<h3 id="successnon-covalent-bondssuccess"><Success>Non-covalent bonds</Success></h3> <div style='float: left; width:50%;font-size:25px;text-align:left;'> </div> <div style='float: right; width:0%;'> <p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-16-chapter-02-non-covalent-bonds-lecture-2_6-n_ptdneuhvu-025-0034.8.jpg"></p> </div>

<h3 id="successchemical-composition-and-covalent-bonds-success"><Success>Chemical composition and Covalent bonds </Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left'> <p><strong>Chemical composition</strong></p> <ul> <li>Small molecules-amino acids, nucleotides, sugars</li> <li>Macromolecules-DNA, RNA, Protein</li> <li>Molecular biology-study of the higher level of molecular organization, interaction etc.</li> </ul> </div> <div style='float: right; width:50%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/78c44b2e-a687-4c3f-032c-67c9f1811500/public" style='width:100%'> <!----> <!----> </div>

<div> <h3 id="successchemical-composition-and-covalent-bondssuccess"><Success>Chemical composition and covalent bonds</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <p><strong>Covalent bonds</strong></p> <ul> <li>Readily forms covalent bonds with other atoms and rarely exists as isolated entities</li> <li>C forms four covalent-bonds</li> <li>N forms four covalent bonds (one pair not involved in bonding-NH3)</li> <li>In $NH_4-N$ forms four covalent bonds</li> <li>Phosphorus can form up to 5 covalent bonds (H₃PO₄)</li> </ul> </div>

<h3 id="successcovalent-bonds-have-characteristic-geometrysuccess"><Success>Covalent bonds have characteristic geometry</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <p><strong>Covalent bonds have characteristic geometry</strong></p> <p><strong>Polar covalent bonds</strong> Electronegativity. Fluorine-4.0 Polar O-H (dipole moment)</p> <ul> <li>Very stable</li> <li>Energies required to break or rearrange them are much higher than the thermal energy available at room temperature</li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/0be5f62b-f7e4-43f7-f3a0-1a805c8a2300/public" width="100%"> <!----> </div>

<h3 id="successcovalent-bonds-have-characteristic-geometrysuccess-1"><Success>Covalent bonds have characteristic geometry</Success></h3> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <p><strong>The making and breaking of bonds</strong></p> </div> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <table> <thead> <tr> <th>Covalent Bond</th> <th>Energy kcal/mcl</th> </tr> </thead> <tbody> <tr> <td>C=N</td> <td>213</td> </tr> <tr> <td>C=O</td> <td>174</td> </tr> <tr> <td>C=C</td> <td>146</td> </tr> <tr> <td>C.F</td> <td>103</td> </tr> <tr> <td>O.H</td> <td>111</td> </tr> <tr> <td>C.H</td> <td>99</td> </tr> <tr> <td>N.H</td> <td>93</td> </tr> </tbody> </table> </div> <div style='float: right; width:50%;font-size:30px;text-align:left;'> <table> <thead> <tr> <th>Covalent Bond</th> <th>Energy kcal/mcl</th> </tr> </thead> <tbody> <tr> <td>C.O</td> <td>86</td> </tr> <tr> <td>C.C</td> <td>83</td> </tr> <tr> <td>C.CI</td> <td>81</td> </tr> <tr> <td>S.H</td> <td>81</td> </tr> <tr> <td>C.N</td> <td>73</td> </tr> <tr> <td>C.S</td> <td>62</td> </tr> <tr> <td>O.O</td> <td>35</td> </tr> </tbody> </table> </div> <div style='float: right; width:0%;'> <!----> </div>

<h3 id="successnon-covalent-bondssuccess-1"><Success>Non-covalent bonds</Success></h3> <div style='float: left; width:55%;font-size:30px;text-align:left;'> <ul> <li>Non-covalent bonds are critical in maintaining the three-dimensional structure of large macromolecules such as proteins and nucleic acids</li> <li>Although weak and transient at physiological temperature, multiple NC-bonds often act together to produce highly stable and specific associations between different parts of a large molecule or between different macromolecules</li> </ul> </div> <div style='float: right; width:45%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/5b2ecc5c-04fd-4f36-bbbe-76d520ff2100/public" style='width:100%'> <!----> </div>

<div> <h3 id="successnon-covalent-bondssuccess-2"><Success>Non-covalent bonds</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li> <p>The energy released in the formation of Non-Covalent bond is only 1-5 KCal, much less than bond energies of single C-C bonds (83 Kcal/mol)</p> </li> <li> <p>Because the average kinetic energy of molecules at RT is~0.6 Kcal/mol, many molecules have enough energy to break the Non-Covalent bonds</p> </li> <li> <p>These bonds are therefore referred to as interactions</p> </li> </ul> </div>

<h3 id="successionic-interactionssuccess"><Success>Ionic interactions</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li> <p>In some compounds, the bonded atoms are so different in electronegativity that the bonding electrons are never shared - NaCI</p> </li> <li> <p>Ionic bonds (or interactions) results from the attraction of a positively charged ion-a cation - for a negatively charged ion - an anion</p> </li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/8cc33b5e-e1b8-4e56-ba85-fce21f1aae00/public" width="80%"> <!----> </div>

