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Chapter 2 chemistry power point
- 1. Chapter 2. The Chemistryof Life
- 2. 2.1 The Natureof Matter Atoms Protons (+) Neutrons (0) Protons and Neutrons have the same mass Protons and neutrons form the nucleus, the center of the atom Electrons (-) In constant motion 1/1840 the mass of proton Equal number of electrons and protons (atoms remain neutral) Forms electron cloud.
- 3. 2.1 The Natureof Matter Elements Element - a pure substance that consists entirely of one type of atom More than 100 elements are known Elements are represented by a one- or two-letter symbol Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 7 neutrons 6 C 12.011
- 4. 2.1 The Natureof Matter Elements Atomic Number – the number of protons in an atom of an element Mass number – the sum of protons and neutrons in the nucleus of an atom Radioactive carbon-14 6 CCarbon 12.011 Atomic Number Element Symbol Atomic Mass Element Name
- 5. 2.1 The Natureof Matter Isotopes Atoms of elements can have different numbers of neutrons Isotopes – atoms of the same element that differ in the number of neutrons they contain Identified by their mass number Because they have the same number of electrons, all isotopes of an element have the same chemical properties. Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 8 neutrons 6 electrons 6 protons 7 neutrons
- 6. 2.1 The Natureof Matter Radioactive Isotopes Some isotopes are radioactive – meaning their nuclei are unstable and break down at a constant rate over time Radiation can be dangerous, but also have a number of important scientific and practical uses Examples: Geologists determine the age of rocks and fossils Can treat cancer Kill bacteria that cause food to spoil Can be used as “tracers” to follow the movements of substances within organisms
- 7. 2.1 The Natureof Matter Chemical Compounds Most elements are combined with other elements Compound – a substance formed by the chemical combination of two or more elements in definite proportions Ex. Water (H20) and table salt (NaCl)
- 8. 2.1 The Natureof Matter Chemical Compounds The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed Let’s examine water and table salt…
- 9. 2.1 The Natureof Matter Chemical Bonds The atoms of compounds are held together by chemical bonds Bond formation involves the electrons. The electrons that are available to form bonds are called valence electrons. The main types of chemical bonds are ionic bonds and covalent bonds.
- 10. 2.1 The Natureof Matter Ionic Bonding Ionic Bond – formed when one or more electrons are transferred from one atom to another Atoms are electrically neutral Loses an electron – positive charge (cations) Gains an electron – negative charge (anions) Called ions Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-) Transfer of electron Protons +11 Electrons -11 Charge 0 Protons +17 Electrons -17 Charge 0 Protons +11 Electrons -10 Charge +1 Protons +17 Electrons -18 Charge -1
- 11. 2.1 The Natureof Matter Covalent Bonding Sometimes electrons are “shared” instead of transferring Covalent bond – forms when electrons are shared between atoms Share two electrons – single covalent bond Share four electrons – double covalent bond Share six electrons – triple covalent bond The structure that results when atoms are joined together by covalent bonds is a molecule, The molecule is the smallest unit of most compounds.
- 12. 2.1 The Natureof Matter Van der Waals Forces Atoms do not all have the same ability to attract electrons Creates regions that may have a tiny positive or negative charge. Van der Waals forces – when molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules.
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- 14. 2.2 Properties ofWater The Water Molecule Earth is called “the Blue Planet.” How much water covers the earth’s surface? Water is the single most abundant compound in most living things Ice is less dense than liquid water.
- 15. 2.2 Properties ofWater The Water Molecule - Polarity A molecule in which the charges are unevenly distributed is called a polar molecule A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms. The negative pole is near the oxygen atoms and the positive pole is between the hydrogen atoms. 8 protons 1 proton + -_
- 16. 2.2 Properties ofWater The Water Molecule – Hydrogen Bonds Because of their partial positive and negative charges, polar molecules can attract to each other. The attraction between H atom of one water molecule and the O of another is an example of hydrogen bonds. Hydrogen bonds are NOT as strong as covalent or ionic bonds.
- 17. 2.2 Properties ofWater The Water Molecule – Hydrogen Bonds A single water molecule can be involved in as many as four hydrogen bonds. Cohesion – an attraction between molecules of the same substance. Adhesion – the attraction between molecules of different substances. Ex. Capillary action.Is this cohesion or adhesion???
