Question 1

Plants convert nitrogen into ammonia. This biological nitrogen fixation is affected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for H⁺ in the balanced reaction equation?

Accepted Answer

The answer of Plants convert nitrogen into ammonia. This biological...

Question 2

Selenium can substitute for sulfur in the amino acid cysteine to make the amino acid selenocysteine because ________

Accepted Answer

Cysteine and selenocysteine have the same chemical structure except that selenium replaces sulfur, which means they have the same valence electron configuration. This similarity allows selenium to substitute for sulfur in cysteine to form selenocysteine.

Question 3

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is  What is the stoichiometric coefficient for the electrons in the balanced reaction equation?

Accepted Answer

The answer of Plants convert nitrogen into ammonia. This biological...

Question 4

The active site of an enzyme typically contains ________

Accepted Answer

The active site of an enzyme typically contains a transition metal. Transition metals are often involved in the catalytic activity of enzymes, as they can readily accept and donate electrons to facilitate chemical reactions. Examples of transition metals commonly found in enzyme active sites include iron, zinc, and copper.

Question 5

Copper is a trace metal in the human body with a typical concentration of 110 mg in 75 kg of body mass. What is this concentration in units of parts per million (ppm)?

Accepted Answer

To convert the concentration of copper in the body to parts per million (ppm), we use the formula: ppm = (mass of solute / mass of solution) x 10^6. Here, the mass of copper is 110 mg and the mass of the body is 75 kg (which is 75,000,000 mg). So, (110 mg / 75,000,000 mg) x 10^6 = 1.47 ppm, which rounds to 1.5 ppm.

Question 6

Vanadium is an ultratrace metal in the human body with a typical concentration of approximately 17 ng/g body mass. How many milligrams of V are there in a person weighing 185 lb? 1 lb = 454 g

Accepted Answer

To find the amount of vanadium in milligrams, first convert the body weight from pounds to grams: 185 lb × 454 g/lb = 83,990 g. Then, multiply by the concentration of vanadium: 83,990 g × 17 ng/g = 1,427,830 ng. Convert nanograms to milligrams: 1,427,830 ng × (1 mg / 1,000,000 ng) = 1.43 mg.

Question 7

Hydroxyapatite, which is a component of tooth enamel, is very insoluble in water. For the following reaction, K_sp = 2.3 $\times$ 10^-59. What is the molar concentration of Ca₅(PO₄)₃⁺ when the pH of the mouth is 4.0?

Accepted Answer

The answer of Hydroxyapatite, which is a component of tooth...

Question 8

Selenium is an ultratrace element that is essential for life. It is used in the synthesis of ________, which is ________.

Accepted Answer

Selenium is used in the synthesis of selenocysteine, which is an amino acid.

Question 9

Chromium is an ultratrace metal in the human body. The typical concentration is 5.0 mg in 70.0 kg of body mass. This concentration can be expressed as ________

Accepted Answer

The correct answer is A because 5.0 mg in 70.0 kg of body mass can be expressed as 0.071 ppm or 71 pp.

Question 10

Adding fluoride ions to toothpaste and drinking water to prevent tooth decay is effective because fluoride ________

Accepted Answer

Fluoride ions react with tooth enamel to form a stronger compound that is more resistant to decay. Additionally, fluoride reduces the solubility of tooth enamel at low pH, meaning it is less likely to dissolve in the presence of acid produced by bacteria in the mouth. However, fluoride does not kill bacteria directly or affect the solubility of enamel at high pH levels. Preventing halitosis is not a primary function of fluoride.

Question 11

What is the dominant role played by iodine in the body?

Accepted Answer

Iodine is a crucial component of thyroid hormones (T3 and T4) that are synthesized by the thyroid gland. The thyroid gland needs iodine to maintain its normal function, which includes regulating metabolism, growth, and development of the body.

Question 12

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the nitrite ion in the balanced reaction equation?

Accepted Answer

The answer of Enzymes in plants convert nitrate into ammonia....

