3.1.2 - carbohydrates Flashcards
what are monosaccharides?
- monomers of carbohydrates
- e.g. glucose (C6H12O6), galactose and fructose.
how are disaccharides formed?
- formed by a condensation reaction between 2 monosaccharides.
what type of bond is formed in between a disaccharide?
- a glycosidic bond.
what is released in a condensation reaction?
- water is released.
which two monosaccharides make up maltose disaccharide?
- two alpha glucose.
which two monosaccharides make up sucrose disaccharide?
- alpha glucose.
- fructose.
which two monosaccharides make up lactose disaccharide?
- beta glucose.
- galactose.
how are polysaccharides formed?
- formed by the condensation of many monosaccharides.
how can glucose be released from starch and glycogen?
- molecules of glucose can be released from starch and glycogen for respiration by a hydrolysis reaction, which uses water and breaks the glycosidic bond between monomers.
what type of polysaccharide is within a plants cell wall?
- cellulose.
- it provides strength and support to plant cells.
how do you test for starch?
- add iodine/potassium iodine solution.
- if starch is present is turns from orange/yellow to blue-black.
what’s the test for reducing sugars? - all monosaccharides and maltose
- add Benedict’s reagent.
- heat to 80 degrees.
- if reducing sugar is present it turns from blue to brick red/orange/green.
- more precipitate (of red copper oxide) indicates higher concentration of reducing sugar.
(all monosaccharides and maltose)
what’s the test for non-reducing sugars? - some disaccharides
- boil in hydrochloric acid (to hydrolyse the disaccharide into its monosaccharides).
- add hydrogen carbonate solution (to neutralise).
- add Benedict’s reagent.
- heat to 80 degrees.
- if reducing sugar is present it turns from blue to orange/green.
what is the key thing to know about the disaccharide lactose?
that it is the main sugar in milk.
what is the key thing to know about the disaccharide sucrose?
- carbohydrates in plants are transported as sucrose as it allows for more efficient energy transfer and increased energy storage.
- quick form of energy = broken apart quickly by a hydrolysis reaction.
what is the key thing to know about the disaccharide maltose?
- it’s a reducing sugar.
- germinating seeds use maltose as an energy and food store.
- animals convert starch to maltose as it absorbs easier.
where is the polysaccharide starch mainly found?
plants.
where is the polysaccharide cellulose mainly found?
plants.
where is the polysaccharide glycogen mainly found?
in animals, fungi and bacteria.
what is the monomer of the polysaccharide amylose (starch)?
alpha glucose.
what type of covalent bonds are in amylose (starch)?
alpha 1,4 glycosidic bonds.
what is the structure of amylose (starch)?
- unbranched polymer.
- coiled/ helical = making it compact for storage.
what is the function of amylose (starch)?
- storage of glucose for respiration.
- storage in plants.
- releases glucose over a long period of time.
- insoluble so doesn’t affect the water potential.
what is the monomer of the polysaccharide amylopectin (starch)?
alpha glucose.
what type of covalent bonds are in amylopectin (starch)?
alpha 1,4 glycosidic bonds and alpha 1,6 glycosidic bonds.
what is the structure of amylopectin (starch)?
- branched polymer.
- branched chains have many terminals so glucose molecules can be rapidly broken off when energy is needed.
- crystalline structure.
what is the function of amylopectin (starch)?
- releases glucose for cellular respiration rapidly when needed.
what is the monomer of the polysaccharide glycogen?
alpha glucose.
what type of covalent bonds are in glycogen?
alpha 1,4 glycosidic bonds and alpha 1,6 glycosidic bonds.
what is the structure of glycogen?
- highly branched.
- spherical shape.
what is the function of glycogen?
- can be broken down very quickly.
- high metabolic rate.
- storage in animals and fungi.
- insoluble so it doesn’t affect the water potential.
what is the monomer of the polysaccharide cellulose?
beta glucose.
what type of covalent bonds are in cellulose?
beta 1,4 glycosidic bonds.
what is the structure of cellulose?
- linear chain.
- alternating orientation = each beta glucose is rotated 180 degrees allowing hydrogen bonds to form between the hydroxyl group of adjacent chains.
- hydrogen bonds form microfibrils.
- microfibrils = bundles into fibres providing high tensile strength.
what is the function of cellulose?
- plant cell wall = structural molecule.
- high tensile strength = helps the cell maintain its shape and resist turgor pressure and chains overlap so there is no weak point.
- flexibility = allows the cell wall to expand as the cell grows.
- protection = protects cells from mechanical damage and pathogens.
- support = allows the plant to stand upright and grow.
which type of glucose is the main substrate of respiration?
alpha glucose.
