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

Macromolecules Are Synthesized and Broken Down within the Cell Dehydration synthesis Removes equivalent of a water molecule to link molecular units Requires energy Builds macromolecules from smaller subunits Hydrolysis Adds the equivalent of a water molecule to break apart macromolecules Releases energy Dehydration synthesis is the reverse of hydrolysis

Sugars Energy Energy Dehydration synthesis Hydrolysis Carbohydrate Figure 2.13

Monomers and Polymers

Carbohydrates: Used for Energy and Structural Support General formula: Cn(H20)n Monosaccharides: simple sugars Glucose Fructose Galactose Ribose Deoxyribose

Oligosaccharides: More than One Monosaccharide Linked Together Monosaccharides can be linked together via dehydration synthesis Disaccharides: two monosaccharides linked together Sucrose: glucose + fructose Maltose: glucose + glucose Lactose: glucose + galactose

a) The five-carbon monosaccharides ribose and deoxyribose. Figure 2.14a

Glucose (a monosaccharide) Fructose (a monosaccharide) Sucrose (a disaccharide) b) Two 6-carbon monosaccharides (glucose and fructose) are joined together by dehydration synthesis, forming sucrose. Figure 2.14b

Polysaccharides Store Energy 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

a) Glycogen is formed by dehydration synthesis from glucose subunits. Figure 2.15a

b) A representation of the highly branched nature of glycogen. Figure 2.15b

Lipids: Insoluble in Water Three important classes of lipids Triglycerides: energy storage molecules Phospholipids: cell membrane structure Steroids: carbon-based ring structures

Triglycerides Also known as fats and oils Composed of glycerol and three fatty acids Fatty acids Saturated (in fats) Unsaturated (in oils) Stored in adipose tissue Energy storage molecules

a) Triglycerides (neutral fats) are synthesized from glycerol and Saturated fatty acid a) Triglycerides (neutral fats) are synthesized from glycerol and three fatty acids by dehydration synthesis. Figure 2.16a

b) Triglycerides with saturated fatty acids have straight tails, allowing them to pack closely together. Figure 2.16b

c) Triglycerides with unsaturated fatty acids have kinked tails, preventing them from packing closely together. Figure 2.16c

Phospholipids Structure Function Glycerol + two fatty acids and phosphate group One end of molecule is water soluble (hydrophilic) Other end of molecule is water insoluble (hydrophobic) Function Primary component of cell membranes

Membrane structure Phosphate Polar head Glycerol Fatty acid Nonpolar tail Figure 2.17

Steroids Structure Examples: Composed of four carbon rings Cholesterol Hormones Estrogen Testosterone

a) Cholesterol: A normal component of the cell membrane. Figure 2.18a

b) Estrogen (estradiol): Female sex hormone synthesized from cholesterol. Figure 2.18b

synthesized from cholesterol. c) Testosterone: Male sex hormone synthesized from cholesterol. Figure 2.18c

Lipid Structure and Function

Proteins Long chains (polymers) of subunits called amino acids 20 different types Amino end, carboxyl end, R group Amino acids are joined by peptide bonds, which are produced by dehydration synthesis reactions

Figure 2.19 Amino acids with nonpolar R groups Amino acids with uncharged polar R groups Alanine (Ala) Asparagine (Asn) Isoleucine (Ile) Cysteine (Cys) Leucine (Leu) Glutamine (Gln) Methionine (Met) Glycine (Gly) Phenylalanine (Phe) Serine (Ser) Proline (Pro) Threonine (Thr) Tryptophan (Trp) Tyrosine (Tyr) Amino acids with positively charged R groups Arginine (Arg) Valine (Val) Amino acids with negatively charged R groups Histidine (His) Aspartic acid (Asp) Lysine (Lys) Glutamic acid (Glu) Figure 2.19

Amino acids with nonpolar R groups Alanine (Ala) Isoleucine (Ile) Leucine (Leu) Methionine (Met) Phenylalanine (Phe) Proline (Pro) Tryptophan (Trp) Valine (Val) Figure 2.19a

Amino acids with negatively charged R groups Aspartic acid (Asp) Glutamic acid (Glu) Figure 2.19b