Question 13

Plants react urea with water to produce ammonia and carbon dioxide. This reaction is an example of a ________ reaction.

Accepted Answer

Hydrolysis is a chemical reaction in which water is used to break down a compound. In the given reaction, plants react urea with water to produce ammonia and carbon dioxide, which is an example of hydrolysis.

Question 14

Chromium is an ultratrace metal in the human body with a typical concentration of 5.0 mg in 75 kg of body mass. What is this concentration in units of parts per billion (ppb)?

Accepted Answer

To find the concentration in ppb, use the formula: (mass of substance/mass of solution) x 10^9. Here, (5 mg / 75,000,000 mg) x 10^9 = 67 ppb.

Question 15

Adding fluoride ions to toothpaste and drinking water converts the mineral in tooth enamel, hydroxyapatite, to fluoroapatite. This conversion is beneficial in preventing tooth decay because fluoroapatite ________

Accepted Answer

Fluoroapatite is less susceptible to acid attack due to its lower solubility in acids compared to hydroxyapatite. This helps prevent tooth decay by making enamel less vulnerable to acid from bacteria in the mouth.

Question 16

Iodine's role is very specific. It is incorporated into a hormone, ________, that regulates energy production and use.

Accepted Answer

Iodine is incorporated into thyroxine, also known as T4, which is a thyroid hormone that regulates metabolism and energy production in the body.

Question 17

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the electrons, e^-, in the balanced reaction equation?

Accepted Answer

The answer of Enzymes in plants convert nitrate into ammonia....

Question 18

Fluoridation to prevent tooth decay replaces ________ with fluoride in hydroxyapatite.

Accepted Answer

Fluoridation to prevent tooth decay involves replacing the hydroxide ions in hydroxyapatite (the mineral form of calcium phosphate that makes up tooth enamel) with fluoride ions. This process creates a more decay-resistant material called fluorapatite.

Question 19

Selenocysteine is an amino acid that gets incorporated into proteins that serve as antioxidants. Evidence points to a need for a minimum daily dose of selenium of 55 $\mu$g. How many moles of selenocysteine (C₃H₇NO₂Se, 168 g /mol) can be synthesized using this amount of selenium?

Accepted Answer

The answer of Selenocysteine is an amino acid that gets...

Question 20

Radioactive ⁹⁰Sr can substitute for ________ in the human body.

Accepted Answer

Radioactive strontium can substitute for calcium in the human body due to their similar properties and ionic sizes.

Quiz 21: The Main Group Elements: Life and the Periodic Table

Plants convert nitrogen into ammonia. This biological nitrogen fixation is affected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for H⁺ in the balanced reaction equation?

Selenium can substitute for sulfur in the amino acid cysteine to make the amino acid selenocysteine because ________

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for the electrons in the balanced reaction equation?

The active site of an enzyme typically contains ________

Copper is a trace metal in the human body with a typical concentration of 110 mg in 75 kg of body mass. What is this concentration in units of parts per million (ppm) ?

Vanadium is an ultratrace metal in the human body with a typical concentration of approximately 17 ng/g body mass. How many milligrams of V are there in a person weighing 185 lb? 1 lb = 454 g

Selenium is an ultratrace element that is essential for life. It is used in the synthesis of , which is .

Chromium is an ultratrace metal in the human body. The typical concentration is 5.0 mg in 70.0 kg of body mass. This concentration can be expressed as ________

Adding fluoride ions to toothpaste and drinking water to prevent tooth decay is effective because fluoride ________

What is the dominant role played by iodine in the body?

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the nitrite ion in the balanced reaction equation?

Plants react urea with water to produce ammonia and carbon dioxide. This reaction is an example of a ________ reaction.

Chromium is an ultratrace metal in the human body with a typical concentration of 5.0 mg in 75 kg of body mass. What is this concentration in units of parts per billion (ppb) ?

Adding fluoride ions to toothpaste and drinking water converts the mineral in tooth enamel, hydroxyapatite, to fluoroapatite. This conversion is beneficial in preventing tooth decay because fluoroapatite ________

Iodine's role is very specific. It is incorporated into a hormone, ________, that regulates energy production and use.

