Biological Molecules

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Organic Chemistry › Biological Molecules

Questions 1 - 10
1

Which element is present in all organic compounds?

Carbon

Nitrogen

Oxygen

Phosphorous

Explanation

By definition, an organic compound is a compound that contains carbon. Organic chemistry is the study of carbon-containing molecules.

2

Which element is present in all organic compounds?

Carbon

Nitrogen

Oxygen

Phosphorous

Explanation

By definition, an organic compound is a compound that contains carbon. Organic chemistry is the study of carbon-containing molecules.

3

An unknown molecule was found to have a molecular formula of . This molecule can be identified as a                     .

None of these

fatty acid

steroid

triaclyglycerol

Explanation

This question is a little bit tricky. At first glance, we would jump to the conclusion that this molecule is a long hydrocarbon chain attached to a carboxylic acid and, therefore, a fatty acid. The premise is correct. However, our conclusion is false because, by convention, a fatty acid must contain a carbon chain of at least 12 carbons. The given formula does not match the description for a steroid or triacylglycerol. The correct answer is none of these.

4

Which of the atoms in the molecules below is/are sp 2 hybridized?

Screen shot 2015 10 24 at 10.11.54 am

1, 3 and 5

3 only

1 and 4

1 and 5

2 and 4

Explanation

The boron in 2 is sp 3 hybridized because of its four substituents and the carbon in 4 is sp hybridized because of its connection to only the nitrogen with a single .

5

What is the name of the following carbohydrate?

Screen shot 2015 11 16 at 12.44.13 pm

Alpha-D-galactopyranose

Alpha-L-galactopyranose

Beta-D-galactofuranose

Alpha-L-glucopyranose

Beta-D-galactofuranose

Explanation

Stereochemistry from second to fifth carbon is R, S, S, R, which indicates D-galactose. The Haworth structure is a six-membered ring, so the molecule is in its pyranose form. The molecule has its anomeric hydroxyl group pointing down, so it's the alpha anomer.

6

What is the name of the following carbohydrate?

Screen shot 2015 11 16 at 12.44.13 pm

Alpha-D-galactopyranose

Alpha-L-galactopyranose

Beta-D-galactofuranose

Alpha-L-glucopyranose

Beta-D-galactofuranose

Explanation

Stereochemistry from second to fifth carbon is R, S, S, R, which indicates D-galactose. The Haworth structure is a six-membered ring, so the molecule is in its pyranose form. The molecule has its anomeric hydroxyl group pointing down, so it's the alpha anomer.

7

Which of the atoms in the molecules below is/are sp 2 hybridized?

Screen shot 2015 10 24 at 10.11.54 am

1, 3 and 5

3 only

1 and 4

1 and 5

2 and 4

Explanation

The boron in 2 is sp 3 hybridized because of its four substituents and the carbon in 4 is sp hybridized because of its connection to only the nitrogen with a single .

8

An unknown molecule was found to have a molecular formula of . This molecule can be identified as a                     .

None of these

fatty acid

steroid

triaclyglycerol

Explanation

This question is a little bit tricky. At first glance, we would jump to the conclusion that this molecule is a long hydrocarbon chain attached to a carboxylic acid and, therefore, a fatty acid. The premise is correct. However, our conclusion is false because, by convention, a fatty acid must contain a carbon chain of at least 12 carbons. The given formula does not match the description for a steroid or triacylglycerol. The correct answer is none of these.

9

Pinene

How many isoprene units does the given molecule, alpha-pinene, have?

None - it is not a terpene

Explanation

Alpha-pinene is a terpene, and is thus composed of isoprene units. A single isoprene unit has 5 carbon atoms. This molecule has 10 carbons, thus it contains 2 isoprene units.

10

What is the name of the following molecule?

Screen shot 2015 11 16 at 12.55.54 pm

Alpha-D-glucofuranose

Beta-L-glucofuranose

Alpha-D-glucopyranose

Alpha-L-galactopyranose

Beta-D-galactofuranose

Explanation

Stereochemistry from second to fifth carbon is R, S, R, R, which indicates D-glucose. The Haworth structure is a five-membered ring, so the molecule is in its furanose form. The molecule has its anomeric hydroxyl group pointing down, so it's the alpha anomer.

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