Topic 2 Cells And Control Flashcards
1
Q
What is the cell cycle?
A
When body cells in multicellular organisms divide to produce new cells.
2
Q
State the three stages of the cell cycle.
A
Stage 1 - interphase
Stage 2 - mitosis
Stage 3 - cytokinesis
3
Q
What is interphase?
A
When DNA is spread out into long strings and then increases subcellular structures. Now, it duplicates a copy of DNA and forms an X-shaped chromosome. Each ‘arm’ of the chromosome is an exact duplicate of the other.
4
Q
What is an example of an organism that uses mitosis to reproduce asexually?
A
Strawberry plants form runners by mitosis, which become new plants.
5
Q
What is a chromosome?
A
Coiled up lengths of DNA molecules.
6
Q
What happens to chromosomes during DNA replication?
A
The DNA in the ‘arm’ of each chromosome (chromatid) is replicated.
7
Q
What is mitosis?
A
A form of cell division that produces two diploid cells, both genetically identical to the parent cell.
8
Q
Why is mitosis important in organisms?
A
- Asexual reproduction
- Growth
- Repair of damaged cells
- Cell replacement
9
Q
State the four stages of mitosis.
A
- Prophase
- Metaphase
- Anaphase
- Telophase
10
Q
Outline prophase.
A
- DNA chromosomes condense, making them shorter and fatter
- Nuclear membrane breaks down so chromosomes can lie free in the cytoplasm
11
Q
Outline metaphase.
A
- Chromosomes line up along the cell equator
12
Q
Outline anaphase.
A
- Spindle fibres pull chromosomes apart
- Chromatids are pulled to opposite ends of the cell
13
Q
Outline telophase.
A
- Nucleus of the cell divides
- Membranes form around each set of chromosomes
14
Q
What does cytokinesis involve?
A
- Division of the cell membrane and cytoplasm
- Two separate cells are produced
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 cell divisions
2^5 = 32 cells
16
Q
What is cancer?
A
- Non-communicable disease
- Uncontrolled cell division due to damaged DNA
- This leads to a mass of abnormal cells called a tumour
- If the tumour invades and destroys surrounding tissues it is called cancer
17
Q
What are percentile charts?
A
A chart used to monitor growth. Measurements of length, mass, and head circumference can be compared to the expected values at a certain age.
18
Q
What does the 95th percentile mean?
A
95% of measurements will be below the value of the 95th percentile.
19
Q
What can doctors determine from percentile charts? (3)
A
- Slower growth than normal (below the bottom line)
- Faster growth than normal (above the top line)
- Abnormal growth (irregular growth patterns)
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 required for replacement and repair.
- Most cells differentiate at an early stage and become specialised. Some adult stem cells retain their ability to differentiate
21
Q
Describe growth in plants.
A
- Cell division can only occur in meristematic tissue (tips of roots and shoots). The rate of cell division remains the same throughout a plant’s life.
- Meristematic 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
22
Q
What are stem cells?
A
Cells that are undifferentiated. They can divide by mitosis to become new cells, which can differentiate.
23
Q
What is meant by ‘differentiation’?
A
The process by which a cell changes to become specialised for its job, having specialised cells allows multicellular organisms to work more efficiently.
24
Q
Why is cell differentiation important?
A
It enables the formation of specialised tissues with specific functions, e.g., muscle tissue.
25
What are embryonic stem cells?
Stem cells found in very early embryos (after fertilisation) that are unspecialised and capable of differentiating into any cell type.
26
What is the function of embryonic stem cells?
Enable the growth and development of tissues in human embryos.
27
What are adult stem cells?
Stem cells can differentiate into a limited range of cell types, e.g., bone marrow stem cells.
28
What is the primary function of adult stem cells?
Replacement of dead cells, e.g., replacement of skin or blood cells.
29
Where are stem cells found in plants?
Meristems.
30
Where is meristem tissue found?
The growing area of plants, e.g., the tips of roots and shoots.
31
What are meristematic stem cells?
Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the life of a plant, e.g., xylem and phloem.
32
How can stem cells be used in medicine?
