BCH2333
Chapter 1: Life
Norman Horowitz proposed a useful set of criteria for living systems: Life possesses the properties of replication, catalysis, and mutability
Biochemistry is the study of life on the molecular level
PROKARYOTES
life is based on morphological units known as cells
->formulation of this concept was by Matthias Schledien and Theodor Schwann but origins were traced to the 17th century observations of early microscopists such as Robert Hooke two major classifications of cells: the eukaroytes(eu:good or true + karyon:kernel or nut)
->has a membrane-enclosed nucleus that contains the DNA(deoxyribonucleic acid) and the prokaryotes(pro:before)
->lacks a nucleus prokaryotes comprise different types of bacteria
->have simple structures and are unicellular eukaryotes are way more complex than prokaryotes though they are multicellular as well as unicellular
Viruses are simple entities than cells
->not classified as living because they lack the metabolic apparatus to reproduce outside their host cell
->essentially large molecular aggregates
A. Form and Function prokaryotes are most numerous and widespread organisms due to their ability to vary and having a highly adaptable metabolism certain types of bacteria can thrive or even require conditions that are hostile to eukaryotes such as unusual chemical environments, high temperatures(high as 130oC) and lack of oxygen rapid reproductive rate of prokaryotes allows them to take advantage of favorable conditions and the ability of many bacteria to form resistant spores aloows them to survive adverse conditions
Prokaryotes Have Relatively Simple Anatomies prokaryotes were first observed in 1683 by the inventor of the microscope, Amtpmoe van Leeuwenhoek prokaryotes' size vary from the range 1 to 10 micrometer
->have one of the three basic shapes: spherodial(cocci), rodlike(bacilli), and helically coiled(spirilla) but all have same general design
->bounded by a thick cell membrane(plasma membrane), membrane consists of a lipid bilayer containing embedded proteins that control the passage of molecules in and out of the cell and catalyze a variety of reactions cells of most prokaryotic species are surrounded by a rigid cell wall that mainly functions to protect the cell from injuiries and to prevent it from bursting some bacteria further encase themselves in a gelatinous polysaccharide capsule that protects them from the defenses of higher organisms though prokaryotes lack the membranous subcellular organelles characteristic of eukaryotes, their plasma membranes can be infolded to form multilayered structures(mesosomes)
->mesosomes are thought to serve as the site of DNA replication and other specialized enzymatic reactions the prokaryotic cytoplasm (cell contents) contains a single chromosome(DNA molecule) that is condensed to form a body known as a nucleoid
->cytoplasm also contains numerous species of RNA(ribonucleic acid), a variety of soluble enzymes(proteins that catalyze specific reactions), and many thousands ribosomes(sites of protein synthesis) many bacterial cells bear one or more whiplike appendages known as flagella(used for locomotion) certain bacteria have filamentous projections named pili, some types of which function as conduits for DNA during sexual conjugation(a process where DNA is transferred from one cell to another; prokaryotes usually reproduce by binary fission) the bacterium Escherichia coil (Ecoil) is the biologically most well-characterized organism since it has been studied over the past 70 years
->cells of this normal inhabitant of the higher mammalian colon are typically 2 micrometer long rods that are 1 micrometer in diameter ans weigh 2x10-12g
->its DNA has a molecular mass of 2.5x109 daltons(D), encodes ~4300 proteins(only~2600 different proteins are present in a cell at any given time)
->altogether an Ecoli cell contains 3-6 thousand different types of molecules including proteins, nucleic acids, polysaccharides, lipids and
