Lab: Using indicator dyes to examine macromolecules in food.

Transcription

1 Lab: Using indicator dyes to examine macromolecules in food. Chemistry deals with the study of matter. Matter: Anything that takes up space and has mass (rock, bug, human). Atoms are the fundamental units of matter. Atoms combine via bonding to make molecules. Molecules found in living organisms can be classified as organic (carboncontaining + H) or inorganic (non-carbon + Hydrogen containing) Compounds 2 or more different elements combine to form a molecule of a compound. A molecule of a compound is the smallest particle that has the specific properties of the compound CH 4 (methane).

2 Chemical reactions used to build molecules and break down foods. Chemical reactions involve the formation or breaking of chemical bonds Reactants: what is put into reaction Products: end result of reaction Synthesis: formation of bonds, requires energy input A + B C + D Reactants Product Decomposition reaction: breaking of bonds, releases energy AB A + B 2

3 Biochemistry: Study of matter in living organisms Two different types of compounds are found in living organisms: inorganic and organic molecules. Inorganic molecules: Electrolytes, minerals, and compounds that do not contain carbon with hydrogen. Ex: oxygen (O 2 ), carbon dioxide (CO 2 ), water (H 2 ), inorganic acids (H + ) and bases (OH - ), salts (NaCl, KCl) Organic molecules: Always contain carbon with hydrogen, and sometimes oxygen Often soluble in water Covalently bonded 4 Major macromolecules found in food: 1. Carbohydrates 2. Fats 3. Proteins 4. Nucleic Acids Elements in Human Body by dry weight % Carbon Nitrogen Oxygen Hydrogen Calcium Phosphorus..3.3 Potassium Sulfur Chlorine Sodium Magnesium..0.3 Trace amounts of B, F Si, V, Cr, Mn, Fe, Co, Cu, Zn, Se, Mo, Sn, I. 3

4 Solutions A solution is a uniform mixture of two or more substances It consists of a solvent, or medium, in which atoms, ions, or molecules of another substance, called a solute, are individually dispersed Solutions are often defined by the concentration of a solute e.g. a teaspoon of sugar dissolved in 1 liter of water. Concentration can be expressed as # of solute molecules in a specific volume of solvent (most often water). 4

5 Concentration of H + ions in solution: ph = -log [H + ] Ex: ph 1 = 10-1 =.01 moles of [H + ] /liter ph 7 = 10-7 = (neutral in water) 5

6 Acids Solute that dissociates and releases hydrogen ions Often referred to as proton donors After losing an electron, a hydrogen ion consists solely as a proton Strong acids dissociate completely Example: hydrochloric acid (HCl) HCl H + + Cl ph below 7 Hydrochloric acid (HCl), a strong acid because it releases hydrogen ions

7 Bases Solute that removes hydrogen ions from solution Proton acceptor Strong bases dissociate completely Example: sodium hydroxide (NaOH) NaOH Na + + OH ph above 7 Sodium hydroxide (NaOH), a strong base because it releases hydroxide ions that remove hydrogen ions from solution

8 What is an indicator? Indicators are chemical compounds used to detect the presence of other compounds. They change shape in the presence of certain compounds as a result of chemical reactions.

9 Standards: Known substance used for comparison in experiment with unknown INDICATOR MACRO- MOLECULE NEGATIVE TEST (color) POSITIVE TEST (color) Benedict s solution simple carbohydrate blue orange Iodine solution complex carbohydrate dark red black Biuret solution protein blue violet, black Sudan IV lipid dark red reddishorange

10 Test for Simple Carbohydrates: Benedict s Benedict's solution is a chemical indicator for simple sugars such as glucose: C 6 H 12 O 6. Unlike some other indicators, Benedict s solution does not work at room temperature - it must be heated first Details: Benedict s reagent changes color when exposed to a reducing agent. A reducing agent is a term for electron gain A molecule that gains an electron is thus reduced A molecule that donates electrons is called a reducing agent A sugar that donates electrons is called a reducing sugar. The electron is donated by the carbonyl group in the sugar. All monosaccharides are reducing sugars Some disaccharides that have free carbonyl s are also reducing sugars (maltose)

11 Test for Complex Carbohydrates: Iodine Solution Iodine is an indicator for complex carbohydrates. Starch is a ploymer made up of hundreds of simple sugar molecules (e.g. glucose). Iodine solution color change = blue to black

12 Test for Protein (amino acids): Biuret solution Proteins are polymers of amino acids. Biuret solution is an indicator of amino acids dark violet blue to pinkish purple

13 Test for Fats (lipids): Sudan IV Sudan IV is a test for lipids. If lipids are present the Sudan IV will stain them reddish-orange (positive test). Structure: Glycerol + fatty acids 4 Types: Triglycerides neutral fats (solid) and oils (liquid) Phospholipids Steroids (testosterone) Eicosanoids (prostaglandin)

14 No Tests Today: Nucleic acids (DNA and RNA) made of nucleotides 5 carbon sugar (Deoxyribose DNA, ribose RNA) Phosphate group Nitrogenous base