Chemistry of Lipids - Lecture Notes 1439/1440 PDF

‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪44‬‬ Definition Classification Biological importance ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 45  Definition Organic substances relatively insoluble in water but soluble...

‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪44‬‬ Definition Classification Biological importance ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 45  Definition Organic substances relatively insoluble in water but soluble in organic solvents like chloroform, ether and benzene ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 46  Structural Precursor of component Protection of Storage form many steroid of cell internal of energy hormones, membrane. organs vitamin D ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 47 Simple Complex Derived lipid lipid lipids ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني دأ‬/‫د‬.‫أ‬ 48 They are esters of Fatty acids with various alcohols Neutral fats or Waxes oils Alcohol is Alcohol is other than GLYCEROL glycerol 49  Glycerol esters (acylglycerols) H H H C OH H C O CO (CH2)n CH3 H C OH H C O CO (CH2)n CH3 H C OH H C O CO (CH2)n CH3 H H Glycerol Triglyceride Triglycerides : most abundant family of lipids in plant and animal cells. major components of the human diet ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 50  Fats and oils are  also called triglycerides.  esters of glycerol+ 3 FA ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 51 When hydrolysis of waxes gives : one fatty acid + alcohol EXAMPLES  Beeswax ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 52  ‫‪Fatty acid‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪53‬‬  ‫‪Classification‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني دأ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪55‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪57‬‬  Contains one double Contains bond more than one double bond ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 58 ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪59‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪60‬‬ Functions OF PUFA : 1.Useful to prevent atherosclerosis. 2.Prostaglandin & eicosanoids are synthesized 3.They participate in structure of all cellular and subcellular membranes and the transporting plasma phospholipids. 4.Essential for skin integrity, normal growth and reproduction. 5.Important role in blood clotting. 6.Important in preventing and treating fatty liver. 7.Important role in health of the retina and vision. 8.They can be oxidized for energy production. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 61 Deficiency: Their deficiency in the diet leads to nutritional deficiency disease. Its symptoms include: 1.Poor growth and health with susceptibility to infections, dermatitis, 2.Decreased capacity to reproduce, 3.Impaired transport of lipids, fatty liver, 4.Lowered resistance to stress. Source: vegetable oils such as corn oil, peanut oil, olive oil, cottonseed oil, soybean oil and many other plant oils, cod liver oil and animal fats. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 62  Property-Rancidity Definition: - It is a physico-chemical change in the natural properties of the fat leading to the development of unpleasant odour or taste or abnormal color particularly on aging after exposure to atmospheric oxygen, light, moisture, bacterial or fungal contamination and/or heat. Types and causes of Rancidity: 1.Hydrolytic rancidity 2.Oxidative rancidity 3.Ketonic rancidity ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 63 1-Hydrolytic rancidity: Due to hydrolysis of the fat by lipase from bacterial contamination at high temperature and moisture. 2-Oxidative Rancidity: oxidation of fat or oil Due to exposure to oxygen, light and/or heat producing peroxide derivatives that are toxic and have bad odor. 3-Ketonic Rancidity: due to contamination with fungi Moisture accelerates ketonic rancidity. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 64 Hydrolytic Rancidity enzymes triglyceride fatty acid diglyceride ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 65 Oxidative Rancidity Radical chain reaction: Initiation RH  R. Propagation R. + O2  RO2. ROO. + RH  R-OOH + R. Termination R. + R.  R-R ROO. + R.  R-OO-R ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن أ‬/‫د‬.‫أ‬ 66 Prevention of rancidity is achieved by: 1.Avoidance of the causes (exposure to light, oxygen, moisture, high temperature and bacteria or fungal contamination). 2.By keeping fats or oils in well-closed containers in cold, dark and dry place. 3.Addition of anti-oxidants. The most common natural antioxidant is vitamin E. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 67 Hazards of Rancid Fats: 1.The products of rancidity are toxic, i.e., causes food poisoning and cancer. 2.Rancidity destroys the fat-soluble vitamins (vitamins A, D, K and E). 3.Rancidity destroys the polyunsaturated essential fatty acids. 4.Rancidity causes economical loss because rancid fat is inedible(Unfit to eat). ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 68  Subclassified according to the type of prosthetic group Phospholipids Glycolipids Lipoproteins ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 69 FA + ALCOHOL + PHOSPHORIC ACID They frequently have nitrogen containing bases ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 70 Phospholipids may be classified on the basis of the type of alcohol present ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 71 A. Glycerophospholipids B. Sphingophospholipids  Examples  Examples  Plasmalogens  Spingomyelins  Cardiolipins ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 72 FA + ALCOHOL[SPINGOSINE] +CARBOHYDRATE WITH NITROGEN BASE Example Cerebrosides Gangliosides ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 73  Chylomicrons Very low density lipoprotein Lipid with (VLDL) prosthetic Low density lipoprotein (LDL) group PROTEIN High density lipoprotein (HDL) ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 74 ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪75‬‬  Example Vitamin A Fatty acids Steroids Cholesterol and D ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 76 ‫أ‪.‬د‪ /‬حسن ميرغني د‪ /‬خالد حامد أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪77‬‬ Proteins chemistry Definition: ‫تعريف‬ Proteins are organic nitrogenous compounds of high molecular weight, consisting largely or entirely of α-amino acids united together by peptide linkages. They are composed of carbon, hydrogen, oxygen and nitrogen, many types of proteins may contain sulfur. Nitrogen is a characteristic component of proteins, forming about 16% of their weight. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 78  Functions of proteins Synthesis of tissue proteins e.g., contractile protein of muscles, collagen …etc... Synthesis of cell organelles as cell membrane ,receptors…….etc Synthesis of enzymes Synthesis of milk proteins. Synthesis of plasma proteins. Synthesis of protein hormones. Synthesis of nucleoproteins. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 79 Amino Acids Amino acid is an organic acid containing one or more amino group and carboxylic group (COOH) carboxylic group (COOH) and amino group (NH2) are both attached to the α-carbon They are the building units of protein. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 80  Hydrogen atom H carboxylic side chain group radicle R C COOH - carbon NH2 atom amino group Representation of  Amino Acid ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 81  Amino acids found in proteins are of L-configuration, this means that the amino group to the left and the hydrogen to the right of the a-carbon D-amino acid L-amino acid Isomerism of amino acids ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 82 Classifications: Amino acids can be classified by different classification: Chemical classification. Nutritional classification. Metabolic classification. Reaction classification (Charge properties). ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 83 1. Chemical classification: A) Aliphatic amino acids: have no ring; These amino acids may be subclassified into: Branched chain amino acids: as valine, leucine, and isoleucine. Hydroxy amino acids: as serine and threonine. Sulphur containing amino acids: as cysteine and methionine. Amino acids with amide group: as asparagine and glutamine. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 84 B) Aromatic amino acids: They have benzene ring in their side chains like Phenylalanine Tyrosine Tryptophan C) Heterocyclic amino acids: They have heterocyclic ring as Histidine, Tryptophan, Proline and hydroxyproline. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 85  2. Reaction classification ( charge properties): Non polar (Neutral): having equal number of amino and carboxyl groups e.g. alanine, serine, valine …etc Polar Basic AA: having more than one amino group and one carboxyl e.g. arginine, lysine, histidine …etc Polar (Acidic): having one amino group and two carboxyl e.g. glutamic acid and aspartic acid ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 86 3. Nutritional classification: They are classified into three groups: Essential amino acids: They are amino acids which cannot be synthesized in the body and must be taken in diet; phenylalanine, methionine, isoleucine, leucine, lysine, valine, threonine and tryptophan. Semi essential amino acids: They are amino acids required in the food of growing children not in the food of adult as histidine and arginine. Non essential amino acids: can be synthesized inside the body as glycine, alanine, serine, cysteine, cystine, aspartic, tyrosine, glutamic, proline and hydroxyproline ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 87 4. Metabolic classification: According to their fate in the body they are classified into three groups: Glucogenic amino acids: give glucose inside the body as glycine, alanine, aspartic and glutamic. Ketogenic amino acid: gives ketone bodies as leucine. Glucogenic and ketogenic amino acids: They give both glucose and ketone bodies as lysine, tryptophan, tyrosine, phenylalanine and isoleucine. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫أ‬ ‫ حسن ميرغني‬/‫د‬.‫أ‬ 88  Peptides and Proteins 20 amino acids are commonly found in protein. These 20 amino acids are linked together through “peptide bond forming peptides and proteins (what’s the difference?). - The chains containing less than 50 amino acids are called “peptides”, while those containing greater than 50 amino acids are called “proteins”. Peptide bond formation: α-carboxyl group of one amino acid (with side chain R1) forms a covalent peptide bond with α-amino group of another amino acid ( with the side chain R2) by removal of a molecule of water. The result is : Dipeptide ( i.e. Two amino acids linked by one peptide bond). By the same way, the dipeptide can then forms a second peptide bond with a third amino acid (with side chain R3) to give Tripeptide. Repetition of this process generates a polypeptide or protein‫هجري‬ of 1439/1440 specific ‫فاروق‬amino acid /‫حسن ميرغني د‬ /‫ د‬.