biomolecules Flashcards
Explain why phenylalanine and tyrosine are classified as amino acids.
both have an
amine / amino / NH2 ;
COOH / carboxyl / carboxylic ;
Name the covalent bond between two adjacent amino acids in a chain of amino acids.
peptide (bond / link) ;
Name the type of reaction involved in breaking this bond and describe what happens in this reaction.
hydrolysis ;
water / H2O , is , added / used / needed ;
Erythrocytes contain haemoglobin, which is a globular protein.Blood vessel walls contain collagen, which is a fibrous protein.
Describe the differences between globular and fibrous proteins using haemoglobin and collagen as examples.
In your answer you should refer to collagen and haemoglobin.
Globular
ball (shaped) / spherical / AW ;
hydrophilic , (R-)groups / regions , on outside (of 3-D
structure) / hydrophobic (R-)groups on inside ;
form H-bonds with water ;
soluble ;
example of globular protein (other than haemoglobin) ;
haemoglobin , carries / transports , oxygen / carbon
dioxide ;
haemoglobin contains , prosthetic group / haem / Fe2+ /
iron ion (to allow oxygen to be carried) ;
(polypeptide chains within) haemoglobin have tertiary
structure (in a ball shape) ;
Fibrous
linear / long (chain) ;
(chains can) form (H) bonds with adjacent , chains
(within a molecule) ;
insoluble / few hydrophilic groups ;
strong / provide strength ;
have structural role ;
collagen has high proportion of glycine , so chains can
lie close together / AW ;
collagen forms , crosslinks / covalent bonds , between
molecules ;
crosslinks / ends of molecules, are staggered to avoid ,
weak points / AW ;
collagen forms part of , tendon / cartilage / ligament /
bone / connective tissue / bronchi / bronchioles /
trachea / skin ;
Describe how to do the emulsion test for lipids and how a positive result would be identified.
mix with / add , ethanol / alcohol , and water ;
(goes) cloudy ;
How might the lipid content of mycoprotein differ from food that comes from animals?
less (overall , lipid / fat) ;
less / no , saturated (fat / lipid / fatty acids) ;
more unsaturated (fat / lipid / fatty acids) ;
Complete the following table to show three other differences in the structures of starch (amylose) and cellulose molecules.
(contains) α / alpha / A / a ,-glucose (contains) β / beta / B / b , -glucose ; α / alpha / A / a 1-4 glycosidic bonds β / beta / B / b 1-4 glycosidic bonds ; all , monomers / AW , in same orientation alternate monomers at , 180° / AW , to each other ; granular / not fibrous fibrous / not granular ; H bonds within molecule / no (H) bonds (between molecules) (H) bonds between adjacent molecules
Which properties of cellulose make it suitable for forming cell walls?
(tensile) strength / strong ;
(H) bonds / links , can form (between adjacent fibrils) ;
insoluble ;
Describe the formation of a hydrogen bond between two molecules of water and explain why water can form these bonds.
1 between O and H (of adjacent molecules) ; 2 between , electropositive / δ+ / delta+ (H), and , electronegative / δ- / delta- (O) ; 3 water molecule , is polar / has charge separation ;
Hydrogen bonds allow water to act as a solvent.Why is the ability of water to act as a solvent important for the survival of organisms?
medium for (metabolic) reactions ;
(because) allows (named) ionic compound(s) to
separate ;
transport ;
two named transport , systems / media
OR
one example of a transport , medium / system , with a
named example of what is transported ;
(organisms can) absorb / take in , (named) minerals /
ions / (named) gas / food ;
able to dilute toxic substances ;
State one property of collagen that makes it a useful component of blood vessel walls.
strength / toughness / insolubility ;
Describe the structure of the collagen molecule.
peptide bonds , between amino acids / in
polypeptide ;
every 3rd amino acids is , same / glycine ;
coil / twist / spiral / helix ;
left-handed (helix) ;
glycine / small R group , allows closeness /
twisting (of polypeptide chains) ;
three polypeptide chains ;
hydrogen / H , bonds between (polypeptide)
chains ;
no / few, hydrophilic (R) groups on outside (of
molecule) ;
(adjacent molecules joined by) crosslinks ;
crosslinks / ends of molecules , being
staggered ;
fibril ;
State one function of haemoglobin.
