Glucocorticoids

1.      Natural glucocorticoids are produced in the cortex of adrenal gland

2.      Glucocorticoids are steroid hormones. Natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands. These forms of hormones are lipids. They can pass through the cell membrane as they are fat-soluble, and then bind to steroid hormone receptors which may be nuclear or cytosolic depending on the steroid hormone, to bring about changes within the cell.  The glucocorticoid receptor is cytosolic

3.      Steroid hormones are not water soluble. Glucocorticoids are lipid soluble so they have to be carried in the blood complex to specific binding globulins.  

4.      Steroid hormones are nonpolar (no net charge), and can thus diffuse across lipid membranes (such as the plasma membrane).  They leave cells shortly after synthesis. Polar substances are water soluble (dissolve in water), nonpolar substances are lipid soluble. Making it a Plasma membrane receptor.

5.      Glucorticoids have a negative feedback loop because the product of the reactions interrupts the activity of the enzyme producing the product.

6.      The name “glucocorticoid” derives from early observations that these hormones were involved in glucose (sugar) metabolism. During times when no food is being taken into the body, glucocorticoids stimulate several processes that serve to increase and maintain normal glucose concentrations in the blood. These processes include:

·         Stimulation of glucose production in cells, particularly in the liver.

·         Stimulation of fat breakdown in adipose (fat) tissues.

·         Inhibition of glucose and fat storage in cells.

They affect all types of inflammatory responses, regardless of the mode of injury or type of disease-causing substance.

7.      The receptors in target molecules need to be suitable for the signaling molecule for glucocorticoids

 

Podcast

Citations:
http://www.stanford.edu/group/hopes/cgi-bin/wordpress/2010/06/glucocorticoids/
http://en.wikipedia.org/wiki/Steroid_hormone

Generation of Carbon Dioxide from Various Carbohydrates

Abstract:

In this lab, we observed cellular respiration; we measured the amount of carbon dioxide produced from various carbohydrates when in contact with yeast. We used several different types of carbohydrates such as potato starch, honey, glucose, and cane sugar.  We used five test tubes, one of which was the control. Every test tube including the control contained 35 milliliters of lukewarm water, 1 gram of yeast, l gram of sugar, and 0.2 grams of salt. In each of the four test tubes we added different carbohydrates. The control was left untouched. We placed a rubber cork with a tube attached to a syringe (placed at l milliliter) in order to measure the amount of carbon dioxide produced. After shaking each tube to mix the contents thoroughly, we placed the tubes into a Styrofoam tube holder to control the temperature and labeled them according to their starch.  We then placed the corks on top and checked the syringe every minute for around 20 minutes to measure the amount of carbon dioxide produced.

 

Question:

Will different types of carbohydrates yield different amounts of carbon dioxide during cellular respiration?

 

Background:

The chemical formula for cellular respiration is: C₆H₁₂O₆ + O₂ → CO₂ + H₂O + Energy (ATP). Cellular respiration occurs in the cytoplasm and mitochondria. Cellular respiration is a metabolic process by which food molecules are converted into energy. This process uses carbohydrates, fats, and proteins. But glucose is most commonly used. Cellular respiration consists of three processes: glycolysis, Krebs cycle, and oxidative phosphorylation. Glycolysis occurs in the cytosol, the 6-carbon sugar breaks into 2 molecules of 3-carbon molecules called pyruvate. This process produces 2 ATP and 2 NADH molecules. In the Krebs cycle occurs in the mitochondrial matrix and produces chemical energy (ATP, NADH, and FADH₂) from oxidation of the pyruvates from glycolysis. In oxidative phosphorylation, the electron transport chain produces chemical energy stored in the NADH and FADH_2. There are 3 ATP produced per NADH and 2 ATP per FADH₂.

 

 

 

Hypothesis:

If glucose or cane sugar is placed in a container with water, yeast, salt, and sugar, it should release more carbon dioxide than  the  control . Also, we expect the potato starch to produce some carbon dioxide but not as much as the glucose or cane sugar but more than the control. Additionally, the honey should produce the least amount of carbon dioxide since it contains less glucose than the plain glucose but produce more than the control.

