Carbohydrates part 2 Flashcards
- what are polysaccharides
a polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions
- example of a polysaccharide
losts of alpha glucose molecules are joined together by glycosidic bonds to form amylose
- what is starch
a mixture of 2 polyasccharides of alpha glucose- amylose and amylopectin
- how do cells get energy
cells get energy from glucose.
Plants store excess glucose as starch ( when a plant needs more glucose for energy, it breaks down starch to release the glucose)
- what is amylose
a long, unbranched chain of alpha-glucose
- explain how amylose is good for storage
the angles of glycosidic bonds give it a coiled structure.
this makes it compact, so it’s really good for storage because you can fit more into a small space
- what is amylopectin
a long branched chain of alpha glucose
- explain how amylopectin helps quicken the release of glucose
its side branches allow the enzymes that break down the molecules to get at the glycosidic bonds easily.
so glucose can be released quickly
- explain why starch is good for storage
starch is insoluble in water and doesn’t affect the water potential so it doesn’t cause water to enter cells by osmosis, which would make them swell
it is compact so a lot can be stored in a small space
when hydrolyzed it forms a-glucose, which is both easily transported and readily used in respiration
the branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
- when is an iodine test done
if you do any experiment on the digestion of starch and want to find out if any is left, youll need the iodine test.
- steps to iodine test
add iodine dissolved in potassium iodine solution to the test sample.
if there is starch present, the sample changes from brown orange to a dark, blue-black colour
- what is the main energy storage material in plants
starch
- what is the main energy storage material in animals
glycogen- another polysaccharude of alpha-glucose
- describe the structure of glycogen
its structure is very similar to amylopectin, except that it has loads more side branches coming off it
- explain why the structure of glycogen is beneficial
highly branched so has more ends that can be acted on simultaneously by enzymes. so, glycogen is rapidly broken down into glucose monomers, which are used in respiration.
this is important to animals which have a higher metabolic rate and therefore respiratory rate than plants because they are more active
its also a very compact molecule, so its good for storage
it is insoluble and therefore does not tend to draw water into the cells by osmosis
being insoluble, it does not diffuse out of cells
- what is cellulose made of
cellulose is made of long, unbranched chains of beta-glucose
- what happens when beta-glucose molecules bond
beta-glucose molecules bond to form straight cellulose chains
the cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils. the strong fibres mean cellulose provides structural support for cells
what 3 parts does a monomer consist of
a phosphate
a pentose sugar
a Nitrogen-containing organic base
what does a condensation reaction between two monosaccharides form
a disaccharide through the formation of a glycosidic bond, and a molecule of water is eliminated.
if these condensation reactions continue to occur then a polysaccharide - held by many glycosidic bonds- will form
what happens when a polymer such as RNA is broken down
A polymer such as RNA is broken down into nucleotides when hydrolysis reactions break the phosphodiester bonds between the monomers.
what happens when a polymer such as Glycogen is broken down
A polymer such as glycogen is broken down into monosaccharides when hydrolysis reactions break the glycosidic bonds between the monomers
what happens when a polymer such as insulin is broken down
a polymer such as glycogen is broken down into amino acids when hydrolysis reactions break the peptide bonds between the monomers
how is cellulose’s structure different to starch
the cellulose chain, unlike that of starch, has adjacent glucose molecules rotated by 180 degrees.
this allows hydrogen bonds to be formed between the hydroxyl groups on adjacent parallel chains that help to give cellulose its structural stability
define fibres
the cellulose molecules are grouped together to form microfibrils which, in turn, are arranged in parallel groups called fibres
what does the cellulose cell wall do apart from keeping the cell rigid
prevents the cell from bursting as water enters it by osmosis.
it does this by exerting an inward pressure that stops any further influx of water.
as a result living plant cells are turgid and push against one another, making non-woody parts of the plant semi-rigid
this is especially important in maintaining stems and leaves in a turgid state so that they can provide the maximum surface area for photosynthesis
how is cellulose suited to its function
cellulose molecules are made up of B-glucose and so form long straight, unbranched chains
these cellulose molecular chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength
these molecules are grouped to form microfibrils which in turn are grouped to form fibres all of which provides yet more strength
