BICD 110 Fall 2020, Dr. Kiger

Problem Set 8 Lectures 7A-7B

Microtubules

1. What statement best describes the basis for how/why microtubules are “tubes”?

___A. tubulin and tubulin assemble into small filament rings that stack into a tube

___B. tubulin dimers assemble into filaments that spiral into a tube

_X_C. tubulin dimers assemble into parallel protafilaments that fold into a tube

___D. MAPs bind and curve the tubulin dimers so that filament assembly forms a tube

___E. ATPase activity of kinesin motor proteins bends a sheet of protafilaments into a tube

2. What is a shared property of both actin and tubulin subunits with respect to microfilament and microtubule dynamics, respectively?

___A. predominantly added to filament/protofilament (+) ends.

___B. predominantly added to filament/protofilament (−) ends.

___C. equally efficient at being added to both ends of filament/protofilament.

___D. added along the length within an assembled filament/protofilament.

3. During dynamic instability of microtubules, within the tubule…

(i)…the -tubulin subunits: (ii)….the -tubulin subunits:

___A. undergo ATP hydrolysis ___A. undergo ATP hydrolysis

___B. undergo GTP hydrolysis ___B. undergo GTP hydrolysis

___C. remain locked in GDP bound state ___C. remain locked in GDP bound state

___D. remain locked in ADP bound state ___D. remain locked in ADP bound state

___E. remain locked in GTP bound state ___E. remain locked in GTP bound state

(iii) Compare and contrast the above properties of tubulin subunits in microtubule ‘dynamic instability’ to those of actin subunits with microfilament ‘treadmilling’, providing key details. What is similar? What is distinct?

4. Define ‘critical concentration’ (Cc) as it relates to microfilament and microtubule formation, as well as to the different ends of the polymers. Define steady state.

5. Fill in the blanks.

Microtubules are typically not static structures. _____Dynamic instability_____ is the phrase used to describe how a microtubule undergoes alternating periods of rapid growth and shrinkage, called _____rescue_______ and ______catastrophy_________, respectively. These dynamics occur with growth happening at the microtubule ____positive (+)_____ ends, since the ____negative (-)_____ ends are typically inaccessible while stabilized at the ______MTOC_______. At the microtubule minus-ends, you will invariably find the specific microtubule subunit, __________________, which directly interacts with another tubulin subunit, __________________ in -TuRC. Growing microtubule ends are normally stabilized by __________________ ‘caps,’ while ___GTP____ hydrolysis can lead to rapid disassembly.

6. Compare and contrast the proteins, -tubulin and formin (what do they do? how do they do it? where do they do what they do?).

7. Name and describe the organization and roles for the three different major classes of microtubules that contribute to mitosis.

Microtubules and Motor proteins

8. Motor proteins are what kinds of enzymes?

9. Draw and label a simple cartoon of the general protein domains found in common between the structures for different types of motor proteins. Indicate the ‘motor’ region and what specific types of proteins interact with the different protein domains.

10. Which of the following properties is not shared by all myosins? May be one or more than one answer.

___A. the ability to bind ATP

___B. the formation of homodimers

___C. the ability to bind F-actin

___D. the presence of a head domain

___E. the ability to do work

___F. the ability to bind G-actin

11. In the model for myosin movement on microfilaments, the power stroke occurs during:

___A. binding of ATP.

___B. hydrolysis of ATP.

___C. release of phosphate (Pi).

___D. release of ADP.

___E. the assembly of a myosin thick filament

12. Match the cell functions on the right with the specific motor (A-F) most likely involved. You may use an answer more than once or not at all.

A. Myosin I ________ Cilia movement

B. Myosin II ________ Cell contraction

C. Myosin V ________ Organelle and vesicle transport (>1 correct!)

D. Kinesin I ________ Microtuble plus-end directed sliding

E. Kinesin 5 ________ Microfilament to membrane tethering

F. Dynein ________ Microfilament plus-end directed vesicle transport

13. All of the following statements describe Kinesin I except:

___A. Kinesin I is a (−) end-directed motor.

___B. Kinesin I transports vesicles along microtubules.

___C. Kinesin I binds and hydrolyzes ATP to produce movement.

___D. Kinesin I is composed of two heavy chains and two light chains.

___E. Kinesin is a (+) end-directed motor.

14. With respect to motor protein function, specifically what effect would the addition of AMP-PNP (a non-hydrolyzable analog of ATP) have on axonal transport? Why?

15. You purify what appears (by protein sequence homology) to be an ATPase protein complex that is required in a cell free assay for endosome intracellular transport. You call it Endomytin. You want to determine if Endomytin acts as a motor protein, and if so, to characterize its motor properties. Name three basic criteria (properties or predictions about protein function) that you expect if Endomytin is a motor protein, AND how you would test Endomytin for each of these properties.

1

Inequalities in American Culture

Inequalities in American Culture

The essence of American exceptionalism is that the United States provides an enabling environment for people from diverse backgrounds to enjoy freedom and pursue their goals. However, persistent inequalities in American culture undermine the quality of life of minorities and women. The social determinants of health, such as race, social-economic status, and geographical region, determine healthcare services access.

