Wednesday, January 9, 2008
Wednes-Day 2
Bio- Section 35.3 is due tomorrow; a two-page summary is acceptable.
we looked at the purpose and actions of the endocrine system, a system of glands that REGULATE/maintain homeostasis by causing relatively long-term or longer lasting changes (usually) in an organism as a result of signals/changes/cues from the environment (internal or external).
We saw that each gland secretes specific hormones directly into the bloodstream; each hormone can only bind to specific "target cells" that the hormone is made for. For example, insulin, secreted by the pancreas, can bind to specific cells in the liver because the protein receptors on those liver cells match the particular shape (lock and key) of the insulin hormone.
Once the hormone binds to the target cells, the target cells will produce particular chemicals or enzymes that helps the body to maintain homeostasis.
We saw that the pituitary gland, which is the master gland because it targets/controls all but one of the other endocrine glands, is directed/controlled by the hypothalamus. The hypothalamus is the nexus or connection between the nervous system, which is always sensing/monitoring the environmental changes of an organism, and the endocrine system.
The hypothalamus has many different cell receptors so it is able to monitor the levels of many of the body's key biochemicals and the hypothalamus will send a hormone/chemical signal to the pituitary if/when any of those biochemicals are in too high or too low a concentration.
The pituitary will then secrete the appropriate hormone so that the appropriate target cells/gland will secrete a substance to maintain homeostasis i.e. raise or lower the level of the deficient or excess chemical.
We then looked at the thyroid gland, which regulates the body's respiratory rate/metabolic rate.
The parathyroid glands, embedded in the four corners of the thyroid gland, regulate the level of calcium ions in the blood and bones.
We also began to discuss the all IMPORTANT concept of negative FEEDBACK, which is THE key feature of maintaining homeostasis.
For example, if the level of calcium ions in the blood is too low, the parathyroid glands will secrete a hormone (parathormone) that targets the BONE CELLS to release some of their stored calcium ions into the blood, thus RAISING the level of calcium ions back to a normal level. Once the normal level of calcium ions is back to normal (this is the "feedback" part!), that normal level of calcium ions in the blood CAUSES the parathyroid glands to STOP secreting its hormone (parathormone). That completes the feedback cycle and calcium homeostasis is maintained.
Chem 7- we learned how to determine whether a molecule that contains POLAR covalent BONDS is overall a POLAR MOLECULE (asymmetric/uneven distribution of charge) or a NONPOLAR molecule (symmetric/even distribution of charge). So, a molecule with polar bonds may be polar or nonpolar DEPENDING on what the particular electron and/or molecular geometry of the molecule is. This geometry can be determined by drawing the correct Lewis structure and seeing how many regions of electrons are around the central atom.
We then looked at one of the covalent bonds that is formed when a polyatomic ion forms: the COORDINATE COVALENT bond. This bond is the same as any covalent bond EXCEPT that BOTH of the electrons that are shared in the bond originally come from ONLY ONE of the two atoms that are bonded. We saw that NH4 + and H3O + contain one coordinate covalent bond each. In order for a molecule to be ABLE to FORM a coordinate covalent bond, it has to already have a NONBONDED, LONE pair of electrons that it can share with an H+ ion or some other particle that has an empty valence orbital.
We then finished up our molecular models lab; you can hand that in on Friday.
Chem 9- we learned how to determine whether a molecule that contains POLAR covalent BONDS is overall a POLAR MOLECULE (asymmetric/uneven distribution of charge) or a NONPOLAR molecule (symmetric/even distribution of charge). So, a molecule with polar bonds may be polar or nonpolar DEPENDING on what the particular electron and/or molecular geometry of the molecule is. This geometry can be determined by drawing the correct Lewis structure and seeing how many regions of electrons are around the central atom.
We then looked at one of the covalent bonds that is formed when a polyatomic ion forms: the COORDINATE COVALENT bond. This bond is the same as any covalent bond EXCEPT that BOTH of the electrons that are shared in the bond originally come from ONLY ONE of the two atoms that are bonded. We saw that NH4 + and H3O + contain one coordinate covalent bond each. In order for a molecule to be ABLE to FORM a coordinate covalent bond, it has to already have a NONBONDED, LONE pair of electrons that it can share with an H+ ion or some other particle that has an empty valence orbital.
we looked at the purpose and actions of the endocrine system, a system of glands that REGULATE/maintain homeostasis by causing relatively long-term or longer lasting changes (usually) in an organism as a result of signals/changes/cues from the environment (internal or external).
