.
Urist MR. Bone: Formation by autoinduction. Science 1965;150:893‑9.
Urist MR, Strates. Bone Morphogenetic proteins. J Dent Res 1971;50:S1392‑406.
Subramaniam M Rao. Bone Morphogenetic Proteins: Periodontal Regeneration, 2014, November 21 IP: 117.208.128.69.
Jaebum L, Andreas S, Cristiano S, Wikesjo ME. Periodontal Regeneration: Focus on Growth and Differentiation Factors. Dent Clin N Am 2010;54:93‑111.
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