Talk About Breasts! Milk!

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Transcript

Oxytocin and Prolactin are two hormones that have very identical functions, while both hormones do have some exclusive functions, such as oxytocin stimulating the uterus contraction during labor childbirth, Oxytocin and Prolactin are both concerned with breast milk. Prolactin is responsible for the triggering the production of milk proteins, or breast milk, while oxytocin is responsible for activating “milk let down” when suckling. For the purpose of this recording, I will only be focusing on oxytocin and prolactin’s roles in breast-feeding. I’ll begin first by explaining prolactin’s qualities.

The most predominant structure of prolactin that is present in the human body is a single-chain polypeptide with 198 amino acids. Prolactin is mostly produced in the anterior pituitary gland, but also produced in breasts. The function of prolactin that I will be focusing on will be stimulating the mammary glands to produce milk; the other function of prolactin is sexual gratification after sexual acts, but I won’t be focusing on that. Prolactin is regulated by the dopaminergic system and levels of prolactin are proportional to the level of estrogen in females, and testosterones in males. In females, estrogen inhibits prolactins on its milk production; it is only the sudden drop of estrogen after child-birth that allows mothers to produce breast milk for their babies. When a baby starts suckling on his mother’s breasts, prolactin is secreted and released into circulation to bind to the mammary epithelial cell receptors in the mammary glands of the mother, which stimulates milk to be produced in a matter of few minutes. When a mother does not breast feed, prolactin levels will return to normal after 7 days, and cause her to stop producing milk, therefore, mothers will usually breast feed multiple times a day to stimulate prolactin production and produce a lot of milk.

Onto oxytocin…Oxytocin is a peptide of 9 amino acids produced in the posterior pituitary glands. Unlike prolactin, which produces milk when stimulated by a baby suckling, oxytocin is responsible for releasing milk from the breasts. When undergoing childbirth or breast feeding, oxytocin is produced and released to the receptors located in the myoepithelial cell of the mammary gland; this stimulates multiple actions. In labor, uterus contractions occur which allows a smoother childbirth, while in breastfeeding, oxytocin acts at the mammary glands allowing milk to be secreted from the nipples. Oxytocin levels also affect social behavior and some degree of sexual response.

Both oxytocin and prolactin are regulated in positive feedback, which is not too common in hormones. For example, during childbirth, when the baby is moving towards the vagina, pressure receptors within the cervix triggers the pituitary gland to produce oxytocin, which then binds to its receptors and cause uterus contraction. The same goes for the stimulation of prolactin and oxytocin production when a baby suckles during breastfeeding. The chemical pathways of both prolactin and oxytocin are neuroendocrines, since they undergo endocrine secretion and are triggered by nervous stimulation such as breastfeeding. Both hormones are lipid soluble hormones, since they belong to the endocrine system and diffuse into a cell to bind with receptors.

And that about concludes my talk about where breast milk comes from!

Cell Respiration Lab

Yeast Cell Respiration Lab

Group members: Sean Yang, Andrew Mao

Abstract
In order to understand the process of cell respiration and how temperatures could affect it, we have created a lab using the fungi yeast to observe the process of cell respiration under different temperatures.

Introduction
Cell respiration occurs in all living cells, and is the process in which organisms produce ATP energy from glucose, with byproducts of carbon dioxide and water. ATP is the energy which cells function upon. Yeast is a type of fungi which can respire only with the presence of oxygen and glucose. Under different environments, yeast will respire differently.

Glucose + Oxygen → Carbon Dioxide + Water

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Hypothesis:
Due to increased molecular movement when under heat, it is likely that cell respiration of yeast will occur at a faster rate due to the fast movement of particles at high temperature.

Materials: Sugar, water, yeast, salt, scale + weighing paper, graduated cylinders, 3 thermometers, 3 airtight syringes, 3 test tubes, an ice box and a warm dry heating bath.

Procedure:

1. Obtain 3 separate set of measurements of 35ml water, 1g of sugar, 1g of yeast and 0.2g of salt.

2. Obtain 3 separate test tubes and mix all contents evenly into the 3 test tubes.

3. Stir up the contents in each test tube and let them all sit for 5 minutes.

4. This step must be done quickly and simultaneously: after 5 minutes, immediately put the airtight syringe over each test tube, make sure there are 2ml of air where the syringe is not losing any gas (airtight).

5. Quickly put each test tube at their locations: one out in the open, one in the ice box, and one in the heat bath.

6. Collect the change (reading minus 2ml) in ml of gas every 1 minute for a total of 5 minutes.

7. Stick thermometers into the ice box and the warm bath to note their temperature.

Safety

-The warm dry heating bath shouldn't be too hot (50 degrees), but don't stick any body parts in just in case.

-Yeast makes a disgusting smell after fermentation, keep away from nose, mouth, eyes and hopefully clothes.

-Test tubes are made of glass, be careful when shoving the syringe into the test tube, don't use too much force, you might shatter it in your hand.

Results

Conclusion
As the graph shows, CO2 produced by yeast cell respiration increases in a much faster rate when at warm temperature. At cold temperature, there is almost no CO2 formed as we believe the enzyme have denatured due to the cold. This is evidence to confirm our hypothesis that cell respiration occurs at a more rapid rate at higher temperatures, we believe that this is due to faster particle movement at higher temperatures.


Revision (2014/3/09):
After having my lab report checked up by my teacher, I realized I was lacking in many parts...so below I will provide additional information to explain the phenomenon that has occured in this lab.

Background Information:
Cell respiration is a complicated process occurring in a cells cytoplasm and mitochondria where cells utilize glucose to produce ATP energy in order to function. Cell respiration has numerous steps and each small process is powered by a different type of enzyme. We have learned in class that enzymes are "catalysts" for the cell and lower activation energy/speed up each small step in cell respiration. We have also learned that when under abnormal temperatures (every enzyme has an ideal temperature) enzymes will denaturalize and fail to achieve their catalyst effects. Our yeast cell respiration lab will test the effectiveness of enzymes under different temperatures by monitoring the amount of CO2 produced when yeast cells go through cell respiration.

Hypothesis rewrite:
If the temperature of the environment in which the yeast is in increases, then we can expect a faster rate of cell respiration and faster rate of CO2 emission; this is because yeast molecules under heat will increase their molecular movement and enzymes will catalyze a chemical reaction at a faster rate.

Conclusion Rewrite:
Although we have not tested a large enough range of temperatures to find the ideal temperature for yeast cell enzymes to undergo cell respiration, we have discovered through our data and graph that the warmer the temperature, the more effective the enzyme and thus the more CO2 produced from respiration. We have proven our hypothesis to be correct as the higher the temperature, the more CO2 we have gotten and the faster rate at which enzymes operate due to increased molecular movement speed.