Carbohydrates Flashcards
what is a condensation reaction?
joining monomers by a covalent bond, by removing water
what is a hydrolysis reaction?
splitting of 2 monomers, by adding water
what is a covalent bond?
sharing of electrons between 2 or more atoms
what does a polar and non-polar bond mean?
polar = equally shared electrons
non-polar = unequally shared electrons (more electronegative)
are covalent bonds strong?
yes because they’re stable so require a lot of energy to break
what is a reducing sugar?
they donate electrons and sugar is the reducing agent
what is a non-reducing sugar?
they can’t donate electrons so can’t be oxidised
give 3 examples of a reducing sugar
maltose, fructose, galactose or glucose
give an example of a non-reducing sugar
sucrose
what is an isomer?
same molecular formula but different structural formula (therefore different properties)
how do you test for a reducing sugar?
Add benedict’s reagent, heat in a water bath.
Positive result - brick-red
eg. soluble copper sulfate is reduced to insoluble copper oxide
how do you test for a non-reducing sugar?
Add HCl to break disaccharide into 2 monosaccharides add sodium hydrogencarbonate to neutralise acid, add benedict’s reagent and heat in water bath
positive result - brick-red
what is starch (amylose and amylopectin) formed from?
a glucose
what is glycogen formed from?
a glucose
what is starch for?
storage in plants
- granules in plastids
what is glycogen for?
storage in animals and fungi
is amylopectin branched?
yes
is amylose branched?
no
is glycogen branched?
yes (most branched)
is amylose in a coiled helix?
yes
is amylopectin in a coiled helix?
no
what type of glycosidic bond does amylose contain?
1,4 (unbranched and compact)
is glycogen in a coiled helix?
no
what type of glycosidic bond does amylopectin contain?
1,4 and 1,6 (branched)
what type of glycosidic bond does glycogen contain?
1,6
what is cellulose formed from?
B glucose
what type of glycosidic bonds are in cellulose?
1,4 (rotate 180° to join)
why is cellulose so strong?
- there are lots of H bonds due to the rotation
- cellulose fibres and other molecules form a matrix
- stretch without breaking
what is a disaccharide?
when 2 monosaccharides are joined in a condensation reaction by a glycosidic bond
give 3 examples of a disaccharide
lactose, maltose and sucrose
what is maltose made from?
2x a glucose molecules (1,4 bond)
what is sucrose made from?
a glucose + fructose (1,2 bond)
what is lactose made from?
a glucose + galactose
give 3 examples of a monosaccharide
glucose, galactose and fructose
give 3 examples of a polysaccharide
starch, glycogen and cellulose