<h3 id="successionic-interactionssuccess-1"><Success>Ionic interactions</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>Unlike covalent or hydrogen bonds, ionic bonds do not have fixed or specific geometric orientations because the electrostatic field around an ion-is uniform in all directions</li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/4ecd5b73-c161-40b3-ec4a-df5816c7da00/public" width="100%"> <!----> </div>

<div> <h3 id="successionic-interactionssuccess-2"><Success>Ionic interactions</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li> <p>Crystals of salts such as Na⁺ Cl^- do have very regular structures because that is the energetically most favorable way of packing together positive and negative ions. The force that stabilizes ionic crystals is called the lattice energy</p> </li> <li> <p>In aqueous solutions, simple lons of biological significance, such as Na⁺, K⁺, Ca²⁺, Mg²⁺, and Cl^-, do not exist as free, isolated entities Instead, each is surrounded by a stable, tightly heid shell of water molecules</p> </li> </ul> </div>

<h3 id="successcharacteristicssuccess"><Success>Characteristics</Success></h3> <div style='float: left; width:60%;font-size:30px;text-align:left;'> <ul> <li>Most ionic compounds are quite soluble in water because a large amount of energy is released when ions tightly bind water molecules</li> <li>This is known as the energy of hydration</li> <li>Oppositely charged ions are shielded from one another by the water and tend not to recombine</li> </ul> </div> <div style='float: right; width:40%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/4ce476f2-6d76-4203-6523-c219c47dd900/public" style='width:100%'> <!----> </div>

<div> <h3 id="successcharacteristicssuccess-1"><Success>Characteristics</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li> <p>Salts like Na⁺ Cl^- dissolve in water because the energy of hydration is greater than the lattice energy that stabilizes the crystal structure</p> </li> <li> <p>In contrast, certain salts, such as [Ca₃(PO₄)₂], are virtually insoluble in water; the large charges on the Ca²⁺ and PO₄^3- ions generate a formidable lattice energy that is greater than the energy of hydration</p> </li> </ul> </div>

<div> <h3 id="successlattice-energysuccess"><Success>Lattice energy</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li>A measure of the strength of bands in that ionic compound</li> <li>Energy change or enthalpy of formation</li> <li>For NaCl, the final step to create NaCl (s) would be</li> <li>Na ⁺ + Cl^- $\rightarrow$ NaCl</li> <li>This process is exothermic</li> </ul> </div>

<h3 id="successh--bondssuccess"><Success>H- Bonds</Success></h3> <div style='float: left; width:60%;font-size:30px;text-align:left;'> <ul> <li>Polar molecules, such as water, have a weak, partial negative charge at one region of the molecule (the oxygen atom in water) and a partial positive charge elsewhere (the hydrogen atoms in water).</li> <li>Normally, a hydrogen atom forms a covalent bond with only one other atom.</li> <li>A hydrogen atom covalently bonded to a donor atom, D, may form an additional weak association, the hydrogen bond, with an acceptor atom</li> </ul> </div> <div style='float: right; width:40%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/4930b488-03e5-4ca6-86bf-e979e5651a00/public" style='width:100%'> <!----> </div>

<h3 id="successh--bondssuccess-1"><Success>H- Bonds</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>In order for a hydrogen bond to form, the donor atom must be electronegative, so that the covalent D-H bond is polar. The acceptor atom also must be electronegative</li> <li>In biological systems, both donors and acceptors are usually nitrogen or oxygen atoms, especially those atoms in amino (NH) and hydroxyl (-OH) groups</li> </ul> </div> <div style='float: right; width:50%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/37f662c3-044d-4e54-4682-68f29933a600/public" style='width:100%'> <!----> </div>

<h3 id="successh--bondssuccess-2"><Success>H- Bonds</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>Because all covalent N-H and O-H bonds are polar, their H atoms can participate in hydrogen bonds. By contrast, C-H bonds are nonpolar, so these H atoms are almost never involved in a hydrogen bond</li> </ul> </div> <div style='float: right; width:50%;'> <img src= "https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/37f662c3-044d-4e54-4682-68f29933a600/public" style='width:100%'> <!----> </div>

<h3 id="successcharacteristicssuccess-2"><Success>Characteristics</Success></h3> <div style='float: left; width:60%;font-size:30px;text-align:left;'> <ol> <li>Most hydrogen bonds are 0.26-0.311 nm long, about twice the length of covalent bonds between the same atoms</li> <li>The hydrogen atom in closer to the donor atom, D, to which it remains covalently bonded, than it is to the acceptor.</li> <li>The length of the covalent D-H bond is a bit longer than it would be if there were no hystrogen bond, because the acceptor “pulls” the hydrogen away from the donor.</li> </ol> </div> <div style='float: right; width:40%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/5f3f77cd-aa47-4121-9fa8-d9ea3d2a7500/public" width="100%"> <!----> </div>

