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Separate Biology Edexcel GCSE > Topic 2 - Cells And Control > Flashcards

Topic 2 - Cells And Control Flashcards

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1
Q

What is the cell cycle?

A

A series of events that take place in a cell involving cell growth, DNA replication and cell division

It is the lifecycle of a cell

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2
Q

State the three stages of the cell cycle

A

Stage 1 = interphase
Stage 2 = mitosis
Stage 3 = cytokinesis

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3
Q

What is interphase?

A

The longest stage of cell cycle that involves cell growth, the synthesis of new organelles and DNA replication

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4
Q

What does DNA replication involve?

A
  • double helix unzips exposing two strands
  • DNA bases align next to complementary bases on the DNA strands
  • complementary bases liars join
  • two indentical DNA molecules formed
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5
Q

What is a chromosome

A

A linear DNA molecule tightly coiled around proteins

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6
Q

What happens to chromosomes during DNA replication?

A

The DNA in the arm of each chromosome ( chromatid ) is replicated

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7
Q

What is mitosis ?

A

A form of cell division that produces two diploid daughter cells , both genetically identical to the parent cell

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8
Q

Why is mitosis important in organisms?

A
  • asexual reproduction
  • growth
  • repair damaged cells
  • cell replace,ent
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9
Q

4 stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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10
Q

What is prophase?

A
  • DNA condenses
  • chromosomes become visible
  • nuclear membrane disappears
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11
Q

What is metaphase?

A
  • chromosomes line up along the cell equator
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12
Q

What is anaphase?

A
  • spindle fibres attach to each chromosome
  • chromatids pulled to opposite poles
  • chromoatdis separate
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13
Q

What is telophase?

A
  • nucleus of the cell divides
  • new membrane forms around each set of chromosomes
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14
Q

What does cytokinesis involve?

A
  • division of the cell ember and and cytoplasm
  • two genetically identical daughter cells
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15
Q

A cell divides by mitosis once every 2 minutes. Calculate the number of identical cells after 10 mins ?

A

10/2 = 5
2^5
32 cells

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16
Q

What is cancer?

A
  • non communicable disease
  • uncontrolled cell division ( due to damages DNA ) results in the formation of a primary tumour
  • tumour cells break off and spread to their tissues forming secondary tumours
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17
Q

What are percentile charts?

A

A chart used to monitor growth
Measurements can be compared to the expected values ata certain age

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18
Q

What does 95th percentile mean?

A

95% of measurements will be below the value of the 95th percentile

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19
Q

What can doctors determine form percentile charts?

A
  • slower growth than normal ( below the bottom line )
  • faster growth than normal ( above the top line)
  • abnormal growth ( irregular growth patterns)
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20
Q

Describe growth in animals

A
  • cell division occurs in all body cells. It occurs at a slower rate in adults than in younger animals as growth stops and cell division is only requires for replacement and repair
  • most cells differentiate at an early stage and become specialised. Some adult stem cells retain their ability to differentiate
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21
Q

Describe growth in plants

A
  • cell division can only occur in meristem tissue. The rate of cell division remains the same throughout a plants life.
  • meristem stem cells can differentiate into any cell type for as long as the plant lives
  • cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant
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22
Q

What are stem cells?

A

Cells that are unspecialised and capable of differentiating into a range of different cell types

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23
Q

What is differentiation?

A

The process by which stem cells become specialised

Some genes switch on or off determining cell type

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24
Q

Why is cell differentiation important?

A

It enables the formation of specialised tissues with specific functions

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25
Q

What are embryonic stem cells?

A

Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type

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26
Q

What is the function of embryonic stem cells ?

A

Enables the growth and development of tissues in human embryos

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27
Q

What are adult stem cells?

A

Stem cells that can differentiate into a limited range of cell types - bone marrow stem cells

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28
Q

What is the primary function of adult stem cells?

A

Replacement of dead cells - replacement of red blood cells which only live for 120 days

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29
Q

Where are stem cells found in plants ?

A

Meristems

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30
Q

Where is meristem tissue found?

A

In regions of the plant where cells are continuously dividing- root tips, shoot tips

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31
Q

What are meristematic stem cells?

A

Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant

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32
Q

How can stem cells be used in medicine ?

A
  • stem cells collected
  • stem cells stimulated to differentiate into specific cell types
  • specialised cells transplanted into the patient
  • used to treat damage or disease - heart disease
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33
Q

Where can embryonic stem cells be collected from?

A
  • donor stem cells removed from embryos
  • patient’s own stem cells removed from the umbilical blood before birth
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34
Q

What are the befits of using stem cells in medicine?

