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Biology Paper 1 > TOPIC 9: CONTROL SYSTEMS > Flashcards

TOPIC 9: CONTROL SYSTEMS Flashcards

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1
Q

Define homeostasis.

A

Maintenance of dynamic equilibrium within an organism

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2
Q

Define the term negative feedback.

A

A regulatory mechanism in which the products of a system act as a stimulus to cause an opposite output in order to maintain dynamic equilibrium

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3
Q

What does the Thymus secrete?

A

Thymosin - regulate reproductive development and maturation of White Blood Cells

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4
Q

State the function of the medulla oblongata

A

Part of the hind brain, the regulatory centre for breathing and heart rate

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5
Q

State the function of the cerebellum

A

Part of the hindbrain, controls fine coordination or motor activity

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6
Q

State the function of the hypothalamus

A

Part of the forebrain, controls autonomic nervous system, thermoregulatory and osmoregulatory centre

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7
Q

State the function of the cerebrum

A

Extension of the forebrain, coordination of voluntary and some involuntary activity

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8
Q

Define summation

A

The additive effect of several sifts in potential difference at a membrane leading to an action potential being generated

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9
Q

State the components of the central nervous system (CNS)

A

Spinal cord and brain

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10
Q

Where is the osmoregulatory centre?

A

Hypothalamus

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11
Q

Where is the thermoregulatory centre?

A

Hypothalamus

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12
Q

Describe the structure of the retina

A
  1. Retina is inverted: light passes through neurones, bipolar neurones before photosynthetic rods/cones can be activated.
  2. Rods distributed all around the retina
  3. Cones mainly found at the fovea
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13
Q

State the two branches of the peripheral nervous system and what they control

A
  1. Somatic: Neurones to skeletal muscle, mostly under conscious control
  2. Autonomic: Neurones to smooth muscle, cardiac muscle and glands, not under conscious control
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14
Q

What does the Pineal gland secrete?

A

Melatonin - reproductive development and daily cycles

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15
Q

What does the Hypothalmus secrete?

A

ADH and Oxytocin - regulate water reuptake, sexual reproduction and childbirth

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16
Q

What does the Pituitary gland secrete

A

Pituitary Gland - Thyroid stimulating hormone, gonadotrophic hormones, growth hormones - regulate the thyroid, gonads and many other organs

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17
Q

What do the Ovaries secrete

A

Oestrogen and Progesterone - regulate ovulation and secondary sexual characteristics and uterus lining.

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18
Q

What does the Thyroid secrete

A

Thyroxin - controls rate or metabolism

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19
Q

What do the Testes secrete

A

Testosterone - regulate sperm production and secondary sexual characteristics

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20
Q

What do the Adrenal glands secrete

A

Adrenaline - increases heart rate and blood sugar levels

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21
Q

What does the Pancreas secrete?

A

Insulin and Glucagon - regulate blood sugar levels

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22
Q

State the importance of maintaining a constant pH, temperature and water potential in the body.

A
  1. pH: for enzyme activity - too acid or too alkali and enzymes denature. Hydrogen bonds are disrupted and charge distribution on active sites change.
  2. Temperature - for enzyme activity - too high and enzymes denature. Too cold and enzyme activity is too low. Temperature affects rate of reaction of enzymes.
  3. Water Potential: To allow efficient exchange of water for transport and exchange of substances. Too high and it will cause swelling and bursting. Too low- will cause shrinkage of cells .
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23
Q

Describe the mode of action of steroid hormones.

A
  1. Lipid soluble hormones diffuse through lipid component of the membrane.
  2. Bind to steroid-hormone receptors to form hormone-receptor complex.
  3. Moves into the nucleus through the nuclear pore
  4. Acts as a transcription factor, binds to DNA to either regulate gene expression or turn sections of DNA off.
  5. mRNA produced and moves back into the cytoplasm.
  6. Translation occurs and new proteins are made which go onto change the process of the cell.
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24
Q

Describe the mode of action of peptide hormones.

A
  1. Peptide hormones are larger hydrophilic molecules which can’t diffuse through a membrane because they are not lipid soluble.
  2. The peptide hormone binds to the specific receptor protein on the cell membrane surface which activates a cascade reaction.
  3. Surface membrane enzyme activated which converts ATP into cAMP.
  4. cAMP is the secondary messenger which goes on trigger intracellular biochemical changes.
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25
Q

What does ATP stand for?

