Biochemistry : Identifying Monomers and Dimers
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Example Questions
Example Question #1 : Identifying Disaccharides
Lactose intolerance is a very common disorder, which involves a decrease in the function of the enzyme lactase. Which of the following should be avoided in a patient with lactose intolerance?
Neither needs to be avoided
Glucose
Galactose
Both should be avoided
Neither needs to be avoided
Lactose is a disaccharide that needs to be broken down to its monosaccharide components in the gut (so that it can be absorbed). Lactose is made up of galactose and glucose monosaccharide units. An enzyme called lactase, found on the intestinal walls, is used to break down lactose to galactose and glucose. A person with lactose intolerance lacks lactase and, therefore, cannot break down lactose to its components. This leads to malabsorption of lactose. However, there is no problem with galactose and glucose absorption. This means that a patient with lactose intolerance can still digest galactose and glucose if given separately.
Example Question #1 : Identifying Disaccharides
Hypoglycemia is a disorder that signifies low levels of glucose in the blood. In some cases of hypoglycemia, glucose levels can be brought back to normal via consumption of sugars. What sugar(s) can be administered to a patient with hypoglycemia?
I. Lactose
II. Galactose
III. Sucrose
I and III
I only
II only
I and II
I and III
As the question states, hypoglycemia is characterized by low levels of glucose in the blood. To bring the glucose levels back to normal, one can ingest foods that contain high amounts of glucose. To solve this question we need to decide which of the stated options can be broken down to glucose. Lactose is a disaccharide that is made up of glucose and galactose. An enzyme, called lactase, breaks down lactose to its components, which can then be absorbed by the intestinal cells; therefore, ingesting glucose will increase glucose levels in the blood. Similarly, sucrose is a disaccharide made up of fructose and glucose; therefore, ingesting sucrose will also increase glucose levels in the blood.
Galactose is a monosaccharide and, therefore, cannot be broken down to any further. It is absorbed as galactose by the intestinal cells. This will not increase the concentration of glucose in the blood.
Example Question #51 : Identifying Biochemical Molecules
Which reducing sugar(s) is/are formed from two glucose molecules connected by a 1 to 4 linkage?
More than one of these
Cellobiose
Sucrose
Lactose
Maltose
More than one of these
Maltose, made from the breakdown of starch, contains a 1 to 4 alpha linkage, and cellobiose, made from the breakdown of cellulose, contains a 1 to 4 beta linkage. Both are disaccharides with different shapes and different properties.
Example Question #1 : Identifying Disaccharides
Which of the following sugars is composed of glucose and galactose?
Lactose
Maltose
Sucrose
Fructose
Xylose
Lactose
To answer this question, we'll need to have some background information on each of the sugars shown in the answer choices.
A glycosidic bond between glucose and galactose will produce the disaccharide lactose, which is thus the correct answer.
Sucrose is a disaccharide composed of glucose and fructose. Maltose is also a disaccharide composed of two glucose molecules. Moreover, fructose and xylose are monosaccharides.
Example Question #1 : Identifying Nitrogenous Bases And Derivatives
Whichof the following is formed from hypoxanthine attached to ribose?
Dihydrouridine
Pseudouridine
Inosine
Guanosine
Inosine
The minor base (modified base) inosine is essential for translation and commonly found in tRNA wobble base pairing.
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