Carbohydrates

1.

1 point

Which of the following is NOT true for monosaccharides?

Aldehydes have O=C located in the middle of the chain.

They are aldehydes and ketones with two or more hydroxyl groups.

They have 3 or more C atoms.

Ketones have O=C located in the middle of the chain.

2.

1 point

You’re drawing a Fischer projection for D-glyceraldehyde! How should you go about drawing it?

COOH at the top, CH2OH at the bottom, OH points to the left.

CHO at the top, CH2OH at the bottom, OH points to the left.

Vertical lines projecting out of the plane of the paper, horizontal projecting behind.

CHO at the top, CH2OH at the bottom, OH points to the right.

3.

1 point

Which of the following is NOT true for pyranose rings?

They adopt an energetically favourable ‘chair’ conformation.

The C1 aldehyde of glucose reacts with the C5 hydroxyl group to form an intramolecular hemiacetal and pyranose ring.

They are formed when hexoses cyclize.

They adopt an energetically favourable ‘boat’ conformation.

4.

1 point

Which of the following statements is NOT true?

Lactose has beta 1,4 glycosidic bonds, and maltose has alpha 1,4 glycosidic bonds.

D- and L-glyceraldehyde are enantiomers.

Epimers differ in the configuration around one atom.

Aldohexoses have 4 chiral centres and 16 stereoisomers, all in the D configuration.

5.

1 point

Anomers:

In a pyranose ring has the C1 hydroxyl group of the beta anomer below the plane of the ring.

Are typically drawn using the Fischer projection, not the Haworth projection.

Are stereoisomers at the asymmetric centre of C1 of a pyranose ring.

In a pyranose ring has the C1 hydroxyl group of the alpha anomer above the plane of the ring.

6.

1 point

You’re a pathologist in a busy lab. A patient wants to know if he has type 2 diabetes, and you must determine the concentration of sugar in his blood sample. You know that the free aldehyde group (-CHO) of a monosaccharide is a reducing agent and that:

It will reduce Cu2+ to Cu+. Cu+ will gain an oxygen to ultimately become Cu2O, while CHO becomes COOH. You can then measure Cu2O concentrations to measure his blood glucose levels.

It will reduce Cu+ to Cu2+. Cu+ will gain an oxygen to ultimately become Cu2O, while CHO becomes COOH. You can then measure Cu2O concentrations to measure his blood glucose levels.

It will oxidize Cu2+ to Cu+. Cu+ will gain an oxygen to ultimately become Cu2O, while CHO becomes COOH. You can then measure Cu2O concentrations to measure his blood glucose levels.

It will reduce Cu+ to Cu2+. Cu+ will gain an oxygen to ultimately become Cu2O, while CHO becomes CO. You can then measure Cu2O concentrations to measure his blood glucose levels.

7.

1 point

A glycosidic bond occurs when:

The –OH of a monosaccharide hydrolyzes with the hemiacetal of another monosaccharide, eliminating H2O.

Biochemistry is hard and I want to nap forever.

The –OH of a disaccharide condenses with the hemiacetal of another disaccharide, gaining a H2O in the bond.

The –OH of a monosaccharide condenses with the hemiacetal of another monosaccharide, eliminating H2O.

8.

1 point

Which of the following is NOT true for lectins?

C-type lectins bind to calcium and have a common 120 amino acid domain which binds to carbohydrates.

Different C-type lectins have different carbohydrate binding specificities.

Lectins are a family of RNA which can recognize carbohydrates.

Calcium interacts with the sugar’s hydroxyl groups to indirectly connect it to the lectin protein.

9.

1 point

Which of the following best describes cellulose?

Glucose units are linked by (beta 1>4) glycosidic bonds, resulting in a long, flat molecule that is stabilized by hydrogen bonding.

Glucose units are linked by (alpha 1>4) glycosidic bonds, resulting in a long, flat molecule that is stabilized by hydrogen bonding.

A series of N-acetylglucosamine residues with an acetylated amino group at C2.

It possesses an open helix structure rather than a linear structure, allowing easy access to sugar when needed.

10.

1 point

Which of the following statements about glycoproteins is NOT true?

O-linked oligosaccharides are linked to the oxygen atom in the side chain of serine or threonine.

N-linked oligosaccharides have sugars linked to the amide side chain of asparagine.

The oligosaccharides can be linked to proteins via asparagine or lysine residues.

They are short oligosaccharide chains covalently attached to proteins in the cell membrane.

Carbohydrates - 1