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edexcel biology > Topic 2 - Cells And Control > Flashcards

Topic 2 - Cells And Control Flashcards

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1
Q

What is a chromosome?

A

-contains coils of DNA

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2
Q

What is a gene?

A
  • short section of DNA that codes for a protein
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3
Q

What is a gamete?

A
  • sex cell e.g. egg & sperm

- has 23 chromosomes ( half) each

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4
Q

What is a diploid cell?

A
  • full amount of chromosomes ( 46)
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5
Q

What is mitosis?

A
  • cell reproduces by splitting to form two genetically identical daughter/ diploid cells
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6
Q

Beginning Phase of mitosis

A

Interphase

- The DNA in chromosomes copies itself ready for mitosis.

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7
Q

1st phase of mitosis

A

Prophase

- chromosomes condense (shorter & fatter) - nucleus membrane breaks down and spindle appearrs

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8
Q

3rd phase of mitosis

A
  • Anaphase

- spindle pulls chromosomes to polar parts of cell & spindle fibres get short while pulling away

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9
Q

4th phase of mitosis

A

Telophase

- nucleus membrane reforms and chromosomes less condense and less visible and spindle disappears

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10
Q

last (sort of) phase of mitosis

A

Cytokenesis

- cell divides into two – mitosis now complete

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11
Q

How does cancer occur?

A
  • small change in cells that leads to uncontrolled cell division
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12
Q

What is a stem cell?

A

-undifferentiated cell which can undergo division to produce more similar cells

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13
Q

What is therapeutic cloning?

A
  • embryo produced with same genes as patient.
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14
Q

Types of stem cells

A
  • embryonic stem cells
  • adult stem cells (found in bone marrow)
  • meristems in plants
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15
Q

Benefits of stem cells

A
  • used to replace damaged or diseased body parts
  • use unwanted stem cells that may have been thrown away
  • further research into differentiation
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16
Q

Disadvantages of stem cells

A
  • hard to control stem cells to form desired cell
  • people have religious & ethical objections
  • expensive and time consuming
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17
Q

What is the CNS?

A
  • central nervous system – brain along w/ spinal cord

- controls conscience, movements, thoughts & emotions etc.

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18
Q

What is the cerebral hemisphere?

A
  • perform variety of functions, including consciousness, memory, intelligence & visual and sensory processing
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19
Q

What is the cerebellum?

A
  • structure found at bottom of brain, on rear side.

- responsible for muscle co-ordination, so can move in complex ways e.g. catching a ball

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20
Q

What is the medulla oblongata?

A
  • small ‘elongated’ structure found at base of the brain.

- responsible for basic autonomic (automatic) bodily functions e.g. breathing, digestion, swallowing and sneezing.

21
Q

What is a CT scan?

A
  • fire X-Ray radiation at brain from different angles to generate 3D image of the brain
  • used to examine bleeding within skull & damage to brain structure
  • not recommended for pregnant woman or children- higher dose of radiation than X- ray
22
Q

What is a PET scan?

A
  • radioactive ‘tracer’ injected into blood before scan.
  • areas with greater blood flow, will be highlighted & tracer will build up
  • used for identifying cancerous tumours, because use more blood than normal tissue
23
Q

What is the nervous system?

A
  • allows us to react to surroundings & coordinate actions in response to stimuli.
24
Q

How does the nervous system work?

A
  • Receptor cells convert stimulus into electrical impulse.
  • electrical impulse travels along cells called sensory neurons to CNS
  • information processed and appropriate response is coordinated
  • then electrical impulse is sent along motor neurons to effectors.
  • effectors carry out the response e.g. muscles contracting
  • impulses travel from sensory, to relay and then motor neuron
25
Q

What is a reflex ?

A
  • Automatic responses that take place before you have time to think
  • they don’t travel through the brain
26
Q

Describe how a reflex works?

A
  • stimulus is detected by receptors.
  • Impulses sent along a sensory neuron– impulse passes to a relay neuron – then a motor neuron.
  • motor neuron passes impulse to an effector and effector stimulates a response
    e. g. moving hand away from hot surface
27
Q

What is a synapse?

A
  • gap between two neurons
28
Q

What is neurotransmitter?

A
  • When impulse reaches end of first neuron, a chemical is released into the synapse.
29
Q

How does a neurotransmitter work?

A
  • chemical released into the synapse.
    -neurotransmitter diffuses across the synapse.
  • When neurotransmitter reaches second neuron it triggers impulse to begin again in next neuron.
    – Different neurotransmitters have different effects on
    the frequency and speed of the impulse in the second neuron.
30
Q

What is the myelin sheath?

A
  • surrounds core of a nerve fiber or axon
31
Q

What is a retina?

A
  • Layer of light sensitive cells found at back of eye.
    When light hits cells are stimulated impulses sent to brain
    -interprets info to create image.
32
Q

What are rod and cone cells ?

A
  • found in retina
    Rod cells
  • sensitive to light – better for seeing in low light
    Cone cells
  • allow to interpret different colours (colour vision)
33
Q

What is the cornea?

A
  • see-through layer at front of eye.

- allows light through and curved surface bends (refracts) and focuses light onto retina

34
Q

What is the iris?

A
  • muscles that surround pupil

- contract or relax to alter size of pupil

35
Q

What are ciliary muscles and suspensory ligaments?

A
  • hold lens in place

- controls its shape & allows us to focus on objects nearer or further away

36
Q

What is the lens ( eye) ?

A
  • Transparent, curved surface on front of eye.

- like cornea, reflects light onto retina.

37
Q

What is short sightedness?

A
  • called myopia.
  • lens is too curved, distant objects appear blurry
  • need concave lens
38
Q

What is long sightedness?

A
  • called hyperopia.
  • lens is too flat, so it cannot refract light enough
  • need convex lens
39
Q

How to focus on a near object

A
  • ciliary muscles contract & suspensory ligaments loosen

- lens becomes thicker and more curved- this refracts light more

40
Q

How to focus on a distant object

A
  • ciliary muscles relax & suspensory ligaments tighten

- lens becomes thinner - light is refracted less.

41
Q

What is a cataract ?

A
  • clouding of the lens of the eye
42
Q

How to treat short and long sightedness?

A
  • concave lenses to spread out the light to treat myopia ( short sightedness)
  • convex lenses to bring the rays together to treat
    hyperopia ( long sightedness)
43
Q

How does laser eye surgery work?

A
  • used to reduce the thickness of the
    cornea -so it refracts light less- to treat short sightedness - used to change its curvature-so it refracts light more strongly- to treat long sightedness
44
Q

Examples of treatment for eyes?

A
  • laser eye surgery
  • wearing glasses or contact lenses
  • replacement lenses
45
Q

Explain cancer

A
  • it is as the result of changes in cells that lead to

uncontrolled cell division

46
Q

2nd phase of mitosis

A
  • Metaphase

chromosomes line up at the equator of the cell

47
Q

Function of the myelin sheath

A
  • insulates impulse from surrounding tissue

- speeds up transmission

48
Q

How is a red blood cell specialised

A
  • no nucleus - so can increase its oxygen carrying capacity
  • contains haemoglobin –to bind to oxygen
  • flexible and small – to get through capillaries

edexcel biology (8 decks)

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