Question
Which of the statements about polysaccharides can be used to describe both amylopectin and
cellulose?
1 adjacent glucose molecules are rotated by 180°
2 contains 1,4 glycosidic bonds
3 polymer of α–glucose
A 2 only
B 3 only
C 1 and 2
D 1 and 3
▶️Answer/Explanation
Answer A
The statement that can be used to describe both amylopectin and cellulose is:
2. Contains 1,4 glycosidic bonds.
Therefore, the answer is A, 2 only.
Amylopectin is a branched polysaccharide that is composed of glucose monomers joined together by alpha-1,4 glycosidic bonds and alpha-1,6 glycosidic bonds.
Cellulose is an unbranched polysaccharide that is composed of glucose monomers joined together by beta-1,4 glycosidic bonds.
Both amylopectin and cellulose contain 1,4 glycosidic bonds. However, they differ in their glycosidic bond orientation, with amylopectin having alpha-1,4 glycosidic bonds and cellulose having beta-1,4 glycosidic bonds.
Question
Which molecule in the key is sucrose?
Answer/Explanation
Answer C
Sucrose is a type of sugar formed by one glucose and one fructose molecule bonded together. Glucose and fructose are hexose sugars.
All the common monosaccharides and disaccharides are reducing sugars, except sucrose.
Question
The structural formula of a carbohydrate molecule can be shown as:
Which of the molecules could be represented by this formula?
▶️Answer/Explanation
Ans:
A
The molecule that could be represented by the given formula is α glucose.
Therefore, the answer is 1)α glucose.
The given formula shows a six-carbon ring structure with five carbon atoms and one oxygen atom. This is the general formula for a monosaccharide, which is the building block of carbohydrates.
Both ribose and deoxyribose are five-carbon monosaccharides, but they have a different arrangement of atoms than the given formula. Ribose has a hydroxyl group (-OH) attached to each carbon atom, while deoxyribose has a hydrogen atom (-H) attached to the 2′ carbon instead of a hydroxyl group (-OH).
Question
What occurs when sucrose is broken down to monosaccharides?
1)condensation of reducing sugars releasing water
2)condensation of reducing sugars using water
3)hydrolysis, releasing reducing sugars and releasing water
4)hydrolysis, releasing reducing sugars and using water4
▶️Answer/Explanation
Ans:
D
When sucrose is broken down to monosaccharides, hydrolysis occurs, releasing reducing sugars and using water.
Therefore, the answer is D) hydrolysis, releasing reducing sugars and using water.
Sucrose is a disaccharide composed of glucose and fructose molecules joined together by a glycosidic bond. Hydrolysis is the process of breaking down a compound by adding water. When sucrose is hydrolyzed, the glycosidic bond is broken, and glucose and fructose are released as monosaccharides. Since glucose and fructose are reducing sugars, they can undergo further reactions, such as oxidation, to produce other compounds.
Question
One naturally occurring polysaccharide is an unbranched chain of the molecule acetylglucosamine linked by β-1, 4 glycosidic bonds. There are –CH2OH groups that alternate on each side of the polysaccharide chain.
Many hydrogen bonds form between these unbranched chains.
Which polysaccharide has a structure similar to that described?
A. amylose
B. amylopectin
C. cellulose
D. glycogen
▶️Answer/Explanation
Ans:
C
The polysaccharide that has a structure similar to the one described is cellulose.
Therefore, the answer is C. cellulose.
Cellulose is an unbranched polysaccharide composed of β-D-glucose units joined by β-1,4-glycosidic bonds. The alternating orientation of the -OH groups on the glucose units results in linear chains that can form many hydrogen bonds between adjacent chains, leading to the formation of strong microfibrils. The acetylglucosamine molecule mentioned in the question is not present in cellulose, but rather in chitin, which is another naturally occurring polysaccharide.