A

Adenosine triphosphate

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26
Q

What does cAMP stand for?

A

cyclic adenosine monophosphate

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27
Q

Describe the effect that auxin has on plant growth

A
  1. Promotes cell elongation
  2. apical growth
  3. root formation
  4. Inhibits cytokinins and abscission
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28
Q

Describe the effect that cytokinins have on plant growth

A
  1. Promotes cell division
  2. lateral bud growth
  3. breaks seed dormancy
  4. No effect on roots and abscission
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29
Q

Describe the effect that Giberellins have on plant growth

A
  1. Promotes breaking seed dormancy
  2. Enhances some of auxins effects
  3. Inhibits root formation
  4. Stimulates fruit development
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30
Q

Explain the interaction between cytokinins and auxins at the apical shoot

A
  1. Auxins are produced at the apical shoot and cytokinins are produced at the lateral bud
  2. Auxins promote apical growth whereas cytokinins promote lateral growth
  3. Auxins inhibit cytokinins therefore no lateral growth at the apex of the plant
  4. Cytokinins overcome apical dominance lower down the stem or when auxin concentration is reduced
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31
Q

Describe how auxins lead to cell elongation

A
  1. Auxins bind to cell surface receptor
  2. Auxins activate H+ ion pump in surface membrane
  3. The now lower pH of the cell wall allows enzymes to break hydrogen bonds between cellulose microfibrils allowing more fluidity.
  4. Increased turgor pressure from osmosis forces the cell to elongate.
  5. Auxins are then destroyed by enzymes and the cell wall regains rigidity.
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32
Q

What are the two types of phytochrome

A
  1. Pr:red light absorbing phytochrome (wavelength of 660nm) - stable, inactive
  2. Pfr: far red light absorbing phytocrhome (wavelength 730nm), active
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33
Q

Explain the difference between short day plants and long day plants

A
  1. Short day plants: Pfr inhibits flowering it needs a short day and long night as all phytochrome is converted to Pr.
  2. Long day plants: Pfr promotes flowering it needs a long day and short night so maximum Pfr is found in the plant
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34
Q

State the function of each of the different lobes of the cerebrum.

A
  1. Frontal lobe: personality, thought and reasoning, decision making, motor cortex
  2. Parietal lobe - sensation, orientation, memory and recognition
  3. Occipital lobe - processing inputs from the eyes
  4. Temporal lobe - processing inputs from the ears, sound recognition and speech
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35
Q

State the branches of the autonomic nervous system along with some of the responses they control.

A
  1. Sympathetic: Dilates pupils, inhibits salivary glands, relaxes bronchi, inhibits peristalsis and gut secretions, stimulates glucose release, stimulates adrenaline secretion, inhibits bladder contraction.
  2. Parasympathetic: Constricts pupils, stimulates salivary glands, constricts bronchi, stimulates peristalsis and gut secretions, inhibits glucose release, stimulates bladder secretion.
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36
Q

Describe how resting potential is established.

A
  1. Active transport of 3 Na+ out and 2 K+ in at Na/K pump
  2. Diffusion of K+ out and diffusion on Na+ in
  3. Membrane is more permeable to K so more + ions leaving the axon to establish -70mV potential difference across membrane.
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37
Q

Describe the sequence of events that lead to an action potential being generated

A
  1. Na+ channels open and Na+ ions diffuse into axon.
  2. Summation takes potential difference of membrane above the depolarisation threshold (-50mV)
  3. Potential difference above the threshold causes depolarisation - Na+ channels to remain open and Na+ continues to diffuse into the axon.
  4. Once action potential is reached (+40mV) Na+ channels close and K+ channels open causing repolarisation - K+ diffuses out of the axon.
  5. Hyperpolarisaiton occurs when the potential difference drops below resting potential (-70mV)
  6. Resting potential re-established through Na/K pumps and diffusion of Na+ and K+.
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38
Q

Explain why transmission speed is greater along myelinated axons as opposed to unmyelinated axons.

