Cells and Control

Question 1

A student investigated mitosis in the root tip of a garlic plant.
Explain why the student used the tip of the root.

Answer 1

• contains meristem
• for growth

Question 2

Describe how to use the microscope to obtain a clear image of the cells (2)

Answer 2

• switch lamp on
• use focusing wheel to obtain a clear image

Question 3

Benefits of stem cells

Answer 3

• can form any type of cell / become specialised
• replace damage cells
• reduce symptoms of a medical condition
• used for cell transplants

Question 4

Risks of stem cells

Answer 4

• new cells don’t function correctly
• stem cells continue to divide
• risk of side effects

Question 5

Describe how cancer develops in the liver (2)

Answer 5

• mutations in DNA
• cell division is uncontrolled
• leading to tumour

Question 6

Mitosis produces….

Answer 6

• 2 genetically identical cells
• diploid cells / 23 pairs (46)
• body cells

• involved in asexual reproduction

Question 7

Meiosis produces..

Answer 7

• 4 genetically different daughter cells
• haploid cells
• gametes

• sexual reproduction

Question 8

Prophase

Answer 8

• nuclear membrane breaks down (disappears)
• chromatids condense
• identical chromatids are joined
• spindle fibres form

Question 9

Metaphase

Answer 9

• chromosomes line up along equator of cell
• spindle fibres attach to chromosomes at the centromere

Question 10

Anaphase

Answer 10

• chromatids are pulled to edges of cell
• by spindle fibres

Question 11

Telophase

Answer 11

• nuclear membrane forms around each sets of chromosomes
• separating them from one another

Question 12

Cytokinesis

Answer 12

• splits cytoplasm
• to create two separate diploid cells
• each with identical chromosomes

Question 13

Describe the function of a meristem in the growth of a plant (2)

Answer 13

• undifferentiated / are stem cells
• meristem cells divide / produce more cells
• by mitosis

Question 14

Describe how to prepare a microscope using a sample of cells (3)

Answer 14

• use a thin layer of cells
• add a stain
• place a cover slip on top of sample

Question 15

Explain how embryonic stem cells could be used to treat macular degeneration (eye defect in which retina cells breaks down)

Answer 15

• embryonic stem cells can be stimulated to produce cells of retina
• which can be transplated into a patient’s eye to replace damaged cells

Question 16

State why mitosis is important in living things

Answer 16

• for growth
• for repair (of tissues/organs)
• for asexual reproduction

Question 17

Describe why a brain tumour is difficult to treat

Answer 17

• brain is protected by skull
• nerves do not repair
• risk of damage to the brain

Question 18

Describe how information detected by retina is transmitted to the brain

Answer 18

• information is transmitted as an electrical signal
• signal travels down a sensory neurone from the receptor to brain /
signal travels along optic nerve

Question 19

Describe how light rays are focused to give normal vision

Answer 19

• light rays refract at cornea / by lens
• light rays converge on the retina / focal point is on the retina

Question 20

Diverging lens

Answer 20

• diverge / spread out light rays

Question 21

Lens

Question 22

Causes of short-sightedness

Answer 22

• 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

Question 23

Causes of long-sightedness

Answer 23

• 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

Question 24

Explain how a diverging lens corrects short-sightedness

Answer 24

• refracts light rays outwards
• so light rays meet/converge/focus on the retina

Question 25

Explain how cataracts are currently treated

Answer 25

• laser eye surgery / removing lens • replace with plastic lens

Question 26

Advantages of using eye drops to treat cataracts

Answer 26

• less risk of eye infection • less risk of permanent damage to eye • less cost / easier to do / no recovery time needed

Question 27

Explain how the size of the pupil changes when a torch is shone into eye of a person

Answer 27

• pupil gets smaller • iris gets bigger • circular muscles contract • radial muscles relax

Question 28

Describe how short/long-sightedness is corrected

Answer 28

• wear glasses / contact lens

Question 29

Short-sightedness lens

Answer 29

• diverging / concave lens

Question 30

Long-sightedness lens

Answer 30

• convex lens

Question 31

Cone cells…

Answer 31

• detects coloured light • send impulses to brain

Question 32

Rod cells…

Answer 32

• detect intensity of light • responds to dim light & responsible for night vision • sends impulses to brain

Question 33

Describe the changes that occur in the eye when a bright light is directed into the eye

Answer 33

• pupil becomes smaller • iris changes shape • light intensity detected by retina/rod/cones

Question 34

In which part if the eye do cataracts form?

Answer 34

Lens

Question 35

Explain why someone with cataracts sees a picture less clear

Answer 35

• lens becomes cloudy • less light reaches retina

Question 36

Function of optic nerve

Answer 36

carries impulses to brain

Question 37

Function of iris

Answer 37

controls amount of light entering eye

Question 38

Which structure of the eye contains light receptor cells?

Answer 38

Retina

Question 39

The optic nerve transfers electrical signals from the eye to the…

Answer 39

central nervous system.

Question 40

The optic nerve is a…

Answer 40

Sensory neurone

Question 41

Name the region of CNS responsible for vision

Answer 41

Cerebrum

Question 42

Which part of the brain contains occipital lobe?

Answer 42

Cerebral hemispheres

Question 43

When the eye changes from focusing on a distant object to focusing on a near object…

Answer 43

the lens gets thicker to bend light rays more

Question 44

State why people who short-sighted cannot see distant objects clearly

Answer 44

• eyeball is too long • light rays meet in front of the retina

Question 45

Describe how an impulse passes from the relay neurone to the motor neurone (3 marks)

Answer 45

• impulse in relay neurone triggers release of a chemical • neurotransmitter diffuses • across the synapse • new impulse triggered in motor neurone

Question 46

Explain the function of a reflex arc

Answer 46

• a process that occurs in response to danger • so there is a quick reaction • protects body from hand —> pulling hand fast away from fire

Question 47

The gap between two neurones is called…

Answer 47

Synapse

Question 48

Explain how the reactions of a person are affected by alcohol

Answer 48

• slows down reaction time • reduces transmission across synapses/reduced neurotransmission

Question 49

Explain why myelination is needed on motor neurones but not on neurones in brain

Answer 49

• myelination speeds up impulses • motor neurones transmit information from CNS • motor neurones transmit information over a greater distance than neurones in brain

Question 50

Explain how a signal is transmitted at a synapse (6 marks)

Answer 50

• 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

Question 51

Explain how painkillers reduce the pain felt by a person

Answer 51

• 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

Question 52

Explain how impulses are transmitted at synapses (4 marks)

Answer 52

• 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

Question 53

Role of sensory neurones (2)

Answer 53

• transmit electrical impulses • from receptors to CNS / brain / spinal cord / relay neurone