Topic 1A Flashcards
Biological Molecules (23 cards)
what are monomers and what are polymers?
monomers are small, basic molecular units that make up polymers. polymers are large, complex molecules made of long chains of more than two monomers bonded together.
what monomers are carbohydrates made from?
monosaccharides
what type of sugar is glucose?
hexose sugar, it has six carbon atoms in each molecule
what are isomers? give an example
isomers are molecules with the same molecular formula but different atom arrangement, for example, alpha and beta glucose.
describe how two monosaccharides form a disaccharide
two monosaccharides undergo a condensation reaction, where a water molecule is in excess. A glycosidic bond is then formed between monosaccharides, creating a disaccharide.
what are the three types of disaccharides and which monosaccharides form them?
maltose is made from two alpha glucoses, sucrose is made from glucose and fructose, and lactose is made from glucose and galactose.
what is the reverse of a condensation reaction, and what does this reaction require?
hydrolysis, it requires water.
how do you test for reducing sugars? what are some examples of reducing sugars?
add Benedict’s reagent to a sample and heat it in a water bath at boiling temperature. If the test it positive, a coloured precipitate will form. The higher the sugar concentration, the further the colour changes (in reverse rainbow). If the test is negative, the precipitate will remain blue.
Reducing sugars include all monosaccharides and some disaccharide e.g. maltose and lactose.
how do you test for non-reducing sugars? give an example of a non-reducing sugar
non-reducing sugars need to be broken down into monosaccharides. First collect a new sample, add dilute HCl, and heat in a water bath that is at boiling. Then neutralise the solution with sodium hydrogen-carbonate, and carry out the rest of the test as you would for reducing sugars. The results are the same for reducing sugars.
An example of a non-reducing sugar is sucrose.
what are polysaccharides?
loads of monosaccharides bonded together.
name three different polysaccharides
starch, glycogen, cellulose
what is the function of starch?
stores glucose in plants.
what is starch made of?
a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.
how are amylose and amylopectin adapted for storage?
amylose has a coiled structure, making it compact and good fro storage. amylopectin has side branches so enzymes can easily break down the glycosidic bonds so that starch can be quickly converted to glucose.
other than the benefits of amylose and amylopectin, how is starch good for storage?
it is insoluble in water so it doesn’t affect water potential
how do you test for starch?
add iodine dissolved in potassium iodide solution to the sample. A positive result will change colour from browny/orange to blue/black.
what is the function of glycogen?
energy store for animals.
what is glycogen?
a polysaccharide of alpha glucose.
how is glycogen adapted for storage?
it is a compact molecule. it has lots of side branches (more than amylopectin) so stored glucose can be released quickly.
what is cellulose?
a polysaccharide of beta glucose.
what is the function of cellulose?
it is a major component of cell walls in plants.
how is cellulose adapted to be a component of cell walls?
they are made up of straight cellulose chains (made from beta glucose) which are linked together by hydrogen bonds to form strong fibres (microfibrils). These microfibrils means cellulose can provide structural support for plant cell walls.
