1.1, 1.2 - Monomers and polymers, carbohydrates

what is indirect evidence for evolution

all life on earth sharing common chemistry

what are carbohydrates used for

used by cells as respiratory substrates and form structural components in plasma membranes and cell walls

what are lipids used for

as bilayer of plasma membranes, certain hormones and as respiratory substrates

what are proteins used for

they form many cell structures and are important as enzymes, chemical messengers and components of the blood

what are nucleic acids used for

they carry genetic code for production of proteins; the genetic code is common to viruses and all living organisms providing evidence for evolution

why is water important

most common component of cells, so search for life in universe involves search for liquid water

basis of human life

biochemical basis similar for all living things

define monomer

monomers are the smaller repeating subunits which make up polymers

define polymer

large molecule made from a large number of repeating monomers joined together

name three examples of monomers

monosaccharides, amino acids, nucleotides

what is a condensation reaction

a condensation reaction joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water

a hydrolysis reaction

a hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule

what is a monosaccharide

monomers from which larger carbohydrates are made

what are common monosaccharides

glucose, fructose, galactose

what bond is formed during a condensation reaction between two monosaccharides

glycosidic bond

how are disaccharides formed

condensation reaction between two monosaccharides

how is maltose formed

condensation reaction between two alpha glucose molecules

how is sucrose formed

condensation reaction between fructose and glucose molecule

where is the hydroxyl on alpha glucose

below the ring on carbon 1

where is the hydroxyl on beta glucose

above the ring on carbon 1

how are polysaccharides formed

condensation of many glucose units

how is galactose formed

condensation reaction between glucose and lactose monomer

negative benedict's test

stays blue

positive benedict's test

red precipitate formed

how to test for reducing sugars

add benedict's reagent, heat in a water bath, positive = brick red precipitate, negative = solution stays blue

which saccharides are reducing sugars

all monosaccharides and some disaccharides but NOT sucrose

how to test for sucrose

carry out benedict's test and observe solution staying blue/negative results, boil with acid and then neutralise with alkali, heat with benedict's and forms red precipitate

how is glycogen forned

condensation of alpha glucose

how is starch formed

condensation of alpha glucose

how is cellulose formed

condensation of beta glucose

what is starch used as

storage carbohydrate in plants

how can starch be used for respiration

it can be hydrolysed to form glucose

what does starch contain

amylose and amylopectin

describe amylose

unbranched, 1-4 glycosidic bonds, straight chain which coils into a helix

describe amylopectin

branched, 1-4 and 1-6 glycosidic bonds, straight chain which coils into a helix

proportions of amylose and amylopectin in starch commonly

20:80

describe and explain 4 structural features of starch

1) coiled, helical, spiral SO its compact and can store a lot in a small space

2) insoluble SO there is no osmotic effect, does not diffuse out of cell or affect water potential

3) large molecule/long chain SO it does not diffuse out of cell and contains large number of glucose units

4) amylopectin has branched chains SO its easy for enzymes to hydrolyse into alpha glucose at faster rate

what is glycogen used as

storage molecule in animal cells, main storage polysaccharide in animal and bacteria cells

describe and explain 3 features of glycogen

1) coiled SO its compact

2) insoluble SO water does not draw into cell via osmosis and does not affect water potential

3) highly branched SO enzymes can rapidly hydrolyse it to form glucose as needed

why is glycogen useful in animal cells

animals have higher respiration rate and therefore higher metabolic rate than plants; glycogen is more branched than starch so has more ends so can be hydrolysed into glucose faster, glucose polymer so provides respiratory substrate for enzymes

what is cellulose used as

structural molecule in plant cells only

how are beta glucose monomers arranged in cellulose

every other beta glucose is inverted

describe cellulose's chains

straight, unbranched, parallel chains in rigid, linear structure

describe what cellulose can be built up to form

cellulose -> fibres -> micofibrils

describe and explain a feature of cellulose

long and straight chains linked together by many hydrogen bonds forming fibrils WHICH provides strength

describe the test for starch

add orange iodine to solution of food sample; positive causes orange to change to blue black; negative causes solution to stay orange

what is a polysaccharide

monosaccharides joined by condensation reactions / glycosidic bonds

what are some biologically important polymers

starch, protein, nucleic acid, DNA, cellulose, glycogen