AP Biology : Understanding Essential Properties of Water

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #21 : Understanding Essential Properties Of Water

What is the best description of a base?

Possible Answers:

A compound that releases 

A compound that mixes well with oil

A nonpolar molecule with covalent bonds

A compound or solution that releases  or takes up 

Correct answer:

A compound or solution that releases  or takes up 

Explanation:

A compound or solution that is a base releases  ions or takes up  ions.  It is not a nonpolar molecule with covalent bonds and does not mix well with oil, which is nonpolar.

Example Question #21 : Understanding Essential Properties Of Water

Which of the following is not considered a major component (element) of life?

Possible Answers:

Iron

Sulfur

Carbon

Oxygen

Nitrogen

Correct answer:

Iron

Explanation:

Iron  is important for many organisms but it isn't found in quantities large enough for it to be a major component. It is part of the trace minerals. Carbon, nitrogen, sulfur and oxygen are all part of the bulk elements, elements that are found in the largest quantities (they make up 96% of organisms). 

Example Question #22 : Understanding Essential Properties Of Water

Which of the following correctly describes a water molecule?

Possible Answers:

Organic

Hydrocarbon

Protein

Nonpolar

Polar

Correct answer:

Polar

Explanation:

Water is a polar molecule because the bonds between oxygen and hydrogen are polar covalent bonds. This means that although they form covalent bonds (normally non-polar) the difference in electronegativity is great enough to make one side more negative (oxygen side) and the other side more positive (hydrogen side). However, the polarity isn't as strong as the polarity in ionic bonds so we donate the charges with the greek letter delta to show that they are partial charges. 

Water   electronegativity

Example Question #22 : Ap Biology

Which of the following reaction is the most common type of catabolic reaction in the human body?

Possible Answers:

Dehydration

Condensation

Hydrolysis

Elimination

Addition

Correct answer:

Hydrolysis

Explanation:

Catabolism means to break something down, usually from a larger starting point to one or more smaller byproducts. Hydrolysis is the most common reaction in the human body. Hydrolysis means "breaking" through the addition of a water molecule. You will see hydrolysis as an important reaction in many pathways in the human body.

Example Question #21 : Understanding Essential Properties Of Water

An alcohol group is indicated by which side chain when looking at the structure of a molecule?

Possible Answers:

Correct answer:

Explanation:

An alcohol group is written as  (hydroxide) in the structural formation of a molecule. The hydroxide group is an oxygen and carbon molecule held together by a covalent bond. Hydroxide is a minor constituent of water. Remember water is usually in the form, .

Example Question #21 : Understanding Essential Properties Of Water

When the concentration of solutes differs on the two sides of a membrane permeable only to water, what will occur?

Possible Answers:

The solutes will move across the membrane from a region of higher concentration to the region of lower concentration.

Water will move across the membrane by plasmolysis.

Water will move across the membrane by osmosis.

Water will move across the membrane by facilitated diffusion.

Water will move across the membrane by active transport.

Correct answer:

Water will move across the membrane by osmosis.

Explanation:

When there is a concentration gradient, water will move across a membrane unassisted by ATP or channel proteins. In contrast, solutes (the dissolved substances) cannot cross the membrane unassisted.

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