Chapter 6 Chemistry in Biology 6.1 Atoms, Elements and Compounds

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

Periodic Table of the Elements

Reading the Periodic Table

Periodic Table of the Elements

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

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

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

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

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

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

Isotopes of an Element

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

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

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

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

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

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

Chapter 6 Chemistry in Biology 6.2 Chemical Reactions

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

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

Balancing Chemical Reactions What you start with (reactants) must equal what you end up with (products) 2H2 + O2 2H2O 2 x 2 H 2 x 2 2 O 2 x 1

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

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

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

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

The reactants that bind to the enzyme are called substrates. Chapter 6 Chemistry in Biology 6.2 Chemical Reactions 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.

Chapter 6 Chemistry in Biology 6.2 Chemical Reactions 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. Factors such as pH, temperature, and other substances affect enzyme activity.

Chapter 6 Chemistry in Biology 6.3 Water and Solutions

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

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

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

Blood pH

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

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

Structure of Water Chemical formula: H2O Water is polar Oxygen end negative Hydrogen end positive

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

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

Water’s Hydrogen Bonds

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

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 CH4 Methane

Carbon Glucose has formula C6H12O6 Fructose has formula C6H12O6 Isomers have same formula but different

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

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

Simple Carbohydrates: Sugars Fructose

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

Starch Carbohydrate storage for plants

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

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

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

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

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

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

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

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

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

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

DNA and RNA

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

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