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CARBON AND THE MOLECULAR DIVERSITY OF LIFE
CHAPTER 4
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ISOMERS FUNCTIONAL GROUPS
Compounds with the same chemical formula but different structures FUNCTIONAL GROUPS See diagram of functional groups
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Figure 4.6 Three types of isomers
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Figure 4.6ax Structural isomers
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Table 4.1 Functional Groups of Organic Compounds
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Figure 4.8 A comparison of functional groups of female (estradiol) and male (testosterone) sex hormones
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Figure 4.8x1 Estrone and testosterone
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THE STRUCTURE AND FUNCTION OF MACROMOLECULES
CHAPTER 5
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SYNTHESIS AND BREAKDOWN
Dehydration synthesis (condensation reaction) – removal of water to join 2 compounds Hydrolysis – addition of water to break a bond between 2 compounds
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Figure 5.2 The synthesis and breakdown of polymers
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CARBOHYDRATES Monosaccharides
Examples: glucose, fructose, and galactose One sugar Disaccharides Examples: Lactose, sucrose and maltose Two sugars Joined by glycosidic linkage via dehydration synthesis Polysaccharides Examples: starch, glycogen, and cellulose Many sugars
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Figure 5.3 The structure and classification of some monosaccharides
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Figure 5.4 Linear and ring forms of glucose
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Figure 5.5 Examples of disaccharide synthesis
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Figure 5.6 Storage polysaccharides
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Figure 5.7a Starch and cellulose structures
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Figure 5.7b,c Starch and cellulose structures
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Figure 5.8 The arrangement of cellulose in plant cell walls
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Figure 5.x1 Cellulose digestion: termite and Trichonympha
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Figure 5.x2 Cellulose digestion: cow
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Figure 5.9 Chitin, a structural polysaccharide: exoskeleton and surgical thread
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LIPIDS Little or no affinity for water (hydrophobic)
Examples: Fat, phospholipids, and steroids Fats – composed of glycerol (an alcohol) and fatty acids Saturated – no double bonds in carbon chain Unsaturated – at least one double bond in carbon chain
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Figure 5.11 Examples of saturated and unsaturated fats and fatty acids
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Figure 5.11x Saturated and unsaturated fats and fatty acids: butter and oil
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Figure 5.12 The structure of a phospholipid
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Figure 5.13 Two structures formed by self-assembly of phospholipids in aqueous environments
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Figure 5.10 The synthesis and structure of a fat, or triacylglycerol
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Figure 5.14 Cholesterol, a steroid
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Figure 5.14x Cholesterol
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Table 5.1 An Overview of Protein Functions
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PROTEIN Polypeptide – polymer of amino acids
There are 20 different amino acids differing only by the R group
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Figure 5.15 The 20 amino acids of proteins: nonpolar
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Figure 5.15 The 20 amino acids of proteins: polar and electrically charged
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Figure 5.16 Making a polypeptide chain
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FOUR LEVELS OF PROTEIN STRUCTURE
Primary – sequences of amino acids Secondary – hydrogen bonds cause coils and folds Pleated sheet and alpha helix Tertiary – irregular contortions due to various weak bonds: Hydrophobic interactions Disulfide bridges Ionic bonds Van der Waals interactions Quaternary – two or more polypeptide chains aggregated into one functional macromolecule Examples: collagen and hemoglobin
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Figure 5.18 The primary structure of a protein
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Figure 5.19 A single amino acid substitution in a protein causes sickle-cell disease
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Figure 5.19x Sickled cells
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Figure 5.20 The secondary structure of a protein
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Figure 5.22 Examples of interactions contributing to the tertiary structure of a protein
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Figure 5.23 The quaternary structure of proteins
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Figure 5.24 Review: the four levels of protein structure
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Figure 5.25 Denaturation and renaturation of a protein
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Figure 5.21 Spider silk: a structural protein
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Figure 5.21x Silk drawn from the spinnerets at the rear of a spider
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NUCLEIC ACIDS Examples: DNA and RNA
We will discuss these in great detail later in the semester!