A

Treat damage of diseases ( heart disease , type 1 diabetes)
Treat diseases that would otherwise be untreatable
Used in scientific research
Growing organs for transplants

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35
Q

What are the risks of stem cell use in medicine?

A
  • transplanted stem cells could cause tumours
  • finding suitable stem cell donors is difficult
  • stem cells may be rejected by the body
  • potential side effects
  • long term risks are unknown
  • stem cells may become contaminated during preparation making patients sicker
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36
Q

What are the ethical issues related to the use of stem cells in medicine?

A

The embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of potential human life

May lead to reproductive cloning of humans

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37
Q

What is the central nervous system?

A

Brain and spinal chord

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38
Q

What is the spinal chord?

A

A long thin structure composed of neurones that extend from the medulla oblongata down the spine

39
Q

What is the function of the spinal chord ?

A

Connects the peripheral nervous system ( nerves outside the CNS ) to the brain

40
Q

Describe the structure of the brain

A

Three main regions -
- cerebrum
- cerebellum
- medulla oblongata

41
Q

Describe the structure of cerebrum

A

Largest region of the brain
Divided into two hemispheres

42
Q

What is the function of the cerebrum ?

A

Involved in
- intelligence
- language
- memory
- emotion
- visual and sensory process

43
Q

What is the function of each cerebral hemisphere ?

A
  • left hemisphere receives sensory information from the right side of the body and controls muscle coordination on the right
  • right hemisphere receives sensory information from the left side of the body and controls muscle coordination on the left
44
Q

Where is the cerebellum located?

A

Lower region of the brain

45
Q

What is the function of the cerebellum?

A

Involved in
- coordination of muscles
- voluntary movement ( walking )
- non voluntary movement ( balance )

46
Q

What is the function of the medulla oblongata?

A

Controls automatic processes in the body - breathing rate, heart rate

47
Q

What methods other than surgery are used by doctors to observe the brain?

A

CT scan
PET scan

48
Q

What is a CT scan?

A

A procedure that used x - rays to produce 3D cross sectional images of the brain

49
Q

Describe how CT scans are useful to investigate brain function

A
  • CT scans shows damaged regions of the brains - areas of swelling , bleeding
  • observations of the patient’s symptoms can enable scientists to determine the function of the damaged region
50
Q

What does a PET scan involve?

A

Radioactive substance injected into a patient’s bloodstream and taken up by tissues in the brain

Radiation emitted by tissues detected, enabling the identification of active and inactive regions of the brain

51
Q

Describe how PET scans are useful to investigate brain function?

A

Show which areas of the brain are active and which areas are not

Comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine the functions of inactive regions

52
Q

Why is it difficult to treat damage to the CNS?

A

Damage to neurones is permanent and cannot be repaired ( as nerve cells don’t divide by mitosis )

Hard to reach some areas of the brain

Risk of further permanent damage to other areas of the CNS during surgery

53
Q

What is the function of the nervous system ?

A

Allows an organism to rapidly react to environmental and internal change

54
Q

What are neurones?

A

Nerve cells adapted to quickly transmit nerve impulses. They are the functional units of the nervous system

55
Q

What is the function of the axon?

A

Carries impulses away from the cell body

Enables the transmission of nerve impulses over long distances

56
Q

What is the function of dendrites and dendrons?

A

Carry impulses towards the cell body

Dendrites provide a lathe surface area to receive impulses

57
Q

What is the role of the myelin sheath?

A

Electrically insulating layer

Surrounds the axon and increases the speed of impulses

58
Q

What is the function of a sensory neurone?

A

Carries impulses from receptors to the central nervous system

59
Q

Describe the structure of a sensory neurone

A
  • long dendrons carries impulses from receptors to the cell body
  • cell body found part way along the neurone
  • short axon carries impulses from the cell body to the CNS
60
Q

What is the function of a motor neurone?

A

Carries impulses from the CNS system to effectors

61
Q

Describe the structure of a motor neurones?

A
  • short dendrites carry impulses from the CNS to the cell body
  • cell body found at one end of the neurone
  • long axon carries impulses from the cell body to the effectors
62
Q

What is the function of a relay neurone?

A

Carries impulses from sensory neurones to motor neurones within the CNS

63
Q

Describe the structure of a relay neurone

A
  • short dendrites carry impulses from sensory neurones to the cell body
  • short axon carries impulses from the cell body to motor neurones
64
Q

Describe how the central nervous system coordinates a response to a stimulus

A
  • stimulus
  • sensory receptors detects stimulus
  • sensory receptors sends impulses along sensory neurone to CNS
  • CNS coordinates response
  • CNS sends information to effector along motor neurone
  • effector produces a response to the stimulus
65
Q

What is a synapse ?