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the electrons, e^-, in the balanced reaction equation?

Fluoridation to prevent tooth decay replaces ________ with fluoride in hydroxyapatite.

Selenocysteine is an amino acid that gets incorporated into proteins that serve as antioxidants. Evidence points to a need for a minimum daily dose of selenium of 55 $\mu$ g. How many moles of selenocysteine (C₃H₇NO₂Se, 168 g /mol) can be synthesized using this amount of selenium?

Radioactive ⁹⁰Sr can substitute for ________ in the human body.

Quiz 21: The Main Group Elements: Life and the Periodic Table

Plants convert nitrogen into ammonia. This biological nitrogen fixation is affected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for H+ in the balanced reaction equation?

Selenium can substitute for sulfur in the amino acid cysteine to make the amino acid selenocysteine because ________

Plants convert nitrogen into ammonia. This biological nitrogen fixation is effected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for the electrons in the balanced reaction equation?

The active site of an enzyme typically contains ________

Copper is a trace metal in the human body with a typical concentration of 110 mg in 75 kg of body mass. What is this concentration in units of parts per million (ppm) ?

Vanadium is an ultratrace metal in the human body with a typical concentration of approximately 17 ng/g body mass. How many milligrams of V are there in a person weighing 185 lb? 1 lb = 454 g

Hydroxyapatite, which is a component of tooth enamel, is very insoluble in water. For the following reaction, Ksp = 2.3 ×\times× 10-59. What is the molar concentration of Ca5(PO4) 3+ when the pH of the mouth is 4.0?

Selenium is an ultratrace element that is essential for life. It is used in the synthesis of ________, which is ________.

Chromium is an ultratrace metal in the human body. The typical concentration is 5.0 mg in 70.0 kg of body mass. This concentration can be expressed as ________

Adding fluoride ions to toothpaste and drinking water to prevent tooth decay is effective because fluoride ________

What is the dominant role played by iodine in the body?

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the nitrite ion in the balanced reaction equation?

Plants react urea with water to produce ammonia and carbon dioxide. This reaction is an example of a ________ reaction.

Chromium is an ultratrace metal in the human body with a typical concentration of 5.0 mg in 75 kg of body mass. What is this concentration in units of parts per billion (ppb) ?

Adding fluoride ions to toothpaste and drinking water converts the mineral in tooth enamel, hydroxyapatite, to fluoroapatite. This conversion is beneficial in preventing tooth decay because fluoroapatite ________

Iodine's role is very specific. It is incorporated into a hormone, ________, that regulates energy production and use.

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the electrons, e-, in the balanced reaction equation?

Fluoridation to prevent tooth decay replaces ________ with fluoride in hydroxyapatite.

Selenocysteine is an amino acid that gets incorporated into proteins that serve as antioxidants. Evidence points to a need for a minimum daily dose of selenium of 55 μ\muμ g. How many moles of selenocysteine (C3H7NO2Se, 168 g /mol) can be synthesized using this amount of selenium?

Radioactive 90Sr can substitute for ________ in the human body.

Plants convert nitrogen into ammonia. This biological nitrogen fixation is affected by enzymes called nitrogenases. The enzymes assist in the transfer of electrons. The unbalanced reaction equation is What is the stoichiometric coefficient for H⁺ in the balanced reaction equation?

Selenium is an ultratrace element that is essential for life. It is used in the synthesis of , which is .

Enzymes in plants convert nitrate into ammonia. The unbalanced half-reaction equation is given below. What is the stoichiometric coefficient of the electrons, e^-, in the balanced reaction equation?

Selenocysteine is an amino acid that gets incorporated into proteins that serve as antioxidants. Evidence points to a need for a minimum daily dose of selenium of 55 $\mu$ g. How many moles of selenocysteine (C₃H₇NO₂Se, 168 g /mol) can be synthesized using this amount of selenium?

Radioactive ⁹⁰Sr can substitute for ________ in the human body.