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- 19. 2.2 Properties ofWater The Water Molecule – Review 1. What kind of bonds join the atoms in a water molecule? 2. Are the hydrogen atoms bonded to each other? 3. Why is the hydrogen end of the molecule positive and the oxygen end negative? PG 40
- 20. 2.2 Properties ofWater Solutions and Suspensions Water is not always pure – it is often found as a mixture. Mixture – a material composed of two or more elements, but are not chemically combined. Ex. Salt and pepper. Two types of mixtures that can be made from water: solutions and suspensions.
- 21. 2.2 Properties ofWater Solutions Look below, sodium and chloride ions are attracted to the polar water molecules. The ions become dispersed in the water, forming a mixture called a solution. Solutions – evenly distributed throughout the solution. Cl- Water Cl- Na+ Water Na+
- 22. 2.2 Properties ofWater Solutions Solute – the substance that is dissolved. Solvent – the substance in which the solute dissolves. What is the solute and solvent in the saltwater solution? Cl- Water Cl- Na+ Water Na+
- 23. 2.2 Properties ofWater Suspensions Some materials do not dissolve, but when placed in water separate into pieces so small they do not settle out. These mixtures are known as suspensions. Ex. Blood
- 24. 2.2 Properties ofWater Acids, Bases, and pH Water can react to form ions. H20 H+ + OH- (water) hydrogen hydroxide ion ion Water is neutral because the number of positive hydrogen ions produced is equal to the number of negative hydroxide ions produced.
- 25. 2.2 Properties ofWater The pH Scale The pH scale is used to indicate the concentration of H+ ions. Ranges from 0-14 7 - neutral Below 7 – acidic (more H+) Ex. Hydrochloric acid in the stomach Above 7 – basic (more OH-) Ex. lye Each scale represents a factor of ten. Buffers – weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes. Ex. Maintain homeostasis Oven cleaner Bleach Ammonia solution Soap Sea water Human blood Pure water Milk Normal rainfall Acid rain Tomato juice Lemon juice Stomach acid Neutral IncreasinglyBasicIncreasinglyAcidic
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- 27. 2.3 Carbon Compounds TheChemistry of Carbon Organic chemistry – the study of all compounds that contain bonds between carbon atoms Why is carbon so important? Has four valence electrons (forms strong covalent bonds) Can bond with: hydrogen, phosphorus, sulfur, and nitrogen Can also bond with other carbon atoms (form chains of unlimited length) Single, double, or triple covalent bonds Can form large and complex structures. Methane Acetylene Butadiene Benzene Isooctane
- 28. 2.3 Carbon Compounds Macromolecules Macromolecules – “giant molecules” The smaller units, or monomers, join together to form polymers. (polymerization) Four groups of organic compounds found in living things are carbohydrates, lipids, nucleic acids, and proteins.
- 29. 2.3 Carbon Compounds Macromolecules Carbon Compounds include thatconsist of which contain that consist of that consist of that consist of which contain which contain which contain Carbohydrates Lipids Nucleic acids Proteins Sugars and starches Fats and oils Nucleotides Amino Acids Carbon, hydrogen, oxygen Carbon, hydrogen, oxygen Carbon,hydrogen, oxygen, nitrogen, phosphorus Carbon, hydrogen,oxygen, nitrogen,
- 30. 2.3 Carbon Compounds Carbohydrates Carbohydrates are compounds made up of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1:2:1. Living things use carbohydrates as a main source of energy. Plants and some animals use carbohydrates for structural reasons. Starch Glucose What is the monomer? What is the polymer?
- 31. 2.3 Carbon Compounds Carbohydrates Simple sugars are called monosaccharides. Ex. Glucose (simple sugar), galactose (found in milk), and fructose (found in many fruits) The large macromolecules formed from monosaccharides are known as polysaccharides. Ex. Glycogen (animal starch), plant starch (store excess sugar), and cellulose in plants (gives plants strength and rigidity)
- 32. 2.3 Carbon Compounds Lipids Lipids – are made mostly from carbon and hydrogen atoms. (composed of glycerol and fatty acids) Three classes: fats, oils, and waxes Can be used for energy, biological membranes, and waterproof coverings. Steroids are also included. Used as a chemical messenger. What’s the difference between saturated and unsaturated fats???
