1.1 - Monomers & Polymers, 1.2 - Carbohydrates Flashcards
Define ‘monomer’
Monomers are smaller units that join together via condensation reactions to form larger molecules.
Give some examples of monomers
-monosaccharides (glucose, fructose, galactose)
-amino acids
-nucleotides
Define ‘polymer’
Polymers are molecules which are formed when many monomers join together through condensation reactions.
Give some examples of ‘polymers’
-polysaccharides
-proteins
-DNA
-RNA
What happens in a condensation reaction?
A chemical bond forms between 2 molecules
A water molecule is released
What happens in a hydrolysis reaction?
The breaking of a chemical bond between molecules using a water molecule.
Name the 3 hexose monosaccharides.
Glucose, fructose and galactose
What is the formula of all 3 hexose monosaccharides
C6 H12 06
Name the type of bond formed when monosaccharides react.
Glycosidic bond
Usually between 1,4 or 1,6
What is a disaccharide?
2 monosaccharides joined together by the formation of a glycosidic bond in a condensation reaction.
What is a polysaccharide?
Multiple monosaccharides joined together by many glycosidic bonds through many condensation reactions.
Name 3 disaccharides
Maltose, sucrose and lactose
How is maltose formed?
Maltose is composed of 2 alpha glucose molecules joined together by a glycosidic bond through a condensation reaction.
How is sucrose formed?
Sucrose is composed of a glucose and a fructose molecule joined by a glycosidic bond through a condensation reaction.
How is lactose formed?
Lactose is composed of a glucose and a galactose molecule joined by a glycosidic bond through a condensation reaction.
What is the chemical formula of all 3 disaccharides (maltose, sucrose + lactose)?
C12 H 22 011
Describe the structure and functions of starch
Polymer of alpha glucose in plant cells
It is insoluble, so has no osmotic effect on cells
It is large so doesn’t diffuse out of cells
It is made of amylose - a long unbranched chain of alpha glucose, attached by 1,4 glycosidic bonds giving it a helical structure = compact, so good for storage
It is also made of amylopectin - a long branched chain of alpha glucose, attached by both 1,4 and 1,6 glycosidic bonds. Branched = many ends for hydrolysis into glucose (quick release of energy)
Describe the structure and functions of glycogen
Main storage polymer of alpha glucose in animal cells (also found in plant cells)
1,4 & 1,6 glycosidic bonds
Highly branched = many ends for hydrolysis
Insoluble = no osmotic effect & doesn’t diffuse out of cells
Compact
Describe the structure and functions of cellulose
Major component of cell walls in plant cells
Polymer of beta glucose
Gives plant cell walls rigidity, preventing them from bursting under turgor pressure & holds stem up
1,4 glycosidic bonds
Straight-chain (unbranched)
Chains linked together parallel by hydrogen bonds to form strong fibres called microfibrils
Describe the Benedict’s test for reducing sugars
Add an equal volume of Benedict’s reagent (which is blue) to sample
Heat in a water bath that has been brought to the boil for approximately 5 mins
If positive: green, yellow, orange or brick-red precipitate forms
What can a Benedict’s test tell us about the concentration of reducing sugars?
The higher the concentration, the further the colour change (green > yellow > orange > brick-red)
To compare volume of reducing sugars in different samples, filter, then weigh the precipitate.
Describe the Benedict’s test for non-reducing sugars.
If you obtain a negative result from the initial Benedict’s test for reducing sugars then…
Get a new sample of the test solution
Add dilute hydrochloric acid
Heat in a water bath that has been brought to the boil for approximately 5 mins, in order to break down sugars into monosaccharides
Neutralise sample with sodium hydrogencarbonate
Then carry out the Benedict’s test as usual
Give examples of reducing sugars
All monosaccharides (e.g. glucose)
And some disaccharides (e.g. maltose and lactose)
Describe the test for starch
Add iodine dissolved in potassium iodine solution to test sample
If present, sample changes from browny-orange to a dark blue-black
