Coordination Flashcards
Explain what is meant by the term transcription factor. (2)
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a protein (1) that will bind to a promoter region (1) of the gene (1) to activate protein synthesis
Weisel and Hubel studied the development of vision during the critical window (critical period) of various mammals.
In one investigation, kittens were used.
(i) Suggest why kittens were used to study the development of vision in humans. (1)
(ii) Suggest why the kittens used were all from one set of parents. (1)
(iii) Give one reason why some people believe that it is ethically unacceptable to use kittens in medical research. (1)
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(i) Kittens have a similar visual system (1) compared to humans which make them suitable to study the development of vision in humans.
(ii) to reduce genetic variation (1)
(iii) aminals cannot provide consent (1)
Describe what happens to the visual pigment in a rod cell when stimulated by light. (2)
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When light is present, rhodopsin absorbs the light which converts cis-retinal into trans-retinal (1). This causes opsin and retinal (1) to split, meaning that the rhodopsin is bleached (1).
A kitten had its right eye covered for the first seven weeks after birth. The right eye was then uncovered. The left eye was not covered. After seven weeks the visual cortex of this kitten was studied.
Explain what happens to the visual cortex when the right eye of this kitten is covered for the first seven weeks after birth. (3)
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As there is no stimulus on the right eye of the kitten, less neurotransmitters (1) would be released as there are fewer electrical impulses which means that synapses are weakened (1). This means that the nerves in the right eye do not develop (1) which causes a difference between the left and right eye of the kitten.
The potential difference across the membrane of a neurone was investigated before and after stimulation. The table below shows the results of this investigation.
(i) Place a cross in the box that completes the following statement. The resting potential for this neurone is (1)
A – 80 mV B – 70 mV C 0 mV D + 30 mV
(ii) Using the information in the table, describe the changes in the potential difference from 1.00 ms to 1.50 ms. (2)
(iii) Suggest an explanation for the change in potential difference across the membrane between 1.00 ms and 1.50 ms. (5)
(iv) This neurone was given a second stimulus at 1.50 ms. This had no effect on the changes in the potential difference shown in the table.
Suggest reasons why the second stimulus had no effect on the changes in the potential difference. (2)
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(i) B (-70 mV) (1)
(ii) As time increases from 1-1.5ms, the potential difference increases by +100mV (1) from negative to positive (1).
(iii) When there is a stimulus, it excites the cell membrane of the neurone which causes the sodium ion channels to open (1). This means that the membrane becomes more permeable (1) to sodium ions which allows more sodium ions to diffuse into the axon (1) down the concentration (1) and electrochemical gradient. This causes the neurone to become less negative as there is an increase of sodium ions inside the neurone (1).
(iv) The second stimulus occurred during the absolute refractory period (1) and the resting potential has not been reestablished (1). Hence, the second stimulus had no effect on the potential difference.
Place a cross in the box next to the answer that correctly compares nervous coordination with hormonal coordination. (1)
A nervous coordination is faster and lasts for a longer time B nervous coordination is faster and lasts for a shorter time C nervous coordination is slower and lasts for a longer time D nervous coordination is slower and lasts for a shorter time
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B (nervous coordination is faster and lasts for a shorter time) (1)
Place a cross in the box below the diagram that shows the direction light takes when it stimulates a rod cell. (1)
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D (1)
Place a cross in the box next to the part of the rod cell that contains rhodopsin. (1)
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A (1)
Place a cross in the box next to the description of what happens when a molecule of rhodopsin is bleached by light. (1)
A opsin changes to retinal B retinal changes to opsin C trans-retinal changes to cis-retinal D cis-retinal changes to trans-retinal
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D (cis-retinal changes to trans-retinal) (1)
Bleaching of rhodopsin leads to hyperpolarisation of the rod cell membrane. Place a cross in the box next to the description of what happens during hyperpolarisation. (1)
A sodium ion channels close while the sodium ion pump stops working B sodium ion channels close while the sodium ion pump continues to work C sodium ion channels open while the sodium ion pump continues to work D sodium ion channels open while the sodium ion pump stops working
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B (sodium ion channels close while the sodium ion pump continues to work) (1)
Coordination in plants involves IAA (auxin). In an experiment, 25 mm lengths of stem were cut and placed in five dishes. A different concentration of IAA was added to each dish. The dishes were left for 24 hours and the mean increase in stem length was recorded. The results are shown in the table below.