We saw that each gland secretes specific hormones directly into the bloodstream; each hormone can only bind to specific "target cells" that the hormone is made for. For example, insulin, secreted by the pancreas, can bind to specific cells in the liver because the protein receptors on those liver cells match the particular shape (lock and key) of the insulin hormone.
Once the hormone binds to the target cells, the target cells will produce particular chemicals or enzymes that helps the body to maintain homeostasis.
We saw that the pituitary gland, which is the master gland because it targets/controls all but one of the other endocrine glands, is directed/controlled by the hypothalamus. The hypothalamus is the nexus or connection between the nervous system, which is always sensing/monitoring the environmental changes of an organism, and the endocrine system.
The hypothalamus has many different cell receptors so it is able to monitor the levels of many of the body's key biochemicals and the hypothalamus will send a hormone/chemical signal to the pituitary if/when any of those biochemicals are in too high or too low a concentration.
The pituitary will then secrete the appropriate hormone so that the appropriate target cells/gland will secrete a substance to maintain homeostasis i.e. raise or lower the level of the deficient or excess chemical.
We then looked at the thyroid gland, which regulates the body's respiratory rate/metabolic rate.
The parathyroid glands, embedded in the four corners of the thyroid gland, regulate the level of calcium ions in the blood and bones.
We also began to discuss the all IMPORTANT concept of negative FEEDBACK, which is THE key feature of maintaining homeostasis.
For example, if the level of calcium ions in the blood is too low, the parathyroid glands will secrete a hormone (parathormone) that targets the BONE CELLS to release some of their stored calcium ions into the blood, thus RAISING the level of calcium ions back to a normal level. Once the normal level of calcium ions is back to normal (this is the "feedback" part!), that normal level of calcium ions in the blood CAUSES the parathyroid glands to STOP secreting its hormone (parathormone). That completes the feedback cycle and calcium homeostasis is maintained.
Chem 7- we learned how to determine whether a molecule that contains POLAR covalent BONDS is overall a POLAR MOLECULE (asymmetric/uneven distribution of charge) or a NONPOLAR molecule (symmetric/even distribution of charge). So, a molecule with polar bonds may be polar or nonpolar DEPENDING on what the particular electron and/or molecular geometry of the molecule is. This geometry can be determined by drawing the correct Lewis structure and seeing how many regions of electrons are around the central atom.
We then looked at one of the covalent bonds that is formed when a polyatomic ion forms: the COORDINATE COVALENT bond. This bond is the same as any covalent bond EXCEPT that BOTH of the electrons that are shared in the bond originally come from ONLY ONE of the two atoms that are bonded. We saw that NH4 + and H3O + contain one coordinate covalent bond each. In order for a molecule to be ABLE to FORM a coordinate covalent bond, it has to already have a NONBONDED, LONE pair of electrons that it can share with an H+ ion or some other particle that has an empty valence orbital.
We then finished up our molecular models lab; you can hand that in on Friday.
Chem 9- we learned how to determine whether a molecule that contains POLAR covalent BONDS is overall a POLAR MOLECULE (asymmetric/uneven distribution of charge) or a NONPOLAR molecule (symmetric/even distribution of charge). So, a molecule with polar bonds may be polar or nonpolar DEPENDING on what the particular electron and/or molecular geometry of the molecule is. This geometry can be determined by drawing the correct Lewis structure and seeing how many regions of electrons are around the central atom.
We then looked at one of the covalent bonds that is formed when a polyatomic ion forms: the COORDINATE COVALENT bond. This bond is the same as any covalent bond EXCEPT that BOTH of the electrons that are shared in the bond originally come from ONLY ONE of the two atoms that are bonded. We saw that NH4 + and H3O + contain one coordinate covalent bond each. In order for a molecule to be ABLE to FORM a coordinate covalent bond, it has to already have a NONBONDED, LONE pair of electrons that it can share with an H+ ion or some other particle that has an empty valence orbital.
# posted by C @ 11:28 AM 
