Biological molecules Flashcards
Amylose (f212 June 14 2ci)
coiled; (contains) α / alpha / A / a ,-glucose; α / alpha / A / a 1-4 glycosidic bonds; all monomers in same orientation; granular/ not fibrous; H bonds within molecule/ no (H) bonds (between molecules);
Cellulose (f212 june14 2ci)
no coiling;
(contains) β / beta / B / b , -glucose;
β / beta / B / b 1-4 glycosidic bonds;
alternate monomers at , 180°, to each other; [every second one is flipped]
fibrous / not granular; [fibres / microfibrils / fibrils / macrofibrils]
(H) bonds between adjacent molecules; [‘(cross)links’ for ‘bonds]
Which properties of cellulose make it suitable for forming cell walls? (F212 June 14 2cii)
(tensile) strength / strong ; [mechanical strength]
(H) bonds / links , can form (between adjacent fibrils) ; [fibres / microfibrils / fibrils / macrofibrils/ crosslinks]
insoluble ;
Hydrogen bonds also form between water molecules.
(i) Describe the formation of a hydrogen bond between two molecules of water and explain
why water can form these bonds. (3mks) f212 june14 4bi
[diagram with 2 water molecules, H bond, delta charges = 2mks]
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? (3mks) f212 June 14 4bii
1) medium for (metabolic) reactions ; [reactions can happen in water; supports metabolic reactions]
2) (because) allows (named) ionic compound(s) to
separate ;
3) transport ;
4) two named transport , systems / media OR one example of a transport , medium / system , with a
named example of what is transported ;
5) (organisms can) absorb / take in , (named) minerals /
ions / (named) gas / food ; [apoplast / sap / blood / symplast / vacuolar pathway / blood / lymph / xylem / phloem / tissue fluid / CSF]
6) able to dilute toxic substances ;
Name the type of reaction involved in breaking this bond (peptide) and describe what happens in this reaction. F212 2015 q1aii
hydrolysis ;
water / H2O , is , added / used / needed
(OH and H put back on amino acid; broken down using water)
Describe the differences between globular and fibrous proteins using haemoglobin and
collagen as examples (8mks)
In your answer you should refer to collagen and haemoglobin. F212 2015 q2c
Globular:
G1 ball (shaped) / spherical;
G2 hydrophilic , (R-)groups / regions , on outside (of 3-D
structure) / hydrophobic (R-)groups on inside;
G3 form H-bonds with water;
G4 soluble;
G5 example of globular protein (other than haemoglobin); [(named) enzyme / hormone / antibody /
channel / carrier]
H1 haemoglobin , carries / transports, oxygen / carbon
dioxide; [refs to buffering]
H2 haemoglobin contains , prosthetic group / haem / Fe2+/ iron ion (to allow oxygen to be carried);
H3 (polypeptide chains within) haemoglobin have tertiary structure (in a ball shape); [haemoglobin has tertiary structure]
Fibrous:
F1 linear / long (chain); [straight / rope-like]
F2 (chains can) form (H) bonds with adjacent , chains
(within a molecule); [ ‘strand’ as AW for ‘chain’ for F2
only; crosslink as AW for bond for F2 only]
F3 insoluble / few hydrophilic groups;
F4 strong / provide strength;
F5 have structural role;
C1 collagen has high proportion of glycine , so chains can lie close together;
C2 collagen forms , crosslinks / covalent bonds , between molecules; [(micro / macro) fibrils / fibres , as AW for molecules]
C3 crosslinks / ends of molecules, are staggered to avoid , weak points; [(micro / macro) fibrils / fibres , as AW for molecules]
C4 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 (2mks) f212 june 2015 q7b
mix with / add , ethanol / alcohol , and water;
(goes) cloudy; [milky / white (emulsion)]
Lipids form an essential part of a balanced diet. Some food, such as mycoprotein, is produced by microorganisms.
How might the lipid content of mycoprotein differ from food that comes from animals? (2mks) f212 june15 q7c
less (overall , lipid / fat) ; [ no / less , cholesterol meat has more]
less / no , saturated (fat / lipid / fatty acids) ; [meat has more]
more unsaturated (fat / lipid / fatty acids) ; [meat has less]
State one property of collagen that makes it a useful component of blood vessel walls. f212 june13 q1bi
strength / toughness /insolubility; [strong / tough]
Describe the structure of the collagen molecule.
