BY 330 Spring 2015Mock Exam 4
1. Microtubules, components of the cytoskeleton, are distributed uniformly across the cytoplasm. Another component, microfilaments, are found mostly in the interior of the cell.
2. Communicating cell junctions allow two cells to share which of the following? Circle all that apply.
a). Cytoplasm
b). Organelles
c). Water
d). Small molecules
e). Electrical impulses
3. Describe the major difference between a desmosome cell junction and a tight cell junction.
An adhering junction functions to stick cells to each other or to other surfaces to resist sheer mechanical force ® water and small molecules can still flow through the cells. Impermeable junctions serve to make sure that NOTHING will be exchanged between the two cells.
4. The nucleus serves to maximize (surface area, volume), and the endoplasmic reticulum serves to maximize (surface area, volume).
5. Draw and label the structure of a nuclear pore.
6. Circle all of the following molecules that will be tagged to travel through the nuclear pore.
a). Ribosomal proteins
b). Na+ ion channel
c). Immature mRNA
d). Proteases
e). Histones
7. Mitochondrial DNA is (heavier, lighter) than nuclear DNA. Why?
More G-C pairs
8. Mitochondrion 1 has a highly convoluted inner membrane, while mitochondrion 2 has a less convoluted inner membrane. Which is more active in ATP production? 1
9. The lac operon in prokaryotes will produce a protein that (increases, decreases) the amount of lactose in the organism. A (high, low) level of allolactose will facilitate a repressor protein that will bind to the promoter region of the gene and ultimately (prevents, enhances) the activity of the protein product of the lac operon. This is an example of negative gene regulation.
10. Multi-gene regulation is accomplished by which proteins? What are two mechanisms by which these proteins work?
Master gene regulatory proteins; work either by binding to multiple genes and turning them on/off or by opening up heterochromatin to making more genes available to transcription factors
11. List four mechanisms of selective decondensation. Describe one in detail.
4 possibilities – phosphorylation, acetylation, polyamines, histone replacement
Phosophorylation – add phosphate to histones to loosen chromatin
Acetylation – neutralize histones with carbon groups
Polyamines – neutralize negatively charged DNA by addition of compounds with multiple amino groups
Histone replacement – replace histones with ones that aren’t charged
12. The general process of cell signaling involves a primary messenger/ligand ,which binds to a receptor on the cell membrane. This receptor stimulates a secondary messenger, which can have a direct or indirect effect on the cell.
13. Distinguish between autocrine and paracrine cell signaling.
Autocrine – cell stimulates itself
Paracrine – cell stimulates adjacent cell
14. List the four types of primary ligands.
Steroid hormones
Amino-acid derived
Peptide/protein
Nucleotides
15. True or False: Second messengers are synthesized slowly and stick around for the entire life of a cell. False
16. PIP2 is derived by adding two phosphate molecules to the lipid phosphotidyl inositol.
17. Describe one way to regulate ligands, receptors, or secondary messengers.
4 possibilities – regulate synthesis, regulate release, regulate degradation, post-translational modifications
18. How is the G-protein complex activated in a G-protein coupled cell signaling system? True or False: G-alpha is the second messenger in this system.
G alpha separates from complex and is activated by removing GDP attached and replacing it with GTP. FALSE.
19. In an enzyme-linked cell signaling system, a primary ligand activates a receptor, which will combine with another receptor in a process called dimerization. This combination facilitates a large amount of enzymatic activity in the cell.
20. What are three major characteristics of a malignant cancer tumor?
Metastasis (caused by de-differentiation of the cell)
Angiogenesis
Stimulating adjacent cells to become cancerous
21. Cancerous cells are produced through the combination of two types of genes. Oncogenes are genes that are turned on when mutated and generally signal the cell to divide. Tumor suppressor genes are those which are turned off and tell the cell to slow division. APC is the first gene altered in the cascade leading to colon cancer. Which of the two types is it? Tumor suppressor