Flashcards in Cellulose and starch Deck (17)
What is cellulose
Cellulose is a polymer of beta glucose, every other beta glucose molecule inverts. Because it is unbranched, it allows cellulose molecules to pack together. Hydrogen bonds hold parallel cellulose chains together to form microfibrils. Multiple hydrogen bonds makes cellulose stable. Larger structure is a microfibril
What is a reason for cellulose strength
Microfibrils are laid down in a cross cross arrangement which adds to strength. Parallel chains of cellulose are held together by hydrogen bonds, forming microfibrils. Individually, hydrogen bonds are relatively weak compared to glycosidic bonds, but the large number of them produces a strong structure.
Pectin and hemicellulose hold microfibrils together
What is structure of starch
Starch is a polysaccharide made from alpha glucose. 2 forms of starch are amylose and amylopectin.
What glycosidic bonds to straight chains lead to
Straight chains lead to 1,4 glycosidic bonds
What glycosidic bonds do branched chains lead to
Branched chains lead to 1,6 glycosidic bonds.
Properties of starch
Properties of starch include: tightly packed, insoluble so doesn’t exert osmotic pressure.
What are similarities and differences between cellulose and starch
Both are polysaccharides
Both contain 1,4 glycosidic bonds
Cellulose contains beta glucose whereas starch has alpha glucose
Cellulose doesn’t have 1,6 glycosidic bonds
Starch is an energy storage molecule in plants, cellulose is a structural molecule of plant cell walls.
Compare properties of cellulose and starch
Cellulose and starch are insoluble, so n osmotic effect
Cellulose has Hbonds between parallel chains to give strength
Cross cross arrangement of cellulose microfibrils make cell wall very strong.
Starch is compact so lots can fit in small area
Large so can’t diffuse out of cell
What is pectin and where is it found
Pectin is a glue which holds the cellulose microfibrils together. It is an important component of middle lamella, it holds cells together.
What is hemicellulose
Hemicellulose is a glue which holds together microfibrils of cellulose
What happens if cell wall isn’t maintained
If cell wall isn’t maintained plant will become flaccid and wilt.
How are cellulose polymers held together and what does this form
Cellulose polymers form H bonds with each other as they are unable to coil and form branches.
This forms microfibrils
What are microfibrils held together by
Microfibrils are held together by polysaccharides hemicellulose and pectin.
Where is the bond between microfibrils that holds them together
The bond is between the O of OH molecule with a H on the adjacent molecule.
Why is glucose soluble
Glucose is soluble because it has a large number of hydroxyl groups (which are polar).
What is the problem with glucose being soluble
Problem with glucose being soluble is that if there is a large amount of dissolved glucose in a cell, it can cause water to enter via osmosis.