(i) Use the information in the table to describe the effect of IAA concentration on the mean increase in stem length. (2)
(ii) Suggest one other variable that needs to be controlled in this experiment. (1)
(iii) It is important that the calculated means are reliable. Using the information in the table, state the mean result that is the least reliable. Give a reason for your answer. (1)
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(i) As IAA concentration increases, the overall mean increase in stem length increases (1). From 0-0.1 mg dm-3, there is a mean decrease in stem length. From 0.1 mg dm-3 and onwards, there is a mean increase in stem length. This means that elongation only occurs at a greater concentration than 0.1 mg dm-3 (1).
(ii) temperature (1)
(iii) dish 4 as the SD is the greatest (1)
The diagram below shows the structure of a motor neurone.
Place a cross in the box next to the part of the neurone labelled T. (1)
A dendrite B node of Ranvier C Schwann cell D synapse
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B (node of Ranvier) (1)
The graph below shows changes in the membrane potential during the transmission of an impulse along the axon of a motor neurone.
(i) Place a cross in the box next to the description of the membrane potential at 0.75 ms on the graph. (1)
A depolarised B hyperpolarised C polarised D repolarised
(ii) Explain how the structure of this motor neurone affects the speed of the impulse along the axon. (2)
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(i) A (depolarised) (1)
(ii) The motor neurone has a myelin sheath (1) which acts as an electrical insulator around the axon. It has tiny gaps known as the nodes of Ravier. Electrical impulses jump from node to node (1) (saltatory conduction) which allows the speed of impulses to be quick (1) along the axon.
The skin of this frog produces a poison that affects sodium ion channels in the axon membrane of a neurone. The poison causes these channels to stay open.
(i) Explain the effect the poison has on the ability of a neurone to transmit impulses. (4)
(ii) Suggest why the neurones of the golden poison frog are not affected if they come into contact with the poison. (2)
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(i) As the sodium ion channels remain open, sodium ions diffuse (1) into the axon down the concentration (1) and electrochemical gradient. This causes the inside of the neurone to become less negative than -70mV as there are more sodium ions present, which leads to depolarisation (1). This means that if the threshold level is reached, the inside of the neurone would become positive (to +40mV). However, as polarisation requires sodium ion channels to be closed, polarisation would never occur, meaning that action potentials would not be generated (1) as the resting potential cannot be reestablished (1).
(ii) The sodium ion channels of golden poison frog are different (1) from other frogs as the poison cannot bind to the sodium ion channels (1).
In one investigation, a coleoptile was exposed to light from one direction. The diagram below shows the appearance of the coleoptile before and after exposure to light from one direction.
Place a cross in the box next to the correct description of the response of this coleoptile after exposure to light from one direction. (1)
A negative phototropism to light shining from the left B negative phototropism to light shining from the right C positive phototropism to light shining from the left D positive phototropism to light shining from the right
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C (positive phototropism to light shining from the left) (1)
Explain what is meant by the term active transport. (2)
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the movement of particles from a low area of concentration to a high area of concentration (1) (against the concentration) through carrier proteins using energy obtained from the hydrolysis of ATP (1)
Suggest what happens to cells in the plant, after the breaking of these hydrogen bonds between adjacent cellulose microfibrils, that allows the response to light from one direction. (2)
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Cells in the plant elongate by breaking hydrogen bonds between the cellulose molecules in the cell wall of the plant cell which causes water to move (1) into the plant cell via osmosis (1). This increases the turgor pressure within the cell which therefore causes elongation (1) and therefore causes bending of the shoot towards the light.
Scientists also investigated the effect of IAA concentration on the elongation of coleoptiles. Coleoptile sections of the same length were placed in Petri dishes containing IAA solutions of different concentrations. The change in length was measured. The graph below shows the percentage change in length when compared to control coleoptile sections placed in water.
(i) Use the information in the graph to describe the effect of IAA concentration on the elongation of coleoptiles. (3)
(ii) The method used by the scientists made sure that a valid comparison could be made from the data collected. Suggest a method the scientists could use to make a valid comparison of the elongation of coleoptiles at each IAA concentration. (4)
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Describe how the resting potential is maintained in a neurone. (3)
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The resting potential (-70mV) is maintained by 2 mechanisms: sodium-potassium pump and facilitated diffusion of potassium ion channels. The sodium-potassium pump (1) actively transports potassium ions into the neurone and sodium ions out of the neurone using energy obtained from hydrolysis of ATP. Using facilitated diffusion, potassium ions can diffuse back out of the neurone, down the concentration gradient (1). As sodium ions cannot diffuse back into the axon (1), polarisation (resting potential) is maintained.
The effect of temperature on the duration of the refractory period was investigated. The table below shows the results of this investigation.
Use the data in the table to describe the effect of temperature on the duration of the refractory period. (2)
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As temperature increases, the mean refractory period decreases. Comparing 29ºC to 35ºC, there is a 1.6ms difference in the mean duration of the refractory period (1). Additionally, as temperature increases, the SD decreases.
