1 Chapter 6 Chemistry in Biology 6.1 Atoms, Elements and Compounds

2 Elements Everything is made of substances called elements About 90 elements occur naturally About 16 elements are man made Of the 90 naturally occurring elements, only 25 are essential to living things

3 Periodic Table of the Elements

4 Reading the Periodic Table

5 Periodic Table of the Elements

6 Needed in Macro-amounts Oxygen 65% Carbon 18.5% Hydrogen 9.5% Nitrogen 3.3% Other elements are needed in trace amounts

7 Trace Elements All organisms need trace elements even though they are needed in very small amounts they are essential for life Plants absorb the trace elements from the soil Animals eat the plants and other animals Examples: iron, magnesium, gold, arsenic, copper and many others

8 Atoms: The Building Blocks of Elements Atoms is the smallest particle of an element that has the characteristics of that element Nucleus contains protons (+) and neutrons (0) Electrons (-) in “cloud” around nucleus Carbon atom

9 Electron Energy Levels Certain numbers of electrons can occupy different regions around the nucleus of an atom Energy Levels  1 st - closest to nucleus:2 electrons  2 nd - next level out:8 electrons  3 rd - further level out:18 electrons

10 Electron Energy Levels Closest energy levels are always filled first Carbon atoms have 6 electrons 2 electrons are in the first energy level The remaining 4 electrons fill the second energy level

11 Potassium Energy Levels 19 total electrons 2 electrons in first energy level 8 electrons in second energy level 9 would be in third energy level but this is unstable  8 electrons in third  1 electron in fourth

12 Isotopes of an Element

13 Isotopes of an Element Atoms that have different numbers of neutron but the same number of protons Have same protons (atomic number) but different numbers of neutrons (atomic mass) Most isotopes are unstable and the nuclei break apart and give off radiation  Useful for X rays  Useful for radioactive dating

14 Chemistry in Biology van der Waals Forces  When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together.  The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons. 6.1 Atoms, Elements, and Compounds Chapter 6

15 Compounds and Bonding Compounds: composed of two or more different elements that are chemically combined (bonded) Chemical bonds hold atoms together so that they are more stable Atoms are more stable when they have their outer electron energy levels filled Bonds can be covalent or ionic

16 Covalent Bonds Atoms share electrons Covalent means cooperate A molecule is a group of atoms held together by covalent bonds

17 Ionic Bonds Ionic bonds involve gaining or losing electrons Na has lost an electron and now has a positive charge Cl has gained and electron and now has a negative charge Opposite charges attract

18 Ionic Bonds Ions are atoms that have gained or lost electrons Lose electron have a positive charge Gain electrons have a negative charge Ionic bonds are not as common as covalent in living organisms

19 Chapter 6 Chemistry in Biology 6.2 Chemical Reactions

20 Chemical Reactions When chemical reaction occur, bonds between atoms are formed or broken causing substances to combine and recombine as different molecules All of the chemical reactions that take place in an organism is called metabolism Chemical reaction depend on many things: temperature, concentration and pH

21 Balancing Chemical Reactions Matter cannot be created or destroyed only changed in form So all atoms must be accounted for in a chemical reaction

22 Balancing Chemical Reactions What you start with (reactants) must equal what you end up with (products) 2H 2 + O 2 2H 2 O 2 x 2 H 2 x 2 2 O 2 x 1

23 Chemistry in Biology  The activation energy is the minimum amount of energy needed for reactants to form products in a chemical reaction. Energy of Reactions 6.2 Chemical Reactions Chapter 6

24 Chemistry in Biology  This reaction is exothermic and released heat energy.  The energy of the product is lower than the energy of the reactants. 6.2 Chemical Reactions Chapter 6

25 Chemistry in Biology  This reaction is endothermic and absorbed heat energy.  The energy of the products is higher than the energy of the reactants. 6.2 Chemical Reactions Chapter 6

26 Chemistry in Biology  A catalyst is a substance that lowers the activation energy needed to start a chemical reaction.  Enzymes are biological catalysts.  It does not increase how much product is made and it does not get used up in the reaction. Enzymes 6.2 Chemical Reactions Chapter 6

27 Chemistry in Biology  The reactants that bind to the enzyme are called substrates.  The specific location where a substrate binds on an enzyme is called the active site. 6.2 Chemical Reactions Chapter 6

28 Chemistry in Biology  Factors such as pH, temperature, and other substances affect enzyme activity. 6.2 Chemical Reactions Chapter 6  The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form.

