Biology Chapter 3 Notes:Week 3
Biology Chapter 3 Notes:Week 3 BIO-101-105
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Adriana Shania Proctor
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This 10 page Class Notes was uploaded by Adriana Proctor on Saturday September 17, 2016. The Class Notes belongs to BIO-101-105 at Chesapeake College taught by Doctor Hatkoff in Fall 2016. Since its upload, it has received 3 views. For similar materials see Fundamentals of Biology I in Science at Chesapeake College.
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Date Created: 09/17/16
Biology Lecture Notes Chapter 3 Carbon:The Backbone of Life Because of the actions of plants, carbon can enter the biosphere. With the use of solar energy, plants transform the atmospheric CO2 into molecules of life, where are thus eaten by planteating animals. Out of every element, carbon(C) can create large and complex molecules when they are bonded to other atoms like ● Hydrogen(H) ● Oxygen(O) ● Nitrogen(N) ● Sulfur(S) ● Although cells are between 75%95% water, the rest consists of carbonbased compounds. ● Carbon has the unparalleled ability to create large and diverse molecules. Carbohydrates Lipids Nucleic Acids Proteins *Remember the elements of life: Carbon hydrogen, oxygen, nitrogen; with more miniscule amounts of sulfur and phosphorus. Organic Chemistry is the study of Carbon Compounds Compounds that contain carbon are claimed to be organic. The branch that studies such a thing specifically is organic chemistry. Carbon is versatileit can be used to create an inexhaustible variety of organic molecules. Organic Molecules and the Origin of Life on Earth At around 1953 Stanley Miller was able to stimulate early conditions on Earth in a lab. He then showed through an experiment how organic molecules could form. Organic MoleculesMolecules that contain carbon(with at least a hydrogen atom), or organic compounds. Living organisms are made of these. Carbon atoms can form Diverse Molecules by Bonding to Four other Atoms ● An atoms electron configuration can determine the kinds and number of bonds that the atom will form with other bonds. ● This is the source of carbon’s versatility. The Formation of Bonds with Carbon Carbon as an element has four(4) valence electrons in its outer shell and can fill this outer valence by sharing its four electrons, so that eight(8) of these electrons are present. These shared electrons establish a covalent bond. CO2 has no hydrogen so we consider it to be inorganic. This(CO2) is the source of carbon for the living part of the world. Carbon is able to bond to a variety of atoms such as: ● Oxygen ● Hydrogen ● Nitrogen Carbon atoms are also able to bond to other carbons, which forms the carbon skeleton of organic compounds. ValenceThe number of covalent bonds an atom can form. It is equal to the number of electrons needed to finish the atom in questions outermost(valence) electron shell. Molecular Diversity Arising from Variation in Carbon Skeletons ● Organic carbon compounds can form chains, branches, or rings. ● Some of these carbon skeletons have double bonds that vary in location as well as numbers. ● Such variations in these carbon skeletons happen to be one important source of the molecular complexity and diversity that characterize living matter. ● The unique properties of an organic compound depend on two main conditions. 1)The size and shape of its carbon skeleton. 2) The groups of atoms that are attached to that skeleton. ● IsomersVariations in the structure of the organic molecule. Isomers also have the same number of atoms but in the different arrangements, and thus different properties. 1. Structural IsomersThese differ in their covalent arrangements of their atoms. They both contain the same molecular formula, but they are different in their covalent arrangements of their carbon skeletons. 2. Cistrans IsomersCarbons that have covalent bonds to the same atoms, but they are different in their spatial arrangements due to their lack of flexibility of double bonds. 3. EnantiomersIsomers that are mirror images of each other yet are different in shape because of the presence of asymmetric carbon, where one is attached to four different atoms or groups of atoms. Sometimes only one isomer is biologically active due to the ability of that forms bond being specific to molecules in an organism. Hydrocarbons HydrocarbonsAre organic molecules consisting of just carbon and hydrogen. They are nonpolar and are, therefore, hydrophobic. Hydrocarbons can undergo chemical reactions that can release a large amount of energy. An example of hydrocarbons are fats and petroleum(fossil fuels). These compounds are hydrophobic(they either repel or fail to mix with water)because of the great majority of their bonds being nonpolar carbontohydrogen linkages. Hydrocarbons