Atoms. Atoms 9/9/2015

Transcription

1 The Chemistry of Life The Nature of Matter, Water,Carbon Compounds, Chemical Reactions and Enzymes The Nature of Matter B.1.9 Both living and nonliving things are composed of compounds, which are themselves made up of elements joined by energy-containing bonds, such as those in ATP. ATP- universal energy source for all cells found in all living things. Atom- basic unit of matter. Subatomic particles- protons, neutrons, and electrons. Atoms Protons are positively charged, and neutrons are neutral in charge, and they both make up the nucleus of an atom. Protons and neutrons make up the mass of an atom. Atoms Electrons are negatively charged particles that orbit around the nucleus. Electrons are attracted to the nucleus and are in constant motion. Atoms are neutral in charge because they have equal number of protons as electrons. 1

2 Elements and Isotopes Elements and Isotopes Element- a pure substance that consists entirely of one type of atom. More than 100 elements are known, but only about two dozen are commonly found in organisms. Elements are represented as either one or two letters and are listed on the periodic table. Elements are listed on the periodic table by the number of protons/electrons that they have. Symbols for Elements All elements are classified and arranged according to their chemical properties in the periodic table of elements. The number of protons and neutrons in atoms of different elements varies widely. Atomic number is the number of protons in an atoms nucleus. Atomic mass = # Protons + # Neutrons 2

3 Carbon Atom Electron Energy Levels Valence Electrons The electrons in the outermost energy level determine the chemical behavior of the different elements. The outermost electrons are called valence electrons 3

4 Bell-Ringer 1. How many protons, neutrons, and electrons does one atom of oxygen have? 2. Draw a model of an oxygen atom. Bell-Ringer How many valence electrons does carbon have? Identifying Atoms 4

5 Identifying Atoms Identifying Atoms Identifying Atoms Valence Electrons The electrons in the outermost energy level determine the chemical behavior of the different elements. The outermost electrons are called valence electrons 5

6 Isotopes Isotopes- atoms of an element that have different number of neutrons. Mass number- the sum of protons and neutrons in the nucleus of an atom. Isotopes have different mass numbers, but the same atomic number. Isotopes Because they have the same number of electrons, all isotopes of an element have the same chemical properties. Radioactive isotopes- have unstable nuclei that break down at a constant rate over time, and are used for dating purposes, and tracers. Isotopes of Carbon Ions Recall that atoms are electrically neutral because they have equal numbers of protons and electrons. An atom that loses electrons becomes positively charged (+) An atom that gains electrons becomes negatively charged (-) Positively and negatively charged atoms are called IONS 6

7 Chemical Bonds Atoms in compounds are held together by chemical bonds. Bond formation involves the electrons that surround a nucleus. Ions atoms that lose or gain electrons Ionic bond- is formed when one or more electrons are transferred from one atom to another (ex. NaCl). Oppositely charged ions have a strong attraction, which is an ionic bond. Chemical Bonds continued Covalent bond- situation where elements share electrons between them, instead of transferring them. Electrons travel in orbits of both elements of a covalent bond. Molecule- the smallest unit of most compounds 7

8 Chemical Compounds Most elements in nature are found combined with other elements. Compound- a substance formed by the chemical combination of two or more elements in definite proportions. Chemical formula- the composition of compounds in terms of types of elements, and numbers of each. The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed. Chemical Bonds continued Van der Waals forces- a slight attraction that develops between oppositely charged regions of nearby molecules. They are weaker than both ionic and covalent bonds. This is how geckos can defy gravity and climb walls that are smooth. Properties of Water Water covers over 75% of the Earth s surface. Water is the single most abundant compound in most living things. It is a liquid at most of Earth s temperatures. It expands when it freezes and is less dense than liquid water. It is neutral in charge, but polar. Polarity- an uneven distribution of electrons. Hydrogen Bonds Not as strong as covalent or ionic bonding. A hydrogen bond is found between the oxygen of one water molecule with the hydrogen of another. Cohesion- an attraction between molecules of the same substance. (allows insects to walk on water) Adhesion- an attraction between molecules of different substances. Capillary action- one of the forces that draw water out of the roots of a plant and up into its stems and leaves. 8

9 Properties of Water Life can not exist without water. Water is the universal solvent because it dissolves more substances than any other liquid. Pure water is 7.0 on the ph scale (Neutral). Water moves against the force of gravity due to capillary action. It is the only natural substance that is found in three states of matter. Water has a high surface tension and a high specific heat index. Solutions and Suspensions Mixtures- a material composed of two or more elements or compounds that are physically mixed together but not chemically combined. Solution- a mixture in which one or more substances are uniformly distributed in another substance. Suspension- mixtures of water and non-dissolved material. (ex. blood) Solutions and Suspensions Solute- part of solution that gets dissolved. Solvent- substance that does the dissolving. Solutions and Suspensions Aqueous- solutions containing water for a solvent. Concentration- the measurement of the amount of solute dissolved in a fixed amount of solution. 9

