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1
Q

advantages of atp

A
  • releases energy instantaneously

- releases relatively small amount of energy

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2
Q

calcium ions and atp role in muscle contraction

A
  1. Calcium ions diffuse into myofibrils from
    (sarcoplasmic) reticulum;
  2. (Calcium ions) cause movement of tropomyosin
    (on actin);
  3. (This movement causes) exposure of the
    binding sites on the actin;
  4. Myosin heads attach to binding sites on actin;
  5. Hydrolysis of ATP (on myosin heads) causes
    myosin heads to bend;
  6. (Bending) pulling actin molecules;
  7. Attachment of a new ATP molecule to each
    myosin head causes myosin heads to detach
    (from actin sites)
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3
Q

Explain how the resting potential of –70 mV is maintained in the sensory neurone when no pressure is applied

A
  1. Membrane more permeable to potassium ions
    and less permeable to sodium ions;
  2. Sodium ions actively transported/pumped out
    and potassium ions in;
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4
Q

Explain how applying pressure to the Pacinian corpuscle produces the changes in membrane potential recorded by microelectrode P.

A
  1. (Pressure causes) membrane/lamellae to
    become deformed/stretched;
  2. Sodium ion channels in membrane open and
    sodium ions move in;
  3. Greater pressure more channels open/sodium
    ions enter;
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5
Q

The membrane potential at Q was the same whether medium or heavy pressure
was applied to the finger tip. Explain why.

A
  1. Threshold has been reached;
  2. (Threshold or above) causes maximal response
    / all or nothing principle;
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6
Q

Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower responses to stimuli.

A
  1. Less/no saltatory conduction / action
    potential/impulse unable to ‘jump’ from node to node;
  2. More depolarisation over length/area of
    membranes;
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7
Q

Suggest why the plasmids were injected into the eggs of silkworms, rather than into the silkworms.

A
  1. (If injected into egg), gene gets into all/most of
    cells of silkworm;
  2. So gets into cells that make silk;
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8
Q

Suggest why the scientists used a marker gene and why they used the EGFP gene

A
  1. Not all eggs will successfully take up the
    plasmid;
  2. Silkworms that have taken up gene will glow;
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9
Q

What would the scientists have inserted into the plasmid along with the spider gene to ensure that the spider gene was only expressed in the silk glands of the silkworms?

A

Promoter (region/gene);

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10
Q

Suggest two reasons why it was important that the spider gene was expressed only in the silk glands of the silkworms.

A
  1. So that protein can be harvested;

2. Fibres in other cells might cause harm;

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11
Q

Explain why the scientists measured the rate of production of oxygen in this investigation.

A
  1. Oxygen produced in light-dependent reaction;
  2. The faster (oxygen) is produced, the faster the
    light-dependent reaction;
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12
Q

The scientists suggested that mutant plants producing more chlorophyll b would grow faster than normal plants in all light intensities.
Explain how these data support this suggestion

A

At all light intensities, chloroplasts from mutant
plants:
1. Have faster production of ATP and reduced
NADP;
2. (So) have faster/more light-independent
reaction;
3. (So) produce more sugars that can be used in
respiration;
4. (So) have more energy for growth;
5. Have faster/more synthesis of new organic
materials;

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13
Q

what causes muscle fatigue

A

lactate from anaerobic respiration

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14
Q

Explain why the student set up Tube 1.

A
  1. To show light does not affect DCPIP;

2. To show chloroplasts are required;

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15
Q

Explain the advantage of the student using the IC50 in this investigation.

A

Can compare different chemicals/weedkillers

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16
Q

Explain how chemicals which inhibit the decolourisation of DCPIP could slow the growth of weeds.

A
  1. Less/no ATP produced;
  2. Less/no reduced NADP produced;
  3. Less/no GP reduced/converted to TP;
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17
Q

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes.

A
  1. (Usually)Type II produce insulin;
  2. Cells/receptors less sensitive/responsive (to insulin)
    OR
    Faulty (insulin) receptors;
  3. (Treated/controlled by) diet/exercise;
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18
Q

Explain how donepezil could improve communication between nerve cells

A
  1. Less/no acetylcholine broken down;
  2. Acetylcholine attaches to receptors;
  3. (More) Na+ enter to reach threshold/for depolarisation/action potential/impulse;
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19
Q

Suggest and explain two reasons why there is a high frequency of the E280A mutation in Yaramul

A
  1. Isolated so inbreeding/low genetic
    diversity/small gene pool;
  2. Allele inherited (through generations) from
    (common) ancestor;
20
Q

Explain why natural selection has not reduced the frequency of the E280A
mutation in the population

A
  1. AD/symptoms develops late/at 49;

2. Have already reproduced;

21
Q

The age at which the E280A mutation is expressed to cause AD can vary
Suggest and explain one reason for this.

