Carbohydrates Flashcards
Elements present in carbohydrates
Carbon, hydrogen, oxygen
General formula of carbohydrates
Cx(H2O)y
Monosaccharide
a simple sugar molecule eg. glucose, fructose, galactose, ribose
Disaccharide
a molecule made up of two monosaccharides joined together by a glycosidic bond eg. lactose, sucrose, maltose
Polysaccharide
a polymer made up of many sugar monomers (monosaccharides) eg. glycogen, cellulose, starch
Pentose monosaccharides
Sugars which contain 5 Carbon atoms. Two important examples - ribose, the sugar present in RNA nucleotides and deoxyribose, the sugar present in DNA nucleotides
Hexose sugar
Sugars which contain 6 Carbon atoms.
Which sugar is present in RNA nucleotides?
Ribose, a pentose monosaccharide
Which sugar is present in DNA nucleotides?
Deoxyribose, a pentose monosaccharide
Triose sugar
Sugars which contain 3 Carbon atoms.
The difference between alpha and beta glucose
In alpha glucose, the hydroxyl group is below the plane of the ring, and in beta glucoses it’s above the plane of the ring.
How are disaccharides formed?
Condensation reaction takes place. A hydroxyl group and hydrogen form a water molecule which is removed, and a glyosidic bond is formed between the monosaccharide.
Example of a triose sugar
triose phosphate - acts as an intermediate in respiration
2 Examples of pentose sugars
Ribose - RNA nucleotides
Deoxyribose - DNA nucleotides
Example of a hexose sugar
Glucose - used as a respiratory substrate, and in blood sugar
3 Polysaccharide examples
Starch
Glycogen
Cellulose
4 Monosaccharide examples
Glucose
Fructose
Galactose
Ribose
3 Disaccharide examples
Maltose
Sucrose
Lactose
Maltose =
glucose + glucose
Sucrose =
glucose + fructose
Lactose =
glucose + galactose
Explain why alpha-glucose links together to form starch whereas beta-glucose links together to form cellulose.
The angle of α 1-4 glycosidic bonds means the glucose chain twists to form a helix. Beta-glucose cannot for coils or branches as one of the glucose molecules is turned upside down so it forms straight chains - cellulose.
Important properties of glucose
- glucose is polar so it is soluble as hydrogen bonds form between OH groups and water molecules -> glucose can dissolve in the cytosol of the cell
Fructose occurs naturally in…
fruit
Sucrose is found in…
cane and table sugar
Lactose is found in…
milk and milk products
Hydrolysis is …
the breakdown of a molecule into two smaller molecules requiring the addition of a water molecule
Condensation is …
a reaction between two molecules resulting in the formation of a larger molecule and the release of a water molecule
List the two different polysaccharides that make up starch.
Amylose and amylopectin