A
  1. Saltatory conduction: action potential jumps from node of Ranvier to node of Ranvier, speeding up neurotransmission.
  2. This is because the myelin sheath acts as an insulator preventing depolarisation.
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39
Q

Describe the sequence of events that lead to neurotransmitters being released

A
  1. Action potential reaches the axon terminal causing Calcium channels to open.
  2. Diffusion of Calcium into axon terminal causes vesicles containing neurotransmitter to move towards cell membrane.
  3. Vesicle fuses with cell membrane and neurotransmitter is released by exocytosis.
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40
Q

State the difference between and endotherm and ectotherm

A
  1. Endotherm: An organism that relies on heat energy generated by internal metabolism for thermoregulation.
  2. Ectotherm: An organism that relies on external heat sources for thermoregulation.
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41
Q

Explain the adaptations of the nephron of desert animals

A
  1. Longer loop of Henle increases the counter current multiplier mechanism.
  2. More water is conserved at the loop of Henle.
  3. More water is reabsorbed at the collecting duct.
42
Q

State the branches of the autonomic nervous system which controls the heat loss and heat gain responses?

A
  1. Heat gain centre: sympathetic

2. Heat loss centre: Parasympathetic

43
Q

Explain the role of osmoreceptors in controlling the volume and concentration or urine produced.

A

Osmoreceptors detect the water potential of the blood

44
Q

State the main function of the Glomerulus + Bowman’s capsule

A

Ultrafiltration

45
Q

State the main function of the Distal convoluted tubule

A

Control of blood pH and water reabsorption

46
Q

State the main function of the Collecting duct

A

Water reabsorption

47
Q

State the main function of the Proximal convoluted tubule

A

Selective reabsorption

48
Q

State the main function of the Loop of Henle

A

Water conservation

49
Q

Describe how urea is produced

A
  1. Deamination: removal of amine group from amino acid.

2. Amine group enters the ornithine cycle where it binds with CO2 to produce urea (CO(NH)2)

50
Q

Where is the cardiovascular control centre?

A

Medulla oblongata

51
Q

State the receptors that detect changing pH of the blood and changes in blood pressure

A

. Chemoreceptors detect changes in pH

  1. Baroreceptors detect changes in blood pressure
52
Q

Describe how heart rate is controlled with increasing blood pressure.

A
  1. Increased blood pressure detected by baroreceptors
  2. Signal sent to medulla in the brain
  3. Parasympathetic nervous system is activated releasing acetylcholine
  4. Causing reduced depolarisation at SAN
  5. Reduced heart rate to reduce pressure in the arteries
53
Q

Describe how heart rate is controlled with increasing levels or exercise.

A
  1. Increased exercise causes increased CO2 and lactic acid from respiration causing decrease in blood pH
  2. Decreased blood pH detected by chemoreceptors
  3. Signal sent to medulla in the brain
  4. Sympathetic nervous system activated releasing noradrenaline
  5. Causing Increased depolarisation at SAN
  6. Increased heart rate to get more oxygen around the body faster and remove CO2/lactic acid faster
54
Q

Explain the effects that adrenaline has on heart rate.

A
  1. Adrenaline has a similar structure to noradrenaline- can act to increase depolarisation at SAN directly.
  2. Increased adrenaline in the blood can also be detected by medulla which activates the sympathetic nervous system causing release of noradrenaline
  3. Both result in increased depolarisation at SAN which causes an increase of heart rate.
55
Q

State the photosynthetic pigment in rods and cones

A
  1. Rods: Rhodopsin - Doesn’t discriminate colour (black and white vision)
  2. Cones: Iodopsin - Discriminates colour
56
Q

Explain the difference between inhibitory and excitatory neurotransmitters at the postsynaptic cell

A
  1. Inhibitory - Binding of neurotransmitter causes Cl- ion channels to open, Cl- diffuses in and causes hyperpolarisation.
  2. Excitatory - Binding of neurotransmitter causes Na+ ion channels to open, Na+ diffuses in and causes depolarisation.
57
Q

Describe the cell surface membrane of an axon

A
  1. They have a phospholipid bilayer
  2. sodium-potassium pump
  3. Voltage gated sodium ion channels
  4. voltage gated potassium ion channels
58
Q

Explain the term positive feedback

A

Positive feedback in Homeostasis is rare but it is when changes are detected and stimulate a response that causes further change. An example of positive feedback occurs in the formation of action potentials in nerves, where a small increase in membrane permeability stimulates further increases.

59
Q

Describe what happens in negative feedback

A

Changes are detected and effectors are stimulated and respond to oppose the change. Once equilibrium has been restored the sensory receptors detect this and communicate with the effectors to halt the response.

