Unit 3-proteins.pptx....................

This PowerPoint presentation provides a clear and concise overview of proteins, covering their structure, functions, digestion, absorption, and metabolism. It also includes details on protein-related disorders and the biologically important compounds synthesized from amino acids.

📘 Contents:

Introduction to Proteins

Classification and Functions

Digestion and Absorption of Proteins

Metabolism of Amino Acids

Disorders Related to Protein Metabolism

Important Compounds Derived from Amino Acids

🎓 Suitable for:
B.Sc Nursing, M.Sc Nursing, Paramedical and Allied Health Science students preparing for exams or presentations.

1. Unit-3:- PROTEINS Akanksha N. Kotangale B.Sc. Nursing

2. Introduction The word protein comes from the Greek word “ Proteios ” meaning “primary” or “of first importance” . Proteins are the most abundant and essential biomolecules in the human body after water. They are complex organic compounds made of carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) . Some proteins also contain sulfur, phosphorus, iron, zinc, copper, etc. Basic building blocks of proteins are amino acids (20 standard amino acids). Amino acids are linked by peptide bonds to form polypeptide chains , which fold into specific structures to form proteins.

3. definition Proteins are complex nitrogenous organic compounds made up of amino acids linked by peptide bonds . They are essential for growth, repair, and maintenance of the body.

4. Classification of protein:- Proteins can be classified in different ways : 1. On the basis of Composition Simple Proteins – yield only amino acids on hydrolysis. Examples: Albumin, Globulin, Histones, Prolamins. Conjugated Proteins – protein + non-protein part (carbohydrate, lipids, nucleic acid, etc.). Glycoprotein → protein + carbohydrate Lipoprotein → protein + lipid Metalloprotein → protein + metal (e.g., Hemoglobin – Fe, Cytochrome – Fe) Nucleoprotein → protein + nucleic acid Derived Proteins – obtained by denaturation or hydrolysis of simple/conjugated proteins. Examples: Proteoses, Peptones, Peptides.

5. 2. On the basis of Shape Fibrous Proteins Long, thread-like, insoluble. Provide structural support. Examples: Collagen, Keratin, Elastin. Globular Proteins Spherical, soluble, biologically active. Examples: Enzymes, Hormones, Antibodies, Hemoglobin .

6. 3. On the basis of Function Structural proteins – collagen (connective tissue), keratin (hair, nails). Enzymes – biological catalysts (pepsin, amylase). Hormonal proteins – insulin, growth hormone. Transport proteins – hemoglobin, transferrin, albumin(plasma protein) Protective proteins – antibodies, fibrinogen. Storage proteins – ferritin (iron storage), casein (milk). Contractile proteins – actin, myosin (muscle movement).

7. Structure of protein:- Primary Structure It is the linear sequence of amino acids in a polypeptide chain. The sequence is linked by peptide bonds . Example: Gly–Ala–Ser–Val–… Even a single change in amino acid can alter the protein’s function (e.g., Sickle cell anemia). 2. Secondary Structure This is the local folding of the polypeptide chain due to hydrogen bonding . Two main types: α- helix – spiral shape (e.g., keratin in hair). β- pleated sheet – zig-zag folding (e.g., silk fibroin). Stabilized by hydrogen bonds between the –CO and –NH groups of the backbone.

8. 3. Tertiary Structure This is the 3D folding of a single polypeptide chain. Stabilized by: Hydrophobic interactions Hydrogen bonds Ionic bonds Disulfide bridges (–S–S–) between cysteine residues Example: Myoglobin. At this level, the protein achieves its specific function . 4. Quaternary Structure Formed when two or more polypeptide chains (subunits) assemble into one functional protein. Example: Hemoglobin (4 subunits – 2 alpha + 2 beta).

9. Amino Acids:- Definition:- Amino acids are the basic building blocks of proteins . They contain two functional groups : Amino group (–NH₂) Carboxyl group (–COOH) General formula: R–CH(NH₂)–COOH

10. Classification of Amino acid:- Based on Essentiality(Nutritional Requirement) Essential amino acid:- cannot be synthesized by the body, must be taken in diet. Ex.:- Histidine, Isoleucine, Leucine, Lysine, Methionine, Valine. Non-Essential amino acid:- can be synthesized in the body. Ex.:- Alanine, Asparagine, Aspartate, glutamate, serine. Semi-Essential amino acid:- Needed during growth and illness. Ex.:- Arginine, Tyrosine, cysteine, glycine, proline.

