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Biology > SB2: Cells and Control > Flashcards

SB2: 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 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 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 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 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 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

What happens during prophase?

A

DNA condenses, chromosomes become visible. Nuclear membrane disappears.

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11
Q

What happens during metaphase?

A

Chromosomes line up along the cell equator.

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12
Q

What happens during anaphase?

A

Spindle fibres attach to each chromosome. ‘arms’ of each chromosome pulled to opposite poles. The chromatids are separated.

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13
Q

What happens during telophase?

A

The nucleus of the cell divides. A new membrane then forms around each set of chromosomes.

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14
Q

What happens during cytokinesis?

A

The 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

10 ÷ 2 = 5
5 cell divisions have taken place.
2^5 = 32 cells.

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16
Q

What is cancer?

A

Uncontrolled cell division due to damaged DNA, this results in the formation of a primary tumour.

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17
Q

What are percentile charts?

A

A chart used to monitor the growth of the baby. Measurements can be compared to the expected values at a certain age. Measurements taken are: Head circumference, Weight and Length

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18
Q

What does the 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 from percentile charts? [3 marks]

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
A
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21
Q

What can doctors determine from percentile charts [3 marks]

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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22
Q

Describe growth in animals

A

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

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23
Q

Describe growth in plants.

A

Cell division only takes place in the meristem tissue. The rate of cell division remains the same throughout the plant’s life. Cell elongation occurs in all cells. Cells expand and enlarge enabling growth of the plant.

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24
Q

What are stem cells?

