Cells and Control Flashcards
A student investigated mitosis in the root tip of a garlic plant.
Explain why the student used the tip of the root.
• contains meristem
• for growth
Describe how to use the microscope to obtain a clear image of the cells (2)
• switch lamp on
• use focusing wheel to obtain a clear image
Benefits of stem cells
• can form any type of cell / become specialised
• replace damage cells
• reduce symptoms of a medical condition
• used for cell transplants
Risks of stem cells
• new cells don’t function correctly
• stem cells continue to divide
• risk of side effects
Describe how cancer develops in the liver (2)
• mutations in DNA
• cell division is uncontrolled
• leading to tumour
Mitosis produces….
• 2 genetically identical cells
• diploid cells / 23 pairs (46)
• body cells
• involved in asexual reproduction
Meiosis produces..
• 4 genetically different daughter cells
• haploid cells
• gametes
• sexual reproduction
Prophase
• nuclear membrane breaks down (disappears)
• chromatids condense
• identical chromatids are joined
• spindle fibres form
Metaphase
• chromosomes line up along equator of cell
• spindle fibres attach to chromosomes at the centromere
Anaphase
• chromatids are pulled to edges of cell
• by spindle fibres
Telophase
• nuclear membrane forms around each sets of chromosomes
• separating them from one another
Cytokinesis
• splits cytoplasm
• to create two separate diploid cells
• each with identical chromosomes
Describe the function of a meristem in the growth of a plant (2)
• undifferentiated / are stem cells
• meristem cells divide / produce more cells
• by mitosis
Describe how to prepare a microscope using a sample of cells (3)
• use a thin layer of cells
• add a stain
• place a cover slip on top of sample
Explain how embryonic stem cells could be used to treat macular degeneration (eye defect in which retina cells breaks down)
• embryonic stem cells can be stimulated to produce cells of retina
• which can be transplated into a patient’s eye to replace damaged cells
State why mitosis is important in living things
• for growth
• for repair (of tissues/organs)
• for asexual reproduction
Describe why a brain tumour is difficult to treat
• brain is protected by skull
• nerves do not repair
• risk of damage to the brain
Describe how information detected by retina is transmitted to the brain
• information is transmitted as an electrical signal
• signal travels down a sensory neurone from the receptor to brain /
signal travels along optic nerve
Describe how light rays are focused to give normal vision
• light rays refract at cornea / by lens
• light rays converge on the retina / focal point is on the retina
Diverging lens
• diverge / spread out light rays
Lens
Causes of short-sightedness
• eyeball too long
• cornea too curved
• lens too curved
• light refracted too much by cornea/lens
• light rays not brought to a focus on retina
• light rats focused in front of retina
Causes of long-sightedness
• eyeball too short
• cornea not curved enough
• lens too thin
• light refracted too little by cornea or lens
• light rays not brought to a focus on retina
• light rays focused behind retina
Explain how a diverging lens corrects short-sightedness
• refracts light rays outwards
• so light rays meet/converge/focus on the retina
Explain how cataracts are currently treated
• laser eye surgery / removing lens
• replace with plastic lens
Advantages of using eye drops to treat cataracts
• less risk of eye infection
• less risk of permanent damage to eye
• less cost / easier to do / no recovery time needed
Explain how the size of the pupil changes when a torch is shone into eye of a person
• pupil gets smaller
• iris gets bigger
• circular muscles contract
• radial muscles relax
Describe how short/long-sightedness is corrected
• wear glasses / contact lens
Short-sightedness lens
• diverging / concave lens
Long-sightedness lens
• convex lens
Cone cells…
• detects coloured light
• send impulses to brain
Rod cells…
• detect intensity of light
• responds to dim light & responsible for night vision
• sends impulses to brain
Describe the changes that occur in the eye when a bright light is directed into the eye
• pupil becomes smaller
• iris changes shape
• light intensity detected by retina/rod/cones
In which part if the eye do cataracts form?
Lens
Explain why someone with cataracts sees a picture less clear
• lens becomes cloudy
• less light reaches retina
Function of optic nerve
carries impulses to brain
Function of iris
controls amount of light entering eye
Which structure of the eye contains light receptor cells?
Retina
The optic nerve transfers electrical signals from the eye to the…
central nervous system.
The optic nerve is a…
Sensory neurone
Name the region of CNS responsible for vision
Cerebrum
Which part of the brain contains occipital lobe?
Cerebral hemispheres
When the eye changes from focusing on a distant object to focusing on a near object…
the lens gets thicker to bend light rays more
State why people who short-sighted cannot see distant objects clearly
• eyeball is too long
• light rays meet in front of the retina
Describe how an impulse passes from the relay neurone to the motor neurone (3 marks)
• impulse in relay neurone triggers release of a chemical
• neurotransmitter diffuses
• across the synapse
• new impulse triggered in motor neurone
Explain the function of a reflex arc
• a process that occurs in response to danger
• so there is a quick reaction
• protects body from hand —> pulling hand fast away from fire
The gap between two neurones is called…
Synapse
Explain how the reactions of a person are affected by alcohol
• slows down reaction time
• reduces transmission across synapses/reduced neurotransmission
Explain why myelination is needed on motor neurones but not on neurones in brain
• myelination speeds up impulses
• motor neurones transmit information from CNS
• motor neurones transmit information over a greater distance than neurones in brain
Explain how a signal is transmitted at a synapse (6 marks)
• neurones transmit electrical impulses
• synapse is a gap between 2 neurones
• triggering the release of neurotransmitters
• which diffuse across the synapse
• as a chemical signal
• neurotransmitters bind to receptors on the next neurone
• triggering an electrical impulse in the next neurone
Explain how painkillers reduce the pain felt by a person
• prevent neurotransmitters binding to receptors in the next neurone
• electrical impulse not triggered
• signal is not received by the CNS
• person does not feel pain
Explain how impulses are transmitted at synapses (4 marks)
• synapse is a gap between neurones
• electrical impulse stimulates the release of chemical
• neurotransmitters diffuse across synapse (gap)
• stimulates an electrical impulse in next neurone
Role of sensory neurones (2)
• transmit electrical impulses
• from receptors to CNS / brain / spinal cord / relay neurone
