BPK 105 Study Guide - Midterm Guide: Ionic Bonding, Hydrogen Bond, Chemical Polarity
27 Apr 2018
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BPK 105: Modules 1-3
● Module 1—Do questions 4 and 8.
4. Differentiate between ionic, covalent and hydrogen bonds. Include an example of each. [5 marks]
An ionic bond is formed when an atom transfers one or more electrons to another atom. The atom that loses
electrons becomes a positively charged ion, whereas the atom that gains electrons becomes a negatively charged
ion. An example of an ionic bond is K2S (Potassium sulphide).
There are two types covalent bonds: polar and nonpolar. In polar covalent bonds, electrons are not shared equally
among two atoms, meaning that the shared electrons are generally closer to a particular atom than to another. This
leads to an area of the molecule with a slightly negative charge, as well as an area with a slightly positive charge. The
electrons in nonpolar covalent molecules are shared equally among two atoms. Thus, there is no dipole moment.
Water is a polar covalent molecule and Methane is a nonpolar covalent molecule.
A hydrogen bond consists of an attractive force between a hydrogen atom in a polar molecule and an atom with
higher electronegativity that is located in either the same polar molecule or another polar molecule. The attractive
force is the result of the opposite charges of the two atoms. The bonds between the oxygen atom and the hydrogen
atoms in a water molecule are hydrogen bonds. (Van Putte et al., 23-25).
Ionic bond involves the complete transfer of valence electrons and not just "one or more electrons". Also, covalent
bonds are strong bonds.
8. Compare and contrast the structure and functional roles of carbohydrates and lipids. Include a general
description of these organic molecules in your discussion. [6 marks]
Carbohydrates are molecules that contain Carbon, Hydrogen and Oxygen; each carbohydrate has the same amount
of Carbon and Oxygen and two times as much Hydrogen (ex. C6H12O6). Monosaccharides, which are the simplest
carbohydrates, are simple sugars that function as sources of energy for cells. Disaccharides consist of two
monosaccharides that are covalently bonded to each other. Polysaccharides are formed when more than two
monosaccharides are joined together in a chain. Lipids contain Carbon, Hydrogen and Oxygen atoms, and dissolve
when placed in nonpolar solvents. Some lipids contain Phosphorus and Nitrogen as well. Lipids have several
functions. For instance, fats are sources of energy and can be stored; fats also provide insulation. Fats are formed
from glycerol and fatty acids. Steroid hormones are responsible for the regulation of numerous physiological
processes
in the body. Lipids also have structural functions; phospholipids, for example, help to form the plasma
membrane. Phospholipids are composed of a glycerol molecule, two fatty acids, and a Phosphorus-containing
molecule. (Van Putte et al., 32).
Carbohydrates also provide structural support e.g cellulose in plants; glycogen is the main storage form of energy in
humans.
● Module 2—Do questions 6, and 8.
6. Absorbing glucose into the cells of the small intestine after digestion requires the use of secondary active
transport. To move this same glucose out of the cell to be taken up the circulation utilizes facilitated
diffusion. Describe these methods of movement across the membrane and clearly describe why we observe
these differences for glucose movement. [4 marks]
There are different methods in which glucose moves across the membrane, depending on if it’s moving with or
against the concentration gradient. In the secondary active transport process in which glucose is absorbed into cells,
Sodium ions are involved. A Sodium-Potassium pump leads to the active transport of Sodium ions through the
plasma membrane of the cell, so that the concentration of Sodium ions is lower inside the cell than it is outside. This
creates a concentration gradient. As the Sodium ions moves with its concentration gradient into the cell using a
Document Summary
Bpk 105: modules 1-3: differentiate between ionic, covalent and hydrogen bonds. An ionic bond is formed when an atom transfers one or more electrons to another atom. The atom that loses electrons becomes a positively charged ion, whereas the atom that gains electrons becomes a negatively charged ion. An example of an ionic bond is k2s (potassium sulphide). There are two types covalent bonds: polar and nonpolar. In polar covalent bonds, electrons are not shared equally among two atoms, meaning that the shared electrons are generally closer to a particular atom than to another. This leads to an area of the molecule with a slightly negative charge, as well as an area with a slightly positive charge. The electrons in nonpolar covalent molecules are shared equally among two atoms. Water is a polar covalent molecule and methane is a nonpolar covalent molecule.
