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Biology > June 2020 QP - Paper 2 AQA Biology AS-level.PDF > Flashcards

June 2020 QP - Paper 2 AQA Biology AS-level.PDF Flashcards

1
Q

0 1 . 1 Littorina littorea is a species of snail found on rocky sea shores.
A student investigated variation in snail shell height in two populations of snails.
Give two ways in which the student could ensure his samples would provide a reliable
measure of the variation between individuals in each population

A
  1. Select at random;
  2. Large sample/number (of snails)/>10;
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2
Q

The student could determine the median, mode and range from his measurement of
shell heights in these populations.
Give two other statistical values the student could calculate from his measurement of
shell heights in these populations.

A

mean and standard deviation

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3
Q

Name the taxon in the hierarchy of classification represented by:
[1 mark]
1 Littorina
2 Iittorea

A

Genus
Species

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4
Q

0 2 box . 1 Describe how a phosphodiester bond is formed between two nucleotides within a DNA
molecule

A
  1. Condensation (reaction)/loss of water;
  2. (Between) phosphate and deoxyribose;
  3. (Catalysed by) DNA polymerase;
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5
Q

0 2 . 3 Name the protein associated with DNA in a chromosome.

A

02.3 Histone; 1

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6
Q

In the process of semi-conservative DNA replication, the two strands within a DNA
molecule are separated. Each then acts as a template for the formation of a new
complementary strand.
Describe how the separation of strands occurs.

A

DNA helicase breaks hydrogen bonds between polynucleotide bases /base bairs that are complementary / AT
and GC

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7
Q

A student investigated the effect of ethanol, hydrochloric acid and temperature on the box
loss of red pigment from beetroot cells.
During the procedure, the student:
* added 10 cm3 water into one test tube
* added 10 cm3 ethanol into a second test tube
* added 10 cm3 hydrochloric acid into a third test tube
* put the three tubes into a 25 o
C water bath
* cut four cylinders of tissue from a beetroot
* put a cylinder into each tube and fitted bungs
* added 10 cm3 water into a fourth test tube and put this tube into a
70 o
C water bath
* placed the fourth cylinder into this tube and fitted a bung
* later removed the cylinders from the tubes
* estimated the intensity of red pigment in each solution by eyesight.
0 4 . 1 Give one way in which the student could ensure the first three beetroot cylinders were
kept at 25 o
C throughout her experiment.

A

Measure temperature (in tube) at intervals and use
appropriate corrective measure (if temperature has
fluctuated);

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8
Q

A student investigated the effect of ethanol, hydrochloric acid and temperature on the box
loss of red pigment from beetroot cells.
During the procedure, the student:
* added 10 cm3 water into one test tube
* added 10 cm3 ethanol into a second test tube
* added 10 cm3 hydrochloric acid into a third test tube
* put the three tubes into a 25 o
C water bath
* cut four cylinders of tissue from a beetroot
* put a cylinder into each tube and fitted bungs
* added 10 cm3 water into a fourth test tube and put this tube into a
70 o
C water bath
* placed the fourth cylinder into this tube and fitted a bung
* later removed the cylinders from the tubes
* estimated the intensity of red pigment in each solution by eyesight.
0 4 . 2 Give two variables that the student did not control in her procedure

A
  1. Length and diameter
    OR
    Surface area
    OR
    Volume
    OR
    Mass/weight (of cylinders);
  2. Time in solution;
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9
Q

What is the uncertainty of taking a reading of 10 cm3 with this measuring cylinder?
Suggest how you could reduce the uncertainty calculated.
[2 marks]
Uncertainty ± cm

A

1

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10
Q

Suggest how you could reduce the uncertainty calculated.

