Topic 2.3: Carbohydrates and Lipids

Question 1

What are the monomers of carbohydrates called?

Answer 1

monosaccharides

Question 2

What is the linkage between two monomers called?

Answer 2

glycosidic linkage

Question 3

What is the role of monosaccharides?

Answer 3

(one sugar unit) are typically sweet-tasting and function as an immediate energy source for cells

Question 4

What is the role of disaccharides?

Answer 4

(two sugar units) are small enough to be soluble in water and commonly function as a transport form

Question 5

What is the role of polysaccharides?

Answer 5

(many sugar units) may be used for energy storage or cell structure, and also play a role in cell recognition

Question 6

What subunit of carbohydrates (one sugar unit) are typically sweet-tasting and function as an immediate energy source for cells?

Answer 6

monosaccharide

Question 7

What subunit of carbohydrates (two sugar units) are small enough to be soluble in water and commonly function as a transport form?

Answer 7

disaccharides

Question 8

What subunit of carbohydrates (many sugar units) may be used for energy storage or cell structure, and also play a role in cell recognition?

Answer 8

polysaccharides

Question 9

What is the structure and function of cellulose?

Answer 9

Cellulose is a structural polysaccharide that is found in the cell wall of plants

It is a linear molecule composed of β-glucose subunits (bound in a 1-4 arrangement)

Because it is composed of β-glucose, it is indigestible for most animals (lack the enzyme required to break it down)

Ruminants (e.g. cows) may digest cellulose due to the presence of helpful bacteria in a specialised stomach
Caecotrophs (e.g. rabbits) will re-ingest specialised faeces that contain digested cellulose (broken down in the caecum)

Question 10

What is the structure and function of starch?

Answer 10

Starch is an energy storage polysaccharide found in plants

It is composed of α-glucose subunits (bound in a 1-4 arrangement) and exists in one of two forms – amylose or amylopectin

Amylose is a linear (helical) molecule while amylopectin is branched (contains additional 1-6 linkages)
Amylose is harder to digest and less soluble, however, as it takes up less space, is the preferred storage form in plants

Question 11

What is the structure and function of glycogen?

Answer 11

Glycogen is an energy storage polysaccharide formed in the liver in animals

It is composed of α-glucose subunits linked together by both 1-4 linkages and 1-6 linkages (branching)

It is akin to amylopectin in plants, but is more highly branched (1-6 linkages occur every ~10 subunits as opposed to ~20)

Question 12

What is the structure of a saturated fatty acid?

Answer 12

no double bonds

Question 13

What is the structure of a monounsaturated fatty acid?

Answer 13

1 double bond

Question 14

What is the structure of a polyunsaturated fatty acid?

Answer 14

greater then 1 double bond

Question 15

What is the linkage between multiple fatty acids called?

Answer 15

ester linkage

Question 16

How are triglycerides formed?

Answer 16

Triglycerides are formed when condensation reactions occur between one glycerol and three fatty acids

The hydroxyl groups of glycerol combine with the carboxyl groups of the fatty acids to form an ester linkage
This condensation reaction results in the formation of three molecules of water