Protein structure
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This document provides information about amino acids, protein structure, and hemoglobin. It discusses: 1. The primary, secondary, tertiary, and quaternary levels of protein structure. The alpha helix and beta pleated sheet are described as examples of secondary structure. 2. Specific amino acids like glycine and tryptophan, as well as collagen structure which contains high amounts of glycine. 3. The roles of vitamins like vitamin C in collagen formation and diseases like scurvy that can result from deficiencies. 4. Additional biomolecules like glutathione and albumin, describing their structures, functions, and relationship to diseases. 5. The structure of hemoglobin including
Protein structure
- 1. For B.Sc Optometry Students Amino acids / Proteins Amino acids / Classification of amino acids Proteins / Structure of amino acids / Collagen structure / Glutathione / Albumin / Hemoglobin Basics in transport of gases / Abnormalities
- 2. Amino Acid – General Structure
- 3. D and L amino acid
- 4. Dissociation of Amino acid
- 5. Titration of Amino acid
- 6. Protein Structure 1. Primary Structure 2. Secondary Structure 3. Tertiary Structure 4. Quaternary Structure
- 7. Primary structure The simplest level of protein structure, primary structure, is simply the sequence of amino acids in a polypeptide chain
- 10. In an α helix, 1. the carbonyl (C=O) of one amino acid is hydrogen bonded to the amino H (N-H) of an amino acid that is four down the chain. 2. the carbonyl of amino acid 1 would form a hydrogen bond to the N-H of amino acid 5 3. each turn of the helix containing 3.6 amino acids. 4. R groups of the amino acids stick outward from the α helix
- 11. In a β pleated sheet • two or more segments of a polypeptide chain line up next to each other, forming a sheet-like structure held together by hydrogen bonds. • The hydrogen bonds form between carbonyl and amino groups of backbone, while the R groups extend above and below the plane of the sheet.
- 16. Glycine 1. the smallest/Simplest of the amino acids. 2. Aliphatic and Non-polar 3. Ambivalent, meaning that it can be inside or outside of the protein molecule. 4. An aqueous solution at or near neutral pH, glycine will exist predominantly as the zwitterion 5. Collagen contains about 35% glycine in collagen's helix structure in conjunction with hydroxyproline 6. inhibitory neurotransmitter in the central nervous system, especially in the spinal cord, brainstem, and retina
- 17. Why glycine is not optically active?
- 18. Tryptophan 1. an essential amino acid 2. Aromatic and Non-polar 3. largest of the amino acids 4. a precursor to the neurotransmitter serotonin and the hormone melatonin. 5. An antidepressant 6. Anti anxiety 7. Induce sleep
- 19. Collagen Structure • polypeptide chain is left handed • 3 amino acid per turn • Three alpha chains is twisted about each other • super helical twist is right handed
- 20. Chain 1 Chain 2 Chain 3
- 22. • The collagen polypeptides have a very specific amino acid composition: – 1/3 Gly – 1/4 Pro – 1/4 Hypro (hydroxyproline) and 5-Hylys (hydroxylysine) • These residues follow a strict sequence where Gly is always repeated every third position – WHY??; 13 Collagen Structure
- 23. • The presence of Gly at every third residue allows each collagen chains to form a tightly wound helix that can accommodate Pro/Hypro (which are otherwise rarely included in helices); • Since the helix has 3 a.a. per turn, having Gly at every third residue means that Gly is always on the same side of the helix; • It just so happens that Gly is always positioned at the center of the triple helix; • This allows close packing of the three helices, which can interact and yield a very strong, rope-like structure. Collagen Structure
- 25. 25 Collagen, Vitamin C and scurvy • The formation of Hydroxy proline requires the enzymatic modification of Pro in a reaction which involves: – Prolyl hydroxylase (an enzyme) – Fe+2 • Ascorbic acid, a derivative of Vit C and an antioxidant, keeps iron in its reduced Fe+2 form, and not the oxidized, more stable Fe+3 form. • Humans cannot make Vit C on their own • In the absence of Vit C, the collagen triple helix cannot assemble properly, leading to a much softer connective tissue.
