Chemistry Of Life Quiz 4
This quiz will help you assess your understanding of the concepts and vocabulary in the MCPS biology unit: chemistry of life.
Questions and Answers
- 1.
A drop of iodine is placed in a test tube containing a sample of an unknown solution. The solution turns blue-black. This indicates that the unknown contains _________.
- A.
Glucose
- B.
Lipid
- C.
Starch
- D.
Protein
Correct Answer
C. StarchExplanation
When a drop of iodine is placed in a test tube containing a sample of an unknown solution and the solution turns blue-black, it indicates the presence of starch. Iodine is commonly used as a reagent to test for the presence of starch because it forms a complex with starch molecules, resulting in the blue-black color. This reaction is specific to starch and is not observed with other substances such as glucose, lipid, or protein. Therefore, the blue-black color change confirms the presence of starch in the unknown solution.Rate this question:
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- 2.
Several drops of iodine is placed in a test tube containing pure water. We would expect that the color of the water would become __________.
- A.
Blue-black
- B.
Yellow-brown
- C.
Green
Correct Answer
B. Yellow-brownExplanation
When several drops of iodine are placed in pure water, we would expect the color of the water to become yellow-brown. This is because iodine is a brownish-yellow colored substance, and when it dissolves in water, it imparts its color to the water, resulting in a yellow-brown color.Rate this question:
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- 3.
Mr. Kissal has a bottle containing a clear, colorless, odorless liquid. He says he thinks it is pure water. You remove a small sample, place it into a test tube, and add several drops of iodine. The color of the liquid in the test tube becomes blue black. What will you tell Mr. Kissal?
- A.
The water is not pure. It definitely has some starch in it.
- B.
Water is a starch.
- C.
The water is pure and contains no contaminants of any kind.
Correct Answer
A. The water is not pure. It definitely has some starch in it.Explanation
The color change to blue black after adding iodine indicates the presence of starch in the water. Starch is a complex carbohydrate commonly found in plants, and it is not normally present in pure water. Therefore, the presence of starch suggests that the water is not pure and contains some contaminants.Rate this question:
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- 4.
Mr. Kissal has a bottle containing a clear, colorless, odorless liquid. He says he thinks it is pure water. You remove a small sample, place it into a test tube, and add several drops of iodine. The color of the liquid in the test tube becomes brown-yellow. What will you tell Mr. Kissal?
- A.
The water is not pure. It definitely has some starch in it.
- B.
The water is pure with no contaminants of any kind.
- C.
The water does not contain starch, but it may contain other contaminants that have not been tested for.
Correct Answer
C. The water does not contain starch, but it may contain other contaminants that have not been tested for.Explanation
The color change in the test tube indicates the presence of starch, as iodine is known to react with starch and produce a brown-yellow color. Since the test tube containing the sample turned brown-yellow, it suggests that the water indeed contains starch. Therefore, you would tell Mr. Kissal that the water is not pure and definitely has some starch in it.Rate this question:
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- 5.
Ms. Puckett placed a thin slice of potato on a microscope slide. She adds one drop of iodine. Under the microscope, Ms. P. should expect to see _______________.
- A.
Cells that are mostly white in color because potatoes are mostly white.
- B.
Cells that are very yellow in color because the iodine stained them and iodine is yellow-brown in color.
- C.
Cells that have large areas of blue-black color because a potato contains the carbohydrate polymer known as starch.
Correct Answer
C. Cells that have large areas of blue-black color because a potato contains the carbohydrate polymer known as starch.Explanation
When iodine is added to a thin slice of potato on a microscope slide, it reacts with the starch present in the cells. This reaction forms a blue-black color, indicating the presence of starch. Therefore, under the microscope, Ms. Puckett should expect to see cells that have large areas of blue-black color because a potato contains the carbohydrate polymer known as starch.Rate this question:
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- 6.
A piece of potato is rubbed on a small sheet of brown paper. What would you expect to see?
- A.
A stained area that allows light to shine through the paper.
- B.
A stained area that does NOT allow light to pass through the paper.
- C.
No change at all on the paper.