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Figure 5.29 The components of nucleic acids
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Figure 5.30 The DNA double helix and its replication
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AN INTRODUCTION TO METABOLISM
CHAPTER 8
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Figure 6.2 Transformations between kinetic and potential energy
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Figure 6.2x1 Kinetic and potential energy: dam
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Figure 6.2x2 Kinetic and potential energy: cheetah at rest and running
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THERMODYNAMICS First Law of Thermodynamics – energy can be transferred and transformed, but not created nor destroyed Second Law of Thermodynamics – every energy transfer or transformation makes the universe more disordered (have more entropy)
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Entropy – measure of disorder or randomness
Most energy transformations involve at least some energy be changed to heat Heat is the lowest form of energy Biological order has increased over time Second law requires only that processes increase the entropy of the universe Organisms may decrease entropy but entire universe must increase entropy
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Figure 6.4 Order as a characteristic of life
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Free energy (G) – energy available to do work when temperature is uniform throughout system
G = H – TS H = system’s total energy (enthalpy) T = temp in Kelvin (° C + 273) S = entropy
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∆ G = G final state – G starting state
∆ G = ∆ H - T∆ S For a spontaneous reaction: ∆ G = negative So must: give up energy (decrease H) and/or give up order (increase S) ∆ G = 0 at equilibrium Free energy increases if move away from equilibrium and decreases if move toward equilibrium
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Figure 6.5 The relationship of free energy to stability, work capacity, and spontaneous change
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Exergonic ∆ G = negative Spontaneous Net release of energy Endergonic ∆ G = positive NOT spontaneous Stores free energy in molecules
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Figure 6.6 Energy changes in exergonic and endergonic reactions
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Cells at equilibrium are dead!
Cells can keep disequilibrium by having products of one reaction not accumulate but instead become reactants of another reaction Energy coupling – an exergoinc reaction drives an endergoinc reaction
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Figure 6.7 Disequilibrium and work in closed and open systems
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ATP = ADENOSINE TRIPHOSPHATE
ATP + H2O ADP + Pi ∆ G = -7.3kcal/mol ADP = adenosine diphosphate Normally the phosphate is bonded to an intermediate compound which is then considered phosphorylated The reverse reaction is endergonic and requires +7.3 kcal/mol to make ATP from ADP
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Figure 6.8 The structure and hydrolysis of ATP
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Figure 6.9 Energy coupling by phosphate transfer
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Figure The ATP cycle
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ENZYMES Catalytic proteins or enzymes – change the rate of reaction without being consumed by the reaction Activation energy (EA) – energy needed to start a reaction Energy needed to contort the reactants so the bonds can change Enzymes lower activation energy by enabling reactants to absorb enough energy to reach transition state at moderate temps
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Enzymes are substrate specific
Substrate – the reactant on which an enzyme works Active site – area on enzyme where substrate fits Induced fit – model of enzyme activity
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Figure 6.12 Energy profile of an exergonic reaction
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Figure 6.14 The induced fit between an enzyme and its substrate
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Figure 6.15 The catalytic cycle of an enzyme
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Effects of pH and Temp Optimal temperatures and pH ranges exist for enzymes
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Figure 6.16 Environmental factors affecting enzyme activity
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Cofactors – non-protein helpers that bind to active site or substrate (zinc, iron)
Coenzymes – cofactors that are organic (vitamins) Enzyme Inhibitors – reduce enzyme activity Competitive inhibitors – block substrate from entering active site Reversible Overcome by adding more substrate Noncompetitive inhibitors – bind to another part of enzyme thereby changing the enzyme’s shape making it inactive Irreversible Examples: DDT, sarin gas, and penicillin
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Figure 6.17 Inhibition of enzyme activity
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Allosteric regulation
Allosteric sites – receptors on enzymes (not the active site) that may either inhibit or stimulate enzyme activity Feedback inhibition End product of a pathway acts as a inhibitor of an enzyme within the pathway Cooperativity – an enzyme with multiple subunits where binding to one active site causes shape changes to rest of subunits which in turn activates those subunits
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Figure 6.18 Allosteric regulation of enzyme activity
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Figure 6.19 Feedback inhibition
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Figure Cooperativity
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