1A - Carbohydrates 1: Monosaccharides and Disaccharides Flashcards
1
Q
importance of carbohydates
A
- usual energy source in cells
- storing energy
- form an important part of cell wall in plants, fungi and bacteria
2
Q
Monosaccharides general formula
A
(CH2O)n
3
Q
Triose sugars (formula and importance)
A
- general formula = C3H6O3
- n = 3
- important in mitochondria (respiration)
4
Q
Pentose sugars (formula and importance)
A
- general formula = C5H10O5
- n = 5
- ribose and deoxyribose are important in the nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) => make up genetic material
5
Q
Hexose sugars (formula and importance)
A
- general formula = C6H12O6
- n = 6
- often taste sweet (glucose, galactose and fructose)
6
Q
disaccharides
A
- two monosaccharides joined together
- two monos join in a condensation reaction to form di and a molecule of water
7
Q
glycosidic bond
A
link between two monosaccharides
8
Q
glucose (source and its monos)
A
- stored in plants such as sugar cane
- glucose + fructose
9
Q
lactose (source and its monos)
A
- milk sugar
- glucose + galactose
10
Q
maltose (source and its monos)
A
- malt sugar (found in germinating barley)
- glucose + glucose
11
Q
How does the benedict solution work?
A
- bright blue solution contains Cu(II) ions
- reducing sugars react readily with the solution when heated gently and reduce the Cu(II) ions to Cu(I) ions
- ppt is formed and the solution goes from blue to orange
- all monosaccharides are reducing sugars, but only some disaccharides are
12
Q
how do prepare a non reducing sugar to be tested with benedict’s solution
A
- heat the non-reducing sugar (eg sucrose) with a few drops of HCl
- allow to cool and then neutralise the solution with NaHCO3 to hydrolyse the glycosidic bonds
- produces the monosaccharide unit and will give a positive test