<div> <h3 id="successcharacteristicssuccess-3"><Success>Characteristics</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ol start="4"> <li>The strength of a hydrogen bond in water (-5 kcal/mol is much weaker than a covalent O-H bond (=110 kcal/mol)</li> <li>An important feature of all hydrogen bands is directionality</li> <li>The strengths of the hydrogen bonds in proteins and nucleic acids are only 1 to 2 kcal/mol, less than water</li> </ol> </div>

<h3 id="successvan-der-waals-interactionssuccess"><Success>Van der waals interactions</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>When any two atoms approach each other closely, they create a weak, nonspecific attractive force that produces a van der Waals interaction</li> <li>These nonspecific interactions result from the momentary random fluctuations in the distribution of the electrons of any atom, which give rise to a transient unequal distribution of electrons, that is, a transient electric dipole</li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/d46e8ff5-86c2-4001-9786-386534c0a600/public" width="70%"> <!----> </div>

<div> <h3 id="successvan-der-waals-interactionssuccess-1"><Success>Van der waals interactions</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li>If two noncovalently bonded atoms are close enough together, the transient dipole in one atom will perturb the electron cloud of the other.</li> <li>This perturbation generates a transient dipole in the second atom, and the two dipoles will attract each other weakly. Similarly, a polar covalent bond in one molecule will attract an oppositely oriented dipole in another</li> </ul> </div>

<h3 id="successvan-der-waals-interactionssuccess-2"><Success>Van der waals interactions</Success></h3> <div style='float: left; width:60%;font-size:30px;text-align:left;'> <ul> <li>The strength of van der Waals interactions decreases rapidly with increasing distance; thus these noncovalent bonds can form only when atoms are quite close to one another. However, if atoms get too close together, they become repelled by the negative charges in their outer electron shells. When the van der Waals attraction between two atoms exactly balances the repulsion between their two electron clouds, the atoms are said to be in van der Waals contact</li> </ul> </div> <div style='float: right; width:40%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/bb209538-898a-42c1-cec2-683a93d69300/public" width="100%"> <!----> </div>

<div> <h3 id="successvan-der-waals-interactionssuccess-3"><Success>Van der waals interactions</Success></h3> </div> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <p><strong>Properties</strong></p> <ul> <li>For a van der Waals interaction, the internuclear distance is approximately the sum of the corresponding radii for the two participating atoms</li> <li>The energy of the van der Waals interaction is about 1 kcal/mol, only slightly higher than the average thermal energy of molecules at 25 °C</li> <li>Van der Waals interactions, as well as other noncovalent bonds, mediate the binding of many enzymes with their specific substrates (the subistances on which an enzyme acts) and of each type of antibody with its specific antigen</li> </ul> </div>

<h3 id="successhydrophobic-interactionsuccess"><Success>Hydrophobic interaction</Success></h3> <div style='float: left; width:100%;font-size:30px;text-align:left;'> <ul> <li>Nonpolar molecules do not contain ions, possess a dipole moment, or become hydrated. Because such molecules are insoluble or almost insoluble in water, they are said to be hydrophobic</li> <li>The covalent bonds between two carbon atoms and between carbon and hydrogen atoms are the most common nonpolar bonds in biological systems</li> <li>Hydrocarbons molecules made up only of carbon and hydrogen are virtually insoluble in water</li> </ul> </div> <div style='float: right; width:0%;'> <p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-16-chapter-02-non-covalent-bonds-lecture-2_6-n_ptdneuhvu-204-1831.2.jpg"></p> </div>

<h3 id="successhydrophobic-interactionsuccess-1"><Success>Hydrophobic interaction</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>The chemical structure of tristearin, or tristearoyl glycerol, a component of natural fats</li> <li>It contains three molecules of the fatty acid stearic acid, CH₃(CH₂)₁₆COOH, esterified to one molecule af glycerol, HOCH₂CH(OH)CH₂OH</li> <li>One end of the molecule is hydrophilic; the rest of the molecule is highly hydrophobic</li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/b7556fc7-1f98-4aa7-0f2d-4b86204c0700/public" widht="100%"> <!----> </div>

<h3 id="successhydrophobic-interactionsuccess-2"><Success>Hydrophobic interaction</Success></h3> <div style='float: left; width:50%;font-size:30px;text-align:left;'> <ul> <li>Phospholipids spontaneously assemble via multiple noncovalent interactions to form different structures in aqueous solutions</li> </ul> </div> <div style='float: right; width:50%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/b7556fc7-1f98-4aa7-0f2d-4b86204c0700/public" widht="100%"> <!----> </div>

<h3 id="successmultiple-noncovalent-bonds-can-confer-binding-specificitysuccess"><Success>Multiple noncovalent bonds can confer binding specificity</Success></h3> <div style='float: left; width:20%;font-size:25px;text-align:left'> </div> <div style='float: right; width:100%;'> <img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/eebedb87-c9f4-441a-2c5b-6aefc459bf00/public" width="50%"> <!----> </div>

<h3 id="successthank-yousuccess"><Success>Thank you</Success></h3> <div style='float: left; width:50%;font-size:25px;text-align:left'> </div> <div style='float: right; width:0%;'> <p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/biology-class-12-unit-16-chapter-02-non-covalent-bonds-lecture-2_6-n_ptdneuhvu-291-2314.8.jpg"></p> </div>