Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 2 CHEMISTRY OF LIFE NATURE OF MATTER Matter - anything that has mass and occupies space -consists of atoms Atom – smallest unit of matter that cannot be broken down by chemical means Atom consists of three particles: electron(-), proton(+), and neutron(0). Electrons are negatively charged and have little mass. Protons are positively charged and have a mass of one. Neutrons have no charge, but have a mass of one. Electrons and protons are opposite charges, so they attract each other. Figure 2.10 Electron configurations of the first 18 elements Electron Configurations of the First 18 Elements Active Periodic Table http://www.colorado.edu/physics/2000/applet s/a2.html Atoms typically have one electron for one proton, so they have no electrical charge. ATOMIC MASS – is the sum of protons & neutrons ELEMENTS - a pure substance made of only one kind of atom Elements differ in the number of protons referred to as the ATOMIC NUMBER. The number of neutrons in an atom is often but not always equal to the number of protons in the atom. Atoms of an element that contain different numbers of neutrons, but same # of protons are called ISOTOPES. Isotopes are written with the symbol and mass. C-12, C-13, C-14 RADIOACTIVE ISOTOPES Atoms that emit radiation are said to be radioactive. Many elements have at least one radioactive isotope. Radioactive isotopes are frequently used as tracers. Tracers are extremely valuable in diagnosing diseases. Radioactive isotopes are used to treat certain diseases. (Co-60 & C-14) Radioactive isotopes can be used to kill bacteria that cause food to spoil. Radiation can damage or kill living things and must be handled properly. Detecting Damaged Heart Muscle An isotope called thallium-201 is used to detect damaged heart muscle after a heart attack. Will accumulate only in normal, undamaged heart muscle Cost, risk to patient advantages & disadvantages CHEMICAL BONDING A force that joins atoms is called a chemical bond. Compound – a substance made of the joined atoms of two or more different elements. Every compound is represented by a chemical formula that identifies the elements in the compound and their properties. COVALENT BONDS Covalent bonds form when two or more atoms share electrons to form a molecule. A molecule is a group of atoms held together by covalent bonds. The arrangement of their electrons determines how atoms bond together Electrons are grouped into different levels. Electrons levels can hold a limited number of electrons. Hydrogen (H) and Helium (He) outer level can hold up to 2. 2nd level can hold 8 electrons Higher levels can hold even greater numbers of electrons Atoms want to achieve a stable level which is 8 electrons in the outer level except H & He If the outer electron level is not full, an atom will react readily with atoms that can provide electrons to fill its outer level. HYDROGEN BONDS The electrons in a water molecule are shared by oxygen (O) and hydrogen (H). The shared electrons are attracted more strongly by the oxygen nucleus than by the hydrogen nuclei. Molecules with an unequal distribution of electrical charge are called POLAR MOLECULES. This attraction between 2 water molecules is an example of hydrogen bond – weak chemical attraction between polar molecules. Hydrogen Bonds Oxygen is one of the most electronegative elements In a water molecule electronegative oxygen “hogs” electrons. This “hogging” of electrons results in which type of bond between oxygen and hydrogen within the water molecule? Polar covalent Hydrogen bonds occur between two polar molecules, or between different polar regions of one large macromolecule. One “relatively” negative region is attracted to a second “relatively” positive region. Figure 3.1 Hydrogen bonds between water molecules IONIC BONDS An atom or molecule that has gained or lost one or more electrons is called an ION. Ions have an electrical charge because they contain an unequal number of electrons and protons. An atom that has lost electrons is positively charged, while the atom that has gained electrons is negatively charged. Ionic Compounds Hard Brittle High melting & boiling point Transfer electrons Conduct electricity when dissolved in water Covalent Compounds Not hard Not brittle Low melting and boiling point Shared electrons Doesn’t conduct electricity when dissolved in water Homework State the question into a complete sentence form P. 30 section review questions 1-6 P. 44 &45 chapter review 1, 2, 6, 19 Section 2 WATER AND SOLUTIONS Water absorbs heat more slowly and retains this energy longer than many other substances do. Water helps cells maintain homeostasis. The hydrogen bonds between water molecules cause the cohesion of liquid water. COHESION An attraction between substances of the same kind. Molecules at the surface of water are linked together by hydrogen bonds, which causes a condition known as surface tension. Surface tension prevents the surface of water from stretching or breaking easily. ADHESION An attraction between different polar substances. Adhesion powers a process, called capillary action, which water molecules move upward through a narrow tube or climb up paper. Mixtures A substance composed of two or more elements that are mixed together but not chemically combined. Unlike chemical compounds, the substances that make up a mixture can be added in varying amounts. Mixtures that are made with water can be of two important types AQUEOUS SOLUTIONS Solutions is a mixture in which one or more substances are evenly distributed in an other substance. Solvent does the dissolving. Solute is being dissolved. Ionic compounds and polar molecules dissolve best in water. Water is the greatest solvent because of its polarity. SUSPENSIONS A mixture containing nondissolved particles distributed within a solid, liquid, or gas. Acids and Bases Hydrogen ions (H+) and hydroxide ions (OH-) form when water molecules break. Acid has an increased number of hydrogen ions lowering the pH level. Bases are compounds that lower the concentration of hydrogen ions. All solutions have a pH values between 0-14. Below 7 is an acid. pH scale Each whole number represents a factor of 10 on the scale pH value of 5 has 100 times as many hydrogen ions as one with a pH value of 7 Homework State question in a complete sentence form Section review p. 33 questions 1-5 Chapt review p. 44 & 45 3, 7, 12 Table 2.1 Naturally Occurring Elements in the Human Body Section 3 CHEMISTRY OF CELLS Body is composed of mostly water and organic compounds. Organic compounds contain carbon , hydrogen, and oxygen. Four classes of organic compounds: lipids, proteins, carbohydrates, and nucleic acids. 