MCAT Biology : Types of Carbohydrates

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #1 : Carbohydrates

Drain cleaners a common household staple, used to open clogged drains in bathtubs and sinks. Human hair is a common culprit that clogs pipes, and hair is made predominately of protein. Drain cleaners are effective at breaking down proteins that have accumulated in plumbing. Drain cleaners can be either acidic or basic, and are also effective at breaking down fats that have accumulated with proteins.

A typical reaction—reaction 1—which would be expected for a drain cleaner on contact with human hair, would be as follows in an aqueous solution:

Pic_1

Another reaction that may occur, reaction 2, would take place as follows in an aqueous solution:

Pic_2

In contrast to the proteins in Reactions 1 and 2, the body uses carbohydrates __________.

Possible Answers:

to store energy for use over many days

to create strucutral elements of cells

to dissolve nonpolar solutes in blood

to store energy for immediate use

to function as a secondary energy source after fatty acids have been oxidized

Correct answer:

to store energy for immediate use

Explanation:

Carboydrates are the main energy currency of cells. They are typically burned first, before fats and proteins, to generate energy. Proteins, in contrast, are usually the functional biomolecules, serving structural and enzymatic roles.

Example Question #2 : Carbohydrates

Which of the following accurately describes glucose?

Possible Answers:

Ketohexose

Aldopentose

Aldohexose

Ketopentose

Correct answer:

Aldohexose

Explanation:

Glucose is composed of six carbons. When not in ring form, there is an aldehyde at the end of the molecule. As a result, glucose is an example of an aldohexose.

Example Question #3 : Carbohydrates

Which of the following carbohydrates is created in animals, but not in plants?

Possible Answers:

Glycogen

Cellulose

Starch

Amylose

Correct answer:

Glycogen

Explanation:

Glucose is stored in animals cells in the form of glycogen. Plants store glucose as either starch or cellulose. Amylose is a specialized component of starch, and plays a key role in plant energy storage.

Plants do not form glycogen, similar to the way that humans cannot form (or break down) cellulose.

Example Question #4 : Carbohydrates

Which of the following statements is true concerning glucose?

Possible Answers:

Maltose and cellulose differ by the type of linkage between the glucose monomers

The 6th carbon attacks the carbonyl carbon in order to create the cyclic structure of glucose

D-glucose has the highest chiral carbon's hydroxyl group pointing to the left

-glucopyranose has the anomeric carbon's alcohol group pointing in the opposite direction of the 6th carbon's alcohol group

Correct answer:

Maltose and cellulose differ by the type of linkage between the glucose monomers

Explanation:

Maltose and cellulose are both composed of glucose monomers that are combined in a 1,4 glycosidic linkage, however they differ by the type of 1,4 linkage used. Cellulose uses a beta 1,4 linkage, while maltose uses an alpha 1,4 linkage.

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