29 January Science 8 Sugar, starch, molecules and the chemistry of life on earth–how it adds up; Your human impact project

  1. Review previous DSN and blogposts. ( http://rfrazier.msblogs.aes.ac.in/2018/01/24/24-january-science-8-fermentation-of-sucrose-by-yeast/  ) and    (http://rfrazier.msblogs.aes.ac.in/2018/01/22/22-january-science-8-reflection-on-carbon-presentations-reading-about-fermentation-respiration-metabolism/ )
  2. Read blogpost for today.
  3. Prepare your DSN for today’s entry.
  4. Examine fermentation experiment from previous class. Clean up bottle.
  5. Salivary amylase:

Today we will try this simple “experiment.” You will get a piece of a cream cracker. Take it into your mouth and hold it–do not swallow. Note the time. Describe the changes in taste as you hold the crack in your mouth. When it becomes sweet, you may swallow. How long did it take for you to notice the change?

Record your time (to sweetness) in this spreadsheet (you’ll need to be added to edit:



Polysaccharides–Read about Saccharides (like glucose) and Polysaccharides (like starch and cellulose) http://www.chem4kids.com/files/bio_carbos.html

5. Build, diagram, and rearrange molecular models to think of how organisms (green plants) could build sucrose and how organisms could use sucrose in their various chains of reactions–to harvest energy and building material. (The chemical reactions that characterize life are the subject of the discipline called biochemistry.) Think of how reactions in cells “add up” in organisms, populations, habitats, and ecosystems to comprise the great biogeochemical cycles on earth–like the carbon cycle.

Record your activity. (Model of sucrose metabolized to glucose and fructose. Model of glucose metabolized by yeast to ethanol and carbon dioxide–as in the yeast fermentation. Overall equation for anaerobic respiration/fermenation: C6H12O6 = 2C2H5OH + 2CO2) (Notice the difference with aerobic respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water)






Sucrose and Saccharomyces cerevisiae: a relationship most sweet

An interesting article about sucrose and yeast–the history of human use, the evolution of the yeast and of sucrose metabolism, the biochemistry. There are details that are beyond what we have studied, but look through the article and try to get as many ideas as you can. The questions that arise are very important in your learning. List them.


Saccharomyces cerevisiae is the scientific name of the yeast we used.

The abstract:

Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugar beet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering.


6. Our next topic focuses on how green plants (and phytoplankton in both salt and fresh water–oceans and lakes) take in carbon dioxide and water and use energy from light (and a constellation of special molecules and cell structures) to carry out an amazing sequence of reactions that results in the synthesis (making) of saccharides (glucose, fructose, starch, etc.).

(From S.E. Jorgensen, 1980, Lake Management:

‘PLANKTON. We’re an indolent lot… shiftless microscopic drifters. Here in the oceans a million trillion trillion of us just float aimlessly and worship the sun. We have no brains at all. And we don’t do anything except procreate with promiscuous abandon and generate most of the earth’s oxygen. And we have no advice at all for you diligent bipeds who use your capacious intellects to so industriously befoul the seas. For about two billion years we got along quite well without you. And Without us, you will suffocate.’ )


7. Assignment from previous class:

See the following link to *Lives of a cell* by Lewis Thomas. This is a significant example of science writing for the general (educated) public. This work just preceded Primo Levi’s Periodic Table that you read or hear about in the Carbon presentations.

As a group pick out one of the chapters to read. Be prepared to share your reading through an annotation: full bibliographic information, description, summary, assessment, reaction. Learning to write good annotations is a skill you will need and use in your human impact project. Do this one together as a group. Be sure that each member has this sample annotation of one of the chapters from Lives of a Cell in her/his digital science notebook.




8. Human Impact on the Earth

You have already selected your topic (by lottery). You should have begun watching for items “in the news” and creating annotations. If you have not, be sure you start now.

In addition to references sent to you by email and posted in the blog, begin searching. Try these sites and journals. Browse environment and science sections. Use wide and narrow search terms from your topic. If you find something a classmate could use, please send it to her/him. Be a good investigative reporter or detective. Make an annotation for each source you examine. If you find a useful site–with references for several topics–please send the information.

Raising Kids in Delhi’s Worsening Air . https://www.newyorker.com/culture/personal-history/raising-kids-in-delhis-worsening-air

Biodiversity is Life’s Safety Net https://www.theatlantic.com/science/archive/2018/01/biodiversity-life-safety-net/550979/

The Problem with Being Young in India https://pursuit.unimelb.edu.au/podcasts/the-problem-with-being-young-in-india

Annotation (for each reference):

  1. Full bibliographic information, author, date, title, publication, volume, edition, page (or equivalent). If web-based, include the url, the date of posting (last edit), and the date you last accessed.
  2. Information about the author and publication–background, expertise, affiliation. If no author, focus on the publication.
  3. Content of the article. Be specific. Big ideas and enough of the significant details to get a sense of what the article is about.
  4. Point of view and usefulness. Is the article a report of original research or a review of research or an opinion-editorial or a reflective essay or some other genre? If a point of view being presented. What kind of evidence is used to support the points made in the article?


( < https://docs.google.com/a/aes.ac.in/spreadsheets/d/1SXx0Zvtkx8C3SixY99dE-F5_GNS0XYM0yjkp3oNGqsg/edit?usp=sharing >)

  1. (Global) CO2–greenhouse effect–global warming–global climate change—shifting of carbon cycle
  2. India(Invasive species in India—loss of native habitat and biodiversity)
  3. (India) Endangered species. Habitat loss. Trade in endangered species. Animal human conflict. Conservation efforts in India.
  4. (Global)Elements in an Ipad-Laptop-Cell phone–Rare earths and conflict minerals—environmental costs of technology
  5. (India)Air quality in Delhi–air pollution
  6. (Global)The Anthropocene and the 6th great extinction
  7. (India)Mining-industrial, economic development, urban sprawl and conservation of nature / habitat / biodiversity in India
  8. (India)Agriculture-pesticides-fertilizer-nutrition and health in India
  9. (Global with local examples) The concept of ecosystem services—re-evaluating economic policy and theory in light of the environment—other ways to assess the value of the environment—international examples—Indian example.
  10. (India) The degradation and altering watersheds—River linking, dams.
  11. (India-Delhi) Access to clean water—sewage—pollution—irrigation—shortage of water.
  12. (Global) New Diseases. Zoonotic diseases. 
  13. (Global) Food security. Genetic engineering. Reduction in genetic diversity of food crops. Selection of herbicide resistant weeds. Loss of pollinator populations and diversity (pesticides and bees, for example).
  14. (Global and local) Deforestation–India, Tropics, Worldwide
  15. (Global and local) Climate denial, science denial, removal of environmental protections
  16. (Global and local) Current state of “green energy.” Renewable energy. Non-carbon based energy technologies
  17. (Global and local) Habitat restoration. “ Rewilding.”E.O. Wilson’s Half-Earth proposal.
  18. (Global and India) Promising environmentally sustainable practices and technologies (other than green energy examples from #16).
  19. (local)AES efforts to implement environmentally friendly practices. Areas for improvement. Suggestions.
  20. You choose—must be distinct from other options.

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