Correct Answer
B. A stained area that does NOT allow light to pass through the paper.Explanation
Rubbing a piece of potato on a small sheet of brown paper would result in a stained area that does not allow light to pass through the paper. This is because potatoes contain starch, which can leave a residue on surfaces. When the potato is rubbed on the paper, the starch from the potato transfers onto the paper, creating a stained area. Since the starch creates a barrier, it prevents light from passing through that particular area of the paper.Rate this question:
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- 7.
Which of the following is NOT considered to be a carbohydrate?
- A.
Table sugar
- B.
Cellulose
- C.
Butter
- D.
Fructose
Correct Answer
C. ButterExplanation
Butter is not considered to be a carbohydrate because it is a type of fat. Carbohydrates are organic compounds that consist of carbon, hydrogen, and oxygen atoms, and they are the body's primary source of energy. Table sugar, cellulose, and fructose are all examples of carbohydrates, as they are composed of sugar molecules. However, butter is primarily made up of saturated and unsaturated fats, which are different types of lipids.Rate this question:
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- 8.
Water is used as a control in experiments to test for the presence of various organic compounds. The reason for this is that ________________.
- A.
Water is inexpensive and therefore it is easy to use
- B.
Water is an excellent solvent and soak up all of the chemicals that are used.
- C.
Water is NOT an organic molecule and therefore it is good to use for comparison.
Correct Answer
C. Water is NOT an organic molecule and therefore it is good to use for comparison.Explanation
Water is used as a control in experiments to test for the presence of various organic compounds because it is not an organic molecule. This means that any changes or reactions observed in the water can be attributed to the presence of organic compounds being tested, rather than any inherent properties of the water itself. Using water as a control allows researchers to establish a baseline for comparison and ensure that any observed effects are due to the organic compounds being tested.Rate this question:
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- 9.
When you are performing tests for organic compounds, you should use _____________ for eye protection.
- A.
Your hands shielding your eyes
- B.
Glasses if you wear them
- C.
Goggles
- D.
No special equipment
Correct Answer
C. GogglesExplanation
When performing tests for organic compounds, it is important to use goggles for eye protection. Goggles provide a barrier between the eyes and any potential hazardous chemicals or substances that may be present during the testing process. This helps to prevent any accidental splashes or spills from reaching the eyes, which could cause serious injury or harm. Goggles are specifically designed to fit securely around the eyes, providing a tight seal and ensuring maximum protection. Using goggles is a necessary safety precaution to protect the eyes from potential harm during tests for organic compounds.Rate this question:
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- 10.
DNA and RNA are examples of __________.
- A.
Polysaccharides
- B.
Amino acids
- C.
Proteins
- D.
Nucleic acids
Correct Answer
D. Nucleic acidsExplanation
DNA and RNA are examples of nucleic acids because they are both long chains of nucleotides. Nucleic acids are biomolecules that store and transmit genetic information in living organisms. DNA carries the genetic instructions for the development, functioning, and reproduction of all known organisms, while RNA plays a crucial role in protein synthesis. Polysaccharides are complex carbohydrates, amino acids are the building blocks of proteins, and proteins are large biomolecules made up of amino acids. Therefore, nucleic acids is the correct answer.Rate this question:
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- 11.
A drop of vegetable oil is placed on a small piece of brown paper. You would expect to see which of the following?
- A.
A small drop that does not soak into the paper because oil molecules are very cohesive with high surface tension.
- B.
A wet spot that does not allow light to pass through.
- C.
A spot that is translucent, i.e. it allows light to shine through it.
Correct Answer
C. A spot that is translucent, i.e. it allows light to shine through it.Explanation
When a drop of vegetable oil is placed on a small piece of brown paper, it is expected to create a spot that is translucent. This is because oil has a lower refractive index compared to paper, allowing light to pass through it. As a result, the spot appears translucent, allowing light to shine through it. The option mentioning that the drop does not soak into the paper due to high surface tension is incorrect, as oil has a lower surface tension compared to water. The option mentioning a wet spot that does not allow light to pass through is also incorrect, as oil does not completely block light.Rate this question:
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