- 26. C10H17N3O6S Structure 1. a tri-peptide 2. a gamma linkage between the first two amino acids (instead of alpha linkage) 3. Gamma linkage resists degradation by intracellular peptidases. Glutathione (GSH)
- 27. Functions 1. Antioxident 2. neutralization of free radicals and reactive oxygen compounds 3. used in metabolic and biochemical reactions such as DNA synthesis and repair, protein synthesis, amino acid transport, and enzyme activation 4. It has a vital function in iron metabolism Glutathione (GSH)
- 28. Structure 1. the most abundant plasma protein in humans 2. A globular protein 3. single polypeptide chain of 585 amino acid 4. 55% α-helix and remaining 45%is the β-structure 5. Liver produces about 12g of albumin per day Albumin
- 29. Functions of Albumin 1. essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. 2. colloid osmotic pressure 3. a plasma carrier /transport protein for Thyroid hormones, fatty acids, Ca2+, Cu2+, K+, Na+ Hemin Vit D Drugs 4. Anticoagulant, Antioxident, Acid base balance in body
- 30. Serum Albumin Test 1. a simple blood test that measures the amount of albumin in blood 2. Normal range of human serum albumin • adults - 3.5 to 5 g/dL. • children - 2.9–5.5 g/dL Urine albumin test 1. Normal Range in urine collected for 24 hrs • Adults at rest: < 80 mg • Adults moving around: < 150 mg
- 31. Hypoalbuminemia • In Blood <3.5 g/dL • may be indicative of liver failure – Cirrhosis – Hepatitis • Malnutrition , Burns, Surgery, acute disease • Nephrotic syndrome • Cause edema Hyperalbuminemia • In blood 4.9 g/dL • Dehydration • Vit A deficiency • High protein diet • In urine – Kidney Damage – Diabetic kidney damage – pregnancy
- 32. Hemoglobin • Hb is globular protein, four subunits • There are two types of protein sub-units i.e., α and β. • 2 alpha (141 aa) chain and 2 beta (146) chain • Both alpha and beta chains have 75% alpha helical structure • Normal Hb% in adult male is 14 to 16 gm • Globin is rich in Histidine and lysine
- 33. Hemoglobin
- 34. Structure of Hemoglobin • Fe2+ ferrous has 6 valencies • Fe is linked to pyrrole ring by 4 co ordinate bonds • A fifth bond is with histidine
- 35. Structure of Hemoglobin showing proximal histidine
- 36. Oxy and deoxy Hemoglobin • Hemoglobin exist in two forms – 1) deoxy form: No oxygen is bound to iron. Oxygen atom bounds to Fe and forms hydrogen bond with distal histidine. – 2) oxy form: dioxygen is bound to iron. A water molecule is present instead of Oxygen between Fe and distal histidine
- 37. Oxy and deoxy Hemoglobin
- 38. What is partial pressure? A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower. total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture.
- 40. Transport of gases Oxygen • In lungs partial pressure of O2 is high • Hb is fully saturated with O2 at lungs • In tissue partial pressure of O2 is less • O2 is released at the tissue Carbon Dioxide • In lungs partial pressure of CO2 is less • CO2 is released from Hb • In tissue partial pressure of CO2 is high • CO2 is taken by Hb at tissue
- 41. Transport of CO2 • Transported in mainly three ways • Dissolved form: Dissolved in plasma (10%) – CO2 + H2O H2CO3 HCO3 - + H+ • By RBC: CO2 is converted to H2CO3 inside the RBC (75%) • As carbamino hemoglobin (15%) – R-NH2 + CO2 R-NH-COOH
- 42. Types of Hemoglobin Type Components Peculiarity Adult Hemoglobin HbA α2 β2 Normal HbA2 α2 δ2 Normal Fetal Hemoglobin α2 γ2 High affinity to oxygen Abnormal β4 Seen in thalassemia
- 43. Sickle cell anemia •Anemia. Normal RBC -120 days sickle cells -10 to 20 days •Episodes of pain. called crises a major symptom of sickle cell anemia. Pain develops when sickle-shaped red blood cells block blood flow through tiny blood vessels of chest, abdomen and joints. Pain can also occur in bones. •Painful swelling of hands and feet •Frequent infections. •Delayed growth •Vision problems
- 44. Thalassemia 1. Alpha thalassemia 2. Beta thalassemia