carbohydrates Flashcards
(27 cards)
what elements does carbohydrates contain? ratio of the elements?
CHO, with H:O is 2:1
3 main classes of carbo
monosaccharides, disaccharides and polysaccharides
why does monosaccharides dissolve easily in water
due to their many polar hydroxyl (-OH) groups which readily forms hydrogen bonds with water
3 types of monosaccharides
glucose, fructose, galactose
3 types of disaccharides
maltose, sucrose, lactose
what bond is formed when 2 monosacc join to form a disacc?
glycosidic bond
formation of α-1,4 glycosidic bond
- btw -OH group of carbon 1 of one α-glucose monomer and -OH group of carbon 4 of another α-glucose monomer
- removal of a water molecule
- catalysed by enzymes
3 types of polysaccharides
starch, cellulose, glycogen
what is starch used for
main storage polysaccharide in plants
what type of glucose is starch made of
α-glucose
what are 2 polymers of α-glucose
amylose and amylopectin
structure of amylose (3)
- unbranched chain structure that consists several hundred α-glucose residues linked by α-1,4 GB
- angle of bonds causes chain to coil helically into a more compact shape, allowing packing of many glucose molecules per unit volume
- most -OH groups projected into interior of helix, hence no free -OH groups to form HB with water, resulting in insoluble molecule
function of structure of amylose (3)
- large no. of glucose molecules present so it serves as a GOOD ENERGY SOURCE in plants, as glucose is oxidised during resp to produce atp [OR]
- GB in amylose can be hydrolysed easily, resulting in release of a large no. of glucose monomers which can be oxidised during resp to produce large amt of atp. hence it acts as an ACCESSIBLE SOURCE OF GLUCOSE
- insoluble nature of starch (amylose) prevents its diffusion out of cell, therefore does not change the wp within the cell, making starch a GOOD STORAGE MOLECULE
structure of amylopectin (2)
- backbone of α-glucose residues held tgt by α-1,4 GB
- highly branched w side chains formed by α-1,6 GB
why is starch a good storage polysaccharide (2)
- GB in starch can be hydrolysed easily, releasing large number of glucose monomers, which can be oxidised during resp to produce large amt of atp. hence it acts as an ACCESSIBLE SOURCE OF GLUCOSE
- the large and insoluble nature of starch prevents its diffusion out of cell and thus does not change the wp within cell, making it a GOOD STORAGE MOLECULE within the cell
what is glycogen used for
main storage polysaccharide in animals
structure of glycogen (4)
- backbone of α-glucose residues held tgt by α-1,4 GB
- highly branched w side chains formed by α-1,6 GB
(compared to amylopectin, glycogen has shorter chains and is more highly branched) - GB in glycogen can be hydrolysed easily
- it is a large polysacc, which makes it insoluble in water
function of structure of glycogen (3)
- large amt of glucose molecules present, it serves as a GOOD ENERGY SOURCE in animals, as glucose is oxidised during resp to produce atp
- the many branched ends allow many hydrolytic enzymes to act on the branched ends at any one time, so glycogen can be easily broken down into its glucose monomers to be used as resp substrates. thus it serves as an accessible source of glucose
- large and insoluble nature prevents its diffusion out of cell and thus does not change the wp within the cell, making it a GOOD ENERGY STORAGE MOLECULE
what is cellulose used for
it is the structural polysaccharide in plants
structure of cellulose (3)
- long chain of β-glucose residues linked by β-1,4 GB which makes cellulose chain straight
- successive β-glucose residues are rotated 180° with respect to its adjacent residue, resulting in -OH groups projecting outwards from each cellulose chain in all directions
- HB are formed btw the -OH groups of neighbouring cellulose chains lying in parallel, resulting in cross-linking that binds the chains rigidly together to form microfibrils and macrofibrils which confer high tensile strength, stability and support
what type of glucose is cellulose made of
(alpha or beta)
β-glucose
function of structure of cellulose (3)
- it is the main structural component of plant cell walls. the high tensile strength of microfibrils prevents plant cell from bursting when water enters by osmosis
- as a plant cell inflates with water, pressure develops inside it and cell becomes turgid. turgid cells help support plants which lack wood
- the arrangement of fibres around the cell helps determine the shape of plant cell as it grows
what is maltose the product of
glucose + glucose
what is sucrose the product of
glucose + fructose