Cell Chemistry INTRODUCTION Since your body is made up of chemicals and all body activities are chemical in nature, it is important to become familiar with the language and fundamental concepts of chemistry. Structure of Atoms Matter- has mass and takes up space. Atomthe smallest particle of an element. Elementa substance whose atoms all have the same number of protons in the nucleus. Atoms consist of a nucleus containing positively charged protons neutral (uncharged) neutrons negatively charged electrons that move around the nucleus in energy levels. Atomic Number The number of protons in the nucleus of an atom The number of protons in the nucleus makes the atoms of one element different from those of another. Since all atoms are electrically neutral, the atomic number = number of electrons Mass vs. Atomic Mass Mass number= sum of protons and neutrons in nucleus Atomic mass (atomic weight) is close to the mass number of its most abundant isotope. Isotope= same # protons, different # neutrons Ions, Molecules, & Compounds Ions atom that gave up or gained an electron formed by ionization written with its chemical symbol and (+) or (-) Cation (+) and anion (-) Na + + Cl - = NaCl (ionic bonding) Molecule atoms share electrons covalent bonding written as molecular formula showing the number of atoms of each element Ex: H 2 O Equilibrium Rules Valence electron(s) electron(s) in the highest occupied energy level of an atom. (Outer shell) Octet ruleatoms react by gaining or losing electrons trying to acquire the stable electron configuration of a noble gas, usually eight valence electrons. CHEMICAL BONDS The atoms of a molecule are held together by forces of attraction called chemical bonds. Probability of chemical bond between two atoms depends on the number of electrons in outermost shells. CHEMICAL BONDS An atom with a valence shell holding eight electrons (2 for H and He) is chemically stable unlikely to form chemical bonds with other atoms. To achieve stability, atoms that do not have a full valence shell tend to empty or fill their valence shell to the maximum extent. Octet Rule. Atoms with incompletely filled outer shells tend to combine with each other in chemical reactions to produce a chemically stable arrangement of eight valence electrons for each atom. Ionic Bonds When an atom loses or gains a valence electron, ions are formed. Combo of nonmetal and metal Positively and negatively charged ions are attracted to one another. The Ionic Bond in Sodium Chloride Sodium loses an electron to become Na + (cation) Chlorine gains an electron to become Cl - (anion) Na + and Cl - are attracted to each other to form the compound sodium chloride (NaCl) table salt Covalent Bonds Covalent bonds are formed by the atoms of molecules sharing one, two or three pairs of their valence electrons. Covalent bonds are common and are the strongest chemical bonds in the body. Two nonmetals Covalent Bonds Atoms share electrons to form covalent bonds Electrons spend most of the time between the 2 atomic nuclei single bond = share 1 pair double bond = share 2 pair triple bond = share 3 pair Polar Covalent Bonds Unequal sharing of electrons between atoms. In a water molecule, oxygen attracts the electrons more strongly than hydrogen Causes two poles (+ and -) on the molecule Hydrogen Bonds Approximately 5% as strong as covalent bonds Useful in establishing links between molecules or between distant parts of a very large molecule Large 3-D molecules are often held together by a large number of hydrogen bonds. Ex: DNA Why weaker bonds? CHEMICAL REACTIONS A chemical reaction occurs when new bonds are formed or old bonds break between atoms. Starting substances= reactants Ending substances= products Metabolism =energy usage for the chemical reactions in the body Balancing Equations Chemical equation: Reactants Products Chemical reactions are described by chemical equations. A chemical equation is balanced when it reflects the law of conservation of mass. The total mass of reactants equals the total mass of the products. (What goes in, must come back out) Balancing Equations CH 4 + O 2 CO 2 + H 2 O 1-C-14-H-22-O-3 CH 4 + O 2 CO 2 + 2H 2 O 1-C-14-H-42-O-4 CH 4 +2 O 2 CO 2 +2 H 2 O 1-C-14-H-44-O-4 Energy & Chemical Reactions Chemical reactions involve energy changes. CChemical bonds contain energy Energy stored in bonds eeg., bonds within sugar molecules IIf the chemical bonds within sugar are broken, energy of sugar can be used to heat the body or create movement. Questions What is the difference between covalent and ionic bonds? What is the difference between covalent and ionic bonds? Identify some chemical reactions that could be occurring in your body right now. (At least 3, bonus pts for naming more up to 5) Identify some chemical reactions that could