(6mks) f212 june13 q1bii
1 peptide bonds , between amino acids / in polypeptide;
2 every 3rd amino acids is, same / glycine; [high proportion of / 35% , glycine / same amino acid]
3 coil / twist / spiral / helix; [in context of single polypeptide or 3 polypeptides]
4 left-handed (helix); [‘α-helix, which is left handed’]
5 glycine / small R group, allows closeness / twisting (of polypeptide chains);
6 three polypeptide chains;
7 hydrogen / H , bonds between (polypeptide)
chains;
8 no / few, hydrophilic (R) groups on outside (of
molecule);
9 (adjacent molecules joined by) crosslinks; [covalent bonds between adjacent molecules]
10 crosslinks / ends of molecules , being staggered;
11 fibril;
Haemoglobin contains a prosthetic group known as haem. Collagen does not contain a prosthetic group.
Describe three other ways in which the structure of haemoglobin differs from that of collagen. f212 june13 q1cii
haemoglobin (has/ is):
1) globular;
2) hydrophobic (R) groups on inside / hydrophilic (R) groups on outside;
3) 4, chains / sub-units / polypeptides;
4) subunits are (two) different types; [in haemoglobin the subunits are not all the same] [“two alpha and two beta chains” = 2 marks]
5) α/ alpha, helix;
6) proportion of glycine similar to that, of other amino acids / in other proteins; [wide(r) range of amino acids]
Using the information in Fig. 2.1, explain why alcohol dehydrogenase is able to break
down both ethanol and DEG. (3mks) f212 june13 q2bi
1 similar, shape / structure; [‘ethanol same shape as part of DEG’]
2 example of similarity; [they both have OH]
3 both, will fit into/ complementary (shape) to/ bind to / bond to , active site (of alcohol dehydrogenase);
Suggest why DEG-contaminated wines with a high ethanol content may result in less DEG poisoning than contaminated wines with a low ethanol content. (3mks) f212 june13 q2bii
1 (ethanol) competes with DEG; [ethanol / DEG= competitive inhibitor]
2 (when at high(er) concentration) ethanol more likely to , collide with / bind to/ bond to, active site; [‘ethanol more likely to form ESC’]
3 less , DEG breakdown / toxic product; [ DEG product is diluted; no DEG breakdown]
State two ways in which a diagram of part of an RNA molecule would appear different from the DNA molecule shown in Fig. 5.1. F212 june13 5aiv
(usually) single stranded / would not have 2 strands; [only one backbone]
uracil / U, instead of thymine / T;
Lipids are used for energy storage and as a respiratory substrate. List three other roles of lipids in the human body. f212 jan13 4bi
membranes ; [ ‘phospholipid bilayer’ ]
absorption of fat soluble vitamins;
electrical insulation / insulation of , neurones / nerve
cells / axons ; [ insulation in context of myelin / Schwann cells]
(thermal) insulation ;
protection of organs ;
(source of) (steroid) hormones / named steroid hormone / named group of steroid hormones ; [ e.g. testosterone, oestrogen, progesterone, aldosterone ,
glucocorticoids, androgens ]
(source of) cholesterol / LDL / HDL ;
waterproofing / skin suppleness / sebum ; [ear wax ]
source of vitamin D ;
buoyancy ;
Describe how you would carry out this test on a food sample 3mks f212 jan13 4dii
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
Describe the structural relationship between deoxyribose and the other components of the
DNA molecule 3mks. f212 jan13
part of nucleotide;
bonded / joined / attached , to (named) base and
phosphate ;
phosphate (joined) to C5 (and C3)/ base (joined) to C1;
(deoxyribose is part of) backbone (of DNA);
idea of linking with (second) phosphate on adjacent
nucleotide;
nucleotide is , monomer / repeating unit ,of DNA /
polynucleotide;
State and explain two ways in which the glucose molecule is well suited to its function in
living organisms. f212 jan13
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;