A 
1. Epigenetics/environment/named factor e.g.
stress, alcohol, toxins, diet, exercise,
smoking;
2. methylation (of genes)
OR
acetylation (of histones);
22
Q

One scientific study which analysed chromosome 14 involved 102 individuals. The scientists recorded a sample size of 204. In this sample they detected 75 E280A mutations but only 74 potential AD cases
Suggest explanations for the figures the scientists recorded

A
  1. One person was homozygous dominant/has

two dominant alleles

23
Q

Suggest why a DNA probe for the mutated triplet was not considered a suitable
method for detection of the E280A mutation

A 
1. (GCA/triplet) is common/found in other
places;
2. Would not know if it was the
mutation/allele/gene
OR
Produces ‘false positives’;
24
Q

Explain why a log scale is used to record the number of cells.

A

Large range/difference/increase in numbers;

25
Q

What is meant by a genome?

A
  1. (All) the DNA in a cell/organism;
26
Q

Explain why the antibody binds to the transcription factor.

A
  1. (Transcriptional factor/antibody) has a
    specific/tertiary structure/shape;
  2. Complementary (shape/structure);
27
Q

Use Figure 8 to explain what ‘precipitated DNA’ consists of

A
  1. DNA, transcription factor and antibody;
28
Q

Suggest how single-stranded cDNA could prevent transcription of the P34 gene.

A
  1. Binds to P34 gene/DNA/mRNA
29
Q

Describe the roles of two named types of enzymes used to insert DNA fragments into box plasmids.

A
  1. Restriction (endonuclease/enzyme) to cut
    plasmid/vector;
  2. Ligase joins gene/DNA to plasmid/vector;
30
Q

Suggest two features of the structure of different proteins that enable them to be separated by gel electrophoresis.

A
  1. Mass/number of amino acids/polypeptides;
  2. Charge;
  3. R groups (differ);
31
Q

Why does substitution mutation change structure of a protein

A
  • Substitution is one base swapped for another
  • This changes the base triplet that that base was part of, the triplet then coded for a different amino acid
  • Different amino acid changes primary structure of protein, which determines the tertiary structure of the protein
  • Tertiary structure of the protein is therefore changed
32
Q

Why decreased calcium ions inhibits muscle contraction

A
  • calcium ions bind to a protein attached to tropomyosin, cause it to change shape, pull tropomyosin out of actin-myosin binding site exposing it
  • so that myosin heads can bind, forms actin myosin cross bridge, pull actin over myosin causing muscle to contract as sarcomere shortens
  • so if calcium ions are decreased, tropomyosin blocks binding sites, less contraction
  • calcium also activates ATP hydrolyse (ATP -> ADP + Pi), energy used for contraction, so if less calcium then less energy
33
Q

Why use pencil instead of ink in chromatography

A
  • Ink would dissolve in solvent and pigments separate as solvent spreads up chromatogram
34
Q

Method to separate pigments

A
  • Place chromatogram in beaker of solvent, solvent shouldn’t go above pencil line
  • Solvent moves up paper and carries different pigments at different rates
35
Q

Why is different coloured pigments in leaves advantageous?

A
  • Can absorb different wavelengths of light
36
Q

Role of glucagon

A
  • Produced in alpha cells in islets of Langerhans in pancreas
  • Activates glycogenolysis and gluconeogenesis, decreases rate of respiration in cells
37
Q

Role of insulin

A
  • Increases permeability of membrane to glucose, more uptake

- Activates glycogenesis

38
Q

Why does inhibiting adenylate Cyclase reduce glucose concentration

A

cannot form cAMP from ATP, does not activate protein kinase a, does not convert glycogen to glucose, process inhibited glucose concentration remains low.

39
Q

photoionisation

A

Light hits chlorophyll, electrons become excited, leave chlorophyll and move to higher energy level, move down ETC

40
Q

What is a DNA probe

A
  • single stranded base sequence complementary to desired gene with label attached
41
Q

How is DNA cut

A
  • Restriction endonuclease, cuts DNA at specific palindromic recognition sequences (recognition sites)
42
Q

reason for lid on petri dish

A

so it wouldn’t evaporate so IAA conc the same in each dish

43
Q

explain the banding pattern from muscle diagram

A
  • The centre of the sarcomere appears darker due to the overlap of both actin and myosin filaments (A band)
  • The peripheries of the sarcomere appear lighter as only actin is present in this region (I band)
  • The dark A band also contains a slightly lighter central region where only the myosin is present (H zone)
44
Q

explain why converting pyruvate to lactate allows the continued production of atp by anaerobic respiration

A

Regenerates / produces NAD

(NAD used) in glycolysis.

45
Q

Explain how two features of the design of this investigation helped to ensure the validity of any conclusions obtained. (zebrafish)

A

large sample size therefore representative

and use of a control group for comparisons

46
Q

gluconeogenesis

A

the synthesis of glucose from non-carbohydrate sources

47
Q

more insulin =

A

more glut4 proteins, absorb more glucose by active transport, reduces glucose conc

A Level Biology (20 decks)

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