Carbohydrates part 2

Question 1

• what are polysaccharides

Answer 1

a polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions

Question 2

• example of a polysaccharide

Answer 2

losts of alpha glucose molecules are joined together by glycosidic bonds to form amylose

Question 3

• what is starch

Answer 3

a mixture of 2 polyasccharides of alpha glucose- amylose and amylopectin

Question 4

• how do cells get energy

Answer 4

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)

Question 5

• what is amylose

Answer 5

a long, unbranched chain of alpha-glucose

Question 6

• explain how amylose is good for storage

Answer 6

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

Question 7

• what is amylopectin

Answer 7

a long branched chain of alpha glucose

Question 8

• explain how amylopectin helps quicken the release of glucose

Answer 8

its side branches allow the enzymes that break down the molecules to get at the glycosidic bonds easily.

so glucose can be released quickly

Question 9

• explain why starch is good for storage

Answer 9

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

Question 10

• when is an iodine test done

Answer 10

if you do any experiment on the digestion of starch and want to find out if any is left, youll need the iodine test.

Question 11

• steps to iodine test

Answer 11

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

Question 12

• what is the main energy storage material in plants

Answer 12

starch

Question 13

• what is the main energy storage material in animals

Answer 13

glycogen- another polysaccharude of alpha-glucose

Question 14

• describe the structure of glycogen

Answer 14

its structure is very similar to amylopectin, except that it has loads more side branches coming off it

Question 15

• explain why the structure of glycogen is beneficial

Answer 15

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

Question 16

• what is cellulose made of

Answer 16

cellulose is made of long, unbranched chains of beta-glucose

Question 17

• what happens when beta-glucose molecules bond

Answer 17

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

Question 18

what 3 parts does a monomer consist of

Answer 18

a phosphate

a pentose sugar

a Nitrogen-containing organic base

Question 19

what does a condensation reaction between two monosaccharides form

Answer 19

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

Question 20

what happens when a polymer such as RNA is broken down

Answer 20

A polymer such as RNA is broken down into nucleotides when hydrolysis reactions break the phosphodiester bonds between the monomers.

Question 21

what happens when a polymer such as Glycogen is broken down

Answer 21

A polymer such as glycogen is broken down into monosaccharides when hydrolysis reactions break the glycosidic bonds between the monomers

Question 22

what happens when a polymer such as insulin is broken down

Answer 22

a polymer such as glycogen is broken down into amino acids when hydrolysis reactions break the peptide bonds between the monomers

Question 23

how is cellulose’s structure different to starch

Answer 23

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

Question 24

define fibres

Answer 24

the cellulose molecules are grouped together to form microfibrils which, in turn, are arranged in parallel groups called fibres

Question 25

what does the cellulose cell wall do apart from keeping the cell rigid

Answer 25

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

Question 26

how is cellulose suited to its function

Answer 26

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