biological molecules

Question 1

what are the four carbon-based compounds?

Answer 1

-carbohydrates
-proteins
-lipids
-nucleic acid

Question 2

what do monomers join together to form?

Answer 2

polymers

Question 3

what is the process by which polymers are formed?

Answer 3

polymerisationg

Question 4

give 2 examples of monomers and the polymers they form

Answer 4

• monosaccharide (glucose) to polysaccharide (starch)
• amino acid to protein/polypeptide
• nucleotides to polynucleotide

Question 5

what biological molecule does not form polymers?

Answer 5

lipids

Question 6

what kind of reaction joins monomers together?

Answer 6

condensation

Question 7

what is a condensation reaction?

Answer 7

the removal of a molecule of water to join two monomers together

Question 8

how is the polymer starch made?

Answer 8

by the joining of hundreds of alpha glucose monosaccharides via condensation reactions

Question 9

what is an unusual feature of carbon?

Answer 9

it is able to form 4 bonds and can bind with a large range of elements

Question 10

what are the three chemical elements in a carbohydrate?

Answer 10

• hydrogen
• oxygen
• carbon

Question 11

what are the functions of carbohydrates in a living organism?

Answer 11

• storing energy
• strengthening cell walls

Question 12

give some examples of reducing sugars

Answer 12

• all monosaccharides
• maltose
• lactose

Question 13

why does benedict’s reagent turn red when heated with a reducing sugar?

Answer 13

• solutions gains electrons from reducing sugar
• turns red

Question 14

what are three monosaccharides?

Answer 14

• glucose
• fructose
• galactose

Question 15

what are three disaccharides?

Answer 15

• maltose
• sucrose
• lactose

Question 16

what are three polysaccharides?

Answer 16

• glycogen
• starch
• cellulose

Question 17

what is the bond between two monosaccharides called?

Answer 17

glycosidic

Question 18

the bonding of which two monosaccharides forms the disaccharide sucrose?

Answer 18

Glucose and fructose

Question 19

the bonding of which two monosaccharides forms the disaccharide maltose?

Answer 19

Glucose and glucose

Question 20

the bonding of which two monosaccharides forms the disaccharide lactose?

Answer 20

glucose and galactose

Question 21

what is the monomer of starch?

Answer 21

a-glucose

Question 22

what glycosidic bonds does starch have?

Answer 22

1-4 and 1-6

Question 23

what is the structure of starch?

Answer 23

• branched
• helical
• compact

Question 24

what is the monomer of glycogen?

Answer 24

a-glucose

Question 25

what glycosidic bonds does glycogen have?

Answer 25

1-4 and more 1-6 than starch

Question 26

what is the structure of glycogen?

Answer 26

highly branched

Question 27

what is the monomer of cellulose?

Answer 27

b-glucose

Question 28

what glycosidic bonds does cellulose have?

Answer 28

1-4

Question 29

what is the structure of cellulose?

Answer 29

- unbranched - straight

Question 30

why is starch well suited to be an energy storing molecule?

Answer 30

- doesnt affect the water potential of the inside of cells - its compact and can be stored in small spaces - forms a-glucose when hydrolysed so easily transported - used in respiration - branched so enzymes can act simultaneously

Question 31

where is glycogen found?

Answer 31

- only in bacterial and animal cells - in small granules in liver and muscles

Question 32

how is glycogen different to starch?

Answer 32

- shorter chains - more branched

Question 33

why is glycogen a good source of quick release energy?

Answer 33

- made from short chains of alpha glucose - more readily hydrolysed than starch - can be released quickly

Question 34

how is cellulose arranged so that it provides good support in cells?

Answer 34

- straight, unbranched chains - chains are parallel to each other - hydrogens bonds cross link

Question 35

why is cellulose so important in cell walls?

Answer 35

- prevents cell from bursting - strong so keeps structure - keeps plant rigid so larger SA for photosynthesis

Question 36

what is the importance of microfibrils in a plant cell?

Answer 36

- they allow water to pass through them via osmosis - stops influx of water so non-woody parts stay rigid

Question 37

what chemical elements do lipids contain?

Answer 37

- carbon - hydrogen - oxygen

Question 38

how is the proportion of oxygen in lipids different to that of a carbohydrate?

Answer 38

smaller proportion of oxygen to carbon and hydrogen in lipids

Question 39

are lipids soluble or insoluble?

Answer 39

- soluble in some solvents (alcohols) - insoluble in water

Question 40

what are lipids made of?

Answer 40

- glycerol molecule - fatty acids

Question 41

describe how lipids are used as an energy source?

Answer 41

lipids provide 2x the amount of calories as carbohydrates and proteins at the same mass

Question 42

describe how lipids are used for waterproofing?

Answer 42

- form a waxy cuticle in plants - mammals produce sebum

Question 43

describe how lipids provide protection?

Answer 43

delicate organs have fat around them

Question 44

what are triglycerides?

Answer 44

a lipid that is made up of one molecule of glycerol and 3 fatty acids

Question 45

what is a phospholipid?

Answer 45

a lipid that is made up of two fatty acids, one glycerol molecule and a phosphate group

Question 46

how does the head of a phospholipid differ to the tail?

Answer 46

the head is polar and hydrophilic whereas the tail is non-polar and hydrophobic

Question 47

what is one consequence of a phospholipid having a polar head and non-polar tail?

Answer 47

- puts hydrophilic head close to the water - creates a bilayer in aqueous environments - forms a hydrophobic barrier between inside and outside of cell

Question 48

when is a fatty acid unsaturated?

Answer 48

when it has more than one double carbon bond

Question 49

what is the primary structure of a protein?

Answer 49

amino acids

Question 50

what is the secondary structure of a protein?

Answer 50

- alpha helix - beta pleated sheet

Question 51

what are the features of hydrogen bonds in the tertiary structure of a protein?

Answer 51

- numerous - easily broken

Question 52

what are the features of ionic bonds in the tertiary structure of a protien?

Answer 52

- weaker than disulphide - easily broken

Question 53

what are the features of disulphide bonds in the tertiary structure of a protein?

Answer 53

strong and not easily broken

Question 54

what is meant by the quaternary structure of a protein?

Answer 54

a combination of polypeptides chains and associated non-protein groups to form a large complex molecule

Question 55

what are the two types of molecular shape that a protein could be?

Answer 55

- fibrous - globular

Question 56

what is the structure of fibrous proteins?

Answer 56

- long chains that are parallel to each other - linked by cross-bridges

Question 57

what is the bond between two amino acids called? and how is it formed?

Answer 57

- peptide bond - condensation reaction

Question 58

how do you test for a reducing sugar?

Answer 58

BENEDICTS TEST - 1cm^3 of test solution to tube - 1cm^3 of benedicts reagent to tube - mix - heat in water bath for 5 mins - check for colour change

Question 59

how do you test for a non-reducing sugar?

Answer 59

- add 1cm^3 of hc acid to 1cm^3 of test solution - put tube in a gently boiling water bath for 5 minutes - add a little bit of sodium hydrogen carbonate to neutralise the solution - add 1cm^3 of benedicts reagent - heat for 5 more minutes - check for colour change

Question 60

how do you test for a protein?

Answer 60

- add sodium hydroxide to a solution of suspected protein - add a few drops of biuret down the side of the tube - look for a blue ring on the surface - mix gently - positive result = purple

Question 61

how do you test for a lipid?

Answer 61

EMULSION TEST - if test substance not in liquid form grind with some ethanol - put 2cm^3 of test solution into a tube with 5cm^3 of ethanol - mix and allow to settle - pour upper layer into 5cm^3 distilled water - positive result = cloudy white