biological molecules Flashcards
what are the four carbon-based compounds?
-carbohydrates
-proteins
-lipids
-nucleic acid
what do monomers join together to form?
polymers
what is the process by which polymers are formed?
polymerisationg
give 2 examples of monomers and the polymers they form
- monosaccharide (glucose) to polysaccharide (starch)
- amino acid to protein/polypeptide
- nucleotides to polynucleotide
what biological molecule does not form polymers?
lipids
what kind of reaction joins monomers together?
condensation
what is a condensation reaction?
the removal of a molecule of water to join two monomers together
how is the polymer starch made?
by the joining of hundreds of alpha glucose monosaccharides via condensation reactions
what is an unusual feature of carbon?
it is able to form 4 bonds and can bind with a large range of elements
what are the three chemical elements in a carbohydrate?
- hydrogen
- oxygen
- carbon
what are the functions of carbohydrates in a living organism?
- storing energy
- strengthening cell walls
give some examples of reducing sugars
- all monosaccharides
- maltose
- lactose
why does benedict’s reagent turn red when heated with a reducing sugar?
- solutions gains electrons from reducing sugar
- turns red
what are three monosaccharides?
- glucose
- fructose
- galactose
what are three disaccharides?
- maltose
- sucrose
- lactose
what are three polysaccharides?
- glycogen
- starch
- cellulose
what is the bond between two monosaccharides called?
glycosidic
the bonding of which two monosaccharides forms the disaccharide sucrose?
Glucose and fructose
the bonding of which two monosaccharides forms the disaccharide maltose?
Glucose and glucose
the bonding of which two monosaccharides forms the disaccharide lactose?
glucose and galactose
what is the monomer of starch?
a-glucose
what glycosidic bonds does starch have?
1-4 and 1-6
what is the structure of starch?
- branched
- helical
- compact
what is the monomer of glycogen?
a-glucose
what glycosidic bonds does glycogen have?
1-4 and more 1-6 than starch
what is the structure of glycogen?
highly branched
what is the monomer of cellulose?
b-glucose
what glycosidic bonds does cellulose have?
1-4
what is the structure of cellulose?
- unbranched
- straight
why is starch well suited to be an energy storing molecule?
- 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
where is glycogen found?
- only in bacterial and animal cells
- in small granules in liver and muscles
how is glycogen different to starch?
- shorter chains
- more branched
why is glycogen a good source of quick release energy?
- made from short chains of alpha glucose
- more readily hydrolysed than starch
- can be released quickly
how is cellulose arranged so that it provides good support in cells?
- straight, unbranched chains
- chains are parallel to each other
- hydrogens bonds cross link
why is cellulose so important in cell walls?
- prevents cell from bursting
- strong so keeps structure
- keeps plant rigid so larger SA for photosynthesis
what is the importance of microfibrils in a plant cell?
- they allow water to pass through them via osmosis
- stops influx of water so non-woody parts stay rigid
what chemical elements do lipids contain?
- carbon
- hydrogen
- oxygen
how is the proportion of oxygen in lipids different to that of a carbohydrate?
smaller proportion of oxygen to carbon and hydrogen in lipids
are lipids soluble or insoluble?
- soluble in some solvents (alcohols)
- insoluble in water
what are lipids made of?
- glycerol molecule
- fatty acids
describe how lipids are used as an energy source?
lipids provide 2x the amount of calories as carbohydrates and proteins at the same mass
describe how lipids are used for waterproofing?
- form a waxy cuticle in plants
- mammals produce sebum
describe how lipids provide protection?
delicate organs have fat around them
what are triglycerides?
a lipid that is made up of one molecule of glycerol and 3 fatty acids
what is a phospholipid?
a lipid that is made up of two fatty acids, one glycerol molecule and a phosphate group
how does the head of a phospholipid differ to the tail?
the head is polar and hydrophilic whereas the tail is non-polar and hydrophobic
what is one consequence of a phospholipid having a polar head and non-polar tail?
- puts hydrophilic head close to the water
- creates a bilayer in aqueous environments
- forms a hydrophobic barrier between inside and outside of cell
when is a fatty acid unsaturated?
when it has more than one double carbon bond
what is the primary structure of a protein?
amino acids
what is the secondary structure of a protein?
- alpha helix
- beta pleated sheet
what are the features of hydrogen bonds in the tertiary structure of a protein?
- numerous
- easily broken
what are the features of ionic bonds in the tertiary structure of a protien?
- weaker than disulphide
- easily broken
what are the features of disulphide bonds in the tertiary structure of a protein?
strong and not easily broken
what is meant by the quaternary structure of a protein?
a combination of polypeptides chains and associated non-protein groups to form a large complex molecule
what are the two types of molecular shape that a protein could be?
- fibrous
- globular
what is the structure of fibrous proteins?
- long chains that are parallel to each other
- linked by cross-bridges
what is the bond between two amino acids called? and how is it formed?
- peptide bond
- condensation reaction
how do you test for a reducing sugar?
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
how do you test for a non-reducing sugar?
- 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
how do you test for a protein?
- 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
how do you test for a lipid?
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
