The Chemistry of Living Things Chapter 2 The Chemistry of Living Things

All Matter Consists of Elements Made of Atoms Chemistry The study of matter Atoms, the smallest functional unit, consist of Protons: positive charge, have mass Neutrons: no charge, have mass Electrons: negative charge, have no discernable mass

Isotopes Same element, same atomic number = same number of protons and electrons Different number of neutrons = different weight

Radioisotopes Are unstable (varies with isotope) Emit energy (radiation) Emit particles

Atoms Combine to Form Molecules Joining atoms requires energy Energy is the capacity to do work Stored energy: potential energy Energy in motion, doing work: kinetic energy Electrons have potential energy Shells: the energy levels of electrons Orbitals describe the probable location of an electron PLAY Animation—Atoms, Ions, and Bonding

Three Types of Chemical Bonds Table 2.1

Elements of Living Organisms Table 2.2

Life Depends on Water Water molecules are polar Water is liquid at body temperature Water can absorb and hold heat energy

Two Important Biological Functions of Water Water is the biological solvent Water helps regulate body temperature PLAY Animation—Water and Chemistry

Water Keeps Ions in Solution Figure 2.8

The Importance of Hydrogen Ions Acids are proton (hydrogen ion) donors Bases accept hydrogen ions pH Scale Hydrogen ion concentration Buffers Minimize pH change Carbonic acid and bicarbonate act as one of the body’s most important buffer pairs

The pH Scale Figure 2.10

The Organic Molecules of Living Organisms Carbon, the building block of living things Comprises 18% of the body by weight Forms four covalent bonds Can form single or double bonds Can build micro- or macromolecules

Carbon Can Bond in Many Ways Figure 2.12

Making and Breaking Biological Macromolecules: Dehydration Synthesis and Hydrolysis Figure 2.13

Dehydration Synthesis Is the Reverse of Hydrolysis Removes equivalent of a water molecule to link molecular units Requires energy Hydrolysis Adds the equivalent of a water molecule to break apart macromolecules Releases energy PLAY Animation—Monomers and Polymers

Carbohydrates are Composed of Monosaccharides Figure 2.14

Carbohydrates are Used for Energy and Structural Support Oligosaccharides Short chains of monosaccharides Disaccharides Sucrose, fructose, lactose

Carbohydrates are Used for Energy and Structural Support Polysaccharides: thousands of monosaccharides joined in chains and branches Starch: made in plants; stores energy Glycogen: made in animals; stores energy Cellulose: indigestible polysaccharide made in plants for structural support

Lipids: Insoluble in Water Triglycerides: energy storage molecules Fatty acids: saturated and unsaturated Phospholipids: cell membranes Steroids: carbon-based ring structures Cholesterol: used in making estrogen and testosterone PLAY Animation—Lipid Structure and Function

Proteins: Complex Structures Constructed of Amino Acids Primary: amino acid sequence Secondary: describes chain’s orientation in space (e.g., alpha helix, beta sheet)

Proteins: Complex Structures Constructed of Amino Acids Tertiary: describes three-dimensional shape created by disulfide and hydrogen bonds Creates polar and nonpolar areas in molecule Quaternary: describes proteins in which two or more tertiary protein chains are associated PLAY Animation—Protein Structure

Proteins: Complex Structures Constructed of Amino Acids Denaturation Permanent disruption of protein structure Can be damaged by temperature or changes in pH Leads to loss of biological function

Enzyme Function Enzymes Are proteins Function as catalysts Speed up chemical reactions Are not altered or consumed by the reaction

Enzyme Function The functional shape of an enzyme is dependent on Temperature of reaction medium pH Ion concentration Presence of inhibitors

Structure and Function of Nucleic Acids Functions Store genetic information Provide information used in making proteins Structure Nucleotides consist of a phosphate group, a sugar, and a nitrogenous base DNA structure is a double helix: two associated strands of nucleic acids RNA is a single-stranded molecule PLAY Animation—Nucleic Acids

Structure of DNA DNA Deoxyribonucleic acid Double–stranded Sugar Deoxyribose

Structure of DNA DNA Nitrogenous bases Adenine Thymine Cytosine Guanine Pairing Adenine–thymine Cytosine–guanine

Structure of RNA RNA Ribonucleic acid Single–stranded Sugar Ribose

Structure of RNA RNA Nitrogenous bases Adenine Uracil Cytosine Guanine Pairing Adenine–uracil Cytosine–guanine

Structure and Function of Adenosine Triphosphate (ATP) Universal energy source Bonds between phosphate groups contain potential energy Breaking the bonds releases energy ATP  ADP + P1 + energy

Structure and Function of Adenosine Triphosphate (ATP) Figure 2.26