Chapter 2 Last lecture.pptm

Organic molecules Lecturer: Ms. Thabisa Mdlangu BCB Department, Life Sciences Building 5th floor, Core 2 [email protected] Carbohydrates Carbon, Hydrogen, Oxygen 1:2:1 Simple sugars and complex carbs Monosaccharides (5 or 6 Carbons) Glucose, Fructose, Ribose Disaccharides: Two monosaccharides joine...

Organic molecules Lecturer: Ms. Thabisa Mdlangu BCB Department, Life Sciences Building 5th floor, Core 2 [email protected] Carbohydrates Carbon, Hydrogen, Oxygen 1:2:1 Simple sugars and complex carbs Monosaccharides (5 or 6 Carbons) Glucose, Fructose, Ribose Disaccharides: Two monosaccharides joined together Glucose bonds to Fructose to form Sucrose Complex carbs: Chains of monosaccharides are collectively called complex carbs Oligosaccharides: 3 to 100 monosaccharides These carbohydrates sometimes attach to a protein to form glycoprotein (sugar protein) Glycoprotein: Important in immunity Blood types: A, B, AB, and O refer to the combination of glycoproteins attached to the surface of red blood cells Polysaccharides: Huge molecules consisting of hundreds or thousands of monosaccharides -Cellulose (Most common): Part of cell walls – Found in diet as fiber - Chitin (2nd most common): Exoskeletons and cell walls of fungi Flexible and biodegradable: Used to manufacture Surgical thread -Glycogen (stored form of glucose) -Starch: Potatoes, Rice, Wheat… Proteins Complex and highly versatile They do more jobs in the cell than any other type of biological molecule Cells produce thousands of kinds of proteins which control all the activities of life Illness or death can occur even if it’s only one protein that is missing or faulty E.g. Protein insulin controls the amount of sugar in the blood, the failure to produce insulin leads to one form of diabetes A protein is a chain of monomers called amino acids Each amino acid has a central carbon atom bonded to four other atoms or groups of atoms: Hydrogen atom, carboxyl group, amino group, R-group Organisms use 20 types of amino acids R- groups distinguish each amino acid from each other Mixing and matching the 20 amino acids can give rise to an endless diversity of unique proteins Dehydration synthesis reaction connects amino acids to each other to form a peptide bond Two linked amino acids form a dipeptide bond and three linked form a tripeptide bond Chains with fewer amino acids are called Peptides Chains with 100 or more amino acids are called Polypeptides A polypeptide is called a protein once it folds into its functional shape A protein may consist of one or more polypeptide chains Protein Folding: fold into unique 3-dimensional structures four levels of protein conformation: Primary (1 ) Structure: The amino acid sequence of a polypeptide chain. This sequence determines all subsequent structural levels Secondary (2 ) Structure: Substructure with a defined shape resulting from hydrogen bonds between parts of the polypeptide. These interactions fold the chain of amino acids into coils, sheets and loops. Each protein can have multiple types of secondary structure Tertiary (3 ) Structure: The overall shape of a polypeptide, arising primarily from interactions between R groups and water Quaternary Structure (4 ): The shape arising from interactions between multiple polypeptide subunits of the same protein The function of the protein is a direct consequence of its shape. The figure shows a few of the thousands of types of proteins Denaturation or Loss of Function Proteins are vulnerable to conditions that alter their shapes: Heat, Excessive salt, wrong pH; altering the shape so that it can no longer carry out its function Nucleic Acids Each protein’s primary structure is encoded in the sequence of a nucleic acid Nucleic acid is a polymer consisting of monomers called nucleotides Cells contain two types of nucleic acids, Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA) Each nucleotide monomer consists of three components. At the center is a five-carbon sugar–ribose in RNA and deoxyribose in DNA. Attached to one of the sugar’s carbon atoms is at least one phosphate group (PO4). Attached to the opposite side of the sugar is a nitrogenous base: adenine (A), guanine (G), thymine (T), cytosine (C), or uracil (U). DNA contains A, C, G and T, whereas RNA contains A, C, G and U A DNA polymer is a double helix that resembles a staircase Alternating sugars and phosphates form the rails of the staircase And nitrogenous base form the rungs (the horizontal steps of a ladder) DNA’s main function is to store genetic information; its sequence of nucleotides tells a cell which amino acids to string together. RNA is single-stranded One function of RNA is to enable cells to use proteinencoding information in DNA Lipids are Hydrophobic and Energy rich Lipids are organic compounds, with one property in common: They do not dissolve in water They are hydrophobic because they contain large areas dominated by nonpolar carbon-carbon and carbonhydrogen bonds Lipids are not polymers consisting of long chains of monomers, instead they have extremely diverse chemical structures Three groups of lipids: Triglycerides, steroids, and waxes Triglyceride – (more commonly known as fat) consists of three long hydrocarbon chains called Fatty Acids bonded to Glycerol, a three-carbon molecule that forms the backbone of the triglyceride molecule Even though they do not have monomers that form them, cells use dehydration synthesis to produce them Enzymes link three fatty acids to one glycerol molecule, yielding three water molecule each fatty acid has a Carboxyl Group A high-fat content characterizes many unhealthy foods Nutrition labels divide fats into two: Saturated and unsaturated fats The degree of saturation is a measure of a fatty acid’s hydrogen content Saturated fatty acid: contains all the hydrogens it possibly can animal fats are saturated and tend to be solid e.g. bacon fat and butter These have single bonds and each carbon has two hydrogens Most nutritionists recommend a diet low in saturated fats, which tend to clog arteries and cause heart disease A fatty acid is Unsaturated when it has at least one double bond between carbon atoms. These have an oily (liquid) consistency at room temperature Steroids are lipids with four interconnected carbon rings Cholesterol is a key part of animal cell membranes. Many hormones are steroids, e.g. testosterone The liver produces the cholesterol that the animal body needs An unhealthy diet can easily contribute to cholesterol levels that are too high, increasing the chances of cardiovascular disease Because saturated fats stimulate the liver to produce more cholesterol, it is important to limit a dietary intake of both saturated fats and cholesterol Waxes are fatty acids combined with alcohols or other hydrocarbons, usually forming a stiff, water-repellent material. Honey bees build honeycombs out of wax Plants form wax too – their leaves, stems, and fruit have a wax covering that prevents water loss Chapter summary Glossary of terms Monosaccharides Disaccharides Oligosaccharides Polysaccharides Amino acids Peptide bond Dipeptide bond Tripeptide bond Peptides Polypeptides Protein Primary (1 ) Structure Secondary (2 ) Structure Tertiary (3 ) Structure Quaternary Structure (4 ) Nucleic Acids DNA RNA Glycerol Lipids Saturated fatty acid Unsaturated fatty acid Steroids Waxes