BI110 Lecture 6: BI110-Lecture 6-Water (Module 6 cont’d) & Cells (Module 13)

The type of macromolecule found in highest concentration on a weight basis in a HeLa cell is

Which of the following statements about water is not true?

Some proteins, once folded “associate” to form higher order structures (i.e., quaternary structure). Within these structures the single protein chain is known as a “subunit” (not to be confused with a protein domain). If two identical protein chains fold and associate, the quaternary structure is named “homodimer” (and the individual subunits are sometimes referred to as “monomers”); for three “homotrimer” and so on. If, on the other hand, the two protein chains that associate have different primary structures, the quaternary structure is named “heterodimer”. Using the dimer as an example, we know that the respective regions of the protein subunit surfaces that are interfaced, are responsible for the “favorable energy of interaction” which stabilizes the dimeric protein complex.

(a). Although, noncovalent bonding interactions are used both for stabilization of the folded protein molecule and its dimerization, the contribution of the “hydrophobic effect” to chain folding is significantly greater than its contribution to subunit association. Define the “hydrophobic effect” and explain why you would expect it to have a more pronounced role in chain folding compared to dimerization of the folded molecules.

(b) As the protein chain folds to the native structure, it loses entropy. Upon dimerization, more protein entropy is lost. Compare and contrast the source of protein entropy loss, which occurs with folding, with that which occurs with dimerization.

1. Use the following definitions and phrases to describe to which molecules of life and their subunits it belongs:

a. Energy-storing molecule, typically water soluble - b. Subunits are called monosaccharides – c. Used to speed chemical reactions - d. Subunits are joined to each other with peptide bonds - e. Most prevalent molecule in cell membranes - f. Some of them function as hormones - g. Used for storing, transmitting, and executing genetic information - h. Subunits are nucleotides

2. Weak hydrogen bonds between water molecules are responsible for the many properties of water. Acidity is expressed as pH. Buffers stabilize pH. a. What characteristics of water molecule makes it polar? Provide two examples why this property is important in microbiology. b. What is the role of buffers in living organisms, including microbes? c. What must be added to pure water to decrease OH- and/or H+ concentration, respectively

3. Carbohydrates serve as storage molecules and structural material. Lipids are hydrophobic molecules; phospholipids are main component of cell membranes. Protein has a complex structure based on identity and sequence of amino acids. Nucleic acids (DNA and RNA) are genetic station of storage information and for synthesis of proteins. ATP serve as the main energy source in the living cell. a. Name the subunits (building blocks) of carbs, simple lipids, proteins, and nucleic acids b. What level of protein structure is described as an alpha helix? c. If DNA is placed in boiling water, what and how the molecule would change?