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Gcse Biology > Topic 2 - Cell Cycle & Eye > Flashcards

Topic 2 - Cell Cycle & Eye 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 described as 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 the cell cycle that involves cell growth, the synthesis of new organelles (sub cellular structures) 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 based on the DNA strands
Complementary base pairs join
Two identical 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 chromosome during DNA replication?

A

The DNA in each chromatid is replicated.

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7
Q

What is mitosis?

A

A form of cell divisions 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 of damaged cells
Cell replacement

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9
Q

State the four stages of mitosis

A

Prophase
Metaphase
Anaphase
Telophase

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10
Q

Outline prophase

A

DNA condense, chromosomes become visible

Nuclear membrane disappears

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11
Q

Outline metaphase

A

Chromosome line up along the cell equator

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12
Q

Outline anaphase

A

Spindle fibres attach to each chromosome
Chromatids pulled to opposite poles
Chromatids separated

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13
Q

Outline telophase

A

Cell begins to separate

New membrane forms around each set of chromosomes

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14
Q

What does cytokinesis involve?

A

Division of the cell membrane and cytoplasm

Two genetically identical daughter cells produced

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15
Q

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

A
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16
Q

What is cancer?

A

Non-communicable disease
Uncontrolled cell division (due to damaged DNA) results in the formation of a primary tumour
Tumour cells breaks off and spread to other tissues forming secondary tumours

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17
Q

What are percentile charts?

A

A chart used to monitor growth

Measurements (e,g fetal length) can be compared to expected values at a certain age

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18
Q

What can doctors determine from percentile charts?

A

Slower growth than normal
Faster growth than normal
Abnormal growth

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19
Q

Describe growth in animals

A

Cell division occurs in all body cells. It occurs at a slower rate in adults that in younger animals as growth stops and cell division is only required for replacement and repair

Most cells differentiate at an early stage and become specialises. Some adult stem cells retain their ability to differentiate.

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20
Q

Describe growth in plants

A

Cell division can only occur in meristematic tissue. The rate of cell division remains the same throughout a plants life.

Meristematic stem cells can differentiate into any cell type for as long as plant lives.

Cell elongation occurs in all cells. Cells expand and enlarge, enabling growth of the plant.

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21
Q

What are stem cells?

A

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

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22
Q

What is meant by differentiation

A

The process by which stems cells become specialised (have a specific functions)
Some genes switch on or off, determining cell type

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23
Q

Why is cell differentiation important?

A

It enables the formation of specialised tissues with specific functions e.g muscle tissues

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24
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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25
Q

What is the function of embryonic stem cells?

A

Enable the growth and development of tissues in human embryos.

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26
Q

What are adult stem cells?

A

Stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells

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27
Q

What is the primary function of adult stem cells?r

A

Replacement of dead cells e,g replacement of red blood cells which only live for 120 days.

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28
Q

Where are stem cells found in plants?

A

Meristems

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29
Q

Where is meristem tissue found?

A

In region of the plant where cells are continuously dividing e,g root tips, shoot tips

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30
Q

Where 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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31
Q

How can stem cells be use in medicine?

A

Stem cells collected
Stem cells stimulated to differentiate into specific cell types e,g heart muscle cells
Specialised cells transplanted into the patient
Used to treat damage or disease e,g heart disease

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32
Q

Where can embryonic stem cells be collected from?

A

Donor stem cells removed from embryos grown in vitro

Patient’s own stem cells removed from the umbilical blood before birth

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33
Q

What are the benefits of using stem cells in medicine?

A

Treats damage or diseases e,g heart disease, Type 1 diabetes
Used in scientific research
Growing organs for transplants

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34
Q

What are the risks of stem cells use in medicine?

A

Transplanted stem cells could cause tumours
Finding suitable stem cell donors is a difficult task
Stems cells may be rejected by the body (immunosuppressive drugs may have be taken)
Potential side effects
Long terms risks of using stem cells unknown
Stem cells may become contaminated during preparation and when transplanted transmit infections to the patient, making them sicker.

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35
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 the reproductive cloning of humans.

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36
Q

What is the spinal cord?

A

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

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37
Q

What is the function of the spinal cord?

A

Connects the peripheral nervous systems (nervous outside of the CNS) to the brain

38
Q

Describe the structure of the brain

A

Cerebrum
Cerebellum
Medulla oblongata

39
Q
A 
A = cerebellum 
B = medulla oblongata 
C = cerebrum
40
Q

Describe the structure of the cerebrum

A

Largest region of the Brain

Divided into two hemispheres

41
Q

What is the function of the cerebrum?

A 
Intelligence 
Language 
Memory 
Emotions 
Visual and sensory process
42
Q

Where is the cerebellum located?

A

Lower regions of the brain

43
Q

What is the function of he cerebellum

A

Coordination of muscles
Voluntary movement
Non-voluntary movement

44
Q

What is the function of the medulla oblongata?

A

Controls automatic processes in the body e,g breathing rate, heart rate, peristalsis

45
Q

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

A

CT scan

PET scan

46
Q

Wha is a CT scan?

