Thursday, October 30, 2008

Hey guys, today in class we took the in class essay for chapters 5 and 8 and finished up Lab 2. We have Chapter 12 Vocab due next week so here are the words:

Density Dependent Inhibition: The phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another.
Cyclin: A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle
Cleavage: The process if cytokinesis in animal cells, characterized by pinching of the plasma membrane. Also, the succession of rapid cell growth during early embryonic development that converts the zygote to a ball of cells.
Centrosomes: Structure present in the cytoplasm of animal cells, important during cell division; functions as a micro tubule-organizing center. A centrosome has two centrioles.
Centromere: The specialized region of the chromosome where two sister chromatids are most closely attached.
Kinetochore: A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.
Sister Chromatid: Either of the two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms. While joined, two sister chromatids make up one chromosome; chromatids are eventually separated during mitosis or meiosis II.
Gamete: A haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.
MPF: (Maturation-promoting factor [M-phase-promoting factor]); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase.

Cell Plate: A double membrane across the mid line of a dividing plant cell, between which the new cell wall forms during cytokinesis.
Cytokinesis: The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.


Centro- the center
Mito- a thread
Meta- between
Telos- an end
Soma- body
Pro- before
Meio- less
Mal- bad or evil
Inter- between
Gen- produce
Gamet- a wife and husband

In class we talked about possible factors that could explain the large variances in the group data. One factor that could account for the drastic differences is the way in which each group their reaction chamber during each experiment. We found that leaving the chamber completely submerged under the water resulted in a slower reaction while holding the chamber at more of a vertical angle resulted in a faster reaction. Another factor is the way in which our enzyme-the catalase (yeast)- was prepared. On the first day (Wednesday), Ms. Lyon prepared the yeast with warm water which caused the oxygen gas to take over the water during the reaction very quickly. Whereas on the second day (Thursday), Ms. Lyon prepared the yeast with cold water which resulted in a much slower reaction.

Here is a video to help you better understand Feedback Inhibition - a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

*I did not know how to upload a video but here is the URL:

Multiple Choice Questions for the Unit Exam on Wednesday!!

1. What determines if an enzyme can act on a specific substrate?
a) temperature
b) pH
c) if the active site of an enzyme fits the substrate properly
d) the specific three-dimensional configurations of enzymes
e) C and D are correct

2. When an enzyme is added to a solution where the substrate and product are in equilibrium, what will happen?
a) More product would be formed
b) More enzyme would be formed
c) The free energy of the system would change
d) Nothing-it would stay at equilibrium
e) The reaction would change from endergonic to exergonic

All of the following are true about exergonic reactions except:
a) energy is released
b) products have less free energy than reactants
c) G is negative
d) reactants have less free energy than products
e) they are spontaneous

4. What is the fastest way to obtain products from an enzyme saturated with substrate?
a) add more substrate
b) add more enzyme
c) heat the solution
d) add a noncompetitive inhibitor
e) B and C are correct

5. The structural level of a protein least affected by a disruption in hydrogen bonding is:
a) primary
b) secondary
c) tertiary
d) quaternary
e) disruption of hydrogen bonds does not affect proteins

answers: E, D, D, B, A


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