 

Materials:

·         5 test tubes

·         5 rubber corks with tubes

·         5 syringes

·         2 Styrofoam tube holders

·         water

·         yeast

·         sugar

·         salt

·         potato starch

·         glucose

·         cane sugar

·         honey

·         labels

·         graduated cylinder

 

Procedure:

1.      Put 35 milliliters of water, 1 gram of yeast, 1 gram of sugar, and 0.2 grams of salt in each 5 test tubes

2.      Add 0.2 grams of glucose, potato starch, honey, and cane sugar in different test tubes

3.      Label each tube according to the different starch

4.      Do not add any carbohydrate to the fifth test tube so that it can be the control

5.      Have your lab partner help you shake the tubes thoroughly so that nothing sticks to the bottom

6.      Then very quickly place the corks with the tubes and syringes(placed at 1 milliliter) on each of the test tubes

7.      Then place the tubes into the Styrofoam tube holders

8.      Then check the syringes every minute for 20 minutes and record your data, make sure that the corks are tightly placed on each of the tubes, they may loosen

  

        

 

Results:

Milliliters of Carbon Dioxide vs. Number of Minutes

 

the y-axis is in milliliters

the x-axis is in minutes

 

Add on Starches	1 minute	2 minutes	3 minutes
Potato Starch	1 ml	1ml	1ml
Glucose	1ml	1ml	1 ml
Honey	1ml	1ml	1ml
Cane Sugar	1ml	1ml	1ml
Control	1ml	1ml	1ml
	4 minutes	5 minutes	6 minutes
Potato Starch	1 ml	1ml	1ml
Glucose	1ml	1ml	1 ml
Honey	1ml	1ml	1ml
Cane Sugar	1ml	1ml	1ml
Control	1ml	1ml	1ml
	7 minutes	8 minutes	9 minutes
Potato Starch	1 ml	1ml	1ml
Glucose	1ml	1ml	1 ml
Honey	1.01ml	1.01ml	1.05ml
Cane Sugar	1ml	1ml	1ml
Control	1ml	1ml	1ml
	10 minutes	11 minutes	12 minutes
Potato Starch	1 ml	1ml	1ml
Glucose	1.02 ml	1.02 ml	1.02 ml
Honey	1ml	1ml	1ml
Cane Sugar	1.05 ml	1.05 ml	1.05 ml
Control	1ml	1ml	1ml
	13 minutes	14 minutes	15 minutes
Potato Starch	1 ml	1.20ml	1.90 ml
Glucose	1.02 ml	1.40 ml	1.80 ml
Honey	1ml	1ml	1ml
Cane Sugar	1.05 ml	1.30 ml	2 ml
Control	1ml	1ml	1ml
	16 minutes	17 minutes
Potato Starch	1.60 ml	1.60 ml
Glucose	2 ml	2 ml
Honey	1ml	1ml
Cane Sugar	2 ml	2 ml
Control	1ml	1ml

 

Conclusion:

 

In this lab, we found that glucose and cane sugar had generated the most carbon dioxide which fails to reject our hypothesis and produced 1 milliliter more carbon dioxide than the control (35 milliliters of water, 1 gram of yeast, 1 gram of sugar, and 0.2 grams of salt). Our hypothesis of the potato starch producing less than glucose and cane sugar but more than the control is also true. The potato starch produced 0.6 milliliters more carbon dioxide than the control. Our hypothesis about the honey was partially rejected, it produced less carbon dioxide than the glucose and the cane sugar as we expected, but the honey did not produce more carbon dioxide than the control. The honey and the control did not produce any carbon dioxide, and the glucose and cane sugar produced the most carbon dioxide.              Even though the control and honey also contained sugar it did not produce carbon dioxide. The two constants in this lab are temperature (from placing the tubes in the Styrofoam tube holders) , and the 35 milliliters of water, 1 gram of yeast, 1 gram of sugar, and 0.2 grams of salt in each test tube. Another constant is also the duration of time for cellular respiration to occur and be measured. Two potential sources of error are not adding equal amounts of the different carbohydrates to each of the different test tubes, and not placing the corks properly on each of the test tubes. If the tubes are not placed properly then carbon dioxide can escape and not be measured in the syringe.  Our data is not completely accurate, we did not properly read the syringes throughout the lab so that may have been the cause , also there could have been a leak in a couple of the tubes which might explain why the potato starch 's level of carbon dioxide decreased near the end of the lab and why the honey and control did not produce carbon dioxide.This lab proves that glucose is a major source of energy and produces more energy faster than other carbohydrates.

 

Citations:

Pearson. "Cell Respiration: Overview of Respiration." Cell Respiration: Overview of Respiration. N.p., n.d. Web. 15 Feb. 2014.