B1.1 - polysaccharides and glycoproteins (2d) Flashcards
what is the role and structure of starch?
starch is a polysaccharide formed from the polymerisation of alpha-glucose
- a store of chemical energy in plants, which doesn’t draw in water by osmosis
- monomers are linked together in chains by condensation reactions, forming 1,4-glycosidic bonds
- a mixture of two alpha-glucose polymers
what is the structure of amylose?
an unbranched polymer of alpha-glucose linked by 1,4-glycosidic linkages; this causes it to have a helical structure overall
what is the structure of amylopectin?
a branched polymer of alpha-glucose linked by 1,4-glycosidic linkages with branches linked by 1,6-glycosidic linkages
what is the role and structure of glycogen?
found in animals and is a branched polymer of alpha-glucose linked by 1,4-glycosidic linkages with branches linked by 1,6-glycosidic linkages
- glycogen has more frequent branches than amylopectin
- a short-term source of chemical energy in animals
how is the structure of starch and glucose related to its functions?
- compact due to coiling and branching during polymerisation
- large molecular size, meaning they are not readily soluble in water, so can be easily stored and doesn’t affect osmotic balance of the tissue
- the accessibility of alpha-glucose momoners allows for easy addition or removal by condensation or hydrolysis to build or mobilise energy stores
which polysaccharide releases the most energy?
glycogen releases the most energy as it is most highly branched, and so more alpha-glucose monomers are available to be removed at one time
what is the relationship between speed of building energy stores and branching?
the more highly branched the glycogen is, the more quickly it can build or mobilise energy stores
what is the role and structure of cellulose?
an unbranched polymer of beta-glucose, which is found in the cells walls of plants
what is required for the polymerisation of beta-glucose?
to allow polymerisation of beta-glucose, alternate glucose molecules must be placed upside down, so that the C1 hydroxyl group is on the same plane as the C4 hydroxyl group and allowing 1,4-glycosidic bonds to be formed by condensation reactions
- the alternating orientation of beta-glucose monomers gives straight chains
what are microfibrils?
straight chains of alternating beta-glucose monomers can be grouped in bundles, called microfibrils
- cross-links of hydrogen bonds can occur between the straight chains, holding them together
- this provides high tensile strength and prevents the cellulose stretching, to provide support and allow turgidity
what are glycoproteins?
glycoproteins are a conjugated molecule of carbohydrate and protein
what are the 3 roles of glycoproteins?
- cell-to-cell chemical communication
- cell-to-cell adhesion
- recognition of ‘self’ (the organism’s body cells) vs. ‘non-self’ for immune system functions e.g) ABO antigens
how do ABO antigens support recognition of ‘self’ cells?
red blood cells can have two possible glycoproteins on their surface, the A and B antigens
- a person’s immune system is not triggered by the antigens found on their own red blood cells
why is someone with type AB blood a universal recipient?
someone with AB blood will not respond to either antigen and they are considered universal recipients
why is someone with type O blood a universal doner?
a person with blood group O is considered a universal donor because they given blood to all ABO blood types, however they can only receive blood from other people with type O blood
