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2- Proteins

2- Proteins. 1. A polypeptide is a polymer of amino acids connected in a specific sequence 2. A protein’s function depends on its specific conformation. 2- Proteins.

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2- Proteins

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  1. 2- Proteins 1. A polypeptide is a polymer of amino acids connected in a specific sequence 2. A protein’s function depends on its specific conformation

  2. 2- Proteins • Their functions include structural support, storage, transport of other substances, intercellular signaling, movement, and defense against microbes. • Some proteins works as enzymes in the cell that regulate metabolism by accelerating chemical reactions. • All protein polymers are constructed from 20 monomers, called amino acids. • Polymers of proteins are called polypeptides. • A protein consists of one or more peptides (polypeptides) folded and coiled into a specific conformation

  3. H O H C C N OH R Amino group Carboxyl group H Side chain • Protein is a polymer of amino acids (constructed from 20 amino acids) (to form Polypeptides). • These components include ahydrogen atom, a carboxyl group, an amino group, and a variable R group (or side chain). General Formula of the Amino Acid: • The side chainR links withـ different compounds • Differences in R groups produce the 20 different amino acids. • The physical and chemical characteristics of the R group determine the unique characteristics of a particular amino acid.

  4. H H O N C C OH R Peptide bond Amino acids Peptide Polypeptide (Protein) The Peptide Bond • Peptide bond formed between the carboxyl group of one amino acid and the amino group of the other by dehydration. O H H N C C H OH H R Dehydration • Amino acids are joined together when a dehydration reaction removes a hydroxyl group from the carboxyl end of one amino acid and a hydrogen from the amino group of another. The resulting covalent bond is called a peptide bond.

  5. 3- LipidsThe Hydrophobic Molecules • 1.Fats store large amounts of energy • Phospholipids are major components of cell membranes • Steroids include cholesterol and certain hormones

  6. 1)- Fats: • Lipids are an exception among macromolecules because they do not have polymers. • The unifying feature of lipids is that they all have little or no affinity for water. • This is because their structures are dominated by non-polar covalent bonds. • Lipids are the componentsof fats, and arehighly diverse in form and function. • Although fats are not polymers, they are large molecules assembled from smaller molecules by dehydration reactions. • A fatis constructed from two kinds of smaller molecules, glycerolandfatty acids.

  7. O H C H C C C C C H C C H OH H C OH H H H H H H H H H H H Glycerol Fatty Acid H O OH Ester link Dehydration • A fat is composed of three fatty acids linked with one glycerol molecule. • Fats are classified into Saturated and Un-saturated fats • Glycerol consists of a three C skeleton with an OH group attached to each C. • A fatty acid consists of a carboxyl group (COOH) attached to a long carbon skeleton, often 16 to 18 carbons long.

  8. Fattyacids may vary in length (number of carbons) and in the number and locations of double bonds. • If there are no carbon-carbon double bonds, then the molecule is a saturated fatty acid (has H at every possible position). • If there are one or more carbon-carbon double bonds, then the molecule is an unsaturated fatty acid - formed by the removal of H atoms from the carbon skeleton.

  9. A)- Saturated Fats • The Fatty acid components are saturated (there is no double bonds between the carbons. All C are linked with H. • Thus, it is saturated with H. • Most animal fats are saturated. • They are solid at room temperature. • Saturated fats-rich diet results in Atherosclerosis. B)- Un-saturated Fats • These double bonds are formed by the removal of H atoms. • Most vegetable fats (oils)and fish fats are unsaturated. • They are liquid at room temperature. • They can be synthetically converted to saturated (solid) by adding H (Hydrogenation).

  10. 2)- Phospholipids: • Are major components of cell membranes • Phospholipids have two fatty acids attached to glycerol and a phosphate group at the third position. • The phosphate group carries a negativecharge. • The fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilichead. • Thus, it is amphipathic

  11. 3)- Steroids: • Include cholesterol and certain hormones • Steroids are lipids with a carbon skeleton consisting of four fused ملتحمة carbon rings. • Different steroids are created by varying functional groups attached to the rings. • Cholesterol, an important steroid, is a component in animal cell membranes. • Cholesterol is also the precursor المادة الخام from which all other steroids are synthesized. • Many of these other steroids are hormones, including the vertebrate sex hormones. • While cholesterol is clearly an essential molecule, high levels of cholesterol in the blood may contribute to Atherosclerosis.

  12. Hydrogenation The Summary F a t s (Composed of Lipids) Saturated Unsaturated Phospholipids Steroids Animal Fats Vegetable Fats Bi-layer of cell membrane Sex Hormones & Cholesterol

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