be occurring in your body right now. (At least 3, bonus pts for naming more up to 5) Inorganic vs Organic Inorganic compounds usually lack carbon simple molecules Organic compounds always contain carbon and hydrogen usually contain oxygen always covalently bonded. typically very large molecules Water Most important and abundant inorganic compound in all living systems. Water is polar uneven sharing of valence electrons causes: partial negative charge near the one oxygen atom two partial positive charges near the two hydrogen atoms Great dissolvent Attractive to (+) and (-) Water enables reactants to collide to form products Inorganic Acids, Bases & Salts Acids, bases and salts always dissociate into ions when dissolved in water acids dissociate into H + and one or more anions bases dissociate into OH - and one or more cations salts dissociate into anions and cations with no H + or OH - Acids and Bases Acid & bases react in the body to form salts and water Many salts are present in the body and are formed when acids and bases react with each other. Electrolytes are important salts in the body that carry electric current (in nerve or muscle) Concept of pH pH scale runs from 0 to 14 in [H + ] ppH = 7 = neutral (distilled water) ppH < 7 = acidic ([H + ] > [OH - ]). ppH > 7 = alkaline ([H + ] < [OH - ]) pH is a logarithmic scale (one step= 10x difference) Acid-Base Balance: Why does this matter? Biochemical reactions are very sensitive to small changes in acidity or alkalinity. pH of blood is 7.35 to 7.45 Major issues occur out of this range Carbons Importance Carbons properties in organic compounds make it very useful to living organisms. It can react with one to several hundred other carbon atoms forms large molecules of many different shapes. Many carbon compounds do not dissolve easily in water useful materials for building body structures. Carbon compounds are mostly or entirely held together by covalent bonds and tend to decompose easily organic compounds are a good source of energy Due to energy in bonds Four Major Macromolecules Four major organic compounds Four major organic compounds Carbohydrates Lipids Proteins Nucleic Acids 1.Carbohydrates Make up sugars and starches Make up sugars and starches Glycogen= Storage form Provide energy to the cells. Provide energy to the cells. Dissolve in water (hydrophilic) Dissolve in water (hydrophilic) 2. Proteins Proteins are the building materials for the body. Proteins are the building materials for the body. Made by the building blocks called amino acids Amino acids peptides polypeptides proteins. Denaturation can cause problems. Denaturation can cause problems. Protein Denaturation The function of a protein depends on its ability to bind to another molecule. Hostile environments such as heat, acid or salts will change a proteins 3-D shape This destroys its ability to function Ex: raw egg white vs. cooked egg white 3. Lipids Lipid large, nonpolar organic molecules that do not dissolve in water. Lipid large, nonpolar organic molecules that do not dissolve in water. Fatty Acid unbranched carbon chain that make up most lipids Two parts to a lipid Head- hydrophilic Tail- hydrophobic Phospholipid Bi-layer Makes up cell membranes Makes up cell membranes Head is the phosphate group. Hydrophilic Tails are the fatty acids. Hydrophobic Creates barrier between internal and ext. environment 4. Nucleic Acids Very large complex organic molecules that store genetic info in the cell. Very large complex organic molecules that store genetic info in the cell. RNA and DNA Most of powerpoint is from8.pdf and Most of powerpoint is from8.pdf and Principles of Human Anatomy and Physiology, 11e8.pdf8.pdf Questions What determines whether a substance is acidic or basic? (hint: NOT pH) What determines whether a substance is acidic or basic? (hint: NOT pH) If the human body creates energy by breaking high energy bonds, how did those bonds get into the body? If the human body creates energy by breaking high energy bonds, how did those bonds get into the body? Hint: If the body cannot make something, what do you have to do? Describe the importance of each macromolecule to the body. Describe the importance of each macromolecule to the body. Types of Carbohydrates Carbohydrates are classified according Carbohydrates are classified according to size. One-ring sugar is a monosaccharide (monomer). monosaccharide Two sugars make a disaccharide. disaccharide Many sugar molecules linked together form a polysaccharide (polymer). polysaccharide Monosaccharide Milk SugarFruit Sugar Types of Carbs Disaccharide Maltose is two glucose molecules; forms in digestive tract of humans during starch digestion. Types of Carbs Polysaccharide Starch is straight chain of glucose molecules with few side branches. Types of Carbs