transport / AW , of, oxygen / O2 ;
Describe three other ways in which the structure of haemoglobin differs from that of collagen.
haemoglobin (has / is):
globular ;
hydrophobic (R) groups on inside / hydrophilic
(R) groups on outside ;
4 , chains / sub-units / polypeptides ;
idea that subunits are (two) different types ;
α / alpha , helix ;
idea that proportion of glycine similar to that ,
of other amino acids / in other proteins ;
Identify two differences and two similarities in the structures of triglycerides and phospholipids
triglyceride phospholipid difference 3 fatty acids 2 fatty acids ; difference 3 ester bonds 2 ester bonds ; difference absence of phosphate presence of phosphate ; similarity (contain) glycerol ; similarity (contain) fatty acids ; similarity (contain) ester bonds ; similarity (contain elements) C,H and O ;
Name the test used to identify the presence of lipids.
emulsion (test) ;
Describe how you would carry out this test on a food sample.
emulsion test
1 add , ethanol / alcohol , (to sample) ;
2 shake / stir / agitate / mix thoroughly / AW ;
3 add (to) water ;
If candidate is clearly describing Sudan III test
5 mix sample with water ;
6 add Sudan III (stain) ;
7 shake / stir / agitate / mix thoroughly / AW ;
If candidate is describing translucent grease mark test
AWARD one mark only ;
State the expected result if lipid is present in the food sample.
(mixture) turns, cloudy / milky / white ;
Name the precise group of carbohydrate molecules of which glucose is an example.
monosaccharides
State and explain two ways in which the glucose molecule is well suited to its function in living organisms.
soluble so can be (easily) , transported / carried
(around organism) ;
small (molecule) so can , be transported / diffuse ,
across (cell) membranes ;
easily / quickly , respired / oxidised / broken down , to ,
release energy / produce ATP ;
molecules can , join / AW , to produce , (named)
disaccharides / (named) polysaccharides
Identify three mistakes made by the student when describing the structure of cellulose.
α-glucose / β-glucose ; some / no , 1–6 bonds or only 1 –4 bonds ; condensation / hydrolysis ; branches / straight chain ;
Suggest the name of a molecule that closely matches the student’s description.
glycogen / amylopectin
identify the type of carbohydrate molecule of which the carbohydrate agarose is an example.
polysaccharide
Suggest two ways in which the reliability of the experiment could be improved.
replicate(s) / repeat(s) ;
more than one sample tested from each tube / sample
each tube twice ;
Name the polymer formed from a chain of amino acids.
polypeptide / protein
Name the bond that is formed when two amino acids are joined together. Describe the formation of this bond.
peptide (bond / link) ; plus any two from ... description of formation between, amine group (of one amino acid) and carboxyl group (of another) ; H (from amine) combines with OH (from carboxyl) ; condensation (reaction) OR water, lost / eliminated / produced / created / AW ;
Many of the physical properties of water arise as a result of these hydrogen bonds.Describe ways in which the physical properties of water allow organisms to survive over a range of temperatures.
In your answer you should make clear links between the properties of water and the survival of organisms.
V1 high latent heat of vaporisation / large amount of energy
required to change from liquid to gas / AW ;
V2 evaporation is (efficient) cooling mechanism / AW ;
V3 example of cooling in living organism ;
H1 high specific heat capacity / large amount of energy needed
to, raise / change, temperature ;
H2 (thermally) stable environment for, aquatic /
named aquatic, organisms ;
H3 (aquatic) organisms use less energy on temperature
control ;
H4 (internal) temperature of organisms changes only slowly ;
H5 (biological) reactions / enzymes / metabolism, function(s)
correctly ;
F1 ice, is less dense than water / floats ;
F2 (surface of) ice provides habitat for, organisms / named
organism ;
I1 water (beneath ice), insulated / remains liquid / doesn’t
freeze ;
I2 (aquatic) organisms, do not freeze / can still swim ;
S1 (effective) solvent ;
S2 medium for reactions / (internal) transport medium / able to
dilute toxic substances ;
C1 cohesion / adhesion ;
C2 example of cohesion / adhesion, in living organism ;
T1 surface tension ;
T2 habitat for (named) invertebrates ;
P1 transparent ;
P2 allows underwater photosynthesis ;
D1 idea of high density ;
D2 allows flotation / support ;
U organisms can still obtain, oxygen / (named) minerals / food /
carbon dioxide, from water ;
List three other examples of where hydrogen bonds are found in biological molecules.
