Molecular Biology Lecture Notes (24/11/2024) PDF

Molecular biology Lec.-6- Dr. Nada Fadil 24/11/2024 Aims of lecture: 1- Define atom and study the structure of it. 2- Explain the isotopes and their importance in treatment and...

Molecular biology Lec.-6- Dr. Nada Fadil 24/11/2024 Aims of lecture: 1- Define atom and study the structure of it. 2- Explain the isotopes and their importance in treatment and diagnosis. 3- Explain the main types of organic compounds ( carbohydrates and proteins).. Atoms: An atom is the smallest part of an element that displays the properties of the element. Atom structure: Protons and neutrons are located within the nucleus of an atom, and electrons move about the nucleus. Mass number: For example, the element carbon atom has six (Protons, neutrons and electrons). Isotopes Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom. For example, the element carbon has three common isotopes: 1 Molecular biology Lec.-6- Dr. Nada Fadil Applications of isotopes: Radioactive isotopes have many useful applications. In medicine, for example: A)Treatment: 1) An isotope of iodine is used in the treatment of goiter. 2) An isotope of cobalt-60 is extensively employed as a radiation source to arrest the development of cancer. B) Diagnosis: Table isotope in diagnosis Low levels of radiation: Radioactive isotopes are very important in the many medical uses. For example, after 131 patient drinks a solution containing a minute amount of I, it becomes concentrated in the thyroid-the only organ to take it up, ( Fig,2.3). Iodine 131 Normal thyroid gland 2 Molecular biology Lec.-6- Dr. Nada Fadil Diseased thyroid gland Missing portion of organ Figure: Imaging of a diseased thyroid gland The missing area in this thyroid scan indicates the presence of a tumor that does not take up radioactive iodine. High levels of radiation: Radioactive substances in the environment can harm cells, damage DNA, and cause cancer. The harmful effects of radiation can be put to good use (Fig. 2.4 ). 3 Molecular biology Lec.-6- Dr. Nada Fadil Organic and Inorganic compounds: Differernce between organic and inorganic compounds The large organic molecules in cells are macromolecules, polymers formed by the joining together of monomers (subunits). 1-Carbohydrates: Are organic molecules composed of carbon, hydrogen, and oxygen atoms, serving as structural and functional components of cells. Carbohydrates also are called ????????????????. The basic formula for carbohydrates is CH2O, example: Types of carbohydrates:- A- simple carbohydrates: 1- Monosaccharides : are contain low number of carbon atoms ( from three to seven), e.g.: glucose, fructose, ???. 4  Molecular biology Lec.-6- Dr. Nada Fadil 2- Disaccharides Are formed by two monosaccharides linked by a glycosidic bond, for example:  Sucrose (Glucose + Fructose),  Maltose (?????? + ??????),  Lactose (Glucose + Galactose), B- Complex carbohydrates (Polysaccharides): Formed by three or more monosaccharides joined by glycosidic linkages, as amylose (unbranched starch), which is formed exclusively by molecules of glucose, amylopectin (branched starch), glycogen, cellulose, chitin.  Glycogen & starch: are the storage forms of carbohydrates in animal and plant cells.  Chitin & cellulose: are the structural forms of carbohydrates in animal and plant cell. 3- Proteins: Proteins are linear polymers of 20 different amino acids. Approximately 50% of dry weight of living matter is protein. Amino acids are linked together by the peptide bonds in chains of, typically, 100- 300 amino acids. Amino acid structure: Peptide bond: 5 Molecular biology Lec.-6- Dr. Nada Fadil Proteins have four levels of structures:- [ Diseases are caused by denatured proteins: Protein misfolding is believed to be the primary cause of Alzheimer's disease, Parkinson's disease, Huntington's disease, Creutzfeldt-Jakob disease, and many other degenerative and neurodegenerative disorders. 6