New York State Chemistry RegentsNew York State Earth Science Regents

 
Homeostasis
Living Environment Regents June 2010 Question 20 PDF Print E-mail
Monday, 30 May 2011 10:45
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Correct Answer: (1) enzymes that clot blood

Enzymes refer to a class of proteins that serve as catalysts, chemical agents that change the rate of reaction without being consumed during the reaction. In the body processes, there are various enzymes used however, when the pH of the blood is not normal (must be near 7.4) then the reaction would not take place as expected. The Le Chatellier's Principle best explains this condition, which states that "if a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure, then the equilibrium shifts to counteract the imposed change and a new equilibrium is established.

The clotting mechanism usually starts with the release of clotting factors from platelets and involves a complex chain of reactions that ultimately transforms fibrinogen to fibrin. So if the pH is not in equilibrium, the reactions in blood clotting mechanism would be disrupted.

Incorrect Answers:

(2) red blood cells that make antibodies

pH can affect the formation of antibodies, however it is not the red blood cells that form antibodies. Antibodies are antigen-binding immunoglobulin, produced by B cells, which is a type of white blood cell that functions as the effector of immune response. On the other hand, red blood cells function for the delivery of oxygen to various parts of the body.

(3) chlorophyll that carries oxygen in the blood

Chlorophyll is a green pigment located within the chloroplasts of plants, while blood is a specialized fluid that transports nutrients, oxygen, and other substances within the body of animals. Blood is absent in plants. Red blood cells, a portion of the blood, serve as a buffer for blood pH.

(4) DNA that controls starch digestion in the blood

DNA or deoxyribonucleic acid is a double-stranded nucleic acid molecule that has the ability to replicate and determine the inherited structure of a cell's proteins. Its activity may be affected by the pH in the blood, however, it does not directly control the digestion of starch. Starch, a complex carbohydrate, is digested in the digestive system and then converted into glucose molecules which are absorbed into the blood. Some of it goes to the liver for storage or converted into energy for the activities of the body.

 
Living Environment Regents June 2010 Question 22 PDF Print E-mail
Thursday, 26 May 2011 15:40
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Correct answer: (4) Dynamic equilibrium is disrupted.

Homeostasis is the maintenance of the dynamic equilibrium of an organism. Sweating is one of mechanisms exhibited by animals to maintain the steady state of the body. Sweating or perspiration is the release of salty liquid from the sweat glands in the skin. This is a body mechanism that manifests when the temperature of the surrounding increases. To maintain the body temperature and prevent temperature increase, the body perspires. The evaporation of the sweat cools down the body temperature. If the body wouldn't perspire, the temperature will increase and this will affect other body processes.

Incorrect answers:

(1) Feedback mechanisms regulate blood sugar levels.

Blood sugar regulation is another mechanism of the body to maintain dynamic equilibrium via feedback mechanism. However, this mechanism takes an entirely different process with perspiration. The pancreas controls the level of glucose in the blood. When the blood sugar level increases, insulin is released to lower the blood sugar level by increasing the ability of the cells to take in glucose from the blood or insulin transforms glucose into its storage form-glycogen.

(2) Gene mutations are increased.

Gene mutation refers to the rare changes in the genes that ultimately create genetic diversity. It is usually caused by chemicals or radiation. Increase in body temperature will not cause gene mutation.

(3) Energy from ATP is not available.

ATP or adenosine triphosphate releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells. The energy of the body comes from the metabolism of biomolecules. When energy becomes unavailable, then all of the body processes would shut down leading to the death of the organism.

 
Living Environment Regents June 2010 Question 38 PDF Print E-mail
Thursday, 26 May 2011 16:19
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Correct answer: (2) ATP

Normally, molecules move from a region with high concentration to a region with low concentration through diffusion to achieve equilibrium. However, movement of molecules from a region of low concentration to a region of high concentration can only occur if the cell expends energy to counteract the force of diffusion. This type of movement of molecules is called active transport. Chemical energy in the form of adenosine triphosphate (ATP) aids this process by changing the shape of the carrier protein that leads the transport of molecule, thus allowing the exit out of the membrane.

Incorrect answers:

(1) DNA

Deoxyribonucleic acid (DNA) is a double stranded, helical nucleic acid molecule responsible for replicating and determining the inherited structure of a cell's proteins. It is not directly involved in the transport of molecules in the cells.

(3) antigens

Antigens are foreign macromolecules that do not belong to the host organism, thus elicit immune response from the host. It is not directly involved in the active transport of molecules.

(4) antibodies

Antibodies are antigen-binding immunoglobulins produced by B cells, and function as the effector in an immune response. It is not involved in the transport of molecules.

Last Updated on Thursday, 26 May 2011 16:20
 
Living Environment Regents June 2010 Question 67 PDF Print E-mail
Monday, 30 May 2011 11:01
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This process is called diffusion or the spontaneous tendency of a substance to move down its concentration gradient, from a more concentrated to a less concentrated area. In this illustration, glucose molecules will move from the dialysis tubing because of high concentration, to the outside which has no glucose molecules.

 


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