tracing matter

Radish seed in the dark

(Based on a question by Janet Batzli)  The following question is based on this experiment: Three batches of radish seeds, each with a starting weight of 1.5g (dry), were placed in petri dishes and provided only with light or water or both, as shown in the photo. After 1 week, the material in each dish was dried and weighed. The results are shown below.


H2S Bacteria

Some bacteria can undertake a type of photosynthesis that uses H2S in place of H2O. Assuming that the process is otherwise similar to green plant photosynthesis, which of the following could represent the overall reaction?

 A. 6 CO2 + 12 H2S -> C6H12S6 + 6 H2S + 6O2

A novel organelle - Kreb cycle

A research group has discovered an organism with cells that contain a previously undescribed organelle. They isolate a large quantity of these organelles and test to see if they are involved in any major metabolic reactions. They incubate the organelles for a period of time and determine changes in the amount of various substances in the suspending solution. (Note: you can assume that various starting substrate materials for the pathways are provided in sufficient quantity by the researchers.) The results are:

Growth and respiration

An agar plate was left uncovered for two weeks. Three different kinds of mold grew on it. Assuming that the plate did not dry out, which of the following is a reasonable prediction of the weight of the plate and mold?

A.  The mass has increased, because the mold has grown.

B.  The mass remains the same as the mold converts agar into biomass.

C.  The mass remains the same as the growing mold converts agar into energy.

D.  The mass decreases as the mold converts agar into biomass and gases.


Plants loosing weight

A potted geranium plant sits in a windowsill, absorbing sunlight. After I put this plant in a dark closet for a few days (but keep it watered as needed), will it weigh more or less (discounting the weight of the water) than before I put it in the closet?

A.  It will weigh less because it is still respiring.

B.  It will weigh less because no photosynthesis is occurring.

C.  It will weigh more because the Calvin cycle reactions continue.

D.  It will weigh the same since no biomass is produced.

Animals loosing weight

Three alternative stems

Jared, the Subway man, lost a lot of weight eating a low calorie diet. Where did all the fat/ mass go?

 You have a friend who lost 15 pounds of fat on a diet. Where did the mass go?

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