60
Q

What is the Endocrine system?

A
  1. Composed of a series of endocrine glands which are groups of specialised cells which secrete hormones.
  2. The hormones are secreted directly into the bloodstream
61
Q

What are Exocrine glands ?

A

Secrete chemicals via ducts into organs or the surface of the body

62
Q

Examples of peptide (non lipid soluble) hormones?

A
  1. TSH
  2. Insulin
  3. Growth hormone
  4. Glucagon
  5. Oxytocin
63
Q

Examples of steroid ( lipid soluble) hormones?

A
  1. Female sex steroids (estrogens)
  2. Make sex steroids (androgens)
    eg:
    testosterone and oestrogen
64
Q

Describe Phototropism

A

Light causes auxin to distribute unevenly cells away from light have a higher auxin concentration so elongate more causing the shoot to bend towards the light

65
Q

Define Synergism

A

When hormones compliment toegther and work together and a greater response as a result is achieved

66
Q

Define Anatgonism

A

When hormones work opposite to each other and have a balancing effect

67
Q

Describe Seed Germination

A
  1. The embryo absorbs water and swells.
  2. This causes the embryo to produce gibberellins which diffuse to the aleurone layer.
  3. This causes stored protein to convert into hydrolytic enzymes (amylase).
  4. The amylase digests the starch reserves in the endosperm.
  5. Maltose can then be transported into the embryo for cellular respiration
68
Q

What are day neutral plants

A

They flower when they are mature enough and day/night length does not matter or effect the plants growth.

69
Q

Define photoperiod

A
  1. The length of the period of light and dark.
70
Q

How are phytochromes involved in flowering?

A
  1. Phytochromes cause chemical changes that affect gene expression. Pfr acts as a transcription factor to stimulae or inhibit the transcriptio process. Florigen is produced and mrna is synthesised
71
Q

What is etiolation?

A
  1. Etiolation is a survival mechanism due to an absence of light.
  2. Characteristics include:
    a) Rapid stem lengthening but little thickening
    b) little root growth
    c) minimal/no leaf growth
    d) Little/no chlorophyll
    e) All phytochrome synthesised is in the pfr form
72
Q

What happens when the shoot breaks through in Etiolation?

A
  1. The stem straightens
  2. Elongation of the stem slows down
  3. The first leaves open
  4. Chlorophyll forms and the seedling begins to photosynthesise

As the stem breaks through the soil; pfr acts as transcription factor for the plant to flower

73
Q

What is the mammalian nervous system composed of ?

A
  1. The Central nervous system ( Brain + Spinal cord)

2. The peripheral nervous system (voluntary system and autonomic system)

74
Q

What is the autonomic system composed of?

A
  1. Sympathetic and Parasympathetic system
75
Q

Key thing to note about the sympathetic and parasympathetic system?

A

They act in antagonism

76
Q

Draw the structure of a cross section of the spinal cord

A

see image

77
Q

What is a Bipolar neurone?

A

Found in the retina

78
Q

What is a Motor neurone?

A

Communicates from CNS to effectors by long axons

79
Q

Draw the structure of a neurone

A

see image

80
Q

What is a synapse?

A

The junction between two neurones. The presynaptic cell releases chemicals when impulses arrive which can stimulate impulses in the postsynaptic cell

81
Q

How do synapses work?

A
  1. Action potentials arrive at the presynaptic neuron
  2. Calcium ion channels open in response and calcium ions diffuse into the neurone.
  3. These calcium ions cause synaptic vesicles to fuse with the presynaptic membrane and the neurotransmitters are released.
  4. Neurotransmitter diffuses across the synaptic cleft.
  5. Neurotransmitter binds to receptors on the postsynaptic membrane
  6. This may generate an action potential in the postsynaptic cleft and depolarisation occurs.
82
Q

What are the two types of Neurotransmitters

A

Acetylcholine and Noradrenaline

83
Q

What are Excitatory postsynaptic potentials (EPSP)

A

Opening of Na+ ion channels reduces the PD closer to the threshold potential, making an action potential more likely.

84
Q

What are Inhibitory postsynaptic potentials (IPSP)

A

Postsynaptic membrane is hyperpolarised, moving further from the threshold and making an action potential less likely

85
Q

Define the Refractory period

A

A brief period following the passage of an action potential by which the neurone is no longer excitable. The refractory period is roughly 5-10 milliseconds in total. It prevents overstimulation and the back flow of an action potential.

