Transcript Topic 2
Topic 2 CELLS Nerve cell 2.1 Cell Theory • Assignment: –Vocabulary Assignment –Biozone-- page 57-60, 62-65, 80, 81, 96, 256, 266 (be prepared for a quiz) –Chapter readings-- pages 4, 5, 9, 52-54, 212, 218, 219 (be prepared for a quiz) –Essay Topic-- Investigate and report on one therapeutic use of stem cells (typed, edited, 1-2 pages) due Friday September 2nd 2.1.1 Outline the Cell Theory 1. All living organisms are composed of cells, and the products of cells (ex. hair and scales) 2. Cells are the smallest units of life 3. Cells only come from pre-existing cells Advances in technology (particularly the electron microscope) greatly increased our knowledge of cells and allowed us to study the ultrastructures in detail Hooke, Schleiden and Schwann Characteristics of Cells Characteristics of Cells (functions of living things) • Metabolism- all the chemical reactions that occur within an organism • Response- to stimuli which is also known as sensitivity • Growth- includes both in cell size and number • Reproduction- whether sexual or asexual (passing heredity molecules to offspring) • Homeostasis- which means maintaining relatively stable conditions inside the body • Nutrition- which means the source of food for nutrients and energy 2.1.2 Discuss the Evidence for the Cell Theory • A series of steps led to the discovery of cells (mostly related to advances in technology) – 1590- Dutch optician Zacharias Jansen invents the compound microscope (compound means 2 or more lenses which provides greater magnification) – 1665- Englishman Robert Hooke studies cork and coins the term “cells” – 1675- Dutchman Antonie van Leeuwenhoek discovers unicellular organisms – 1838- German Mathias Schleiden suggests all plants are made of cells Evidence (cont.) • 1839- German Theodor Schwann suggests all animals are made from cells • 1840- Czech Jan Evangelista Purkinje names the cells contents “protoplasm” • 1855- German Rudolf Virchow suggests that all cells come from other cells (biogenesis) • 1860s- scientists disproved the theory of spontaneous generation (ex. Louis Pasteur) Evidence for the Cell Theory • Inductive reasoning – Using verifiable observations and measurements to draw conclusions – General principles from a large number of specific observations – ex. All living things are made of cells • Deductive reasoning – Inquiry – questions, hypotheses, testing – Predictions tested through experiments – If then type of logic from general to specific – ex. Humans are made of cells What is Protoplasm? The Cell Theory 2.1.3 State that unicellular organisms carry out all the functions of life • Organisms such as paramecium, euglena, chlamydomonas and amoeba have only one cell and this single cell has to carry out all the functions of life (metabolism, response, homeostasis, growth, reproduction and nutrition) Viruses vs. Unicellular Organisms • Viruses- have no cytoplasm or organelles, no metabolism, depend on host cells for metabolism and reproduction (NOT considered living) • Unicellular organisms – Bacteria = prokaryotic – Protista = eukaryotic (ex. amoeba, euglena, paramecium, chlamydomonas) – Carry out all the functions of life draw and label each protista above as well as describe (autotroph, heterotroph, location, size????) 2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells using appropriate SI units • SI stands for International System of Units (from French: Système International) • 100 cm = 1 m • 10 mm = 1 cm • 1000 mm = 1 m • 1000 μm = 1 mm (so there are 1000000 µm in a meter) • 1000 nm = 1 μm or 1000000 nm = 1 mm Table of Relative Sizes • Most useful units for measuring the sizes of cells and structures within them are micrometers (μm) and nanometers (nm) Biological Structure Typical Size Molecules (e.g. DNA double helix is 2 nm in diameter and a hydrogen atom is 0.1 nm) 0.1 – 2 nm Cell Membrane Thickness 7.5 – 10 nm Viruses (sizes vary) HIV is 100 nm Bacteria (sizes vary) 1-4 μm or 1000-4000 nm Mitochondrion 0.5-5 μm Chloroplast Organelles 2-10 μm Nucleus 10-20 μm Prokaryotic Cell 1-5 μm Eukaryotic Cell 10-100 μm Sizes of Cells and Organelles Vary • • • • Animal cells are often smaller than plant cells The yolk of an egg is one cell Each sap filled vesicle of an orange is one cell The largest known bacterium (Epulopiscium) was found in fish in the tropical waters surrounding Lizard Island, Australia is over 1 mm in length