Chapter 3 Lecture 1.pptx

CELLS Chapter 3 Lecture 1 Lecturer: Ms Thabisa Mdlangu [email protected] Pracs: [email protected] Tuts: [email protected] The cell history 1660 Robert Hooke – English physicist melted spun glass to create lenses Focused on bee stings, fish scales, fly legs, and any type of insect that he could...

CELLS Chapter 3 Lecture 1 Lecturer: Ms Thabisa Mdlangu [email protected] Pracs: [email protected] Tuts: [email protected] The cell history 1660 Robert Hooke – English physicist melted spun glass to create lenses Focused on bee stings, fish scales, fly legs, and any type of insect that he could hold still Used the lens to look at a cock from the bark of an oak tree… it appeared to be divided into little boxes He called these cells because they looked like cells for monks Although he did not realize the significance of his work at the time, he was the first person to see cells His discovery initiated a new science, CELL BIOLOGY 1673 – Antony van Leeuwenhoek of Holland improved lenses further He created the earliest microscopes One of the 1st objects he studied was tartar scraped from his teeth He viewed bacteria and protists that people didn’t know existed He also described microscopic parts of larger animals, including human red blood cells and sperm However, he failed to see the single-celled animalcules reproduce https://www.researchgate.net/profile/Ahmed-Adeel/publication/31708627 1/figure/fig3/AS:507654741413889@1498045730583/Leeuwenhoeks-mi croscope.png The Cell theory In the 19th century, more powerful microscopes with improved magnification and illumination revealed details of structures within the cell In the early 1830’s, a Scottish Surgeon: Robert Brown, noted a roughly circular object in cells from orchid plants He saw the structure in every cell, then identified it in cells of a variety of organisms He named it a nucleus Soon, microscopists distinguished the translucent moving material that made up the rest of the cell, calling it a cytoplasm In 1839, a German Biologist Matthias J Schleiden and Theodore Schwann proposed a new theory based on many observations made with microscopes Schleiden first observed that cells are the basic units of life and Schwann compared animal cells to plant cells After observing many similarities in many different plant and animal cells, Schleiden and Schwann formulated a cell theory, which originally had two main components: - All organisms are made up of one or more cells, - The cell is the fundamental unit of life German physiologist Rudolf Virchow added a third component to the cell theory in 1855, when he proposed that all cells come from preexisting cells….. This idea contradicted spontaneous generation In 1859, Louis Pasteur finally disproved spontaneous generation and he provided additional evidence in support of the cell theory Electron microscope Dissecting microscope Compound/Light microscope Microscopes Magnify Cell Structures Cells are too small to observe with the naked eye and require the use of a Microscope: a) Light Microscopes Generating true-colour views of living or preserved cells Light pass through the object to reveal internal features, Specimens must be transparent or thinly sliced Uses two or more lenses to focus visible light through the specimen Can magnify up to 1600 x b) Transmission Electron Microscopes (TEM) Sends a beam of electrons through a very thin slice of a specimen It uses a magnetic field rather than a glass lens to focus the beam Microscope translates the contrasts in electron transmission into a high-resolution, two-dimensional image showing internal features Can magnify up to 50 million x c) Scanning Electron Microscopes (SEM) Scans a beam of electrons over the surface of a metal-coated, three dimensional specimen Salmonella bacteria viewed under Scanning Electron Microscope Salmonella bacteria viewed under Light/Compound microscope All cells have some features that are common Even though cells may appear very different they all share some features that reflect their shared evolutionary history. These structures allow them to reproduce, grow, respond to stimuli, and obtain energy DNA: the cell’s genetic information RNA: which is instrumental in protein synthesis Ribosomes: structures that manufacture proteins Proteins: carry out all of the cell’s work Cytoplasm: includes all cell contents Cytosol: the fluid portion of the cytoplasm Lipid-rich Cell Membrane (Plasma Membrane): forms a boundary between the cell and its environment Different Cell Types Characterize Life’s Three Domains Until recently, biologists organized life into just two categories: Prokaryotic and Eukaryotic Prokaryotes: the simplest and most ancient forms of life are organisms whose cells lack a nucleus Eukaryotes have cells that contain a nucleus In 1977, a microbiologist, Carl Woese studied key molecules in many cell types and detected differences suggesting that Prokaryotes actually include two forms of life that are distantly related to each other Then Biologists divided life into three domains: Bacteria, Archaea and Eukarya Domain Bacteria Most abundant and diverse organisms on Earth. Some species such as Streptococcus and Escherichia coli, can cause illness, Others essential to good health and found on the skin and in the intestinal tract. Bacteria cells are structurally simple. The nucleoid is the area where the cell’s circular DNA molecule congregates. A rigid cell wall surrounds the cell membrane protecting the cell and preventing it from bursting if it absorbs too much water. Many bacteria can swim in fluids by using flagella/tail-like appendages that enable these cells to move Domain Archaea Comprises organisms structurally very similar to bacteria that differ in the composition of their phospholipids, cell walls, and flagella Domain Eukarya’s Members are typically large in size. The cytoplasm is divided into Organelles, compartments that carry out specific functions. An elaborate system of membranes creates these compartments. The cells are nucleated Cell History Summary Year Scientist 1660 Robert Hooke 1673 Antony van Leeuwenhoek Early 1830's Robert Brown 1839 MatthiasJ Schleiden and Theodore Schwann 1855 Rudolf Virchow 1859 LouisPasteur 1977 Carl Woese Discovery Discovered cells on the cock froman poak tree usinglenses frommelted spun glass Created the Earliest Microscopes & birthed the idea of spontaneous generation Discovered a neucleus fromcells of orchid plants Proposed the early cell theory with only two components Added the 3rd component on the early cell theory Finally disproved the idea of spontaneous generation Detected differences suggesting that Prokaryotes actually includes two forms of life that are distantly related to each other (Domain Archaea and Domain Bacteria) Glossary of terms Cell Animalcules Spontaneous generation The Early Cell theory Additional ideas to the modern cell theory Prokaryotes Eukaryotes Domain Bacteria Domain Archaea Domain Eukarya Flagella Nucleoid