AP Bio: The Chemistry of Life

Match the letter words with their numbered descriptions. Can be used once, more than once or not at all: a. Lipids b. Peptide bonds c. Alpha helix d. Unsaturated fatty acids e. Cellulose 1. Contain one or more double bonds which "kink" to form the carbon backbone 2. The major class of biological molecules that are not polymers 3. Linkages between the monomers of proteins 4. A secondary structure of proteins 5. A structural carbohydrate found in plants

1/D: Unsaturated fatty acids contain one or more carbon-carbon double bonds, where as saturated fatty acids contain no double bonds. 2/A: Lipids are the only one of the four major classes that are not polymers. They are grouped together because they are hydrophobic. 3/B: The linkages between the amino acids of proteins are peptide bonds. Peptide bonds are covalent bonds formed in dehydration reactions. 4/C: One common secondary structure of proteins is the alpha helix, the other is the beta pleated sheet. The secondary structure of a protein refers to the hydrogen bonding along the backbone. 5/E: Cellulose is the polysaccharide that forms the strong cell walls of plant cells. It is a polymer of glucose.

An organic compound that is composed of a carbon, hydrogen and oxygen in a 1:2:1 ratio is known as a: a. lipid b. carbohydrate c. salt d. nucleic acid e. protein

B is correct.

Which of the macromolecules below could be the structural parts of the cell, enzymes, or involved in cell movement or communication? a. nucleic acids b. proteins c. lipids d. carbohydrates e. minerals

B is correct. Proteins have many functions which encompass most of the cell's metabolic activity.

Which list of components characterizes RNA? a. a PO3 group, deoxyribose and uracil b. a PO3 group, ribose, and uracil c. a PO3 group, ribose and thymine d. a PO2 group, deoxyribose, and uracil e. a PO2 group, deoxyribose, and thymine

B is correct. RNA is made up of a phosphate group, a ribose sugar and one of the following four bases: cytosine, guanine, uracil and adenine.

If the pH of a solution is decreased from 7 to 6, it means that the: a. concentration of the H+ has decreased to 1/10 of what it was b. concentration of the H+ has increased to 10 times what it was c. concentration of OH- has increased to 10 times what it was d. concentration of the OH- has increased by 1/7 of what it was e. solution has become more basic

B is correct. Since the pH scale is logarithmic, each unit change is by a factor of ten.

Which of the following is NOT considered to be an emergent property of water? a. cohesion b. transpiration c. moderation of temperature d. insulation of bodies of water by floating ice e. a versatile solvent

B is correct. Transpiration refers to the evaporation of water from pores in leaves. Transpiration is possible because of cohesion and adhesion but it is not an emergent property of water.

Which macromolecule is the main component of all cell membranes? a. DNA b. phospholipids c. carbohydrates d. steroids e. glucose

B. Phospholipids are unique macromolecules. Their hydrophilic heads and hydrophobic tails contribute to the semi-permeability of cell membranes.

Which two functional groups are always found in amino acids? a. amine and sulfhydryl b. carbonyl and carboxyl c. carboxyl and amine alcohol and aldehyde e. ketone and amine

C is correct. An amino acid is composed of a central carbon, bonded to a hydrogen, with a variable (R) group and with a carboxyl (the acid part) at one end, an amino group at the other end. Aldehydes and ketones are found in sugars; the sulfhydryl group is found in one amino acid.

The process by which protein conformation is lost or broken down is: a. dehydration synthesis b. translation c. denaturation d. hydrolysis e. protein synthesis

C is correct. Denaturation is the process by which proteins lose their overall structure as a result of changes in pH, temperature, or salt concentration.

Which of the following molecules would contain a polar covalent bond? a. Cl2 b. NaCl c. H2O d. CH4 e. C6H12O6

C is correct. The answer is water, H2O. Polar covalent bonds are those in which valence electrons are shared between atoms but unequally.

Polymers of carbohydrates and proteins are all synthesized from monomers by: a. the joining of monosaccarides b. hydrolysis c. dehydration reactions d. ionic bonding of monomers e. cohesion

C is correct. The monomers in the macromolecules are joined when a molecule of water is removed during the dehydration reaction or condensation reactions.

If three molecules of a fatty acid that has the formula C16H22O2 are joined to a molecule of glycerol (C3H8O3), then the resulting molecule would have the formula: a. C48H96O6 b. C48H98O8 c. C51H68O6 d. C51H106O8 e. C51H104O9

C is correct. To get this answer, you first need to add up all the C, H, and O. This should be 51 C, 74 H and 9 O. The, recall to join two molecules by dehydration synthesis, one molecule of water must be removed. Since three fatty acids chains will be attached to one glycerol, three water molecules must be removed.

The partial negative charge at one end of the water molecule is attracted to a partial positive charge of another water molecule. What is this type of attraction called? a. a polar covalent bond b. an ionic bond c. a hydration shell d. a hydrogen bond e. a hydrophobic bond

D is correct. The negative charge comes from the electronegative oxygen of one molecule attracted to the partial positive charge of hydrogen of another water molecule.

Three terms associated with the travel of water from the roots up through the vascular tissues of the plant are: a. adhesion, cohesion and translocation b. adhesion, cohesion and transcription c. cohesion, hybridization and transpiration d. cohesion, adhesion, and transpiration e. transpiration, neutralization and adhesion

D is correct. The three terms you should keep in mind are COHESION: water molecules stick together because of hydrogen bonds, ADHESION: water molecules stick to the plant cell walls and resist gravity and TRANSPIRATION: water evaporates from the plants leaves

Hydrolysis is involved in which of the following? a. formation of starch b. hydrogen bond formation between nucleic acids c. peptide bond formation of proteins d. the hydrophilic interaction of lipids e. the digestion of maltose to glucose

E is correct. Recall that hydrolysis means to use water to split a molecule, so look for a large molecule reduced to its monomers.

Which of the following statements regarding carbon is false? a. Carbon has a tendency to form covalent bonds b. Carbon has the ability to bond with up to four other atoms. c. Carbon has the capacity to form single and double bonds. d. Carbon has the ability to bond together to form extensive, branched or unbranched "carbon skeletons" e. Carbon has the capacity to form polar bonds with hydrogen.

E is correct. Use this question to review the properties of carbon. Since it has four valence electrons it will form four covalent bonds. It does not form polar bonds.