Topic 8 - Carbohydrates Flashcards
Carbohydrate
Biological macromolecule (polymer) in which the ratio of carbon to hydrogen to oxygen is 1:2:1
- Molecular formula (CH2O)n, where n represents number of carbons
What is the function of carbohydrates?
- Serve as energy source and structural support in cells; form arthropods’ cellular exoskeleton
What is the monomer of carbohydrates?
Monosaccharides
- Aldose: R-CHO (aldehyde group)
- Ketose: RC(=O)R’ (ketone group)
- Triose: 3 carbons
- Pentose: 5 carbons (ex. ribose)
- Hexose: 6 carbons (ex. glucose)
True or false: monosaccharides can exist as a linear chains or as ring-shaped molecules
True
Name some common monosaccharides.
Glucose, fructose, ribose, deoxyribose
Name the 2 different forms of glucose in a ring structure.
- α-glucose - hydroxyl (OH) group is below carbon 1; 1,4 OH have the same orientation
- β-glucose - hydroxyl (OH) group is above carbon 1; 1,4 OH have the opposite orientation
Disaccharides
Two monomers linked by a glycosidic bond
Glycosidic bond
A type of covalent bond between two monosaccharides; formed by dehydration synthesis
Name some common disaccharides.
Lactose, maltose, and sucrose
Polysaccharides
Long chains of monosaccharides linked by glycosidic bonds; may be branched or unbranched
Name some examples of polysaccharides.
Starch, glycogen, cellulose, and chitin
Describe the structure/function of starch (including the polymers that form it)
Polysaccharide used for energy storage in plants
- Amylose: α-1,4-glycosidic bonds (linear, unbranched)
- Amylopectin: α-1,6-glycosidic bonds (branched)
Describe the structure/function of cellulose
Polysaccharide that comprises the plants’ cell wall; provides structural support to the cell
- Formed by β-1,4-glycosidic bonds
- Opposing β-glucose can form parallel strands held together with hydrogen bonds
- Hydrogen bonds and 1,4 linkage of β-glucose make cellulose a strong, sturdy structure for plants
Describe the structure/function of glycogen
Polysaccharide used for energy storage in animals
- Highly branched
- 1,4 linkage of α-glucose extensively branched through 1,6 linkage of α-glucose
Describe the structure/function of chitin
Nitrogen-containing polysaccharide used for structural support in arthropods and in the cell walls of yeast and fungi
- Hydrophobic
- Contains hydrogen bonds
Describe the general functions of carbohydrates (AKA why they are important)
- Quick energy (mono and disaccharides)
- Water soluble and contain many C-H bonds; easily transported and broken down - Storage (glycogen and starch)
- Less soluble - better for storage
- Can still be quickly converted to mono and disaccharides when necessary
Why are polysaccharides like starch and glycogen used for energy storage?
Polysaccharides have many C-H bonds which store chemical energy. The more C-H bonds, the more energy can be stored.
Describe the structural difference between starch and cellulose.
Starch is made out of a chain of α-glucose molecules and can be linear or branched. Cellulose is a chain of β-glucose molecules that can form hydrogen bonds between the chains to create orderly rows, creating a rigid, elongated structure.
