section 2: biological molecules - topic 3: carbohydrates Flashcards
most carbohydrates are …?
polymers.
what 3 chemical elements are all carbohydrates made up of?
carbon.
hydrogen.
oxygen.
how many of each element is in a carbohydrate?
every 1 carbon atom - 2 hydrogens & 1 oxygen.
what are the monomers that make up carbohydrates called?
monosaccharides.
name 2 monosaccharides.
glucose.
ribose.
how many carbon atoms does glucose have?
6 carbon atoms.
(hexose monosaccharide)
what are the 2 forms of glucose?
alpha.
beta.
how many carbon atoms does ribose have?
5 carbon atoms.
(pentose monosaccharide)
what is ribose?
the sugar component of RNA nucleotides.
how are monosaccharides joined together?
by glycosidic bonds.
describe the condensation reaction.
during synthesis, a hydrogen atom on 1 monosaccharide bonds to a hydroxyl (OH) group on the other, releasing a molecule of water.
what is the reverse of the synthesis reaction?
hydrolysis.
^ a molecule of water reacts with the glycosidic bond, breaking it apart.
how is a disaccharide formed?
when 2 monosaccharides join together.
examples of disaccharides?
2 alpha glucose molecules are joined together by a glycosidic bond to form maltose.
sucrose = alpha glucose + fructose
lactose = either alpha or beta glucose + galactose
how is a polysaccharide formed?
when more than 2 monosaccharides join together.
example of a polysaccharide?
lots of alpha glucose molecules are joined together by glycosidic bonds to form amylose.
what is starch?
the main storage material in plants.
cells get energy from glucose & plants store excess glucose as starch (when a plant needs more glucose for energy it breaks down starch to release the glucose).
why is starch good for storage?
because it’s insoluble in water - so it doesn’t cause water to enter cells by osmosis (would make them swell).
what is starch a mixture of?
2 polysaccharides:
amylose.
amylopectin.
what is amylose?
a long, unbranched chain of alpha glucose.
the angles of the glycosidic bonds give it a coiled structure, almost like a cylinder.
this makes it compact - really good for storage as you can fit more into a small space.
what is amylopectin?
a long, branched chain of alpha glucose.
its side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily.
^ this means that a the glucose can be released quickly.
what is glycogen?
the main energy storage material in animals.
animals store excess glucose as glycogen.
what is the structure of glycogen?
very similar to amylopectin, but has loads more side branches coming off it.
why is the structure of glycogen useful?
lots of branches means that stored glucose can be released quickly - important for energy release in animals.
it’s also a very compact molecule - good for storage.
what is cellulose?
the major component of cell walls in plants.
what is the structure of cellulose?
made of long, unbranched chains of beta glucose.
when beta glucose molecules bond, they form straight cellulose chains.
^ these are linked together by hydrogen bonds to form strong fibres (microfibrils).
why is the structure of cellulose useful?
the strong fibres mean cellulose provides structural support for cells.
