New York State Chemistry RegentsNew York State Earth Science Regents

 
Homeostasis
Living Environment Regents August 2010 Question 21 PDF Print E-mail
Friday, 27 May 2011 13:00
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Correct answer: (2) maintain homeostasis

Homeostasis is the steady-state physiological condition of the body. Plants maintain homeostasis through the use of different mechanisms and structures such as the stoma (stomates, plural). The guard cells of the stomates mediate the balance between transpiration and photosynthesis. Through photosynthesis, carbon dioxide and water are converted into glucose and oxygen. Transpiration, on the other hand, is the evaporative loss of water from the plant. The stomates are in charge of getting rid of excess water in the plant. When there is too much water, the guard cells open to evaporate water. When there is water deficiency, abscisic acid signals the guard cells to close the stomates.

Incorrect answers:

(1) produce light energy

Chloroplasts are the organelles that absorb light energy produced by the sun and use that energy to drive the synthesis of organic compounds from carbon dioxide and water.

(3) decompose organic matter

The stomates are not involved in decomposition. Decomposers, such as fungi and bacteria, are the organisms that break down dead organic materials from plants and animals, and convert them into inorganic forms.

(4) synthesize minerals

Stomates do not synthesize minerals. Minerals found in plants usually come from the soil, absorbed through the roots.
Last Updated on Friday, 27 May 2011 13:11
 
Living Environment Regents August 2010 Question 58 PDF Print E-mail
Friday, 27 May 2011 17:43
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When blood glucose increases, the hormone insulin is released in the pancreas. Insulin lowers the blood glucose levels by stimulating virtually all body cells (except brain cells) to take up glucose from the blood. Insulin can also decrease blood glucose levels by retarding the breakdown of glycogen in the liver and blocking the conversion of amino acids and fatty acids to sugar.

Patients with diabetes suffer from high glucose levels in the blood due to deficiency of insulin or reduced responsiveness in target cells due to some alteration in insulin receptors.
 


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