Question

21. Of the following choices, which would be a proposed mechanism by which a basic molecule affects an acid solution? a) It prevents the disassociation of H.O molecules therefore raising the pH toward 7.0. b) The base releases OH which can combine with H in the solution, therefore raising the pH toward 70 c) bases are ionic molecules that combine with the polar H,O molecules.) They counteract the burning sensation caused by acids by cooling the cells lining the stomache) None are true 22 Of the following molecules, which is a complex biological molecule formed by dehydration synthesis during the period of Chemical Evolution? a) Polysacharides, b) DNA c) Polypeptides, d) Phospholipids, e) All are 23. Based on your understanding of Chemical Evolution explain the following observation. The contents of the cell (the cytoplasm) contain mostly H.O with dissolved molecules. However, there are also some non polar molecules (ie, steroids) that function inside the water based cytoplasm One would expect that these non-polar molecules are: a) dissolved in water, b) charged, c) are attached to the non polar part of molecules that also have polar or lonic groups, d) are hydrophilic, e) probably these are all are true. 24. Which statement is NOT true about ionic bonds? a) The two ions share 2 clectrons. b) Electrons are completely lost or gained in ion formation c) An ionic interaction occurs between positive ions and negative ions. d) One atom acts as an electron donor and the other acts as an electron acceptor. e) A salt such as CaCl is formed by an ionic reaction.

Answer 1

21) bases can release OH- and acids release H+, OH- and H+ combine to form water, so when acid and base are mixed the pH of the solution increases so the answer is b) the base releases OH- which can contribute with H+ in the solution, therefore, raising the pH toward 7.0.

22) when 2 amino acids are linked via peptide bond one water molecule is released, OH of the carboxyl group reacts with the H of the NH2 to release water when nucleotides are linked together, Oh of the phosphate group and H on the OH group on the 3`-OH combines to form water, when 2 sugar molecules react to make polysaccharides water molecule is released. a phospholipid has 2 fatty acids attached to the OH group of the glycerol and one phosphate group attached to the third OH of the glycerol when these groups react with OH group of the glycerol water molecule is released.

so the answer is e) all are.

23) hydrophobic steroids are not soluble in the water, so in the water-based solution like cytoplasm those hydrophobic molecules are bound with other molecules which have both hydrophobic and hydrophilic regions, hydrophobic regions interact with the hydrophobic steroid molecules and hydrophilic region interact with water so the answer is c) are attached to the non-polar part of the molecule that also have polar of ionic groups.

24) ionic bonds are formed between ions, one ion is negatively charged and the other ion is positively charged, negatively charged ion has one extra electron and the positively charged ion have lost one electron so the answer is a) two ions share 2 electrons.