BIOL210A Exam 1 Study Guide Fall page 1 Layout References Mailings Review View H
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BIOL210A Exam 1 Study Guide Fall page 1 Layout References Mailings Review View Help Tell me what you want to do 1 Normal 1 No Spac.. Heading 1 Headin Font Paragraph Styles 24)Understand that it is the DIFFERENCE IN ELECTRONEGATIVITY between the two atoms that determines whether electrons are shared equally or unequally in a covalent bond. If two atoms have the same or similar electronegativity they will share the electrons equally in a covalent bond (non-polar covalent bond). If there is a big difference in electronegativity between the two atoms, one will have a much stronger pull on those shared electrons and they will share unequally (polar covalent bond). 25)Understand the difference between polar versus non-polar, hydrophilic versus hydrophobic 26)Hydrogen bonds: be able to explain how and why and where they occur 27)Know the functional groups that we covered in lecture. They are in the powerpoints and in your textbook. You don't need to be able to draw them, but just identify them. 28)Also, you need to know which ones are ionized in biological systems (not Phosphate, which is normally ionized.) 29)Know the isomers we covered in class and be able to identify them 30)Know details on Carbon that we covered in lecture 31)Know the 4 common ways that a Carbon skeleton can differ Properties of H2O: ch.3 32)cohesion/surface tension/ adhesion 33)high specific heat &high heat of vaporization solid H,O less dense than liquid HoExplanation / Answer
24. A water molecule is an example of a polar covalent bond.
Oxygen needs 2 electrons to complete its octet while hydrogen needs 1 electron to get a stable electronic configuration.
Oxygen shares one electron each from the 2 hydrogen atoms to complete ts octet and the 2 hydrogen atoms share 1 electron each from the oxygen atom. But the electrons face a greater pull by the oxygen atom, resultng in an unequal sharing of the electrons. The oxygen atom in the water molecule has slightly negative charge and the hydrogen atom has a slight postive charge.
25. Polar versus non-polar--
In Non- Polar bonds the electrons are shared equally between the two atoms and they do not have any indvidual charge on them. It is a non polar covalent bond.
Example is the bond between two carbon atoms. Carbon atom is unique because t has 4 electrons in its outermost shell and t always shares electrons with other atoms to gain a stable confguration.
Polar bonds are those n which one atom has a slightly greater pull over the shared electron and hence gets a slight negative charge. Example is the bond in a water molecule.
Hydrophobic versus Hydrophilic compounds--
Hydrophobic means ' water fearing '. So, such molecules do not have any affinity for water. They are non-polar. When put in water, these molecules cluster together and form micelles. Examples are alkanes, oils, fats and other greasy substances.
Hydrophilic means ' water loving '. So, such compounds have an affinity for water. They are polar molecules and dissolve readily n water. They are charge polarised and capable of hydrogen bonding.
26. Hydrogen bonds-
A hydrogen bond s a partially electrostatic attraction between a hydrogen whch s bound to a more electronegative atom such as nitrogen, oxygen or any halogen. Hydrogen bonds are of two types--
i] IIntermolecular hydrogen bondng, which is between a hydrogen and any other atom. Example H2O molecul.
ii] Intramolecular hydrogen bonding, which is between two hydrogen atoms as in H2 molecule.
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