- Stem cells collected
- Stem cells stimulated to differentiate into specific cell types, e.g., new cardiac muscle cells
- Specialised cells transplanted into the patient
- Used to treat damage or disease, e.g., heart disease
33
Where can embryonic stem cells be collected from? (2)
- Extracting stems cells from very early human embryos to grow in the needed conditions
- Donations of bone marrow stem cells
34
What are the benefits of using stem cells in medicine? (4)
- Treat damage or disease e.g. heart disease
- Treat diseases that would otherwise be untreatable
- Used in scientific research
- Growing organs for transplants
35
What are the risks of stem cell use in medicine? (6)
- Transplanted stem cells could cause tumours as they might divide uncontrollably
- Finding suitable stem cell donors is a difficult task
- Stem cells may be rejected by the body (if no drugs are taken)
- Potential side effects
- Long-term risks of using stem cells unknown
- Stem cells may become contaminated during preparation and, when transplanted, transmit infections to the patient
36
What are the ethical issues related to the use of stem cells in medicine? (2)
- 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
37
What is the central nervous system?
Brain and spinal cord.
38
What is the spinal cord?
A long column of neurones (nerve cells) that run from the brain down the spine. At several places down the code, neurones branch off and connect with parts of the body.
39
What is the function of the spinal cord?
To relay information between the brain and the rest of the body.
40
What are the structure of the brain?
Consists of three main regions:
- Cerebrum
- Cerebellum
- Medulla oblongata
41
Describe the structure of the cerebrum.
- Largest region of the brain
- Divided into two cerebral hemispheres
42
What is the function of the cerebrum? (5)
Involved in:
- Intelligence
- Language
- Memory
- Emotion
- Vision
43
What is the function of each cerebral hemisphere?
The left hemisphere controls muscles on the left side, and right does the opposite.
44
Where is the cerebellum located?
Lower region of the brain.
45
What is the function of the cerebellum? (3)
Involved in:
- Coordination of muscles
- Voluntary movement e.g. walking
- Non-voluntary movement, e.g., balance
46
What is the function of the medulla oblongata?
Controls unconscious activities like breathing and heart rate.
47
What methods, other than surgery, are used by doctors to observe the brain?
- CT scan
- PET scan
48
What is a CT scan?
Uses x-rays to produce an image of the brain showing the main structures in the brain, but not the function of them.
49
Describe how CT scans are useful to investigate brain function.
- The CT scan shows a diseased or damaged brain structure, meaning the patient has lost a brain function.
- We would ask the patient if anything has changed, e.g, vision. If so, that area of the brain is involved in vision.
50
What does a PET scan involve?
They involve using radioactive chemicals to show which parts of the brain are active. They are very detailed and used to investigate the structure and function of the brain.
51
Describe how PET scans are useful to investigate brain function.
They can show if areas in the brain are inactive or active, so they are useful for studying disorders that change brain activity.
52
Why is it difficult to treat damage to the CNS?
- Damage to neurones is permanent and can not 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
What is the function of the nervous system?
Allows an organism to rapidly react to environmental and internal changes.
54
What are neurones?
- Nerve cells adapted to quickly transmit nerve impulses.
- They are the functional units of the nervous system
- They have a cell body with a nucleas and other subcellular structures
- They can be very long, which speeds up the impulse instead of many short neurones
55
What is the function of the axon?
Carries nerve impulses away from the cell body.
56
What is the function of the dendrites and dendrons?
Carry impulses towards the cell body.
57
What is the role of the myelin sheath?
Electrical insulator, which speeds up the electrical impulses for some axons.
58
Outline the function of a sensory neurone.
Carries impulses from the receptor cells to the CNS.
59
Describe the structure of a sensory neurone
- 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
60
Outline the function of a motor neurone.
Carries impulses from the central nervous system to effector cells.
61
Describe the structure of a motor neurone.
- Short dendrites carry nerve 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
Outline the function of a relay neurone.
Carries nerve impulses from sensory neurones to motor neurones within the CNS.
63
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
64
Describe how the central nervous system coordinates a response to a stimulus.
- Stimulus
- Sensory receptor detects stimulus
- Sensory receptor sends electrical impulses along sensory neurone to CNS
- CNS coordinates response
- CNS sends information to effector (muscle or gland) along motor neurons
- Effector produces a response to the stimulus like contract a muscle or secrete a gland
65
What is a synapse?