A

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

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25
What is meant by the term 'differentiation'?
The process where stem cells differentiate and become specialised. This is where some genes switch on or off, determining cell type.
26
Why is cell differentiation important?
It enables the formation of specialised cells with specific functions. (e.g. muscle tissue)
27
What are embryonic stem cells?
Stem cells found in very early embryos that are undifferentiated and capable of differentiating into any cell type.
28
What is the function of embryonic stem cells?
Enable the growth and development of tissues in human embryos.
29
What are adult stem cells?
Stem cells that can differentiate into a limited range of cell types (e.g. bone marrow stem cells)
30
What is the primary function of adult stem cells?
Replacement of dead cells (e.g. replacement of red blood cells which only live for 120 days)
31
Where are stem cells found in plants?
Meristems
32
Where is meristem tissue found?
In regions of the plant where cells are continuously dividing (e.g. roots and shoots)
33
What are meristemic stem cells?
Stem cells found in meristems that are undifferentiated and are capable of differentiating into any cell type during the life of a plant.
34
How can stem cells be used in medicine?
Stem cells can be collected and stimulated to differentiate into specific cell types. These specialised cell types are then transplanted into the patient and used to treat damage or disease (e.g. heart disease)
35
Where can embryonic stem cells be collected from? [2 marks]
Donor stem cells removed from embryos grown or patient's own stem cells removed from the umbilical blood before birth.
36
What are the benefits of using stem cells in medicine? [4 marks]
Treat damage or disease, Treat disease that would otherwise be untreatable, Used in scientific research & Growing organs for transplants.
37
What are the risks of stem cells use in medicine? [6 marks]
1. Transplanted stem cells could cause tumours 2. Finding suitable stem cell donors is a difficult task 3. Stem cells may be rejected by the body 4. Potential side effects 5. Long term risks of using stem cells are unknown 6. Stem cells may become contaminated during preparation and when transplanted transmit infections to the patient, making them sicker.
38
What are the ethical issues related to the use of stem cells in medicine? [2 marks]
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.
39
What is the central nervous system made of?
Brain and spinal cord.
40
What is the spinal cord?
A long, thin structure composed of neurones that extend from the medulla oblongata down the spine.
41
What is the function of the spinal cord?
Connects the peripheral nervous system (nerves outside the CNS) to the brain.
42
Describe the structure of the brain?
The brain consists of three main regions: Cerebrum, Cerebellum & Medulla Oblongata.
43
Describe the structure of the cerebrum?
Largest region of the brain. Divided into two hemispheres.
44
What is the function of the cerebrum?
Involved in: 1. Intelligence 2. Language 3. Memory 4. Emotion 5. Visual and Sensory processes
45
What is the function of each cerebral hemisphere?
THE LEFT HEMISPHERE receives sensory information from the right side of the body and controls muscle coordination on the right. THE RIGHT HEMISPHERE receives sensory information from the left side of the body and controls muscle coordination on the left.
46
Where is the cerebellum located?
Lower region of the brain.
47
What is the function of the cerebellum?
Involved in: 1. Coordination of muscles 2. Voluntary movement (e.g. Walking) 3. Non-voluntary movement (e.g. balance)
48
What is the function of the medulla oblongata?
Controls automatic processes in the body (e.g. breathing rate, heart rate)
49
What methods, other than surgery, are used by doctors to observe the brain?
CT Scan or PET Scan
50
What is a CT Scan?
A scan that uses X-rays to produce 3D cross-sectional images of the brain.
51
Describe how CT Scans are useful to investigate brain function.
CT scans show damaged regions of the brain (e.g. areas of swelling, bleeding). Observations of the patient's symptoms can enable scientists to determine the function of the damaged region.
52
What does a PET Scan involve?
Radioactive substance injected into a patient's bloodstream and absorbed by the tissues in the brain. Radiation is then emitted from the radioactive tracer allowing us to identify the damaged parts of the brain.
53
Describe how PET Scans are useful to investigate brain function.
Shows which areas of the brain are functioning and which areas are not functioning properly. Comparisons of brain activity in healthy brain and patients with brain damage allows doctors to determine whether it is a healthy or unhealthy brain.
54
Why is it difficult to treat damage to the CNS?
Damage to neurones are 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.
55
What is the function of the nervous system?
Allows an organism to rapidly react to environmental and internal changes.
56
What are neurones?
Nerve cells adapted to quickly transmit nerve impulses. They are the functional units of the nervous system.
57
What is the function of the axon?
Carries impulses away from the cell body. Enables the transmission of nerve impulses over long distances.
58
What is the function of the dendrites and dendrons?
Carry impulses towards the cell body. Dendrites provide a large surface area to receive impulses.
59
What is the role of the myelin sheath?
Electrically insulating layer. Surrounds the axon and increases the speed of impulses.
60
Outline the function of a sensory neurone.
Carries impulses from receptors to the CNS.
61
Describe the structure of a sensory neurone.
Long dendron carries impulses from receptors to the cell body. Short axon carries impulses from the cell body to the CNS.
62
Outline the function of a motor neurone.
Carries impulses from the central nervous system to effectors.
63
Describe the structure of a motor neurone.
Short dendrites carry impulses from the CNS to the cell body. Long axon carries impulses from the cell body to the effectors.
64
Outline the function of a relay neurone.
Carries impulses from sensory neurones to motor neurones within the central nervous system.
65
Describe the structure of a relay neurone.
Short dendrites carry impulses from sensory neurones to the cell body. Short axon carries impulses from the cell body to motor neurones.
66
Describe how the central nervous system coordinates a response to a stimulus.
Stimulus---Sensory receptor detects stimulus---Sensory receptor sends impulses along sensory neurones to the CNS---CNS coordinates response---CNS sends information to effector along the motor neurone---Effector produces a response to the stimulus.
67
What is a synapse?
A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters.
68
How are nerve impulses transmitted across a synapse?
Nerve impulses reaches the 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.
69
Why do synapses slow down the transmission of nerve impulses?
It takes time for the neurotransmitters to diffuse across the synapse and bind to receptors on the postsynaptic neurone.
70
What is a reflex?
Automatic response to a stimulus by the body. It is involuntary so it does not involve the conscious part of the brain.
71
Describe the reflex arc.
Stimulus---Sensory receptor---Sensory neurone---Relay neurone---Motor neurone---Effector--Response
72
List the structures of the eye. [7 marks]
Cornea Iris Ciliary muscle Lens Suspensory ligaments Retina Optic nerve
73
Outline the structure and function of the cornea.
Transparent outer covering of the eye. Refracts light entering the eye.
74
Outline the structure and function of the iris.
Pigmented ring of circular muscles and radial muscles. Controls the size of the pupil to alter how much light enters the eye.
75
What is the pupil?
A hole in the centre of the iris that allows light rays to enter.
76
Outline the structure and function of the lens.
Transparent biconvex structure. Suspensory ligaments attach the lens to a ring of ciliary muscle. Refracts light, focusing it onto the retina.
77
What is the function of the ciliary muscle and suspensory ligaments?
Change the shape of the lens (accomodation) to focus light onto the retina.
78
Outline the structure and function of the retina.
Light sensitive layer composed of rod and cone cells. Converts light energy into neural signals which are sent to the brain via the optic nerve.
79
What are rod cells?
Cells in the retina that are sensitive to low light intensity (dim light)
80
What are cone cells?
Cells found in the retina that are sensitive to high light intensity (bright light) and can detect colours.
81
What is the function of the optic nerve?
Transmit nerve impulses to the brain from the retina.
82
Describe how dim light affects the size of the pupil.
The pupil dilates (widens) so more light enter the pupil.
83
Describe how bright light affects the pupil.
The pupil contracts so less light enters the pupil.
84
Why is the iris reflex important?
It prevents bright light from damaging the retina.
85
What is accommodation?
Process by which the elastic lens changes its shape (with the help of ciliary muscles and suspensory ligaments) to focus on near or distant objects.
86
Describe how the eye focuses on near objects.
Near object---Ciliary muscles contract---Suspensory ligaments relax---Lens become more convex (rounded)---Light is refracted more---Light rays focused onto the retina
87
Describe how the eye focuses of distant objects.
Distant object---Ciliary muscles relax---Suspensory ligaments tighten---Lens become less convex (less rounded)---Light is refracted less---Light rays focused onto the retina.
88
What is long-sightedness?
can focus on distant objects clearly. Cannot focus on near objects.
89
What are the causes of long-sightedness?
Eyeball is too short. Lens is less elastic (usually age-related). Therefore light rays are not focused onto the retina, instead converging (meet) behind the retina.
90
How is long-sightedness treated?
Using a convex lens (causes light rays to converge) in glasses or contact lenses. Replacement lenses. Laser eye surgery.
91
What is short-sightedness?
Can focus on near objects clearly. Cannot focus on distant objects.
92
What are the causes of short-sightedness?
Eyeball is too long. Lens is too thick and too rounded. Therefore light rays are not focused onto the retina, instead converging in front of the retina.
93
How is short-sightedness treated?
Using a concave lens (causes light rays to diverge) in glasses or contact lenses. Replacement lenses. Laser eye surgery.
94
What are cataracts?
A cloudy patch forms on the lens of the eye which affects vision. Vision becomes blurry, difficult to see the intensity of colours, problems with glare.
95
How are cataracts treated?
The clouded lens is exchanged for a synthetic lens during surgery.
96
What is colour-blindness?
A deficiency of the eye that makes it difficult to distinguish between colours. (e.g. Individuals with red-green colour blindness have difficulty telling the difference between red and green)
97
What is the cause of colour-blindness?
Damage to cone cells in the retina.

Biology (3 decks)

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