86
Q

How can the drug Nicotine affect the synpases and nervous system?

A
  1. Synapses in the brain and peripheral nervous system have synapses that have nicotinic acetlylcholine (ACh) receptors;
    which are normally stimulated by acetlycholine but also respond when nicotine binds.
  2. This can cause increased heart rate and blood pressure due to nerves being stimulated. In the brain it results in dopamine being released.
87
Q

How can the drug Lidocaine affect the synpases and nervous system?

A
  1. Lidocaine is an anaesthetic that prevents impulses from being conducted along nerve fibres responsible for causing pain sensations.

Mechanism:

  1. Blocks Na+ ion channels in the postsynaptic membrane.
  2. Na+ ions cannot enter the ell when neurotransmitter binds.
  3. Action potentials cannot form in the postsynaptic cell
88
Q

How can the drug Cobra venom affect the synpases and nervous system?

A
  1. Cobra venom affects synapses to cause paralysis. In some cases it can be fatal.

Mechanism:

  1. Binds to acetylcholine receptors
  2. Prevents binding of neurotransmitter
  3. Postsynaptic membrane not stimulated to depolarise
89
Q

Characteristics of Rods

A
  1. More sensitive to light than cones
  2. No colour
  3. Detect Dim light
  4. Rhodopsin is the photosynthetic pigment
  5. Low acuity
  6. Located in the periphery
90
Q

Characteristics of Cones

A
  1. Less sensitive to light than rods
  2. colour
  3. Detect bright light
  4. Iodopsin is the photosynthetic pigment
  5. Higher acuity
  6. Located in the fovea
91
Q

What causes high acuity of cones and low acuity of rods

A
  1. Several rod cells are connected to one bipolar neurone and optic nerve and synapse (convergence) so the brain wouldnt be able to tell which cell received light ( low acuity)
  2. One cone cell is connected to one bipolar neurone and optic nerve fibre so higher acuity
92
Q

Why are cone cells less sensitive than rods?

A

The photosynthetic pigment iodopsin is less sensitive to light than the rhodopsin in rods. In addition, a single cone cell affects a single bipolar cell.

93
Q

What is meant by acuity?

A

The level of detail seen and the ability to distinguish between two close points

94
Q

Explain the difference in visual acuity between rods and cones.

A
  1. Rods have a poor visual acuity and cones have a good visual acuity
  2. Cones synapse with 1 optic nerve fibre
  3. When multiple cones stimulated each generated an individual impulse- easy to distinguish between points
  4. Multiple rods synapse at 1 optic nerve fibre this is called convergence
  5. Multiple rods stimulated on the same nerve fibre only generate 1 impulse-difficult to distinguish between points.
95
Q

What is rhodopsin?

A

Rhodopsin is the light-sensitive pigment found in rods that detects light and initiates action potentials. It is composed of opsin and retinal.

96
Q

Describe the changes in a rod cell that would be caused by light

A
  1. Retinal would be converted from the 11- cis isomer to the all- trans isomer by light and break away from opsin.
  2. Opsin would cause Na+ to be blocked and the cell would become hyperpolarised.
  3. This would prevent inhibitory neurotransmitter release and allow the bipolar cell to stimulate the sensory nerve fibre to produce action potentials
97
Q

What happens to the rod cells in darkness?

A
  1. Na+ ions diffuse into rod through open channels
  2. Na+ ions actively pumped out of the rod cell but leakage of Na+ back into the cell causes partial depolarisation.
  3. This allows secretion of a neurotransmitter which inhibits depolarisation of the bipolar neurone.
98
Q

What nervous system is responsible for control of heart rate?

A

The autonomic nervous system

99
Q

Where are chemoreceptors and baroreceptors located?

A

The carotid and aeortic bodies

100
Q

Explain how the Sinoatrial node (SAN) ensures that Oxygenated blood enters the aorta

A
  1. The sinoatrial node generates an impulse.
  2. This causes the atria to contract.
  3. Forcing oxygenated blood into the left ventricle.
  4. Electrical activity from the sinoatrial node is received by the atrioventricular node and makes its way up the bundle of his/purkinje fibres.
  5. Causing left ventricle to
    contract forcing blood into the aorta

Biology Paper 1 (17 decks)

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