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Chapter 2 Chemistry Comes to Life Suggested Lecture Presentation Susan Capasso, Ed.D., CGC St. Vincent’s College Copyright © 2009 Pearson Education, Inc. Chemistry Comes to Life Basic chemistry helps us understand human biology The nature of atoms Compounds and chemical bonds The role of water in life Carbohydrates, lipids, proteins, and nucleic acids are the major molecules of life Copyright © 2009 Pearson Education, Inc. Basic Chemistry Helps Us Understand Human Biology Everything that takes up space and has mass is called matter Copyright © 2009 Pearson Education, Inc. Chemistry and Biology All matter is made of atoms, each containing a nucleus with protons and neutrons surrounded by a cloud of electrons Atoms are units of matter that cannot be broken down into simpler substances by ordinary chemical means Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.1a–b Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.1c Chemistry and Biology PLAY Animation—Atoms, Ions and Bonding Copyright © 2009 Pearson Education, Inc. Chemistry and Biology An element A form of matter that cannot be broken down into simpler substances. Made of many atoms that are all the same Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Each element has an atomic number and atomic weight Atomic number The number of protons in the nucleus Atomic weight The number of protons plus the number of neutrons Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.2 Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Table 2.1 Chemistry and Biology Elements with the same number of protons but different number of neutrons are called isotopes Common isotopes of carbon include 12C, 13C and 14C Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Radiation is energy moving through space, such as radio waves, light, and heat Some elements have both stable and unstable isotopes A radioisotope is unstable and emits radiation Radiation can be very harmful causing the death of cells, or very beneficial as evidenced by its use in medicine Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.4 Chemistry and Biology Two or more elements may combine to form a compound A compound’s characteristics are usually different from those of its elements Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.7a Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.7b Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.7c Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.7d Chemistry and Biology The atoms in a compound are held together by covalent, ionic, or hydrogen bonds Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.8 Chemistry and Biology Covalent bonds The strongest bonds They form when two or more atoms share the electrons in their outer shells Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.9a Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.9b Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.9c Chemistry and Biology Molecule A chemical structure held together by covalent bonds The chemical structure shows the number of each element forming the molecule Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Ion An atom or group of atoms with a positive or negative electrical charge Ionic bonds Weaker than covalent bonds Result from the attraction of oppositely charged ions, rather than shared electrons Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.10 Chemistry and Biology When the electrons of a covalent bond are shared unequally, the bond is called polar The resulting molecules are called polar molecules Water is a polar molecule Its unique properties such as its high heat capacity, high heat of vaporization, and its ability as a dissolving agent can be traced to its polarity Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Hydrogen bonds The attraction formed between a slightly positively charged hydrogen atom and another slightly negatively charged atom. Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Hydrogen bonds account for the unique properties of water and the geometric shape of many biological molecules Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.11a Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Figure 2.11b Chemistry and Biology PLAY Animation—Water and Chemistry Copyright © 2009 Pearson Education, Inc. Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Table 2.2 Chemistry and Biology Acids and bases react differently to water Acids release hydrogen ions (H+) when placed in water Bases produce hydroxide ions (OH–) when added to water Copyright © 2009 Pearson Education, Inc. Chemistry and Biology pH The negative logarithm of the concentration of the H+ ion in solution The lower the pH on the pH scale, the greater the acidity The higher the pH, the more basic a solution Copyright © 2009 Pearson Education, Inc. Chemistry and Biology H+ concentration (moles/liter) pH 100 0 10–1 1 10–2 2 10–3 3 10–4 4 10–5 5 10–6 6 10–7 7 10–8 8 10–9 9 10–10 10 10–11 11 10–12 12 Acid Neutral 10–13 13 10–14 14 Battery acid Beer Urine Human blood Baking soda Household ammonia Base Copyright © 2009 Pearson Education, Inc. Oven cleaner Figure 2.13 Chemistry and Biology Copyright © 2009 Pearson Education, Inc. Table 2.3 Chemistry and Biology Buffers Prevent dramatic changes in pH Remove excess H+ from solutions when concentrations of H+ increase Add H+ when concentrations of H+ decrease Many body fluids have the buffering capacity to maintain a constant internal environment Copyright © 2009 Pearson Education, Inc. Acid Rain Acid rain Usually defined as rain with a pH lower than 5.6, the pH of natural precipitation Caused largely by the burning of fossil fuels in cars, factories, and power plants Has devastating effects on the environment Copyright © 2009 Pearson Education, Inc. Acid Rain Copyright © 2009 Pearson Education, Inc. Figure 2.14a The Major Molecules of Life Biological macromolecules The giant molecules of life They are long chains called polymers made of repeating units called monomers Copyright © 2009 Pearson Education, Inc. The Major Molecules of Life When polymers are made, water is removed, and the reaction is called dehydration synthesis Copyright © 2009 Pearson Education, Inc. The Major Molecules of Life Copyright © 2009 Pearson Education, Inc. Figure 2.15a The Major Molecules of Life PLAY Animation—Monomers and Polymers Copyright © 2009 Pearson Education, Inc. The Major Molecules of Life Conversely, when the same molecules are broken apart, water is added and the reaction is called hydrolysis Copyright © 2009 Pearson Education, Inc. The Major Molecules of Life Copyright © 2009 Pearson Education, Inc. Figure 2.15b Carbohydrates Carbohydrates Polymers, made of monosaccharides Composed only of C, H, and O Copyright © 2009 Pearson Education, Inc. Carbohydrates Copyright © 2009 Pearson Education, Inc. Figure 2.16 Carbohydrates Copyright © 2009 Pearson Education, Inc. Table 2.4 (1 of 3) Carbohydrates Sugars and starches are carbohydrates Provide fuel for the body Sucrose and lactose are examples of disaccharides Double sugars Copyright © 2009 Pearson Education, Inc. Carbohydrates Copyright © 2009 Pearson Education, Inc. Figure 2.17 Carbohydrates Copyright © 2009 Pearson Education, Inc. Table 2.4 (2 of 3) Carbohydrates Polysaccharides Chains of monosaccharides that store energy or provide structure The storage polysaccharide in plants is starch In animals it is glycogen, which humans store mainly in the cells of liver and muscles Copyright © 2009 Pearson Education, Inc. Carbohydrates Copyright © 2009 Pearson Education, Inc. Figure 2.18a Carbohydrates Copyright © 2009 Pearson Education, Inc. Table 2.4 (3 of 3) Carbohydrates Cellulose A common example of an indigestible polysaccharide made of repeating units of glucose Humans lack the enzyme necessary to digest cellulose It is an important form of dietary fiber in the human diet Copyright © 2009 Pearson Education, Inc. Carbohydrates Copyright © 2009 Pearson Education, Inc. Figure 2.18b Lipids Lipids Water-insoluble molecules made of C, H, and O Store long-term energy Protect vital organs Form cell membranes Copyright © 2009 Pearson Education, Inc. Lipids Fats and oils are examples of triglycerides Polymers made of one molecule of glycerol and three fatty acids Copyright © 2009 Pearson Education, Inc. Lipids The fatty acids bond to glycerol through dehydration synthesis Copyright © 2009 Pearson Education, Inc. Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.19a Lipids If there are double bonds between carbon atoms and fatty acids, triglycerides are classified as unsaturated; if not, they are called saturated Copyright © 2009 Pearson Education, Inc. Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.19b Lipids PLAY Animation—Lipid Structure and Function Copyright © 2009 Pearson Education, Inc. Lipids Phospholipid molecules have A glycerol head that is polar and water soluble (hydrophilic) A fatty acid tail that is nonpolar and water insoluble (hydrophobic) These traits are critical to their function as a membrane Copyright © 2009 Pearson Education, Inc. Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.20a Lipids Phospholipids are arranged in a bilayer with the hydrophilic heads of each layer facing inside the cell Copyright © 2009 Pearson Education, Inc. Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.20b Lipids Steroids A unique group of lipids that consist of four ring compounds attached to molecules that vary from one steroid to the next Estrogen and testosterone are examples of steroids, as is cholesterol, which is a risk factor for heart disease when found in high levels in the blood Copyright © 2009 Pearson Education, Inc. Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.21 (1 of 3) Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.21 (2 of 3) Lipids Copyright © 2009 Pearson Education, Inc. Figure 2.21 (3 of 3) Proteins Amino acids The building blocks of proteins Consist of a central carbon atom bound to a hydrogen (H) atom, an amino group (NH2), and a carboxyl group (COOH) in addition to a unique side chain called a radical (R) Copyright © 2009 Pearson Education, Inc. Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.22 Proteins Amino acids that form proteins are linked by bonds called peptide bonds, which are formed through dehydration synthesis Copyright © 2009 Pearson Education, Inc. Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.23 Proteins Chains of only a few amino acids are called peptides Chains of 10 or more amino acids are called polypeptides Copyright © 2009 Pearson Education, Inc. Proteins Proteins Polypeptide chains of at least 50 amino acids that provide structure, transport, and movement for the body. Copyright © 2009 Pearson Education, Inc. Proteins Proteins have four distinct levels of structure that affect their function in the body Primary Secondary Tertiary Quaternary Copyright © 2009 Pearson Education, Inc. Proteins PLAY Animation—Protein Structure Copyright © 2009 Pearson Education, Inc. Proteins Changes in the chemical environment of a protein can cause it to lose its structure, resulting in a loss of function. This is called denaturation. Copyright © 2009 Pearson Education, Inc. Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.24 (1 of 4) Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.24 (2 of 4) Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.24 (3 of 4) Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.24 (4 of 4) Proteins A special group of proteins are called enzymes They serve as catalysts for chemical reactions Without enzymes, chemical reactions within our cells would occur far too slowly to sustain life Copyright © 2009 Pearson Education, Inc. Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.25a Proteins Copyright © 2009 Pearson Education, Inc. Figure 2.25b Proteins Enzymes Speed up a reaction while not being consumed Are very specific in their activity Specificity is due to the unique shape of each enzyme’s active site Copyright © 2009 Pearson Education, Inc. Proteins Enzymes bind to substrates at a specific active site, forming an enzyme-substrate complex Sometimes cofactors, often called coenzymes, bind at the active site to facilitate the reaction The substrate is converted to one or more products Copyright © 2009 Pearson Education, Inc. Nucleic Acids Genes are segments of polymers called deoxyribonucleic acid (DNA) Copyright © 2009 Pearson Education, Inc. Nucleic Acids DNA and ribonucleic acid (RNA) are the two types of nucleic acids Both are polymers of smaller units called nucleotides Copyright © 2009 Pearson Education, Inc. Nucleic Acids A nucleotide is made up of five-carbon sugar bonded to one of five nitrogencontaining bases and a phosphate group Copyright © 2009 Pearson Education, Inc. Nucleic Acids Copyright © 2009 Pearson Education, Inc. Figure 2.26 Nucleic Acids The sequencing of the nucleotides in DNA and RNA determines the sequence of amino acids in proteins Copyright © 2009 Pearson Education, Inc. Nucleic Acids RNA and DNA have structural differences related to sugar, bases, and number of strands Copyright © 2009 Pearson Education, Inc. Nucleic Acids Copyright © 2009 Pearson Education, Inc. Table 2.5 Nucleic Acids RNA Is single-stranded Has the sugar ribose Has the nitrogenous bases adenine, guanine, cytosine, and uracil Copyright © 2009 Pearson Education, Inc. Nucleic Acids Copyright © 2009 Pearson Education, Inc. Figure 2.27 Nucleic Acids PLAY Animation—Nucleic Acids Copyright © 2009 Pearson Education, Inc. Nucleic Acids DNA Has two strands that form a distinctive double helix Has the sugar deoxyribose Has the nitrogenous bases adenine, guanine, cytosine, and thymine Copyright © 2009 Pearson Education, Inc. Nucleic Acids Hydrogen bonds Phosphate Copyright © 2009 Pearson Education, Inc. Deoxyribose Nitrogen-containing base Phosphate Figure 2.28 ATP A special nucleotide is adenosine triphosphate (ATP) A molecule capable of storing energy in its phosphate-to-phosphate bonds Copyright © 2009 Pearson Education, Inc. ATP Copyright © 2009 Pearson Education, Inc. Figure 2.29 Nucleic Acids All energy from the breakdown of molecules, such as glucose, must be channeled through ATP before the body can use it ATP is often described as the energy currency of cells Copyright © 2009 Pearson Education, Inc.