11. Based on structure of side chain 1. Aliphatic amino acid:- side chain is straight . Ex.- Glycine(R=H), Alanine(R=CH3), Valine, Leucine, Isoleucine. 2. Hydroxy amino acid:- contain hydroxyl (-OH) group. Ex.- Serine(R=CH2OH), Threonine(R=CH(OH)-CH3), Tyrosine. 3. Sulphur containing amino acid:- contain sulphur(S) group. Ex.- Cysteine(R=CH2SH), Methionine(R=CH2-CH2-S-CH3) . 4. Acidic amino acid and their amides:- extra –COOH group in their side chain so they can donate a proton and making them acidic in nature. Ex.- Aspartic acid(R=CH2-COOH), Glutamic acid(R=CH2-CH2-COOH), Glutamine. 5. Basic amino acid:- extra –NH₂ (amino) group in the side chain, so they can accept protons and giving them basic nature. Ex.- Lysine(R= CH2-CH2- CH2- CH2-NH2), Arginine, Histidine. 6. Aromatic amino acids:- stable ring in their side chain. Ex.- Phenylalanine(R= CH₂–C₆H₅), Tyrosine. 7. Imino acid :- Unique, cyclic structure. Ex.- Proline

12. C. Based on metabolism Glucogenic Amino Acid:- A glucogenic amino acid is one whose carbon skeleton can be converted into glucose. Ex.- Alanine, Glycine, Serine, Valine Ketogenic Amino Acid:- Ketogenic amino acids are amino acids whose carbon skeletons are converted into ketone bodies (acetoacetate or acetyl-CoA) during metabolism. Ex.- Leucine, Lysine. Both Glucogenic and ketogenic:- converted into glucose and ketone. Ex.- Isoleucine, tyrosine, tryptophan.

13. Digestion of Protein:- Stomach :- Gastric juice :- Acidic gastric juice helps in the denaturation of proteins and activation of pepsin. Enzymes:- enzyme pepsin, activated from pepsinogen by hydrochloric acid, begins breakdown of proteins into smaller peptides. Small intestine:- Pancreatic enzymes:- partially digested proteins enter the small intestine, they are mixed with pancreatic juices containing enzymes such as trypsinogen, chymotrypsinogen and Procarboxypeptidase. These enzymes are secreted in inactive form by the pancreas in the duodenum, this prevents the enzymes from digesting proteins in the pancreas itself. These enzymes further breakdown peptides into smaller oligopeptides and amino acids.

14. 3) Brush border enzymes:- Enterokinase (enteropeptidase) activates trypsinogen into trypsin(activated form). Trypsin then activates chymotrypsinogen to chymotrypsin and Procarboxypeptidase to carboxypeptidase. Peptides (aminopeptidase, carboxypeptidase, dipeptidase, Tripeptidase , enteropeptidase) located on the surface of the intestinal villi complete the digestion of peptides into free amino acids.

15. Absorption of protein:- 1. Site of Absorption:- Takes place mainly in the small intestine (jejunum & ileum) . End products of protein digestion = Amino acids, dipeptides, tripeptides . 2. Transport across the intestinal lining:- Peptide transport:- short peptides are absorbed into the intestinal cells via transporters like PepT1 (Peptide transporter 1). This transporter uses a proton gradient to co-transport peptides into the cell. 3. Inside the enterocytes:- Short peptides are further broken down into amino acids by intracellular peptidase. Amino acid transport(active transport):- free amino acids are absorbed through sodium dependent transporters and energy and sodium independent transporters.

16. 4. Transport into the bloodstream:- through basolateral transporters. 5. Circulation and distribution:- Amino acids are carried out via portal vein to liver where they can be metabolized or released into the general circulation to be used by various tissues for protein synthesis and other functions.

17. Metabolism of protein:- Definition:- Protein metabolism = the processes by which dietary proteins are broken down into amino acids, used for body building, repair, enzyme & hormone synthesis , and excess is broken down for energy. Steps of Protein Metabolism:- A. Digestion & Absorption:- Dietary proteins → amino acids (absorbed in small intestine) → carried to liver via portal vein.