protein secondary structure / α-helix / -pleated sheet ;
(protein) tertiary structure ;
between polypeptide chains in (named) quaternary
structure ;
(between chains of) cellulose ;
(between, strands of / bases in) DNA ;
State two roles of cholesterol in living organisms.
regulates fluidity of / stabilises / AW, membranes / phospholipid bilayer ;
(converted to) steroid / named steroid, hormone(s) ;
waterproofing the skin ;
making Vitamin D ;
making bile (salts) ;
Identify one way in which the molecular structure of cholesterol is similar to the molecular structure of a carbohydrate.
contains C and H and O ;
has, OH / hydroxyl, groups ;
hex / 6-membered, ring ;
Cholesterol is transported in the blood within molecules of low-density lipoprotein (LDL).Name two molecules that combine with cholesterol to form LDLs.
(saturated) lipids / fats / triglycerides ;
protein / polypeptide ;
Explain why glycogen makes a good storage molecule.
insoluble ;
does not , change / affect , water potential / Ψ , of cell ;
can be , broken down / hydrolysed / built up ,
quickly / easily ;
lots of branches for enzymes to attach ;
compact ;
(therefore) high energy content for mass / energy dense
/ AW ;
When glycogen is hydrolysed, mole A is produced.
State the precise name of molecule A
State one function of molecule A.
α /alpha , glucose ;
respiratory substrate / used for respiration ;
source of / releases / provides, energy ;
formation of ATP ;
conversion into named compound ;
Complete the table below to give three differences in the structures of glycogen and cellulose.
glycogen cellulose no hydrogen bonding hydrogen bonding α / alpha , glucose β / beta , glucose ; 1,4 and 1,6-glycosidic bonds or 1,6-glycosidic bonds present 1,4-glycosidic bonds (only) or 1,6-glycosidic bonds not present ; branched not branched / linear / straight ; no , fibres / fibrils fibres / fibrils ; granules no granules ; all glucose units in same orientation adjacent glucose units in opposite orientation
Name the monomers that make up:
proteins
RNA
amino acid(s) ; nucleotide(s) ;
Describe how a hydrogen bond is formed.
between oxygen and hydrogen (atoms) ;
(between) electronegative / δ-, and electropositive / δ+ ;
suggest what would happen to the iodine-amylose complex if the solution was heated to 60 °C
hydrogen / H, bonds break ;
helix, lost / unravels / AW ;
iodine, released / no longer in complex / AW ;
Haemoglobin is a globular protein.Describe the structure of a haemoglobin molecule.
In your answer, you should include details of the secondary, tertiary and quaternary structure of the molecule.
sequence / chain, of amino acids ;
(amino acids) joined by peptide bonds ;
secondary
alpha / α, helix ;
small regions of, beta / β, pleated sheet / fold ;
hydrogen / H, bonds ;
tertiary
secondary structure / helix / polypeptide chain, undergoes
further, coiling / folding ;
3 bonds / interactions from: disulfide / ionic / hydrogen /
hydrophobic or hydrophilic ;
hydrophilic R groups on outside (of molecule) / hydrophobic
R groups on inside (of molecule) ;
quaternary
4, polypeptides / subunits ;
2, alpha / α, chains and 2, beta / β, chains ;
1 haem (group) per polypeptide / 4 haems (per molecule) ;
prosthetic group (is) haem, (which) contains Fe2+ ;
Describe the ways in which the structure of collagen is similar to the structure of haemoglobin.
(collagen has) amino acid, chain / sequence ; peptide bonds ; helical / helix ; 3 bonds / interactions from: disulfide / ionic / hydrogen / hydrophobic or hydrophilic ; quaternary structure ; more than one polypeptide / subunit ;
