L9 - Carbohydrates Flashcards
Carbohydrates. How common? ..are the product of?
Most abundant compound in nature
Product of photosynthesis
Carbohydrates:
Potato example
- Mostly Water
- Little bit of fat and protein
- Whole lot of carbohydrates (17%):
- Some as sugars: fuel for potato and the consumer
- A bit more is fiber: structure for the cell walls
- Most is starch: storage form of fuel
Carbohydrates
What are they made of?
What lenght?
These molecules belong to?
• Biological molecules made of Carbon, Hydrogen and Oxygen
For each carbon (C), there is one water molecule (H2O)
- Carbohydrate chains come in different lengths
- Biologically important molecules belong to
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
- Mono sacchar: One sugar
- Simple sugars, most common is glucose
- Formula is (CH2O)n and contain 3-7 Carbon
- Most oxygens in hydroxyl (OH) groups
- One oxygen in carbonyl (C=O)
- Position of carbonyl C=O is used to categorize sugars
- Aldose vs. ketose
- Named according to their number of carbons: i.e. triose, pentose, hexoses
Most important Monosaccharide?
- Glucose is most important monosaccharide
- Isomers are
- Galactose (part of lactose, found in milk)
- Fructose (Fruit)
• Six-carbon sugar: C6H12O6
- glucose and galactose : stereoisomers (different 3D organization of atoms around one of their assymetric carbons)
- fructose is a structural isomer of glucose and galactose (its atoms are bonded in a different order)
Monosaccharides form?
- Linear or ring
5 or 6 carbon sugars can be either of the two
- Ring form strongly favored
- In aqueous solution, 99% of glucose is in ring form
- when the hydroxyl is opposite of the CH20H its (a) when its in the same side its (b)
What are Disaccharides?
Two monosaccharides, joined via dehydration (or condensation)
Hydroxyl group of one monosaccharide combines with hydrogen of another,
Releasing water and forming glycosidic linkage
Common Disaccharides
Lactose:
Glucose + Galactose
Maltose:
Glucose x 2
Sucrose:
Glucose + Fructose
Polysaccharides. What are they?
- Long chain of many (poly) monosaccharides linked with glycosidic bonds
- Chain can be branched or unbranched, made up of different types of monosaccharides
Common Polysaccharides?
- Startch
- Glycogen
- Cellulose
- Chitin
What is Starch?
Product of photosynthesis: Glucose
Made up of two polysaccharides;
- Amylose unbranched glucose chains
- Amylopectin branched glucose chains
Excess stored as starch in different plant parts (i.e. roots, seeds)
Provides food for embryo in seeds, and serve as food source for humans and other animals, who break it down into glucose
What is Cellulose? What is it composed of?
• Major component of plant cell walls
(structure)
- Wood and paper mostly cellulose
- Unbranched chains of β-glucose monomers
Difference of Cellulose with amylose
- Contains β-glucose monomers
- Not helical, but long straight chain
- Animals cannot break down β-glycosidic linkages
What is Hemicellulose?
-Binds to cellulose fibrils in plant cell wall by hydrogen-bond
-Cross linking glycans.
They are polysaccharides built of monosaccharides such as Xylan, Glucose, Arabinose etc.
-bind together with pectin to cellulose network to form crosslinked fibers
Pectin. Usage and most important component of it?
-in the middle lamella
-rich in galacturonic acid
Used as gelling agent, in food: jellies, but also in the lab: agar and agarose
