Carbohydrates Flashcards
What are the hexose sugars?
galactose, alpha glucose, beta glucose, fructose
What are isomers?
molecules with the same chemical formula but different structural formula
What is the chemical formula for all hexose sugars?
C6H12O6
How does the structural formula of beta glucose differ from the structural formula of alpha glucose?
The formula is different because the hydroxyl group and H-atom are inverted at carbon-1
How are disacchirides formed?
When two monosacchirides join in a condensation reaction
What is meant by a condensation reaction?
A reaction where a molecule of water is also produced
What does glucose and glucose form?
Maltose and water
What does glucose and fructose form?
Sucrose and water
What does glucose and galactose form?
Lactose and water
What is the bond that joins the two monosacchirides called?
Glycosidic bond
What is the chemical formula of maltose, sucrose and lactose?
C12H22O11
What is a hydrolysis reaction?
A reaction that involves splitting a larger molecule into a smaller molecule by the chemical insertion of a water molecule
How does the hydrolysis of sucrose work?
A water molecule is inserted. It breaks the glycosidic bond. The hydroxil group of H20 bonds with fructose to make it stable because it is left with a free bond. The H+ atom bonds with glucose to make it stable.
How can hydrolysis happen?
Enzyme reactions (e.g. sucrase breaks down sucrose) Heat with an acid (e.g. in stomach)
What are the 4 important polysaccharides?
Starch, glycogen, cellulose and chitin
What is starch a polymer of and where is it found?
Alpha glucose (in the form of amylose and amylopectin) found in plant cells
Why does starch have a helical shape?
Because amylose contains only one type of bond (alpha 1-4 glycosidic bonds), therefore there is a strain on the chain
Why is amylopectin a branched molecule?
It contains two types of bond - alpha 1-4 and alpha 1-6 glycosidic
How do you test for starch?
Add 2-3 drops of iodine solution - a colour change for orange to blue/black
What is glycogen a polymer of and what types of bonding does it have?
Alpha glucose, alpha 1-4 and alpha 1-6
How does glycogen’s structure differ to amylopectin?
Although they are similar, amylopectin is more densely branched
What 4 features make a good storage molecule?
Insolubility - osmotically inert Easily accessible (in respiration) Compact shape (take up less space in cells) Large molecules (can't leave through plasma membrane)
What is cellulose a polymer of?
Beta glucose
What happens during condensation reactions between molecules of ß glucose?
Alternate molecules rotate by 180 degrees so that glycosidic bonds can form on either side of the chain
What forms between the parallel chains of ß glucose?
Hydrogen bonds which form microfibrils
Why is it important that cellulose is strong?
It prevents osmotic lysis of the cells (they won’t burst)
What is the monomer of Chitin?
Glucosamine (similar to beta glucose but some of the OH groups are replaced by amino acids)
Where do you find chitin?
In fungi cell walls and exoskeletons of insects
