BY 330 Spring 2015Mock Exam 1

  1. The average width of a double-stranded DNA helix is 2 nm. Express this value in micrometers and millimeters.

2 nm = 0.002 micrometers = 0.000002 millimeters

  1. Cell A has a surface area to volume ratio of 10. Cell B has a surface area to volume ratio of 14. Which cell would be more effective in transporting materials into and out of the cell? Why?

Cell B – it has a higher surface area to volume ratio, which makes the cell smaller and it easier for materials to diffuse across the cell membrane.

  1. What does it mean for a molecule to be hydrophobic? Give an example.

A hydrophobic molecule is one that cannot bind to or organize around water. An example of a hydrophobic molecule would be a methyl group.

  1. Every monosaccharide will have at least one ketone group or one aldehyde group AND one hydroxyl group. Cellulose is a polysaccharide with a structural role.
  2. Instead of having free fatty acids floating around, a cell will store fatty acids in the form of what molecule? Describe this molecule (a drawing may help).

Cells store fatty acids in the form of a triglyceride molecule. A triglyceride molecule is made up of a glycerol molecule that has three carbons, with a fatty acid chain attached to each carbon through the carboxyl group.

  1. Draw two amino acids joined by a peptide bond. Label the bond.
  1. List three major functions of the nucleotide and provide examples.

Provide energy – ATP

Used as signaling molecules – cAMP

Building blocks to form nucleic acids – DNA and RNA

  1. Draw a single stranded DNA molecule containing two purines. Label the 5’ and 3’ ends.

  1. Define a van der Waals interaction.

Electrons on adjacent atom shells line up and are attracted to the positively charged nucleus of the adjacent atom. This is the weakest of the weak bond interactions and is fleeting. A drawing might help to explain this better!

  1. What are the five proteins used by the cell to form chromatin? Why do these proteins associate with DNA?

H2A, H2B, H3, H4, H1 (four nucleosomer histones + one non-nucleosomer histone). These proteins are positively charged, so they will be attracted to the negatively charged DNA in the cell.

  1. A protein has one carboxyl end and one amino end. What is the highest level of structure that this protein can obtain? How many domains does this protein have?

The highest level of structure that this protein can obtain is tertiary. Can’t tell how many domains the protein will have without more information.

  1. R-group (interactions) are involved in every level of protein structure. True or false?

False – only involved in tertiary and quaternary

  1. Though primarily weak bond interactions occur between R-groups in a protein, covalent bonds can also be formed. For example, a disulfide bridge is formed when the sulfur groups of adjacent cysteine amino acids interact with each other. This happens largely in proteins that function outside the cell.
  1. The cell uses ATP to assemble the higher-order quaternary structure of a protein. True or false?

False – proteins undergo self-assembly, so it takes no extra energy to assemble them.

  1. A substrate ligand will bind to the active site of an enzyme, while a regulatory ligand will bind to another site and alter the surface area of the enzyme.
  1. What is the fastest way to regulate the rate of enzyme activity in the cell?

Change the value of the Michaelis constant (Km)

  1. What is the Michaelis constant and how is it related to affinity or efficiency of an enzyme?

The Michaelis constant is the substrate concentration at half of the maximum velocity. It is inversely proportional to enzyme affinity/efficiency. If the Michaelis constant is increased, the affinity of the enzyme for its substrate will decrease and vice versa.

  1. Draw a typical graph plotting enzyme activity versus substrate concentration. Indicate normal activity with a solid line and the activity of a positive modulator with a dashed line. Label Vmax, ½ of Vmax, and Km for each of two curves.

  1. State the first law of thermodynamics.

Energy cannot be created or destroyed within the universe, only borrowed.

  1. A carbon atom bonded to an oxygen atom is said to be oxidized. What is the most stable form of carbon while in this state? CO2
  2. Distinguish between a catabolic and an anabolic reaction. Be specific.

A catabolic pathway is one that breaks down organic molecules and produces energy in the form of ATP. It also harvests electrons in the form of hydride sinks, like NADH. An anabolic pathway uses energy to build large macromolecules from smaller organic molecules. A drawing might help here like the one Dr. Watts drew describing the two processes.

  1. Hydrides are generally transferred to hydride sinks during a catabolic reaction. What is a hydride? Name three molecules that act as hydride sinks.

A hydride is the form in which electrons move – two electrons and one hydrogen ion. NAD, NADP, and FADH can act as hydride sinks.

  1. A chemical reaction in a cell releases 100 kcal of heat energy. Four molecules of ATP are produced during this reaction. What is the efficiency of energy capture for the reaction?

4 * 7.3 = 29.2

29.2/100 * 100 = 29.2% efficiency