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  1. 6

    AS Biology P1 MCQs Preparation Thread

    there are 2 types of non competitive inhibition one is by binding to the allosteric site (ie. anywhere not on active site) and change the structure of active site. this type of inhibition only occurs when the substrate is NOT bond to enzyme yet. The question states that the inhibitor binded to...
  2. 6

    A level Biology: Post your doubts here!

    theoretically its correct but practically its wrong. light microscopes have something like a maximum of x1500 magnification even when you have enough resolution, 300nm x 1500 = 0.45mm on the best light microscopes in the world. so you cannot distinguish them
  3. 6

    Biology As paper 1 help

    it says RNA stop codon is UAG, meaning the base on the mRNA is UAG the complementary DNA code that will form UAG is ATC so if you insert a T between AC, the stop codon forms. hence answer is B
  4. 6

    Biology As paper 1 help

    aphid collects sucrose from the phloem. and sucrose is non reducing sugar, so after benedict test + hydrolysis will yield positive result.
  5. 6

    A level Biology: Post your doubts here!

    answer is C here's a short summary primary structure = peptide bonds only, but between molecules NOT ADJACENT STRANDS (they often try to trick students with the adjacent strand Q) secondary = hydrogen bonds only (some syllabus includes hydrostatic forces) tertiary = hydrogen bond, covalent...
  6. 6

    A level Biology: Post your doubts here!

    apoplast pathway is the movement of water between cell walls from root to xylem. and water moves in the xylem via mass flow of water mainly due to transpiration.
  7. 6

    A level Biology: Post your doubts here!

    np if you have anymore questions don't hesitate to ask, I'm helping my sister prepare her paper 1 as well
  8. 6

    A level Biology: Post your doubts here!

    An adult human has approximately 5 dm3 of blood, which circulates about once a minute. 100 cm3 of arterial blood carries 19 cm3 of oxygen. 100 cm3 of venous blood carries 12.5 cm3 of oxygen. What is the approximate volume in cm3 of oxygen taken up per minute in the lungs? arterial blood...
  9. 6

    A level Biology: Post your doubts here!

    w08 q4 you measure the closest distance from the inner alveolar wall to the membrane of the red blood cell, which is roughly 6-8mm depending on where you measure magnification is x2500 so 6mm or 8mm divide by 2500 = 2.4 or 3.2 micrometers so answer is B w10 qp11 q16 its obvious that answer is...
  10. 6

    AS Biology P1 MCQs Preparation Thread

    no answer is C its 3.14*125*125=4.9*10^4 the radius is 50 small divisions and we know that 40 small divisions = 0.1mm or 100micrometers each small division is therefore 100/40 = 2.5 micrometers radius is thus 50x2.5= 125 micrometers
  11. 6

    A level Biology: Post your doubts here!

    I actually have no idea what telomere is so this is just some guesses and logical reasoning that I would have if I was to get this question in an exam, 1. telo-mere, the prefix is the same as telophase which means termination and ending 2. three quarters of the mitotic cycle is interphase so the...
  12. 6

    A level Biology: Post your doubts here!

    D, RER because the ribosomes on the RER is the site of protein synthesis. (protein is the folding of polypeptide chains made of amino acids) second closest answer would be A, but Golgi is the site of protein packaging
  13. 6

    AS Biology P1 MCQs Preparation Thread

    firstly you immediately eliminate C and D because its "percentage saturation of haemoglobin in the blood leaving an active muscle" which must have lower partial pressure of oxygen now this is probably one of the more tricky questions, we know in an active muscle CO2 is produced. the CO2 forms...
  14. 6

    A level Biology: Post your doubts here!

    Q1 from the first diagram we know that 0.2mm equates to 80 small divisions so 0.2mm/80 = 2.5 micrometers each chloroplast is roughly 4 divisions so 2.5x4 = 10 micrometers Q4 frist diagram we know that 0.2mm is 100 divisions so 0.2mm/100 = 2 micrometers growth is around 10 divisions so 10x 2 =...
  15. 6

    A level Biology: Post your doubts here!

    from the graph we can tell that the ratio of initial to final length is increasing, meaning that the length of potato chip is decreasing. If the chip is decreasing, it means water is taken out of the chip via osmosis. water potential of distilled water is 0, as water is taken out the solute...
  16. 6

    Chemistry: Post your doubts here!

    5bi production of O2 given cathode equation from question: 2H2O(l) + 2e– -> H2(g) + 2OH–(aq), find E value in data booklet = -0.83V now we find anode equation, we know the reaction was neutral at the start so reactant must be ph7 (H2O) so must be O2 + 4H+ + 4e– ⇌ 2H2O = +1.23V E = (1.23 –...
  17. 6

    Physics: Post your doubts here!

    its an AC current with 5.6A RMS current. we know that a DC current of 5.6A causes 2.4g increase on the balance to find the maximum AC current we multiply 5.6 x root 2 and the force (or mass) caused is proportional to the current (F = BIL) so the maximum mass will be 2.4 x root 2 = 3.4g and AC...
  18. 6

    Chemistry: Post your doubts here!

    conversion of indigo (C16H10N2O2) to -> C16H28N2O2 total of 18 H gained, so must be 9H2 in the reactants ie. full equation something like this C16H10N2O2 + 9H2 -> C16H28N2O2 next we calculate mol of indigo n(C16H10N2O2)= 2.5 / (12x16 +10 + 2x14 + 2x16) = 2.5/262 = 9.54x10^-3 mol and we know...
  19. 6

    Chemistry: Post your doubts here!

    0.04 mol of NaOH reacted with ethanoic acid. Since CH3COOH reacts with NaOH in 1 to 1 ratio so there was 0.04 mol of CH3COOH left in the equilibrium. and we know reaction CH3CO2H + ROH -> CH2CO2R + H2O happens in 1:1:1:1 ratio and CH3CO2H same initial amount as ROH so ROH must be 0.o4mol as well...
  20. 6

    SO3 reacts with H2O as soon as they contact forming H2SO4

    SO3 reacts with H2O as soon as they contact forming H2SO4
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