- 33. 2.3 Carbon Compounds Lipids Saturated – fatty acids contain the maximum possible number of hydrogen atoms. Unsaturated – if there is at least one carbon-carbon double bond in a fatty acid Polyunsaturated – lipids whose fatty acids contain more than one double bond. Unsaturated Saturated
- 35. 2.3 Carbon Compounds NucleicAcids Nucleic acids – are macromolecules containing hydrogen, oxygen, nitrogen, and phosphorus Nucleic acids are polymers that are composed of monomers called nucleotides. Nucleotides consist of three parts: a 5 carbon sugar, a phosphate group, and nitrogenous base. Nucleic acids store and transmit heredity, or genetic, information.
- 37. 2.3 Carbon Compounds Proteins Proteins – are macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. Proteins are polymers of molecules called amino acids. Amino acids contain an amino group one end and a carboxyl group on the other. General structure Alanine Serine Carboxyl group Amino group
- 39. 2.3 Carbon Compounds Proteins More than 20 amino acids found in nature Amino acid can bond to any amino acid at the amino group Instructions for arranging amino acids into a protein is found in DNA. Uses for proteins: control the rate of reaction (enzymes), regulate cell processes, some are used to form muscle and bone, others transport substances in and out of cells Van der Waals forces and hydrogen bonds help maintain a proteins shape. Amino acids 1. Protein chains. 2. Protein can be twisted or folded. 3. Protein chain can fold itself.
- 40. 2.4 Chemical Reactionsand Enzymes Chemical Reactions Chemical Reactions – a process that changes, or transforms, one set of chemicals into another. Reactants – the elements or compounds that enter into a chemical reaction. Products – the elements or compounds produced by a chemical reaction Chemical reactions always involve changes in chemical bonds that join atoms in compounds.
- 41. 2.4 Chemical Reactionsand Enzymes Chemical Reactions Ex. Conversion of carbon dioxide to carbonic acid in the human body. CO2 + H20 H2CO3 H2CO3 CO2 + H20 Reactants Products
- 42. 2.4 Chemical Reactionsand Enzymes Energy in Reactions Energy is released or absorbed whenever chemical bonds form or are broken Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy. Ex. Hydrogen gas burning with oxygen to produce water vapor. 2H2 + 02 2H20 How is energy released?? Living organisms need a constant source of energy to survive!!!!
- 43. 2.4 Chemical Reactionsand Enzymes Activation Energy Not all chemical reactions that release energy occur spontaneously. Chemists call the energy needed to get a reaction started the activation energy. Energy-Absorbing Reaction Energy-Releasing Reaction How would you compare the energy of the products and reactants in the two types of reactions? Reactants Products Activation Energy Reactants Activation Energy Products
- 44. 2.4 Chemical Reactionsand Enzymes Enzymes Some chemical reactions that are responsible for life are too slow. These reactions are helped by catalysts Catalyst – a substance that speeds up the rate of a chemical reaction. Enzymes – proteins that act as biological catalysts. They speed up chemical Reaction pathway without enzyme Activation energy without enzyme Activation energy with enzyme Reaction pathway with enzyme Reactants Products
- 45. 2.4 Chemical Reactionsand Enzymes Enzymes Enzymes end in –ase (Example. Carbonic anhydrase) Enzymes are very specific Enzymes provide a site where reactants can be brought together to react. The reactants of enzyme- catalyzed reactions are known as substrates. The substrates bind to a site on the enzyme called the active site.
- 46. 2.4 Chemical Reactionsand Enzymes Enzymes Glucose Substrates ATP Substrates bind to enzymeSubstrates are converted into products Enzyme-substrate complex Enzyme (hexokinase) ADP Products Glucose-6- phosphate Products are released Active site
- 47. 2.4 Chemical Reactionsand Enzymes Enzymes Enzymes can be affected by many different variables. pH, temperature, etc. Enzymes play an essential role in regulating chemical pathways, making materials that cells need, releasing energy, and transferring information.