‫أ‬ sequence. 89 ‫أ‪.‬د‪ /‬حسن ميرغني د‪ /‬خالد حامد أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪90‬‬  Peptide bond formation: - Each polypeptide chain starts on the left side by free amino group of the first amino acid enter in chain formation. It is termed (N- terminus). - Each polypeptide chain ends on the right side by free COOH group of the last amino acid and termed (C-terminus). ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 91 Examples on Peptides: 1- Dipeptide ( two amino acids joined by one peptide bond): Example: Aspartame which acts as sweetening agent being used in replacement of cane sugar. It is composed of aspartic acid and phenyl alanine. 2- Tripeptides ( 3 amino acids linked by two peptide bonds). Example: GSH which is formed from 3 amino acids: glutamic acid, cysteine and glycine. It helps in absorption of amino acids, protects against hemolysis of RBC by breaking H2O2 which causes cell damage. 3- octapeptides: (8 amino acids) Examples: Two hormones; oxytocine and vasopressin (ADH). 4- polypeptides: 10- 50 amino acids: e.g. Insulin hormone ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 92  Protein structure: There are four levels of protein structure (primary, secondary, tertiary and quaternary) Primary structure: The primary structure of a protein is its unique sequence of amino acids. – Lysozyme , an enzyme that attacks bacteria, consists of a polypeptide chain of 129 amino acids. – The precise primary structure of a protein is determined by inherited genetic information. – At one end is an amino acid with a free amino group the (the N-terminus) and at the other is an amino acid with a free carboxyl group the (the C-terminus). ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 93  High orders of Protein structure A functional protein is not just a polypeptide chain, but one or more polypeptides precisely twisted, folded and coiled into a molecule of unique shape (conformation). This conformation is essential for some protein function e.g. Enables a protein to recognize and bind specifically to another molecule e.g. hormone/receptor; enzyme/substrate and antibody/antigen. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 95 2- Secondary structure: Results from hydrogen bond formation between hydrogen of –NH group of peptide bond and the carbonyl oxygen of another peptide bond. According to H-bonding there are two main forms of secondary structure: α-helix: It is a spiral structure resulting from hydrogen bonding between one peptide bond and the fourth one β-sheets: is another form of secondary structure in which two or more polypeptides (or segments of the same peptide chain) are linked together by hydrogen bond between H- of NH- of one chain and carbonyl oxygen of adjacent chain (or segment). ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 96 Hydrogen bonding in α-helix: In the α-helix CO of the one amino acid residue forms H-bond with NH of the forth one. Supersecondary structure or Motifs : occurs by combining secondary structure. The combination may be: α-helix- turn- α-helix- turn…..etc Or: β-sheet -turn- β-sheet-turn………etc Or: α-helix- turn- β-sheet-turn- α-helix Turn (or bend): is short segment of polypeptides (3-4 amino acids) that connects successive secondary structures. e.g. β-turn: is small polypeptide that connects successive strands of β-sheets. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 100  Tertiary structure is determined by a variety of interactions (bond formation) among R groups and between R groups and the polypeptide backbone. a. The weak interactions include:  Hydrogen bonds among polar side chains  Ionic bonds between charged R groups ( basic and acidic amino acids)  Hydrophobic interactions among hydrophobic ( non polar) R groups. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 101 b. Strong covalent bonds include disulfide bridges, that form between the sulfhydryl groups (SH) of cysteine monomers, stabilize the structure. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 102  Quaternary structure: results from the aggregation (combination) of two or more polypeptide subunits held together by non-covalent interaction like H-bonds, ionic or hydrophobic interactions. Examples on protein having quaternary structure: – Collagen is a fibrous protein of three polypeptides (trimeric) that are supercoiled like a rope. This provides the structural strength for their role in connective tissue. – Hemoglobin is a globular protein with four polypeptide chains (tetrameric) – Insulin : two polypeptide chains (dimeric) ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 103 ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪104‬‬ ‫أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫أ‪.‬د‪ /‬حسن ميرغني‬ ‫‪105‬‬ ‫‪Nucleic Acids‬‬ ‫أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫أ‪.‬د‪ /‬حسن ميرغني‬ ‫‪106‬‬ NUCLEIC ACIDS Nucleic acids are polymers Monomer— nucleotides Nitrogenous bases Purines Pyrimidines Sugar Ribose Deoxyribose Phosphates +nucleoside=nucleotide Nucleosides consist of a base (pyrimidine or purine) attached to a sugar (ribose or deoxyribose). Nucleotides are nucleoside phosphates.  