18. B. Utilization of Amino Acids:- Protein Synthesis Amino acids used to build body proteins (muscle, enzymes, hormones, plasma proteins). Transamination Transfer of amino group (–NH₂) from one amino acid to keto acid. Helps in synthesis of non-essential amino acids. Enzyme: Transaminase . Deamination Removal of amino group (–NH₂) from amino acid. Occurs mainly in liver . Produces ammonia (NH₃) and keto acids. Ammonia Detoxification (Urea Cycle) Ammonia is toxic → converted to urea in liver (ornithine cycle). Urea → excreted in urine by kidneys. Keto Acid Utilization Formed after removal of amino group. Used for: Energy (via Krebs cycle) Gluconeogenesis (→ glucose) Lipogenesis (→ fat storage)

19. Ornithine Cycle (Urea Cycle):- 1. Definition:- The ornithine cycle (also called the urea cycle ) is the process in the liver by which toxic ammonia (NH₃) , produced from protein breakdown, is converted into urea , which is excreted by the kidneys. 2. Location:- Occurs in liver cells (partly in mitochondria and partly in cytoplasm). 3. Steps of Ornithine Cycle (a) In mitochondria:- Ammonia (NH₃) + CO₂ + ATP → Carbamoyl phosphate Enzyme: Carbamoyl phosphate synthetase I Carbamoyl phosphate + Ornithine → Citrulline Enzyme: Ornithine transcarbamylase Citrulline moves to cytoplasm.

20. (b) In cytoplasm:- - Citrulline + Aspartate → Argininosuccinate Enzyme: Argininosuccinate synthetase - Argininosuccinate → Arginine + Fumarate Enzyme: Argininosuccinate lyase - Arginine → Urea + Ornithine Enzyme: Arginase Ornithine goes back to mitochondria → cycle continues. 4. End Products:- Urea → excreted in urine. Fumarate → enters Krebs cycle (link between urea cycle & energy metabolism).

21. Related disorder:- Disorder Cause / Enzyme Deficiency Symptoms / Effects Kwashiorkor Severe protein deficiency (adequate calories) Edema, fatty liver, growth retardation Marasmus Deficiency of both protein & calories Severe wasting, no edema Phenylketonuria (PKU) Lack of enzyme phenylalanine hydroxylase Mental retardation, seizures, musty odor of urine Alkaptonuria Deficiency of homogentisic acid oxidase Black urine on standing, joint pain Maple Syrup Urine Disease Deficiency of branched-chain keto acid dehydrogenase Sweet odor in urine, neurological damage Urea Cycle Disorder Defect in enzymes of urea synthesis Accumulation of ammonia (hyperammonemia) Protein-energy malnutrition Inadequate dietary protein Poor immunity, delayed wound healing

22. Biologically important compounds synthesized from various amino acids (only names) :- From Tyrosine -Thyroxine -Adrenaline (Epinephrine) -Noradrenaline (Norepinephrine) -Melanin From Tryptophan -Serotonin -Melatonin -Niacin (Vitamin B₃)

23. From Glycine -Creatine -Porphyrins (e.g., Heme ) -Purines -Glutathione From Glutamic acid - γ- Aminobutyric acid (GABA) From Arginine -Nitric oxide -Creatine From Histidine -Histamine From Cysteine -Coenzyme A -Taurine -Glutathione

24. Inborn Errors of Aromatic Amino Acid Metabolism:- Disorder Defective Enzyme Amino Acid Key Feature Phenylketonuria Phenylalanine hydroxylase Phenylalanine Mousy odor urine Alkaptonuria Homogentisic acid oxidase Tyrosine Black urine Tyrosinemia Fumarylacetoacetate hydrolase / Tyrosine aminotransferase Tyrosine Liver & skin lesions Albinism Tyrosinase Tyrosine Lack of pigment

25. Plasma Proteins:- 1. Definition:- Plasma proteins are large molecular weight substances present in blood plasma (except clotting factors in serum). Normal total plasma protein: 6–8 g/dL (average 7.0 g/dL) 2. Major Types and Normal Values:- Type Normal Value (g/dL) Percentage Main Site of Synthesis Albumin 3.5 – 5.0 ~60% Liver Globulins 2.0 – 3.5 ~36% Liver & Plasma cells Fibrinogen 0.2 – 0.4 ~4% Liver