A

Uses X rays to produced 3D cross sectional image of the Brain

47
Q

Describe how CT scans are useful investigate brain function

A

CT scans show damaged regions of the brain e,g area of swelling, bleeding

Observations of the patients symptoms can enable scientists to determine the function of damaged region

48
Q

What does a PET scan involve?

A

Radioactive substances 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

49
Q

Describe how PET scans are useful to investigate brain function?

A

Show which areas of the brain are active and which are not
Comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine the functions of inactive regions.

50
Q

Why is it difficult to treat damage to the CNS?

A

Damaged 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 damaged to other areas of the CNS during surgery.

51
Q

What is the function of the nervous system?

A

Allows an organism to rapidly react to environmental and internal changes

52
Q

What are neurones

A

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

53
Q

What is the function of the axon

A

Carries imputes away from the cell body

Enables the transmission of nerve impulses over long distances

54
Q

What is the function of the dendrites and dendrons?

A

Carry impulses towards the cell body

Dendrites provide a large surface area to receive impulses

55
Q

What is the role of the myelin sheath?

A

Electrically insulating layer

Surrounds the axon and increases the speed of impulses

56
Q

Outline the functions of a sensory neurone

A

Carries impulses from receptors to central nervous system

57
Q

Describe the structure of a sensory neurone

A

Long dendron 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

58
Q

Outline the function of a motor neurone

A

Carries impulses from the central nervous system to effectors

59
Q

Describe the structure of a motor neurone

A

Short dendrites carry impulses from CNS to cell body
Cell body found at one end of neurone
Long axon carries impulses from cell body to the effectors.

60
Q

Outline the function of a relay neurone

A

Carries impulses from sensory neurones to motor neurones within the CNS

61
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

62
Q

Describe how central nervous system coordinates a response to a stimulus

A

Stimulus
Sensory receptor detects stimulus
Sensory receptor 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

63
Q

What is a synapse?

A

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

64
Q

How are nerve impulses transmitted across a synapse?

A

Nerve impulses reacts presynaptic neurone
This triggers the releases of neurotransmitters
Neurotransmitters diffuse across the synapse
They bind to receptors on the postsynaptic neurone
This stimulates an impulse in the postsynaptic neurone

65
Q

Why do synapse 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.

66
Q

What is a reflex?

A

Automatic response to a stimulus by the body
Involuntary - does not involve conscious part of the brain
Protective mechanisms e,g withdrawal reflex is initiated when a hot object is touched to prevent burns.

67
Q

Describe the reflex arc?

A
68
Q
A
69
Q

Outline the structure and function of the cornea

A

Transparent outer covering of the eye

Refracts light entering the eye

70
Q

Outline the structure and function 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

71
Q

What is the pupil?

A

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

72
Q

Outline the structure and function of the lens

A

Transparent, bi-convex structure
Suspensory ligaments attach the lens to a ring of ciliary muscle
Refracts light, focusing it onto the retina

73
Q

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

A

Change the shape of the lens (accommodation) to focus light onto the retina.

74
Q

Outline the structure and function of the retina

A

Light sensitive layer composed of rod and cone cells

Converts light energy into neural signals which are sent to the brain via optic nerve

75
Q

What are rod cells?

A

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

76
Q

What are cone cells?

A

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

77
Q

What is the function of the optic nerve?

A

It transmits nerve impulses to the brain from the retina

78
Q

Describe how dim light affects the size of the pupil

A 
Rods detect dim light 
Circular muscles relax 
Radial muscles contract 
Pupil dilated 
More light enters the pupil
79
Q

Describe how bright light affects the size of the pupil

A 
Cones detect bright light 
Circular muscles contract 
Radial muscles relax 
Pupil contracts 
Less light enters the pupil
80
Q

Why is the iris reflex important?

A

It prevents bright light from damaging the retina

81
Q

What is accommodation?

A

Process by which the elastic lens changes its shape (with aid of ciliary muscles and suspensory ligaments) to focus on near or distant objects.

Light is focused onto the retina

82
Q

Describe how the eye focuses on near objects

A 
Near object 
Ciliary muscles contract
Suspensory ligaments slacken
Lens becomes more convex (more rounded)
Light is refracted more 
Light rays focuses onto the retina
83
Q

Describe how the eye focuses on distance objects

A 
Distant object 
Ciliary muscles relax 
Suspensory ligaments tighten 
Lens becomes less convex (less rounded)
Light is refracted less
Light rays focused onto the retina
84
Q

What is long-sightedness?

A

Can focus on distance objects clearly

Cannot focus on near objects

85
Q

What are the causes of long-sightedness?

A

Eyeball is too short
Lens is less elastic (usually age-related)
Light rays are not focused onto the retina instead converging behind the retina

86
Q

How is long-sightedness treated?

A

Using a convex lens or laser eye surgery

87
Q

What are cataracts?

A

A cloudy patch forms on the lens of the eye which negatively affects Vision

Vision becomes blurry, difficulty to see the intensity of colour, problems with glare

88
Q

How are cataracts treated?

A

The clouded lens is exchanged for a synthetic lens during surgery.

89
Q

What is colour-blindness?

A

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

Individuals with red-green colour blindness have difficulty differentiating between red and green

90
Q

What is the cause of colour-blindness

A

Damage to cone cells in the retina

Gcse Biology (14 decks)

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