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11 Acids and Bases OH- hydroxide ion H+ hydrogen ion acid- number of hydrogen ions is greater than hydroxide ions. base- number of hydroxide ions is greater than hydrogen ions ph scale- measures the amount of hydroxide and hydrogen ions that are present. 11

12 Acids and Bases (cont.) Acids and Bases (cont.) Why are buffers important? Buffers- chemical substances that neutralize small amounts of an acid or a base of a solution. There are different ph levels throughout cells and the body. Some molecules will be destroyed if the ph is not right B.1.5. Because they help maintain homeostasis within an organism by keeping ph at a nearly constant value. In humans, for example, a ph shift of only about.4 units is fatal. Determining ph of Solutions Determining ph of Solutions Procedures 1. Find an open lab station with a labeled solution 2. Take the ph of the solution by dipping a strip of ph paper into the solution 3. Match the color of the ph paper with the guide to approximate the ph. 4. Record the ph in your data table 5. Set the ph paper on the paper towel. 6. Repeat steps 1-5 with all solutions 12

13 Determining ph of Solutions Cautions Do not smell, taste, or touch the solutions Place the ph paper on the paper towel when done. After you are done with the lab, wash your hands Carbon Atom CARBON BONDING Carbon has four electrons in the outer orbital. (Valence Electrons) Carbon forms four covalent bonds. Carbon forms bonds with other elements as well as with carbon (chains unlimited in length). Carbon forms chains, branches, and rings. B.1.6 The Major Elements of Life Carbon, hydrogen, oxygen, phosphorus, sulfer, and nitrogen are the most essential elements for all living things 13

14 Carbon Compounds Organic chemistry- compounds that contain bonds between carbon atoms. Macromolecules- giant molecules that are made from thousands or even hundreds of thousands of smaller molecules. Carbon Compounds Polymerization- large compounds are built by joining smaller ones together. Monomers are smaller compounds that join together to make polymers. Monomers may be the same molecules repeated, or different ones. Carbohydrates Carbohydrates cont. Carbohydrates- compounds made up of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1:2:1. Used primarily by living things for energy. Plants and animals also use them for structural purposes. (ex. Cellulose makes up the cell walls of plants) Plants store energy as starch, and animals store it glycogen. Sugars are the monomers and starches and cellulose are the polymers. Single sugar molecules are called monosaccharides, two sugars are disaccharides, and starches and cellulose are polysaccharides. Fructose, dextrose, glucose, galactose, ribose, sucrose, and maltose are examples of mono and disaccharides. Starches contain hundreds of sugar monomers and cellulose contain around three thousand. 14

15 Lipids Lipids are made mostly from carbon and hydrogen atoms. Common types are fats, oils, steroids, and waxes. They are generally not soluble in water. They are used primarily to store energy, insulation, making cell membranes, and waterproofing. The monomers are glycerols and fatty acids. Saturated fats- have the maximum possible number of hydrogen atoms attached to carbon. Lipids cont. Unsaturated fats- have at least one carbon-carbon double bond. Polyunsaturated fats- have more than one carboncarbon double bond. Lipids, like other molecules (ATP) have high energy bonds. B.1.10 Unsaturated fats tend to be liquids at room temperature. 15

16 Nucleic Acids (DNA) Nucleic Acids (DNA) Contain hydrogen, oxygen, nitrogen, carbon, and phosphorus. Nucleotides are monomers of which there are only four types found in DNA and RNA. Adenine Thymine Cytosine Guanine DNA and RNA are polymers of Nucleic Acids. Nucleic acids store and transmit heredity, or genetic information. Proteins Contain nitrogen, carbon, oxygen, sulfur, and hydrogen. Amino acids are the monomers of protein. There are roughly 20 amino acids found in nature. 16

17 Proteins Amino acids have an amino group on one end that joins with a carboxyl group of another. 17

18 Proteins Some proteins control the rate of reactions and regulate cells processes. (ENZYMES) Others transport substances into or out of cells, or fight diseases, or build things. Examples include enzymes, hormones, hemoglobin and the cell wall. Each has: 20 Different Amino Acids -a carbon core atom -an amine group NH3 -a carboxyl group COOH -a hydrogen atom -and an R-group, which makes them all different Chemical Reactions and Enzymes Chemical Reactions and Enzymes Chemical reaction- a process that changes one set of chemicals into another set of chemicals. Reactants- elements or compounds that enter a reaction. Products- elements or compounds that are produced by a chemical reaction. Some chemical reactions occur slowly, while others are very sudden. Chemical reactions always involve the breaking of bonds in reactants and the formation of new bonds in products. 18