26. 3. Functions:- A. Albumin:- Maintains colloidal osmotic (oncotic) pressure of plasma. Acts as transport protein for hormones, fatty acids, bilirubin, calcium, and drugs. Serves as amino acid reserve for tissue protein synthesis. ↓ Decrease causes: Edema, liver disease, malnutrition. B. Globulins:- Types: α₁, α₂, β, and γ- globulins Type Main Functions α₁ & α₂ Globulins Transport of lipids, hormones, metals (e.g., transferrin, ceruloplasmin) β Globulins Transport of iron & lipids; part of complement system γ Globulins (Immunoglobulins) Antibodies – provide immunity (IgG, IgA, IgM, IgE , IgD )

27. C. Fibrinogen:- Essential for blood clot formation → converted to fibrin by thrombin. ↑ Levels in inflammation or tissue injury. 4. Albumin/Globulin (A/G) Ratio:- Normal: 1.2 – 1.5 : 1 ↓ Ratio: Seen in liver disease, nephrotic syndrome, chronic infections.

28. 1. Proteinuria:- Definition: Presence of abnormal amount of protein in urine. Normal: <150 mg/day Causes:- A. Physiological (temporary) -After heavy exercise -Fever -Pregnancy -Emotional stress → Usually mild & reversible B. Pathological Renal causes -Glomerulonephritis – increased permeability of glomeruli -Nephrotic syndrome – massive protein loss in urine -Pyelonephritis – inflammation of kidneys Pre-renal causes -Overflow proteinuria – due to excess plasma proteins (e.g., multiple myeloma – Bence Jones protein) Post-renal causes -Infection or inflammation in urinary tract (urethritis, cystitis)

29. 2. Hypoproteinemia :- Definition: Decreased plasma protein level (<6 g/dL) Causes:- Category Examples ↓ Synthesis Liver disease (hepatitis, cirrhosis), malnutrition, malabsorption ↑ Loss Nephrotic syndrome (urinary loss), burns, protein-losing enteropathy ↑ Utilization / Catabolism Fever, trauma, malignancy Hemodilution Excess IV fluids, pregnancy Effects:- Edema (↓ plasma oncotic pressure), poor wound healing.

30. 3. Hyper-Gamma Globulinemia:- Definition: Increased γ-globulins (immunoglobulins) in plasma. Causes:- Type Examples / Conditions Polyclonal (↑ many types of antibodies) Chronic infections (tuberculosis, hepatitis), autoimmune diseases (RA, SLE) Monoclonal (↑ single antibody type) Multiple myeloma , Waldenström’s macroglobulinemia Effect:- Increased serum viscosity, rouleaux formation of RBCs, impaired circulation.

31. Electrophoresis:- 1. Definition:- Electrophoresis is a laboratory technique used to separate charged particles (like proteins or nucleic acids) based on their electric charge and size when an electric current is passed through a medium (e.g., agar gel, cellulose acetate). 2. Principle:- Molecules with negative charge (like most plasma proteins at pH 8.6) move toward the positive electrode (anode) . Molecules with positive charge move toward the negative electrode (cathode) . The rate of movement depends on: Net charge of the molecule Size and shape Strength of electric field Nature of supporting medium

32. 3. Normal Electrophoretic Pattern of Plasma Proteins:- On serum protein electrophoresis , 5 main bands are seen (at pH 8.6): Fraction % of Total Protein Major Proteins / Function Albumin 55–65% Maintains osmotic pressure, transports substances α₁- globulin 2–4% α₁- antitrypsin, HDL α₂- globulin 6–10% Haptoglobin, ceruloplasmin β- globulin 8–12% Transferrin, complement proteins γ- globulin 12–20% Immunoglobulins (antibodies)

33. 4. Abnormal Electrophoretic Patterns:- Condition Electrophoretic Change Hypoalbuminemia (e.g. liver disease, nephrotic syndrome) ↓ Albumin band Acute inflammation ↑ α₁ and α₂ globulins Chronic inflammation ↑ γ- globulin (broad band) Multiple myeloma Sharp M-spike in γ region (monoclonal immunoglobulin) Cirrhosis of liver β–γ bridging (fusion of β and γ bands)

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