A

A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters

66
Q

How are nerve impulses transmitted across a synapse?

A
  • nerve impulse reaches a presynaptic neurone
  • this triggers the release of neurotransmitters
  • neurotransmitters diffuse across the synapse
  • they bind to receptors on the postsynaptic neurone
  • this stimulates an impulse in the postsynaptic neurone
67
Q

Why do synapses slow down the transmission of nerve impulses?

A

It takes time for the neurotransmitters to diffuse across the synapse and bind to receptors on the postsynaptic neurone

68
Q

What is a reflex?

A
  • automatic response to a stimulus by the body
  • involuntary - does not involve conscious part of the brain
  • protective mechanism - a withdrawal reflex is initiated when a hit object is touched to prevent burns
69
Q

Describe the reflex arc

A

Stimulus - sensory receptors - sensory
Neurone - relay neurone - motor
- neurone - effector - response

70
Q

What is structure and function of the cornea?

A
  • transparent outer covering of the eye
  • refracts light entering the eye
71
Q

What is the function and structure of the iris?

A
  • pigmented ring of circular muscles and radial muscles
  • controls the size of the pupil to alter how much light enters the eye
72
Q

What is the pupil?

A

A hole in the iris centre that allows light rays to enter the eye

73
Q

What is the structure and function of the lens?

A
  • transparent bi convex structure
  • suspensory ligaments attach the lens to a ring of ciliary muscles
  • refracts light focusing it onto the retina
74
Q

What is the function of the ciliary muscles and suspensory ligaments ?

A

Change the shape of the lens to focus light onto the retina

75
Q

What is the structure and function of the retina?

A

-light sensitive layer composed of rods and cone cells
- converts light energy into neural signals which are sent to the brain via the optic nerve

76
Q

What are rod cells?

A

Cells in the retina that are sensitive to low light intensity ( dim light )

77
Q

What are cone cells?

A

Cells found in the retina that are sensitive to high light intensity ( bright light) and can detect different colours

78
Q

What is the function of the optic nerve ?

A

It transits nerve impulses to the brain from the retina

79
Q

Describe how dim light affect the size of the pupil

A
  • light receptors detect dim light
  • circular muscles relax
  • radial muscles contract
  • pupil dilates
  • more light enters the pupil
80
Q

Describe how bright light affects the size of the pupil

A
  • light receptors detect bright light
  • circular muscles contract
  • radial muscles relax
  • pupil contracts
  • less light enters the pupil
81
Q

Why is the iris reflex important?

A

It prevents bright light from damaging the retina

82
Q

What is accommodation?

A
  • process by which the elastic lens changes its shape ( with the aid of ciliary muscles and suspensory ligaments ) to focus on near or distant objects
  • light is focused onto the retina
83
Q

Describe how the eye focuses on near objects

A
  • ciliary muscles contract
  • suspensory ligaments slacken
  • lens become more convex
  • light is refacrcted more
  • light rays focused onto the retina
84
Q

Describe how the eye focuses on distant objects

A
  • ciliary muscles relax
  • suspensory ligaments tighten
  • lens becomes less convex
  • light is refracted less
  • light rays focused onto the retina
85
Q

What is long- sightedness?

A
  • can focus on distant objects clearly
  • cannot focus on near objects
86
Q

What are the causes of long sightedness?

A
  • eyeball is too short
  • lens is less elastic
  • light rays are not focused onto the retina , instead converging behind the retina
87
Q

How is long sightedness treated?

A
  • using a convex lens in glasses or contact lenses ( causes light rays to converge)
  • replacement lenses
  • laser eye surgery
88
Q

What is short sightedness?

A

Can focus on near objects clearly
Cannot focus on distant objects

89
Q

What are the causes of short sightedness

A
  • eyeball is too long
    • lens is too thick and too rounded
  • light rays are not focused onto the retina, instead converging in front of the retina
90
Q

How is short sightedness treated?

A
  • using a concave lens ( causes light rays to diverge ) in glasses or contact lenses
  • replacement lense s
  • laser eye surgery
91
Q

What are cataracts?

A
  • cloudy patch forms on the lens of the eye which negatively affects vision
  • vision becomes blurry, difficult to see the intensity of colours, problems with glare
92
Q

How are cataracts treated?

A

The clouded lens is exchanged for a synthetic lens during surgery

93
Q

What is colour blindness

A

A deficiency of the eye that makes it difficult to distinguish between colours

94
Q

What is the cause of colour blindness ?

A

Damage to cone cells in the retina

Separate Biology Edexcel GCSE (5 decks)

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