my downfall

Which of the following best describes the formation of the bond shown in Figure 1?

• An ionic bond is formed between a carbon atom of one amino acid and the nitrogen atom of the other amino acid.

• An ionic bond is formed when the negative charge of an OH group is balanced by the positive charge of a hydrogen ion.

• A covalent bond is formed between a carbon atom and a nitrogen atom along with the formation of H2O .

• 
  A covalent bond is formed that replaces the hydrogen bond between the OH group and the H atom.

Which of the following is an accurate description of the process shown in Figure 1 ?

• The linking of amino acids with an ionic bond as an initial step in the protein synthesis process

• The formation of a more complex carbohydrate with the covalent bonding of two simple sugars

• The hydrolysis of amino acids with the breaking of covalent bonds with the release of water

• The formation of a covalent peptide bond in a dehydration synthesis reaction

Which statement is the most accurate description of the reaction shown in Figure 1?

• 
  It represents monomers linked by dehydration synthesis

• It represents a polypeptide chain that folds to form the tertiary structure.

• It represents a polypeptide chain that is denatured into the primary structure.

• It represents a polypeptide chain that is broken down through a hydrolysis reaction.

Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?

• Based on the molecular structures shown in the figure, which molecule is likely to be solid at room temperature?

• Linoleic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together.

• Palmitic acid, because the absence of carbon-carbon double bonds allows the molecules to pack closely together.

• Palmitic acid, because the presence of carbon-carbon double bonds prevents the molecules from packing closely together.

Which of the following best describes the structures of carbohydrates?

• They only occur as disaccharides.

• They occur as monomers, chains of monomers, and branched structures.

• 
  They only occur as long and branched structures.

• They occur as chains of monomers that hydrogen bond with complementary chains of monomers.

Which of the following best describes how amino acids affect the tertiary structure of a protein?

• The number of amino acids determines the tertiary structure of the protein.

• The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

• The interactions of the different R-groups with other R-groups and with their environment determine the tertiary structure of the protein.

• The sequence of the amino acids in the polypeptide chain determines the protein’s primary structure but has no effect on its tertiary structure.

The CFTR protein is made up of 1,480 amino acids linked together in a chain. Some humans produce a version of the CFTR protein in which phenylalanine (an amino acid) has been deleted from position 508 of the amino acid chain.

Which of the following best predicts how the amino acid deletion will affect the structure of the CFTR protein?

• It will have no observable effect on the structure of the CFTR protein.

• It will affect the primary, secondary, and tertiary structures of the CFTR protein.

• It will affect the primary structure of the CFTR protein, but the other levels of protein structure will not be affected.

• It will affect the secondary and tertiary structures of the CFTR protein, but the primary structure will not be affected.

Researchers compared similar proteins from related organisms in different habitats. They found that the proteins from organisms living in harsh environments had a greater number of cysteine amino acids than did proteins from organisms not living in harsh environments. The structure of cysteine is shown. Bonds can form between the sulfur atom of different cysteine amino acids (S-S bonds).

Which of the following best describes the effect of a greater number of cysteine amino acids on the stability of the proteins?

• The change has no effect on the stability of the protein because only one type of amino acid is involved.

• The change leads to increased protein stability because of an increased number of S-S bonds in the tertiary structure of the proteins.

• The change leads to decreased protein stability because of an increased number of S-S bonds in the tertiary structure of the proteins.

• The change leads to increased protein stability only when the added cysteine amino acids are next to other cysteine amino acids in the primary structure.

Which of the following best describes a structural difference between DNA and RNA?

• 
  DNA contains four types of nitrogenous bases, whereas RNA contains only two types of nitrogenous bases.

• The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose.

• C

  A DNA molecule is composed of two parallel strands with the same 5′ to 3′ directionality, whereas an RNA molecule is composed of only one 5′ to 3′ strand.

  D

• Phosphate groups provide rigidity to DNA, but RNA is flexible and contains no phosphate groups.

Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA?

• The 5′ to 3′ orientation of the nucleotide chain

• The identity of each nitrogenous base

• The charges on the phosphate groups

• The type of bond linking the nucleotides together