A severe head injury can damage the brain and lead to epilepsy.
Epilepsy involves a sudden increase in the electrical activity of neurones in the brain. This can cause uncontrolled shaking due to the repeated contraction
of muscles.
Carbamazepine is a drug used to treat epilepsy.
In an investigation, scientists stimulated neurones in a control solution and immediately measured the potential difference across the axon membrane.
They repeated this using neurones in a solution containing carbamazepine. The table below shows the results of this investigation.
Use the information in the table to suggest how carbamazepine is able to treat epilepsy. (4)
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Carbamazepine binds to sodium ion channels (1) on the pre-synaptic membrane which inhibits sodium ions from diffusing (1) into the pre-synaptic knob. The means that depolarisation (1) does not occur since action potentials (1) in the post-synaptic neurones would not be triggered. Hence, this reduces muscle contraction (1) and therefore treat epilepsy.
Krabbe disease is an inherited condition caused by a mutation of the GALC gene. The neurones in people with Krabbe disease gradually lose their myelin sheaths.
Galactosylceramidase is an enzyme involved in maintaining the myelin sheath in neurones.
The dominant allele of the GALC gene is involved in the synthesis of galactosylceramidase.
(a) Describe how the GALC gene is transcribed in the synthesis of galactosylceramidase. (4)
(b) Suggest how the transmission of a nerve impulse is affected by Krabbe disease. (2)
(c) Krabbe disease can affect the function of different parts of the brain.
Complete the table by naming the part of the brain most likely to be affected by Krabbe disease. (2)
(d) Explain why two healthy parents can produce a child with Krabbe disease. (2)
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(a) DNA helicase breaks hydrogen bonds (1) between the bases of a specific part of the DNA and unzips it. Free RNA nucleotides pair up with the bases on one of the strands on the template strand (1) by complementary base pairing (1) (C-G, A-U), starting at the start codon. RNA polymerase links the RNA nucleotides together by condensation reaction which forms phosphodiester bonds (1) to form a strand called pre-mRNA. When the RNA polymerase (1) reaches a stop codon on the DNA, the RNA polymerase detaches the pre-mRNA. The pre-mRNA then undergoes splicing to form an mRNA (1).
(b) As Krabbe disease causes myeline sheaths to be gradually lost, saltatory conduction cannot occur in originally myelinated neurones which means that impulses can no longer travel from node to node (1). This means that the speed of transmission would decrease (1).
(c) loss of vision - cerebral hemisphere (1); difficulty in walking - cerebellum (1)
(d) Krabbe disease is a homozygous recessive disease which means that two healthy parents that are heterozygous (1) can produce a child that is homozygous recessive (1) at 25%.
Insecticides are widely used to reduce populations of insect pests such as locusts.
Pyrethrin is an insecticide produced naturally by chrysanthemum flowers found in East Africa.
(a) Pyrethrin is a neurotoxin that works by binding to protein channels in the membranes of insect neurones and delaying their closure.
Suggest why pyrethrin does not affect mammalian neurones. (2)
(b) High concentrations of some insecticides can affect the contraction of muscles that control pupil diameter in the human eye.
Explain why people who absorb high concentrations of these insecticides have pupils with a small diameter. (2)
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(a) Mammals have different protein channels (1) than insects which means that pyrethrin may not be able to bind (1) to the protein channels in mammals like insects.
(b) This is because the insecticides cause circular muscles to contract (1) and radial muscles to relax (1) which causes the pupil to constrict and hence causing the pupils to have a small diameter.
Sand flies are insects that spread a disease called leishmaniasis. This disease causes ulcers to develop in the skin, mouth and nose. Scientists investigated the effect of the concentration of pyrethrin and of an organochlorine insecticide on the survival of two species of sand fly, species A and species B. The graphs below show the results.
(a) Compare the effect of the insecticides on the survival of each species of sand fly. (3)
(b) Some insecticides also inhibit the synthesis of IAA (auxin) in plants. Suggest how this inhibition affects these plants. (2)
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(a) As the concentration of pyrethrin/organochlorine increases, the percentage of sand flies killed increases (1). For all concentrations of pyrethrin, the percentage of species A killed is greater than species B (1). For all concentration of organochlorine, the percentage of species B is greater than species A (1). All sand flies are killed using concentrations of pyrethrin greater or equal to 4.6μg per dm3, whereas all sand flies are killed using concentrations of organochlorine greater or equal to 5.4 μg per dm3 (1).
(b) This causes the plants to have more stunted growth (1) as there would be less positive phototropism for the plant to elongate (1) towards the light.