Nucleic Acids Nucleic acids are molecules that store information for cellular growth and reproduction There are two types of nucleic acids: - deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) These are polymers consisting of long chains of monomers called nucleotides A nucleotide consists of a nitrogenous base, a pentose sugar and a phosphate group: ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 108 Nucleotides “Energy rich” compounds Chemical signals Enzyme co-factors Nucleic Acids DNA and RNA Polymers of nucleotides 3 components Nitrogenous “base” Ribose (or deoxyribose) Phosphate ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 109 Bases ” A G 2 purine bases Adenine: A Guanine: G C T U Bases Pyrimidines Purines 2 pyrimidine bases (in DNA) Cytosine: C Thymine: T or Uracil: U (in RNA, instead of Thymine) ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 110 Ribose carbons numbered: 1’,2’,3’,4’,5’ DNA: 2’ Deoxyribose 5’ or just deoxyribose 1’ 4’ 3’ 2’ ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 111  Polymerise Nucleotides nucleotides can be linked phosphates linked to 2 pentoses phosphodiester linkages Link PO4 at 5’ end to 3’ OH of next nucleotide chain has POLARITY –distinct ends 5’ end 3’ end –usually “read” 5’ -> 3’ ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 112 Nucleotides as Energy Carriers ATP Adenosine triphosphate ADP, AMP Adenosine diphosphate Adenosine monophosphate ATP ADP + PO4 ADP AMP + PO4 Main energy exchange reactions in cells 113 ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ Names of Nucleosides and Nucleotides ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 114 Structure of DNA? The Genetic Material Crick and Watson Race with Linus Pauling to predict structure Chargaff’s rules: Chemical analysis: [A] = [T] [G] = [C] Constant for each organism over time across all tissues ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 115 The Double Helix 3.4Å per basepair 10 basepairs per turn 10-11 in aqueous solution 2 anti-parallel strands ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 117  What is the function of RNA? Carries DNA’s message code Helps make protein Three Main Types of RNA 1. Messenger RNA (mRNA) - Carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell (serve as “messenger”)  Three Main Types of RNA 2.Ribosomal RNA (rRNA) – Makes up the major part of ribosomes, which is where proteins are made. Ribosomal RNA Three Main Types of RNA 3. Transfer RNA (tRNA) - Transfers amino acids to ribosomes during protein synthesis  ‫‪Enzymes:‬‬ ‫‪“Helper” Protein molecules‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني د‪ /‬خالد حامد أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪125‬‬ Chemical reactions of life Processes of life building molecules synthesis breaking down molecules + digestion + ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 126 Nothing works without enzymes! How important are enzymes? all chemical reactions in living organisms require enzymes to work building molecules enzyme synthesis enzymes breaking down molecules + digestive enzymes enzyme We can’t live without enzymes! + enzymes speed up reactions “catalysts” ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ خالد حامد أ‬/‫ حسن ميرغني د‬/‫د‬.‫أ‬ 127 Enzymes A protein catalyst Enzymes are important proteins found in living things. An enzyme is a protein that changes the rate of a chemical reaction. They speed metabolic reactions. ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 128 Examples  synthesis enzyme +  digestion enzyme + ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 129 Enzymes are proteins Each enzyme is the specific helper to a specific reaction each enzyme needs to be the right shape for the job enzymes are named for the reaction they help sucrase breaks down sucrose proteases breakdown proteins lipases breakdown lipids Oh, I get it! DNA polymerase builds DNA They end in -ase ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫أ‬ ‫ حسن ميرغني‬/‫د‬.‫أ‬ 130 Enzymes aren’t used up Enzymes are not changed by the reaction used only temporarily re-used again for the same reaction with other molecules very little enzyme needed to help in many reactions substrate product active site enzyme ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫أ‬ ‫ حسن ميرغني‬/‫د‬.‫أ‬ 131 It’s shape that matters! Lock & Key model shape of protein allows enzyme & substrate to fit specific enzyme for each specific reaction ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 132 Induced Fit Model In the induced-fit model of enzyme action: - the active site is flexible, not rigid - the shapes of the enzyme, active site, and substrate adjust to maximumize the fit, which improves catalysis - there is a greater range of substrate specificity This model is more consistent with a wider range of enzymes ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 133  ‫‪2‬‬ ‫‪1‬‬ ‫‪3‬‬ ‫أ‪.‬د‪ /‬حسن ميرغني أ‪.‬د‪ /‬رحاب فاروق ‪ 1439/1440‬هجري‬ ‫‪134‬‬ Enzyme vocabulary Enzyme helper protein molecule Substrate molecule that enzymes work on Products what the enzyme helps produce from the reaction Active site part of enzyme that substrate molecule fits into ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني أ‬/‫د‬.‫أ‬ 135 What affects enzyme action Correct protein structure correct order of amino acids why? enzyme has to be right shape Temperature why? enzyme has to be right shape pH (acids & bases) why? enzyme has to be right shape ‫ هجري‬1439/1440 ‫ رحاب فاروق‬/‫د‬.‫ حسن ميرغني دأ‬/‫د‬.‫أ‬ 136