can release a lot of energy. ● Polysaccharides, the polymers of sugar, have storage and structural roles ● The structure and function of a polysaccharide are determined by its sugar monomers and the positions of bonds. Storage Polysaccharides ● Starch, a storage polysaccharide of plants,consists entirely of glucose monomers ● Plants store surplus starch as granules. Glycogen is a storage polysaccharide in animals ● Humans and other vertebrates store glycogen mainly in liver and muscle cells Structural Polysaccharides ● The polysaccharide cellulose is a major component of the tough wall of plant cells ● Cellulose is a polymer of glucose What happens when we ingest cellulose? ● Enzymes that digest starch by hydrolyzing αlinkages can’t hydrolyze β linkages in cellulose ● Cellulose in human food passes through the digestive tract as insoluble fiber Lipids are a diverse group of hydrophobic molecules Lipids have little or no affinity for water! Lipids are hydrophobic! Lipids are important in longterm energy storage! The most biologically important lipids are fats, phospholipids , and steroids Fats Fats are constructed from two types of smaller molecules: glycerol and 3 fatty acids. ● Fatty acids vary in length (number of carbons) and in the number and locations of double bonds ● Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds ● Animal fats, solid at room temperature ● Unsaturated fatty acids have one or more double bonds. ● Plant and fish fats, can be called oils, liquid at room temp Phospholipids and steroids are important lipids with a variety of functions Phospholipids are the major component of all cell membrane . Phospholipids cluster into a bilayer of phospholipids. ● Phospholipids and steroids are important lipids with a variety of function ● A common component in animal cell membranes a starting material for making steroids Proteins include a diversity of structures, resulting in a wide range of functions ● Proteins account for more than 50% of the dry mass of most cells ● Protein functions include defense, transportation, storage, cellular communication, movement, and structural support. ● Life would not be possible without catalysts ● Enzymatic proteins act as catalysts, to speed up chemical reactions without being consumed in the reaction ● Proteins are unbranched polymers built from the same set of 20 amino acids Protein Structure and Function A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape The amino acid sequence of each polypeptide leads to a protein’s threedimensional structure A protein’s structure determines its function. Four Levels of Protein Structure ● Proteins are very diverse, but share three levels of structure called primary, secondary, and tertiary structure ● A fourth level, quaternary structure, arises when a protein consists of two or more polypeptide chains The primary structure of a protein is its unique sequence of amino acids. Secondary structure, found in most proteins, consists of localized coils and folds in the polypeptide chain. Tertiary structure is the fully folded polypeptide chain(protein). Proteins have a wide range of functions and structures ● If a protein’s shape is altered, it can no longer function. ● In the process of denaturation, a protein unravels, loses its specific shape, and loses its function. ● Proteins can be denatured by changes in salt concentration, changes in pH, or high heat. Nucleic acids store, transmit, and help express hereditary information ● The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene. ● Genes are made of DNA, a nucleic acid made of monomers called nucleotid s. The Roles of Nucleic Acids There are two types of nucleic acids: ● Deoxyribonucleic acid (DNA) ● Ribonucleic acid (RNA) ● DNA provides directions for its own replication ● DNA also directs synthesis of messenger RNA(mRNA) and, through mRNA, controls protein synthesis. Nucleic acids are polymers of nucleotides ● RNA is usually a single polynucleotide strand. DNA nitrogenous bases are ● adenine (A) Adenine>Thymine and Cytosine>Guanine ● Thymine(T) ● cytosine (C) ● guanine (G) ● RNA also has A, C, and G, but instead of T, it has uracil (U). *These do not match with anything else. At all. What is the difference between DNA and RNA? DNADeoxyribonucleic acid, is a molecule that carries genetic information used in development, growth, reproduction, and function of all living organisms as well as various viruses. It is a DOUBLE HELIX. It also has THYMINE, NOT URACIL. RNARIbonucleic acid, it is a nucleic acid that is present in all living cells. It acts as a messenger that carries instructions from DNA for controlling the synthesis of proteins. However, some viruses with RNA instead of DNA carry the genetic information. It is a SINGLE STRAND. It also has URACIL, NOT THYMINE.
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