95% of all known compounds contain carbon CARBOHYDRATES are a key source of energy for the cell (4 calories per gram) Building blocks are monosaccharide's (single sugar) ex. Glucose, fructose, & galactose (ose) C6H12O6 Disaccharides - 2 sugars table sugar - sucrose (1 glucose & 1 fructose) Lactose Milk sugar– 1 glucose & 1 galactose C12H22O11 Carbon has four valence electrons and makes covalent bonds, it can form molecules that are long chains. There are several different kinds of these we will be discussing: hydrocarbons, carbohydrates, lipids, proteins, and DNA. A functional group is a group of atoms of a particular arrangement that gives the entire molecule certain characteristics. Functional groups are named according to the composition of the group. For example, COOH is a carboxyl group. Structural Formula vs Chemical Formula Structural Formula – shows not only kinds & numbers of atoms, but arrangement Chemical Formula– show kinds and numbers of atoms Isomers - having same chemical formula, but different structural formulas Polysaccharides is a macromolecule function as storehouses of the energy contained in sugars. Starch made by plants and glycogen made by animals are examples. Cellulose is a polysaccharide that provides structural support for plants and humans can not digest it. It is considered fiber Macromolecule A very large molecule, such as a polymer or protein, consisting of many smaller structural units linked together. Also called supermolecule or polymer. Upper right - tailpin bacterial virus T7 punctures E. coli cell wall Reactions of Biological Compounds Condensation Reactions also called dehydration synthesis or anabolism– when smaller molecules are bonded together to make large molecules, water is given off Hydrolysis or Catabolism – breaking down large molecules to smaller molecules by adding water http://nhscience.lonestar.edu/biol/dehydrat/de hydrat.html Dehydration synthesis Hydrolysis Lipids Lipids are nonpolar molecules. Fats, steroids, waxes, and phospholipids (Found in cell membrane) Fats store energy.(9 calories per gram) Saturated fatty acids are generally solid at room temperature – mostly animal Unsaturated fatty acids are generally liquid at Fatty acid is the basic building block of lipids Glycerol is a trihydric alcohol (containing three -OH hydroxyl groups) that can combine with up to three fatty acids to form monoglycerides, diglycerides, and triglycerides Protein is usually a large molecule formed by linked smaller molecules called amino acids. (4 calories per gram) Amino acids are the building blocks of proteins. There are 20 different amino acids found in proteins. Proteins can be enzymes which promote chemical reactions. Collagen found in skin, ligaments, tendons, & bones. Humans can produce 10 of the 20 amino acids do not have all the enzymes required for the biosynthesis of all of the amino acids. Bonds between amino acids are called peptide bonds NUCLEIC ACIDS A nucleic acid is a long chain of smaller molecules called nucleotide. A nucleotide has three parts: sugar, a base, and a phosphate group. Two types of nucleic acids: DNAdeoxyribonucleic acid consists of two strands of nucleotides spiral around each other Chromosomes contain long strands of DNA, which stores heredity information. RNA ribonucleic acid, single strand of nucleotides. RNA plays many key roles in the manufacture of proteins. ATP – adenosine triphosphate – food energy is temporarily stored in ATP Cells need a steady supply of ATP to function. HOMEWORK Restate the question in complete sentence form SECTION 3 PAGE 37 Chapter review p. 44 & 45 quest. 8,9, 13, 17 STP 1-3 Bonus quest. 18 quest 1-5 Section4 Energy and Chemical Reactions Energy is the ability to move or change matter. (many forms) Energy can be stored or released by chemical reactions. Chemical reaction is a process during which chemical bonds between atoms are broken. Starting materials called reactants. Newly formed substance is called products. Energy is either released or absorbed during a chemical reaction. Metabolism is the term used to describe all of the chemical reactions that occur within an organism. Types of chemical reactions An exothermic reaction is a chemical reaction that releases energy in the form of heat.. An endothermic reaction is any chemical reaction that absorbs heat from its environment. These examples could be written as chemical reactions, but are more generally considered to be endothermic or heatabsorbing processes: melting ice cubes melting solid salts evaporating liquid water converting frost to water vapor (melting, boiling, and evaporation in general are endothermic processes) splitting a gas molecule cooking an egg Activation Energy The energy needed to start a chemical reaction is called Activation Energy. Enzymes are substances that increase the speed of chemical reactions. Act as catalysts which reduces activation energy. Most enzyme-assisted reactions are reversible. Enzyme Specificity Substrate is a substance on which an enzyme acts during a chemical reaction. An enzyme’s shape determines its activity. Active sites is one or more deep folds on an enzyme’s surface Factors in Enzyme Activity Any factor that changes the shape of an enzyme can affect the enzyme’s activity Temperature and pH level are some factors that affect enzyme activity. Another limiting factor is amount of available enzyme Homework Restate questions in complete sentence form P. 42 q. 1-6 P. 44 & 45 q. 4, 10, 11, 16