Singh, G. K., Daus, G. P., Allender, M., Ramey, C. T., Martin, E. K., Perry, C., Reyes, A., & Vedamuthu, I. P. (2017). Social determinants of health in the United States: addressing major health inequality trends for the nation, 1935-2016. International Journal of MCH and AIDS, 6(2), 139–164. https://doi.org/10.21106/ijma.236

The authors report a growing focus on healthcare inequalities in the United States and the underlying social determinants. This article's key strength is apparent in its focus on the reports that have been prepared by reputable institutions and other studies that have focused on the subject. Besides highlighting key public health trends from 1935 and 2016, this article also provides a holistic framework to understand the influence of diverse social determinants. The life-tables, adjusted rates, risk ratios, and prevalence were tested for a statistical significance of 0.05. As a result, the data shared in these articles provide an effective indication of the health differential in these communities.

The authors reported that life expectancy rates are highest for Asian/ Pacific Islanders (87.7 years) and lowest among African Americans (75.7 years). Life expectancy is lower in rural areas as compared to urban areas. Similarly, infant and child mortality rates are higher in rural communities than in urban areas. Black infants were observed to be 2.3 times higher among African Americans than in white infants (Singh, 2017). Within rural communities, black infants and children in low-income areas registered three times higher mortality rates than their white counterparts in the affluent areas.

The article highlights the impact of differences in social determinants of health in determining these healthcare disparities. For example, racial/ethnic, geographical, and socioeconomic differences influence obesity, homicide, HIV/AIDS, smoking, access to preventive care, and hypertension. However, this article does not adequately propose solutions to these disparities and must complement other studies that discuss interventions that can be adopted to resolve this problem. Nonetheless, the article calls for a multi-sectoral approach in reducing health disparities across the United States.

Bloome, D. (2014). Racial Inequality Trends and the intergenerational persistence of income and family structure. American Sociological Review, 79(6), 1196–1225. https://doi.org/10.1177/0003122414554947

The author discusses the trends in racial inequality regarding differences in income and family structures. The article notes that racial inequality has remained stable in the last four decades despite the social and political reforms that have been enacted across the United States. The author argues that the fact that social-economic status is transmitted from parents to children creates an opportunity to offset these differences gradually. The study relied on the cross-sectional and panel analysis of data collected from the Current Population Survey and the Panel Study of Income Dynamics. Besides Census and National Vital Statistics, data was also applicable in this analysis. The methodology ensures that this study can highlight both the implications of economic gains and demographic trends on the prevalence of racial inequalities in society.

The findings of this study demonstrate that African Americans are experiencing low upward mobility and discontinuity. As a result, racial inequality has continued to persist across the United States. Furthermore, intergenerational discontinuities are creating new forms of inequality in contemporary society. An important contribution of this article is that new forms of racial inequality are entrenching racial inequalities. Despite the equalizing potential of economic growth, demographic trends and shifting family structures perpetuate social-economic inequalities with the labor-market gains not reflected in household incomes.

The author does not sufficiently discuss the changing forms of inequality in contemporary society. As a result, it should be complemented by another study that defines and discusses the emerging forms of discontinuity. Nonetheless, the fact that the African American household income has remained unchanged from the 60 % of white households documented in 1960 demonstrated that social-economic disparities continue to disadvantage them.

Stamarski, C. S., & Son Hing, L. S. (2015). Gender inequalities in the workplace: the effects of organizational structures, processes, practices, and decision-makers' sexism. Frontiers in Psychology, 6, 1400. https://doi.org/10.3389/fpsyg.2015.01400

Stamarski and Son (2015) observed that gender inequality is a complex phenomenon that continues to be evident in organizational structures, processes, and practices. The article noted the role of Human Resource policies in entrenching gender inequalities in the United States. The observation is supported by the fact that HR policies affect the recruitment, training, compensation, and promotion of women. The article's strength is that it demonstrates the reciprocal relationship between gender inequalities in the HR decision-making processes and the structure, processes, and practices of the organization.

The study relies on a model of the root causes of gender discrimination in the HR decision-making process and the enactment of policies. Subsequently, the study demonstrates that gender inequality is a systemic problem that requires both cultural and structural changes. The approach identifies the link between institutional discrimination and the encounters that individuals have with gender inequality. The study is important because gender inequalities in the workplace have a consequential effect on the psychological health and well-being of the affected women and single-mothers' ability to achieve social-economic mobility.

The article demonstrates that decision-makers' sexism has a consequential effect on their management of gender diversity in the organization. The article has documented the importance of culture, strategy, leadership, and strategy in perpetuating gender differences in an organization. The authors portray gender inequalities in an organization as a self-reinforcing system, highlighting the need for a multi-pronged intervention. They note that women are paid less than men are and have less access to mentoring opportunities.

Conclusion

The inequalities in the United States undermine its ability to achieve parity in access to care. The social-economic disparities across the United States have perpetuated healthcare disparities across the country. Besides, gender inequality and racial inequality continue to undermine women's and minorities' ability to achieve social-economic mobility.

References

Bloome D. (2014). Racial inequality trends and the intergenerational persistence of income and family structure. American Sociological Review, 79(6), 1196–1225. https://doi.org/10.1177/0003122414554947

Singh, G. K., Daus, G. P., Allender, M., Ramey, C. T., Martin, E. K., Perry, C., Reyes, A., & Vedamuthu, I. P. (2017). Social determinants of health in the United States: Addressing major health inequality trends for the nation, 1935-2016. International Journal of MCH and AIDS, 6(2), 139–164. https://doi.org/10.21106/ijma.236

Stamarski, C. S., & Son Hing, L. S. (2015). Gender inequalities in the workplace: The effects of organizational structures, processes, practices, and decision-makers' sexism. Frontiers in Psychology, 6, 1400. https://doi.org/10.3389/fpsyg.2015.01400