Microbiology 223: Chapter 2 Homework

Understanding the structural and molecular interactions that induce shape and function for a protein has been an obstacle for some of your students. You decide to plan a lesson to introduce them to the basic amino acid structure and then use that concept to introduce the different levels of protein structure. To reinforce your lesson on amino acids, you need to aid the students in understanding that most naturally occurring amino acids have a shared base structure. Each amino acid has an amine group, an alpha-carbon (or central carbon), an R-side group, and a carboxyl group. The R-side group is what gives each amino acid its distinctive characteristics--for example, whether the amino acid will be acidic or basic, hydrophilic or hydrophobic, or charged.

Amino acids always contain a sulfur atom in their R-side group.

Answer: It has 12 neutrons in its nucleus.

Question:

Which of the following statements regarding protein structure is FALSE?

Tertiary structures are formed only from covalent bonds.

Part complete While writing your lecture notes, you are trying to develop a way to impart to your students how the removal of a water molecule, a hydroxyl and a hydrogen atom, will be used in making macromolecules. A molecule is a collection of atoms joined through different types of bonds. A macromolecule is the joining of numerous molecules into something that is relatively quite large. The addition of a molecule to a macromolecule, as well as the removal of a molecule from the macromolecule, involves a molecule of water. From past experience you are aware that when you state this to your students many will unfortunately assume you are referring to liquid water. Your students must understand that in biological reactions water, H2O, is actually a hydroxyl group (-OH) and a hydrogen atom (H+) that will be removed or added when altering macromolecules. A dehydration synthesis (removal of water) reforms atomic bonds between molecules to create a larger macromolecule. In a dehydration reaction, a hydroxyl group is removed from one reactant molecule while a hydrogen atom is stripped from another reactant molecule. Reactant (with hydroxyl group) + Reactant (with hydrogen ion) = Product + H2O The open bonds will be reformed joining the two molecules, while the hydroxyl and hydrogen atom will be released as water. The reverse of a dehydration synthesis is a hydrolysis reaction, in which a bond between two molecules is stressed by an enzyme and a hydroxyl group when a hydrogen atom is added into the bond. Whereas a dehydration synthesis creates a macromolecule, a hydrolysis reaction breaks one apart.

Using energy, an enzyme removes a hydroxyl group from the carboxyl group of one amino acid and a hydrogen atom from the amino group of another amino acid to join the amino acids in a dehydration synthesis reaction that releases water. Alternatively, another enzyme breaks the peptide bond and uses a water molecule to join a hydroxyl group to the carboxyl group of one amino acid and a hydrogen atom to the amino group of another amino acid in a hydrolysis reaction.

Which type of molecule is composed of (CH2O) units?

carbohydrate

What is the type of bond holding hydrogen and oxygen atoms together in a single H2O molecule?

covalent bond

What is the type of strong chemical bond between carbon, hydrogen, and oxygen atoms in a single organic molecule?

covalent bond

Part complete The equation below is what type of reaction? Molecule AB → Molecule A + Molecule B

decomposition reaction

Amino acids are joined together in a specific type of dehydration synthesis reaction that results in the formation of a peptide bond. This bond links the carboxyl group of one amino acid to the amino group of another amino acid. The formation of a peptide bond to link two amino acids together is a special type of __________.

dehydration synthesis reaction that removes a hydroxyl group from the carboxyl end of the amino acid and reforms the bond with the nitrogen from the amino group that has lost a hydrogen atom

Which of the following is the type of bond between molecules of water in a beaker of water?

hydrogen bond

Part complete Which are the primary molecules making up plasma membranes in cells?

lipids

What do genes consist of?

nucleic acids

Gastric juices have a pH of 1 or 2. This would indicate which of the following?

numerous H+ ions and a low pH