19 Energy in Reactions Energy is released or absorbed whenever chemical bonds form or are broken. Chemical reactions that release energy often occur spontaneously. (exothermic) Chemical reactions that absorb energy will not occur without a source of energy. (endothermic) Energy in Reactions Activation energy- energy that is needed to get a reaction started. Activation energy is a factor in whether the overall chemical reaction releases energy or absorbs energy. Enzymes Some chemical reactions are too slow, or the activation energy is too high to work in living systems. Catalyst- a substance that speeds up the rate of a chemical reaction. Enzyme- proteins that act as biological catalysts. 19

20 Enzymes Enzymes speed up reactions that take place in cells by lowering activation energies. Enzymes are very specific in that they usually only do one job. Many different types of enzymes exist in organisms. Enzyme Action Enzymes provide a site so that reactants can be brought together to react. Active site- location where reactants meet in an enzyme. Substrates- the reactants that meet in the active site. Emil Fisher proposed the lock and key method to describe how substrates fit into enzymes. Once the reaction is over, the products are released and the enzyme remains unchanged, so that it can work on more substrate. Enzymes are affected by ph, temperature, and amount of substrate. 20

21 LOCK AND KEY MODEL Chapter 2 Review Describe the structure of an atom An atom of Calcium contains 20 protons, how many electrons does it have? Why do all isotopes of an element have the same chemical properties? Compare the structure of Carbon-12 and Carbon-14 21

22 Chapter 2 Review Chapter 2 Review What is a compound? What are two types of bonds that hold the atoms within a compound together? A potassium ion loses one valence electron, What type of bond will it form with a chlorine atom? What does it mean when a molecule is said to be polar? Why is water such a good solvent? What is an acid? What is a base? Chapter 2 Review What are the major elements of life? What are the 4 groups of organic molecules (macromolecules)? What happens to chemical bonds during a chemical reaction? Chapter 2 Review Why is the melting of ice not a chemical reaction? What is activation energy? What is a catalyst? What are enzymes? 22

23 The Major Elements of Life Carbon, hydrogen, oxygen, phosphorus, sulfur, and nitrogen are the most essential elements for all living things (CHOPSN) The Organic Compounds of Life (Macromolecules) Carbohydrates Lipids Protein Nucleic Acids The positively charged particle in an atom is called the: A. neutron B. ion C. proton D. electron The positively charged particle in an atom is called the: A. neutron B. ion C. proton D. electron 23

24 Two or more different atoms are combined in definite proportions in any: A. symbol B. isotope C. element D. compound Two or more different atoms are combined in definite proportions in any: A. symbol B. isotope C. element D. compound A covalent bond is formed by the: A. transfer of electrons B. sharing of electrons C. gaining of electrons D. losing of electrons A covalent bond is formed by the: A. transfer of electrons B. sharing of electrons C. gaining of electrons D. losing of electrons 24

25 When you shake sugar and sand together in a test tube, you cause them to form a A. compound B. mixture C. solution D. suspension When you shake sugar and sand together in a test tube, you cause them to form a A. compound B. mixture C. solution D. suspension A compound that produces hydrogen ions in solution is a(n): A. salt B. acid C. base D. polymer A compound that produces hydrogen ions in solution is a(n): A. salt B. acid C. base D. polymer 25

26 Compared to most other substances, a great deal of heat is needed to raise the temperature of water by a given amount. This is because water A. is an acid B. readily forms solutions C. has a high heat capacity D. acts as a buffer Compared to most other substances, a great deal of heat is needed to raise the temperature of water by a given amount. This is because water A. is an acid B. readily forms solutions C. has a high heat capacity D. acts as a buffer The monomers of carbohydrates are called: A. sugars B. nucleic acids C. nucleotides D. amino acids The monomers of carbohydrates are called: A. sugars B. nucleic acids C. nucleotides D. amino acids 26

27 Proteins are polymers formed from: A. lipids B. carbohydrates C. amino acids D. nucleic acids Proteins are polymers formed from: A. lipids B. carbohydrates C. amino acids D. nucleic acids An enzyme speeds up the rate of reaction by: A. lowering the activation energy B. raising the activation energy C. releasing energy D. absorbing energy An enzyme speeds up the rate of reaction by: A. lowering the activation energy B. raising the activation energy C. releasing energy D. absorbing energy 27

28 In a chemical reaction, a reactant binds to an enzyme in a region known as the: A. catalyst B. product C. substrate D. active site In a chemical reaction, a reactant binds to an enzyme in a region known as the: A. catalyst B. product C. substrate D. active site 28