A
  1. Use instrument with closer/finer/smaller
    intervals/graduations/scale;
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11
Q

Using Figure 3, what can you conclude about the damage caused to beetroot cells by
water, ethanol, hydrochloric acid and different temperatures?
Provide explanations for your conclusions

A
  1. Water/25oC caused no damage/no pigmentrelease (in E);
  2. HCL (Damage to) cell(-surface) membrane;
    (By acid) altering membrane protein
  3. Ethanol/acid caused some/similar/identical
    damage;
  4. (By) ethanol dissolving phospholipid bilayer

70oC caused most damage;
OR
5. (By) 70oC denaturing/altering membrane protein
OR
(By) 70oC increasing fluidity/permeability of
membrane;

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12
Q

0 5 box . 1 A student investigated starch hydrolysis using the enzyme amylase.
During the procedure, the student:
* treated the starch to make it soluble
* prepared 10 cm3 of different concentrations (mg dm−3) of starch solution
* added an identical concentration of amylase to each starch solution
* measured the time in minutes to completely hydrolyse starch.
He repeated the procedure and calculated the mean time to completely hydrolyse
starch in each concentration of starch solution.
Draw a table the student could use to record all of his results.
You only need to show completed column headings.

A
  1. Starch (solution) in first column;
  2. Headings for starch concentration/solution and time for
    (starch) hydrolysis/digestion with mg dm-3 and
    minutes/mins/min/m/seconds/s;
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13
Q

A student investigated starch hydrolysis using the enzyme amylase.
During the procedure, the student:
* treated the starch to make it soluble
* prepared 10 cm3 of different concentrations (mg dm−3) of starch solution
* added an identical concentration of amylase to each starch solution
* measured the time in minutes to completely hydrolyse starch.
He repeated the procedure and calculated the mean time to completely hydrolyse
starch in each concentration of starch solution.
Draw a table the student could use to record all of his results.
You only need to show completed column headings.
[2 marks]
0 5 . 2 Describe the results you would expect the student to obtai

A
  1. As starch concentration increases, time to
    hydrolyse/digest starch increases;
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14
Q

A competitive inhibitor decreases the rate of an enzyme-controlled reaction.
Explain how.

A
  1. Inhibitor similar shape to substrate;
  2. Fits/binds to active site;
  3. Prevents/reduces enzyme-substrate complex forming
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15
Q

When bread becomes stale, the structure of some of the starch is changed. This
changed starch is called retrograded starch.
Scientists have suggested retrograded starch is a competitive inhibitor of amylase in
the small intestine.
Assuming the scientists are correct, suggest how eating stale bread could help to
reduce weight gain

A
  1. Less hydrolysis of starch;
  2. (To) maltose;
  3. (So) less absorption (of glucose)
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16
Q

0 6 . 3 Give one reason why trout eggs produced by meiosis are genetically different.

A

0 6 . 3 Give one reason why trout eggs produced by meiosis are genetically different.

17
Q

A trout body cell contains 80 chromosomes. box
Farmed female trout are treated so that they produce diploid egg cells.
0 6 . 4 Give the number of chromosomes in body cells of the offspring produced from treated
farmed female trout and untreated farmed male trout.

A

120

18
Q

0 6 . 5 The offspring produced from farmed trout are sterile. Suggest and explain why.

A
  1. Too many/extra set/three copies of
    chromosomes;
  2. (Homologous) chromosomes do not pair
    OR
    (Homologous) chromosomes do not separate
    (evenly);
  3. (So) no meiosis;
19
Q

0 9 box . 2 Describe how the structure of a protein depends on the amino acids it contains.

A
  1. Structure is deternmined by (relative) position of
    amino acid/R group/interactions;
  2. Primary structure is sequence/order of amino
    acids;
  3. Secondary structure formed by hydrogen
    bonding (between amino acids);
  4. Tertiary structure formed by interactions
    (between R groups);
  5. Creates active site in enzymes
    OR
    Creates complementary/specific shapes in
    antibodies/carrier proteins/receptor (molecules);
  6. Quaternary structure contains >1 polypeptide
    chain
    OR
    Quaternary structure formed by
    interactions/bonds between polypeptides;

Biology (13 decks)

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