Carbohydrates

Question 1

Many hydroxyl groups are useful in carbohydrates because….

Answer 1

Carbs are strongly hydrophilic, and therefore small carbs are very water soluble and easy to diffuse

Question 2

Moderate number of C-C and C-H bonds help carbohydrates because….

Answer 2

Moderate amount of potential energy that can be released in oxidation reactions

Question 3

Oscillate between ring and chain form is useful because….

Answer 3

Relatively easy to convert from one form to another in solution (α / β)

Question 4

Keto- and aldo- groups in chain form (functional for primates) help us….

Answer 4

Interact with taste buds to produce sensation of sweetness (indicates ripeness of fruit) and alerts us to presence of monosaccharide

Question 5

What kind of chemical reaction commonly takes place in a dissaccharide?

Answer 5

Condensation synthesis

Question 6

What is the technical name for a simple sugar (monomer)?

Answer 6

Monosaccharide

Question 7

What is the technical name for a double sugar?

Answer 7

Disaccharide

Question 8

What is the technical name for a short chain of linked sugars?

Answer 8

Oligosaccharide

Question 9

What is the technical name for a long chain of linked glucose molecules?

Answer 9

Polysaccharide

Question 10

A simple glycosidic linkage that is characteristic of all carbohydrates larger than monosaccharides?

Answer 10

C - O - C

Question 11

α-glucose is the common product of photosynthesis and the most important source of energy for almost all life forms. How would it be modified to form β-glucose?

Answer 11

Switch the H and the OH on carbon #1 so that the OH is pointing up.

Question 12

Which glucose monomer is involved in the formation of starches?

Answer 12

α- glucose.

Question 13

Why are starches called storage polysaccharides?

Answer 13

Starches can easily be hydrolyzed to yield glucose again when energy is required.

Question 14

Amylopectin

Answer 14

A much more branched starch with branches every 20-30 residues. It is a storage form of starch found in starch granules of plant cells. In potato starch, amylopectin makes up 80% of the starch.

Question 15

Glycogen

Answer 15

A highly branched starch, with branches approximately every dozen residues. It is the main storage carbohydrate in animals. The high branching rate means there are many ends at which the enzyme amylase can hydrolyze glucose (or maltose) when energy demands suddenly increase.

Question 16

What molecule is made from strings of β-glucose units?

Answer 16

Cellulose

Question 17

How do starch and cellulose chains differ in shape?

Answer 17

While starch molecules form helices, cellulose molecules are linear (pleated)

Question 18

What is the main function of cellulose?

Answer 18

Cellulose is made by plants to make cell walls.

Question 19

Why can’t animals with starch digesting enzymes break down cellulose?

Answer 19

Enzymes bind to their substrates based on shape. Starch metabolism evolved early in the history of life, and enzymes that match the helical shape of starch are nearly ubiquitous in life. Cellulose cell walls evolved much later, and most lines of eukaryotes do not seem to have come up with an enzyme that can bind to and hydrolyze cellulose.

Question 20

How do cellulose consuming animals, such as termites, rabbits and cattle, get energy from cellulose?

Answer 20

A few bacteria, the great master chemists of the living world, along with some fungi, have evolved enzymes that will hydrolyze cellulose. All cellulose digesting animals depend on symbiotic bacteria (or protists that themselves have probably borrowed bacterial functions in the case of termites.)