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Understanding Negative Feedback, Hormones, pH Levels, and Types of Chemical Bonds, Assignments of Physiology

Southwestern Illinois CollegePhysiology

The concept of negative feedback in hormone regulation, the relationship between ph levels and hydrogen ion concentration, and the differences between hydrogen bonds, ionic bonds, and polar covalent bonds. It includes mathematical calculations, real-life examples, and explanations of the functions of cells and types of chemical bonds.

Typology: Assignments

Pre 2010

Uploaded on 12/14/2009

cflanigan
cflanigan 🇺🇸

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1. Whywouldtheinabilitytomakeahormonebealossofnegativefeedback?
Ifahormonesecretionisregulatedbynegativefeedback,whenglandAreleaseshormoneA,cellsare
stimulatedtoreleasehormoneZ.WhenhormoneZisinexcess,glandAdetectsitandasaresultit
inhibitsthereleaseofhormoneA.
Ifapersonweretoeatacandybar,theglucoseisabsorbedintheintestinecausingbloodglucoselevels
torise.Theincreaseinbloodglucosestimulatesendocrinecellsinthepancreastoreleaseinsulin.Insulin
promotesthe“absorption”ofglucosebycellswhichcausesbloodglucoselevelstofall.Whenblood
glucoselevelsfallsufficientlylow,thestimulusthatresultedininsulinsecretionisgoneandinsulinisno
longerreleased.
Ifthebodywasnolongerabletoproduceinsulin,bloodglucoselevelswouldriseunchecked.The
negativefeedbackloopwouldbebroken.Theendocrinecellsthatdetectchangesinbloodglucoselevels
wouldactasareceptor–butwithouttheeffector,nothingisdone.Thisisalossofnegativefeedback.
2. WouldpHlevelsgodownorupwhentheconcentrationofH+increases?Why?
ThepHlevelswouldgodown.pHiseffectivelythemeasurementofhydrogenions(H+)presentin
solution.It’seasiertoprovethismathematically.
MethodsofCalculation
[OH‐][H+]=1x10‐14
pH=‐log[H+]
InapH‐neutralsolution,[H+]is1x10‐7.
pH=‐log(1E‐7)=7
If[H+]isincreasedto1x10‐4,thepHcanbecalculatedasfollows:
pH=‐log(1E‐4)=4
ThepHsignificantlydecreasedindicatingthatthesolutionisnowacidic.
If[H+]isdecreasedto1x10‐12,thepHcanbecalculatedasfollows:
pH=‐log(1E‐12)=12
ThepHsignificantlyincreasedwhen[H+]wasdecreasedindicatingthatthesolutionisnowbasic.
Thiscanalsobeprovenmathematicallybyconsideringtherulethattheproductoftheconcentrationsof
hydroxideanddissolvedhydrogenionswillequal1x10‐14.
3. SolutionAishyperosmotictosolutionB.IfsolutionAisseparatedfromsolutionBbya
selectivelypermeablemembrane,doeswatermovefromsolutionAintosolutionBorvice
versa?Explain.
pf2

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1. Why would the inability to make a hormone be a loss of negative feedback? If a hormone secretion is regulated by negative feedback, when gland A releases hormone A, cells are stimulated to release hormone Z. When hormone Z is in excess, gland A detects it and as a result it inhibits the release of hormone A. If a person were to eat a candy bar, the glucose is absorbed in the intestine causing blood glucose levels to rise. The increase in blood glucose stimulates endocrine cells in the pancreas to release insulin. Insulin promotes the “absorption” of glucose by cells which causes blood glucose levels to fall. When blood glucose levels fall sufficiently low, the stimulus that resulted in insulin secretion is gone and insulin is no longer released. If the body was no longer able to produce insulin, blood glucose levels would rise unchecked. The negative feedback loop would be broken. The endocrine cells that detect changes in blood glucose levels would act as a receptor – but without the effector, nothing is done. This is a loss of negative feedback. 2. Would pH levels go down or up when the concentration of H+^ increases? Why? The pH levels would go down. pH is effectively the measurement of hydrogen ions (H +^ ) present in solution. It’s easier to prove this mathematically. Methods of Calculation [OH‐][H+^ ] = 1 x 10 ‐^14 pH = ‐log [H+] In a pH‐neutral solution, [H+] is 1 x 10 ‐^7. pH = ‐log(1 E‐7) = 7 If [H+] is increased to 1 x 10 ‐^4 , the pH can be calculated as follows: pH = ‐log(1 E‐4) = 4 The pH significantly decreased indicating that the solution is now acidic. If [H +] is decreased to 1 x 10 ‐^12 , the pH can be calculated as follows: pH = ‐log(1 E‐12) = 12 The pH significantly increased when [H+^ ] was decreased indicating that the solution is now basic. This can also be proven mathematically by considering the rule that the product of the concentrations of hydroxide and dissolved hydrogen ions will equal 1 x 10 ‐^14. 3. Solution A is hyperosmotic to solution B. If solution A is separated from solution B by a selectively permeable membrane, does water move from solution A into solution B or vice versa? Explain.

Water will diffuse from a hypo‐osmotic solution to a hyper‐osmotic solution. Therefore, water will move from solution B into solution A. Water flows from solution B (low solute concentration) to solution A (high solute concentration.) This happens to create equilibrium of osmotic pressure – no net movement of water.

4. Predict the function of a cell with numerous mitochondria. I would predict that the cell function as a muscle cell, or any type of cell that requires and uses a lot of energy/ATP. Physical training can cause an increase in the number and size of mitochondria present in both slow‐twitch and fast‐twitch muscle fibers. 5. What is the similarity and difference between hydrogen bonds, ionic bonds and polar covalent bonds? Ionic bonds are intra‐molecular and occur when elements of low electro‐negativity react with elements of high electro‐negativity. This results in a complete transfer of electrons. Ionic bonds are usually between metals and non‐metals and result in a definite anion and cation. When solid solubility is high, the bond increases in strength. Hydrogen bonds are inter‐molecular and occur between partial charges of different molecules. A great example of hydrogen bonding is water. There is a net‐dipole favoring the oxygen atom which possesses a partial negative charge. The electrons on the oxygen are attracted the partial positive charge of the hydrogen ions of other molecules. Polar covalent bonds are intra‐molecular and occur when one atom is more electronegative than another; enough so that the electron cloud is denser in one particular area. This effect results in a net dipole and introduces the property of polarity. Polar covalent bonds usually occur between non‐metals. As for similarities, hydrogen and ionic bonding is the result of an attraction of two pieces of matter given opposite charges. Polar covalent bonding occurs for the same reason, but the resultant molecule is polar in nature. All three types of bonding are all electrostatic in nature. They all result from the different abilities of atoms to gain/lose/share electrons. They all also have an effect on the physical properties of the substance (for example, melting point and boiling point). In principle, all chemical bonding is about the attraction of negatively charged electrons to the positively charged protons of the nucleus. The electron bond occurs through the interaction of an unpaired electron on each atom. The electrons in each of the atoms must have opposing spins.