BIOL 235: Assignment 1 (2018): Athabasca University |( 100% VERIFIED ANSWERS, ALREADY GRADED A)
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Athabasca University (AU
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BIOL 235: Assignment 1 (2018): Athabasca University
Assignment 1: Biology 235: Human Anatomy and Physiology (2018)
Weight: 5%
Minimum Pass Grade: 50%
Each question is worth 10 marks.
1. Maintenance of calcium ion homeostasis is critical to neurological, cardiac and skeletal muscle function. Consid...
biol 235 assignment 1 2018 athabasca university assignment 1 biology 235 human anatomy and physiology 2018 weight 5 minimum pass grade 50 each question is worth 10 marks 1 maintenance o
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Assignment 1 :: Biology 235: Human Anatomy and Physiology
Each question is worth 10 marks.
1. Maintenance of calcium ion homeostasis is critical to neurological, cardiac and skeletal muscle
function. Consider the roles of two hormones involved in the regulation of the concentration of
calcium ions in the blood. Parathyroid hormone increases the concentration of calcium ions in the
blood, while calcitonin decreases the concentration. Based on this information predict the body’s
response to restore calcium balance if a person swallowed 100 antacid tablets made of a calcium
compound in 10 minutes. Include in your answer the definition of homeostasis, the type of feedback
loop involved and all of the components of a feedback loop.
Answer:
Homeostasis is the condition of equilibrium in the body’s internal environment due to the constant
interaction of the body’s regulatory processes. In this case, the level of calcium ion in blood normally stays
between a narrow range to maintain homeostasis. Multiple negative feedback systems will be involved in
the situation described above, including hormones such as calcitonin, parathyroid hormone, and caltitriol
etc.in order to maintain the balance of calcium ion level in blood. In summary, their functions are:
Calcitonin – to decrease blood calcium ion level
Parathyroid hormone- to increase blood calcium ion level
Calcitriol- to decrease calcium absorption from dietary sources
After swallowing 100 anatacid tablets the person’s blood calcium level would rise considerably in 10
minutes. One negative feedback loop is: high level of calcium ion in blood will
stimulateparafollicular cells (receptors) in the thyroid gland (control centre) to secret calcitonin (the
output). Calcitonin inhibits activity of osteoclasts (effector), speeds blood calcium ion uptake by
bone (effector), and accelerates calcium ion deposition into bones. The result is that calcitonin
promotes bone formation and decrease blood calcium ion level.
At the same time, another negative feedback loop is involved: high level of calcium ion in blood will
be detected by parathyroid gland cells (receptor), and consequently lower parathyroid hormone (the
output) produced by parathyroid gland. Osteoclasts (effector) activities decrease, and kidney
(effector) to release less calcitriol, which decreases the absorption of calcium ion from dietary
sources-in this case, anatacid tablets.
, 2. Provide one important example (in the human body) of each of the following:
a. a molecule containing ionic bonds
NaCl
b. a molecule containing covalent bonds
H2O
c. a molecule containing hydrogen bonds
deoxyribonucleic acid (DNA)
What is the function of each of these three molecules you have identified in the human body? Explain
why each of these three molecules must have its specific types of bonds in order to perform that
molecule’s function.
Answer:
NaCl: it’s important for conducting electrical currents, especially in nerve and muscular tissues. In the ionic
compound, Na lost one valence electron and became a positively charged cation; while Cl gained one
valence electron and became a negatively charged anion. In the body, NaCl breaks down into positive Na
and negative Cl ions and are dissolved in the body fluids as electrolytes, which are able to carry the electric
currents.
H2O: H2O is the medium for most reactions in the body, participates as reactant or product in certain
reactions, helps to maintain body temperatures, and is a major component of lubricating fluids throughout
the body. In the molecule, oxygen atom shares a pair of electrons between each of the two hydrogen atoms,
forming two single covalent bonds. And because the oxygen atom attracts the electrons more strongly then
do the hydrogen atoms, the oxygen atom has greater electronegativity, and the covalent bonds between O
and H are polar covalent bonds. The electronegative oxygen atom attracts the cations, and electropositive
hydrogen atoms attract anions. This property makes water and excellent solvent for other ionic or polar
substances, and an ideal medium for metabolic reactions.
DNA: DNA forms the inherited genetic material inside each human cell. It is made of two stands twisted in
a spiral staircase-like structure called a double helix. The nitrogenous bases of the two stands pair together
through hydrogen bonding to form the steps of the double helix. Hydrogen bonds form when a hydrogen
atom with a partial positive charge attracts the partial negative charge of neighboring oxygen or nitrogen
atoms. Hydrogen bonds are weaker than ionic and covalent bonds, each time DNA is copied, the hydrogen
bonds break, the two strands unwind and each strand serves as the template or mold on which to construct a
new second stand. Even though single hydrogen bonds are weak, DNA molecules contains large amount of
these bonds and acting collectively, hydrogen bonds provide considerable strength and stability to help
determine the 3-dimensional shape of DNA.
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