MED1003 Week 5 Lecture (Online materials) PDF

Molecules, Cells and Genes by Siu Wai (Phyllis) TSANG, PhD TUNG WAH COLLEGE email: [email protected] Office#: 3190-6713 Prepared by SWT 2024 email: [email protected] 1 Classification of organisms ─ 3 domains...

Molecules, Cells and Genes by Siu Wai (Phyllis) TSANG, PhD TUNG WAH COLLEGE email: [email protected] Office#: 3190-6713 Prepared by SWT 2024 email: [email protected] 1 Classification of organisms ─ 3 domains We humans are “Eukaryotes” as we belong to the domain “Eukarya” Human cells are eukaryotic cells as they have true nuclei Prepared by SWT 2024 email: [email protected] 2 Classification of organisms ─ 7 levels https://study.com/cimages/multimages/16/animal_taxonomy_triangle.png Before the domain taxon was introduced during the 1990s, the kingdom ranked as the highest taxonomic level in classification Most scientists today recognize six kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, or Animalia Prepared by SWT 2024 email: [email protected] 3 Taxonomy Taxon (pl. taxa) is a scientifically classified group or entity It is generally accepted that there are eight levels of taxa domain, kingdom, phylum (pl. phyla), class, order, family, genus (pl. genera) and species Taxonomy is the part of the science of systematics that deals with identifying, describing and categorizing organisms from species to higher taxa Nomenclature is a system of giving names to organisms based on rules established for the process Prepared by SWT 2024 email: [email protected] 4 Binomial nomenclature Each species has its own scientific name, composed of the genus name and species epithet e.g., the lion’s scientific name is Panthera leo e.g., the tiger’s scientific name is Panthera tigris https://microbenotes.com/wp- content/uploads/2022/02/Binomial-Nomenclature.jpeg Prepared by SWT 2024 email: [email protected] 5 Binomial nomenclature Some species include groups with such distinctive traits that they are classified as subspecies; the subspecies name is added to the end of the species name e.g., Panthera tigris altaica a subspecies of Panthera tigris include the Siberian tiger e.g., Panthera tigris tigris a subspecies of Panthera tigris include the Indian or Bengal tiger Prepared by SWT 2024 email: [email protected] 6 Binomial nomenclature (cont’d) The system of binomial nomenclature was introduced by the Swedish natural scientist Carl Linnaeus Multiple local names make it extremely difficult to identify an organism globally and keep a track of the number of species The scientific name of humans is presented as Homo sapiens; ‘Homo’ represents the genus and ‘sapiens’ represents a particular species All the scientific names of organisms are usually Latin, so they are written in italics The name of the genus starts with a capital letter and the name of the species starts with a small letter This is the formal naming system for all living things Prepared by SWT 2024 email: [email protected] 7 Binomial nomenclature (cont’d) https://media.geeksforgeeks.org/wp-content/uploads/20230601122106/Binominal-Nomenclature.webp Prepared by SWT 2024 email: [email protected] 8 Binomial nomenclature (cont’d) https://media.geeksforgeeks.org/wp-content/uploads/20240415180202/Scientific-Names-of-Animals-And-Plants.webp Prepared by SWT 2024 email: [email protected] 9 Molecules, Cells and Genes All organisms are made up of cells Cells are the basic vital unit for all forms of life Organisms can be multicellular or unicellular Most recent estimates that the number of cells in the average human body is at ~30 trillion, i.e., 30,000,000,000,000 cells There are >200 cell types in the human body Cell types can vary in size and shape, and carry out distinct roles within the body Organelles are special and organized structures found in living cells Prepared by SWT 2024 email: [email protected] 10 Molecules, Cells and Genes (cont’d) https://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/14704956/U1CP1-1_SizeScale_ksm.jpg Prepared by SWT 2024 email: [email protected] 11 Molecules, Cells and Genes (cont’d) Prepared by SWT 2024 email: [email protected] 12 Isolation of cells https://www.open.edu/openlearn/mod/oucontent/view.php?printable=1&id=13785 When a suspension of cells is placed in an appropriate physiological solution and disrupted, e.g., by detergents / ultrasound / homogenization, many of the organelles such as nuclei, mitochondria and Golgi apparatus remain intact Prepared by SWT 2024 email: [email protected] 13 Centrifugation An indispensable procedure in the molecular biology laboratory A technique used to collect cells and separate cell organelles The process involves the use of the centripetal force Prepared by SWT 2024 email: [email protected] 14 Centrifugation (cont’d) The rate of centrifugation is specified by the acceleration applied to the sample, typically measured in rotations per minute (RPM) or relative centrifugal force (RCF), i.e., gravity (g) × force https://chem.libretexts.org/@api/deki/files/404364/clipboard_e629c6697813a373bee6e5abefb1574d9.png?revision=1 Prepared by SWT 2024 email: [email protected] 15 Before and after centrifugation Whole blood Prepared by SWT 2024 email: [email protected] 16 Differential centrifugation Prepared by SWT 2024 email: [email protected] 17 Patch clamp technique A technique in electrophysiology that allows the study of individual ion channels in cells It is used to evaluate the current or voltage in the membrane associated with ion channel activity via direct measurement in real time Ultra-sensitive amplifiers, high-quality data acquisition systems and powerful software are needed in the patch clamp experiments e.g., this technique can be used to study excitable cells such as neurons, myocytes, muscle fibers and beta cells of the pancreas… http://2018.brs.org.tr/wp-content/uploads/2018/02/patch-2-1.jpg Prepared by SWT 2024 email: [email protected] 18 Ion channels Ion channels are selective pores at the membrane https://uen.pressbooks.pub/app/uploads/sites/38 2/2024/03/U13-008-Voltage-gated-channel-1.png Ion channels have ion selectivity (specific tunnels) They only allow passage of specific molecules Ion channels are not open continuously Upon conformational changes  open and close Prepared by SWT 2024 email: [email protected] 19 Prepared by SWT 2024 email: [email protected] 20 Prepared by SWT 2024 email: [email protected] 21