pollysachharides: glycogen,starch,cellulose,chitin Flashcards
what are polysaccharides?
large molecules or polymers consisting of chains of monosaccharides linked together by glycosidic bonds
what is the main function of both starch and glycogen?
they are both storage pollysaccharides that can both store and release glucose
where is starch found?
in plants
what is starch made of?
monomer of starch is alpha glucose
a mixture of amylose and amylopectin
what is the shape of amylose?
forms coiled molecules
what is the shape of amylopectin?
it is a branched molecule
what are the bonds in amlopectin?
bonds between glucose molecules WITHIN a branch are 1,4 glycosidic bonds
at branching points the bonds are 1,6 glycosidic bonds
what is the structure of amylose? Hydrogen bonds
hydrogen bonds can form between the delta negative oxygen on the c2 of one glucose molecule and delta positive C3 of the next glucose molecule in the chain
as a result, amylose molecule coils up to form a helix
what is the function of starch?
insoluble store of glucose
how does the structure of starch lead to its function?
it is a compact molecule
helix can compact to fit a lot of glucose in a small space, this makes it ideal for storage
branched structure: increases surface area for for rapid hydrolysis back to glucose
insoluble: doesnt affect the water potential of the cell which it is stored in so starch is osmotically stable
how does starch release the glucose when it is needed
glycosidic bonds are hydrolysed and glucose is released
what is glycogen formed from?
alpha glucose
what is glycogen in ?
animals and is found in muscle and liver cells
what is the structure and bonding of glycogen?
glycogen is a HIGHLY BRANCHED molecule due to 1,4 glycosidic bonds and 1,6 glycosidic bonds
how does the structure of glycogen lead to its storage function?
branched structure: high surface area for hydrolysis of glycosidic bonds for the release of glucose. glucose can be used in respiration
insoluble: doesn’t affect water potential of the cell which it is stored in so it is osmotically stable
what type of pollysaccharide is cellulose
structural pollysacharide
where is cellulose found and what for?
Structural strength in cell wall in plant cells
what monomer is cellulose made from?
BETA GLUCOSE
What is the bonding in cellulose?
1,4 glycosidic bonds
and hydrogen bonds between chains of beta glucose
what do the 1,4 glycosidic bonds in cellulose result in?
CH3OH group being on opposite sides of the chain of the adjacent glucose molecules
within a cellulose chain adjacent glucose
molecules are parallel so OH groups are aligned and a water molecule can be removed to form a glycosidic bond
why is cellulose not branched?
hydrogen bonds dont form within glucose molecules in the same chain but they do in different chains
what is the structure of cellulose?
long straight chains
forms long threads called fibrils
lots of hydrogen bonds between chains of beta glucose
why does cellulose form long threads (fibrils)
hydrogen bonds form cross linkages which holds chains parallel together this makes cellulose form long threads called fibrils
how does the structure (hydrogen bonding) of cellulose link to its function of providing strength?
difficult to digest: due to the very high number of hydrogen bonds between chains of beta glucose
this also gives cellulose high TENSILE STRENGTH- it is difficult to break when stretches this means that cells with cellulose in their cell wall are more resistant to osmotic lysis (bursting of cell due to too much water) so they are not likely to burst as cellulose stops too much water from entering the cell
insoluble in water: water molecules can NOT easily break the high number of hydrogen bonds in cellulose so it is insoluble
this means that it wont affect water potential in the cell