29 Chapter 6 Chemistry in Biology 6.3 Water and Solutions

30 Mixtures and Solutions Mixtures are combinations of substances in which the individual components retain their own properties, like sand and salt mixed together, no chemical reactions have taken place Solutions are a type of mixture where one substance dissolves in another substance  Solvent does the dissolving: water  Solute gets dissolved: sugar Solutions are very important in living things as we are ~75% water

31 Acids and Bases pH is a measure of how acidic or basic a substance is

32 Ph Scale Most of our foods are acidic Most of our cleaning supplies are basic (alkaline)

33 Blood pH

34 Chemistry in Biology  Buffers are mixtures that can react with acids or bases to keep the pH within a particular range. 6.3 Water and Solutions Chapter 6

35 Importance of Water Most life’s process (chemical reactions) can only happen in water Water is a transport medium: blood and sap Water has a high specific heat; holds heat and requires more heat to change its temperature; works like an insulator Water expands when it freezes, less dense; ice floats on top

36 Structure of Water Chemical formula: H 2 O Water is polar  Oxygen end negative  Hydrogen end positive

37 Polar Covalent Bonds The electron in the covalent bond between the hydrogen and oxygen spends more time with the oxygen Causes the oxygen end to be slightly negative, hydrogen end to be slightly positive

38 Hydrogen Bonds Form due to Polarity Hydrogen bonds are weak bonds between molecule Positive end of one molecule is attracted to negative end of another molecule Causes cohesion Causes adhesion

39 Water’s Hydrogen Bonds

40 Chapter 6 The Chemistry of Life 6.4 The Building Blocks of Life

41 Carbon Carbon is the element present in all life substances Carbon has a unique structure  Shares four electrons  Forms four covalent bonds  Can have single, double, or triple bonds  Because of bonding some molecules of the same formula can have different shapes CH 4 Methane

42 Carbon Glucose has formula C 6 H 12 O 6 Fructose has formula C 6 H 12 O 6 Isomers have same formula but different

43 Carbohydrates Contain carbon, hydrogen, and oxygen Subunit : glucose Two types simple and complex

44 Simple Carbohydrates: Sugars Monosaccharides: one sugar  Glucose  Fructose  Galactose Disaccharides: two sugars  Sucrose: glucose and fructose  Maltose: glucose and glucose  Lactose: glucose and galactose

45 Simple Carbohydrates: Sugars Fructose

46 Complex Carbohydrates: Polysaccharides Include starch, cellulose and glycogen All are chains of glucose Difference is how the chains are put together and type of bonds holding the glucose together

47 Starch Carbohydrate storage for plants

48 Cellulose Carbohydrate structural support for plants and algae Found in the cell wall to give the cell structure and support

49 Glycogen Carbohydrate storage for animals Found in liver and can move to any location Found in muscle and only stays in that muscle Liver Cell

50 Lipids Contain carbon, hydrogen, and oxygen Subunit: fatty acid Three types:  Diglycerides  Triglycerides  Sterols Many more carbon-hydrogen bonds to store large amounts of energy

51 Fatty Acids Can be saturated with hydrogen and have no double bonds (most animal fats) Can have double bonds and be unsaturated (most plant fats) Health risks associated with saturated fats

52 Diglycerides A Phosphodiglyceride is the main part of cell membranes Not a large component of our body Not a large component of the food we eat Contain a glycerin backbone and two fatty acid chains

53 Triglycerides The most common lipid Found in our bodies Found in the food we eat Called fats and oils Contain a glycerin backbone and three fatty acid chains

54 Sterols Contain four interconnected carbon rings Common one is cholesterol Many other sterols are made from cholesterol Some hormones are sterols

55 Proteins Contain, carbon, hydrogen, oxygen and nitrogen Subunit: amino acid  20 different amino acids  Linked by peptide bond Types: structural protein and enzymes  Structural- build a part  Enzymes- control the rate of chemical reactions

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57 Enzymes Works on a specific substrate Lock and key fit with the substrate Products are released After reaction the enzyme resumes its original shape and can react again with another substrate

58 Nucleic Acids Contain carbon, hydrogen, oxygen, nitrogen and phosphorus Subunits: nucleotide  Phosphate group  Sugar  Nitrogen base Types: RNA and DNA Nucleotide

59 DNA and RNA

60 DNA Deoxyribonucleic acid Information storage for cell in cell’s nucleus Directs cell’s activities Genetic code blueprint Double helix

61 RNA Ribonucleic acid Needed by DNA to make proteins Working copy of DNA Leaves the nucleus