Carbohydrates 3 Flashcards
Structure, Function & Analysis
What is the general formula for carbohydrates?
CnH2nOn OR Cn(H2O)n.
What is the formula for pentose monosaccharides?
C5H10O5.
What is the formula for hexose monosaccharides?
C6H12O6.
Explain the difference between pyranose monosaccharides and furanose polysaccharides.
Pyranose monosaccharides have SIX carbon atoms in their ring.
Furanose monosaccharides have FIVE carbon atoms in their ring.
What is a stereoisomer?
An isomer that has the atoms in the molecule in the same order, but the 3D arrangement of atoms in the space differs (e.g. they are flipped upside down, or left to right etc.).
These hexose pyranoses are……………?They all have the chemical formula C6H12O6.
Galactose
Glucose
Mannose
Stereoisomers.
What makes a carbon atom ‘chiral’ in a carbon ring?
Chiral carbon atoms must be attached to four DIFFERENT groups attached to them, therefore each covalent bond the carbon atom forms is unique!
True or false? Monosaccharides cannot be structurally rearranged, they are permanently in one form.
False! When dispersed in water, monosaccharides can structurally rearrange, causing variations in the anomeric carbon.
What is an anomeric carbon? Where is it found in the ring and linear forms of a monosaccharide?
In a ring carbon, the anomeric carbon is the one which forms a bond with the hydroxyl (OH) group and the ring oxygen.
In a linear monosaccharide, te anomeric carbon is the carbonyl carbon of the aldehyde or ketone.
Which are more stable? Linear or cyclical monosaccharides?
Cyclical.
Monosaccharides can react with each other in …………………….. reactions to form ………………… linkages.
Condensation, glycosidic.
What are heteropolysaccharides?
Polysaccharides made from more than one form of monosaccharide.
Name two linear homopolysaccharides.
Amylose and cellulose.
Give an example of a linear heterosaccharide.
Inulin.
Amylopectin and glycogen both have what monosaccharide composition and geometry?
They are both branched homopolysaccharides.
Arabinoxylan and galactomannan both have what monosaccharide composition and geometry?
They are both branched heteropolysaccharides.
What dictates the secondary structure of polysaccharides?
Glycosidic linkages - the orientation on the anomeric carbon, either alpha or beta, and the bond position on the connecting sugar.
Amylose is a polymer of glucose with alpha 1,4 linkages. Cellulose is a polymer of glucose with beta 1,4 linkages. What impact does this difference in linkages have on their secondary structures?
Amylose is a helical structure.
Cellulose is a linear structure.
Name the carbohydrate:
‘formed in plants in photosynthesis and the calvin cycle. A small molecule which is easily transported through plants. Can form polysaccharides for energy storage and react with proteins and lipids. Essential for short-term energy management’.
Simple sugars.
In food and feed, what contributes to the perceived sweetness of foods and adds texture. It can also be fermented to form ethanol and acids, for example in kombucha.
Simple sugars.
In vivo, what can be rapidly absorbed in the small bowel and facilitates nutrient transport through the blood. It is crucial for cellular energetic processes and any excess can be converted to glycogen for storage.
Simple sugars.
What forms long-term energy reserves in plants and is composed of two polysaccharides, amylose and amylopectin?
Starch.
What can disrupt the native granular structure of starch to make it easier for humans to digest? Name this process.
Heat, shear and water. Gelatinisation.
Name some of the uses of non-starch polysaccharides in food production.
Thickening, emulsification and gelling.