Amino acids with uncharged polar R groups Asparagine (Asn) Cysteine (Cys) Glutamine (Gln) Glycine (Gly) Serine (Ser) Threonine (Thr) Tyrosine (Tyr) Figure 2.19c

Amino acids with positively charged R groups Arginine (Arg) Histidine (His) Lysine (Lys) Figure 2.19d

Amino acids Isoleucine (Ile) Alanine (Ala) Valine (Val) Polypeptide Figure 2.20

Protein Function Depends on Structure Primary structure Amino acid sequence Stabilized by peptide bonds Secondary structure Alpha helix Beta pleated sheets Stabilized by hydrogen bonds

Protein Function Depends on Structure Tertiary structure Three-dimensional shape Stabilized by disulfide and hydrogen bonds Creates polar and nonpolar areas in molecule Quaternary structure Two or more polypeptide chains are associated

Primary structure (sequence of amino acids) Figure 2.21a

Hydrogen bonds Secondary structure (orientation in space of chains of amino acids) Alpha helix Beta sheet Random coil Figure 2.21b

Tertiary structure (three-dimensional shape) Alpha helix Tertiary structure (three-dimensional shape) Random coil Beta sheet Figure 2.21c

(number of polypeptide Quaternary structure (number of polypeptide chains and their association) Figure 2.21d

Protein Function Depends on Structure Denaturation Permanent disruption of protein structure Can be damaged by temperature or changes in pH Leads to loss of biological function

Protein Structure

Enzymes Facilitate Biochemical Reactions Are proteins Function as biological catalysts Speed up specific chemical reactions Are not altered or consumed by the reaction Without enzymes, many biochemical reactions would not proceed quickly enough to sustain life Each enzyme is specific for a specific chemical reaction

Enzyme Reactants Product Reactants approach enzyme Reactants bind to enzyme Enzyme changes shape Products are released Figure 2.22

Enzymes Facilitate Biochemical Reactions The functional shape of an enzyme is dependent on Temperature pH Ion concentration Presence of inhibitors

Nucleic Acids Store Genetic Information Two types DNA: deoxyribonucleic acid RNA: ribonucleic acid Functions Store genetic information Provide information used in making proteins Nucleic acids are long chains containing subunits known as nucleotides

Nucleic Acids Store Genetic Information Nucleotides: building blocks of nucleic acids Each nucleotide contains 5 carbon sugar DNA nucleotides: deoxyribose RNA nucleotides: ribose Nitrogenous base Phosphate group

Adenine (A) Cytosine (C) Thymine (T) Guanine (G) Phosphate Deoxyribose Figure 2.23

Nucleic Acids Store Genetic Information Structure of DNA (deoxyribonucleic acid) Double–stranded Nucleotides contain Deoxyribose (sugar) Nitrogenous bases Adenine Guanine Cytosine Thymine Pairing Adenine - Thymine Guanine - Cytosine

Base pair Phosphate Sugar Nucleotide Figure 2.24

Nucleic Acids Store Genetic Information Structure of RNA (ribonucleic acid) Single–stranded Nucleotides contain Ribose Nitrogenous bases Adenine Guanine Cytosine Uracil

Phosphate Ribose Uracil Figure 2.25

Nucleic Acid Function --- Nucleic Acids Store Genetic Information DNA: instructions for making RNA RNA: instructions for making proteins Proteins: direct most of life’s processes DNA → RNA → Proteins

ATP Carries Energy Structure and function of adenosine triphosphate (ATP) Nucleotide – adenosine triphosphate Universal energy source Bonds between phosphate groups contain potential energy Breaking the bonds releases energy ATP → ADP + P + energy

Adenosine Adenine (A) Triphosphate Ribose a) The structure of ATP. Figure 2.26a

produces useful energy for the cell Hydrolysis of ATP produces useful energy for the cell Adenosine Adenosine Energy for ATP synthesis comes from food or body stores of glycogen or fat b) The breakdown and synthesis of ATP. The breakdown (hydrolysis) of ATP yields energy for the cell. The reaction is reversible, meaning that ATP may be resynthesized using energy from other sources. Figure 2.26b