The connection between two neurones.
66
How are nerve impulses transmitted across a synapse?
- Nerve signal is transferred by diffusion from chemicals called neurotransmitters
- They set off new electrical signals in the next neurone
67
Why do synapses slow down the transmission of nerve impulses?
It takes time for the neurotransmitters to diffuse across the synapse.
68
What is a reflex?
- Automatic response to a stimulus by the body
- Involuntary - does not involve conscious part of the brain
- Protects the body
69
Describe the reflex arc.
stimulus → sensory receptor → sensory neurone → relay neurone → motor neurone → effector → response
70
Identify the structures of the eye.
- cornea
- iris
- ciliary muscle
- lens
- suspensory ligaments
- retina
- optic nerve
- pupil
71
Outline function of the cornea.
Refracts light entering the eye.
72
Outline the function of the iris.
Controls the size of the pupil to alter how much light enters the eye.
73
What is the pupil?
A hole in the iris centre that allows light rays to enter the eye.
74
Outline the function of the lens.
Refracts light, focusing it onto the retina.
75
What is the function of the ciliary muscles and suspensory ligaments?
Change the shape of the lens (accomodation) to focus light onto the retina.
76
Outline the function of the retina.
The light-sensitive part covered in receptor cells called rods and cones.
77
What are rod cells?
Cells in the retina that are sensitive to low light intensity and can't sense colour.
78
What are cone cells?
Cells found in the retina that are sensitive to high light intensity (bright light) and can detect different colours.
79
What is the function of the optic nerve?
It carries information from light, which is converted into electrical impulses from the receptors to the brain.
80
Describe how dim light affects the size of the pupil.
- Light receptors detect dim light
- Recpetors send a message along a sensory neurone to the brain
- Message travel along a relay neurone to a motor neurone
- Tells circular muscles to relax
- Makes the pupil larger
81
Describe how bright light affects the size of the pupil.
- Light receptors detect bright light
- Recpetors send a message along a sensory neurone to the brain
- Message travel along a relay neurone to a motor neurone
- Tells circular muscles to contract
- Makes the pupil smaller
82
Why is the iris reflex important?
It prevents bright light from damaging the retina.
83
Describe how the eye focuses on near objects.
- Near object
- Ciliary muscles contract
- Suspensory ligaments slackens
- Lens becomes more convex
- Light is refracted more
84
Describe how the eye focuses on distant objects.
- Distant object
- Ciliary muscles relax
- Suspensory ligaments pull tight
- Lens becomes less convex
- Light is refracted less
85
What is long-sightedness?
Cannot focus on near objects.
86
What are the causes of long-sightedness?
- Eyeball is too short
- Lens is the wrong shape (usually age-related)
- Light from near objects are brought into focus behind the retina
87
How is long-sightedness treated?
- Using a convex lens (causes light rays to converge) in glasses or contact lenses
- Replacement lenses
- Laser eye surgery
88
What is short-sightedness?
Cannot focus on distant objects.
89
What are the causes of short-sightedness?
- Eyeball is too long
- Lens is wrong shape (too thick and too rounded)
- Light from distance objects is brought into focus in frount of the retina
90
How is short-sightedness treated?
- Using a concave lens (causes light rays to diverge) in glasses or contact lenses
- Replacement lenses
- Laser eye surgery
91
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, etc
92
How are cataracts treated?
The clouded lens is replaced for an artificial lens during surgery.
93
What is colour-blindness?
- When people can't tell the difference between certain colours
- Usually red-green colourblindness
94
What is the cause of colour-blindness?
When cone cells in the retina are damaged or not working properly.
95
What is an example of a disease that PET scanning can show and how?
Alzheimer's disease since activities in certain areas if the brain is reduced and can be compared to a healthy brain.
96
What are the two examples of diseases in the CNS?
Alzheimers and Parkinsons.
97
What is a stimulus (stimuli)?
Change in internal or physical environment.
98
What is a receptor?
Different receptors detect different stimuli.
- Receptors in your eyes detect light
- Receptors in your skin detect touch (pressure) and temperature change
99
Why can't colourblindness be treated at the moment?
There is no replacement of cone cells.
100
